{/* Copyright 2024 Adobe. All rights reserved.
This file is licensed to you under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License. You may obtain a copy
of the License at http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software distributed under
the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR REPRESENTATIONS
OF ANY KIND, either express or implied. See the License for the specific language
governing permissions and limitations under the License. */}

import {Layout} from '@react-spectrum/docs';
export default Layout;

import docs from 'docs:react-aria-components';
import sharedDocs from 'docs:@react-types/shared';
import {PropTable, HeaderInfo, TypeLink, PageDescription, StateTable, ContextTable, ClassAPI, VersionBadge} from '@react-spectrum/docs';
import styles from '@react-spectrum/docs/src/docs.css';
import packageData from 'react-aria-components/package.json';
import Anatomy from './TreeAnatomy.svg';
import ChevronRight from '@spectrum-icons/workflow/ChevronRight';
import {Divider} from '@react-spectrum/divider';
import {ExampleCard} from '@react-spectrum/docs/src/ExampleCard';
import {ExampleList} from '@react-spectrum/docs/src/ExampleList';
import {Keyboard} from '@react-spectrum/text';
import Collections from '@react-spectrum/docs/pages/assets/component-illustrations/Collections.svg';
import Selection from '@react-spectrum/docs/pages/assets/component-illustrations/Selection.svg';
import DragAndDrop from '@react-spectrum/docs/pages/assets/component-illustrations/DragAndDrop.svg';
import Checkbox from '@react-spectrum/docs/pages/assets/component-illustrations/Checkbox.svg';
import Button from '@react-spectrum/docs/pages/assets/component-illustrations/Button.svg';
import treeUtils from 'docs:@react-aria/test-utils';
import {StarterKits} from '@react-spectrum/docs/src/StarterKits';

---
category: Collections
keywords: [disclosure, collapse, expand, aria, tree, grid]
type: component
---

# Tree

<PageDescription>{docs.exports.Tree.description}</PageDescription>

<HeaderInfo
  packageData={packageData}
  componentNames={['Tree']}
  sourceData={[
    {type: 'W3C', url: 'https://www.w3.org/WAI/ARIA/apg/patterns/treegrid/'}
  ]} />

## Example

This example's MyTreeItemContent is from the [Reusable Wrappers](#reusable-wrappers) section below.

```tsx example
import {
  Tree,
  TreeItem,
  TreeItemContent,
  Button,
  Collection
} from 'react-aria-components';
import {Info} from 'lucide-react';

<Tree aria-label="Files" style={{height: '300px'}} defaultExpandedKeys={['documents', 'photos', 'project']} selectionMode="multiple" defaultSelectedKeys={['photos']}>
  <TreeItem id="documents" textValue="Documents">
    <MyTreeItemContent>
      Documents
      <Button aria-label="Info"><Info size={20} /></Button>
    </MyTreeItemContent>
    <TreeItem id="project" textValue="Project">
      <MyTreeItemContent>
        Project
        <Button aria-label="Info"><Info size={20} /></Button>
      </MyTreeItemContent>
      <TreeItem id="report" textValue="Weekly Report">
        <MyTreeItemContent>
          Weekly Report
          <Button aria-label="Info"><Info size={20} /></Button>
        </MyTreeItemContent>
      </TreeItem>
    </TreeItem>
  </TreeItem>
  <TreeItem id="photos" textValue="Photos">
    <MyTreeItemContent>
      Photos
      <Button aria-label="Info"><Info size={20} /></Button>
    </MyTreeItemContent>
    <TreeItem id="one" textValue="Image 1">
      <MyTreeItemContent>
        Image 1
        <Button aria-label="Info"><Info size={20} /></Button>
      </MyTreeItemContent>
    </TreeItem>
    <TreeItem id="two" textValue="Image 2">
      <MyTreeItemContent>
        Image 2
        <Button aria-label="Info"><Info size={20} /></Button>
      </MyTreeItemContent>
    </TreeItem>
  </TreeItem>
</Tree>
```

<details>
  <summary style={{fontWeight: 'bold'}}><ChevronRight size="S" /> Show CSS</summary>

```css hidden
@import "@react-aria/example-theme";
@import './Button.mdx' layer(button);
@import './ToggleButton.mdx' layer(togglebutton);
@import './Checkbox.mdx' layer(checkbox);
```

```css
.react-aria-Tree {
  display: flex;
  flex-direction: column;
  gap: 2px;
  overflow: auto;
  padding: 4px;
  border: 1px solid var(--border-color);
  border-radius: 6px;
  background: var(--overlay-background);
  forced-color-adjust: none;
  outline: none;
  width: 250px;
  max-height: 300px;
  box-sizing: border-box;

  &[data-focus-visible] {
    outline: 2px solid var(--focus-ring-color);
    outline-offset: -1px;
  }

  .react-aria-TreeItem {
    display: flex;
    align-items: center;
    gap: 0.571rem;
    min-height: 28px;
    padding: 0.286rem 0.286rem 0.286rem 0.571rem;
    --padding: 16px;
    border-radius: 6px;
    outline: none;
    cursor: default;
    color: var(--text-color);
    font-size: 1.072rem;
    position: relative;
    transform: translateZ(0);

    .react-aria-Button[slot=chevron] {
      all: unset;
      display: flex;
      visibility: hidden;
      align-items: center;
      justify-content: center;
      width: 1.3rem;
      height: 100%;
      padding-left: calc((var(--tree-item-level) - 1) * var(--padding));

      svg {
        rotate: 0deg;
        transition: rotate 200ms;
        width: 12px;
        height: 12px;
        fill: none;
        stroke: currentColor;
        stroke-width: 3px;
      }
    }

    .react-aria-Button[slot=drag] {
      display: flex;
      align-items: center;
      justify-content: center;
    }

    &[data-has-child-items] .react-aria-Button[slot=chevron] {
      visibility: visible;
    }

    &[data-expanded] .react-aria-Button[slot=chevron] svg {
      rotate: 90deg;
    }

    &[data-focus-visible] {
      outline: 2px solid var(--focus-ring-color);
      outline-offset: -2px;
    }

    &[data-pressed] {
      background: var(--gray-100);
    }

    &[data-selected] {
      background: var(--highlight-background);
      color: var(--highlight-foreground);
      --focus-ring-color: var(--highlight-foreground);

      &[data-focus-visible] {
        outline-color: var(--highlight-foreground);
        outline-offset: -4px;
      }

      .react-aria-Button {
        color: var(--highlight-foreground);
        --highlight-hover: rgb(255 255 255 / 0.1);
        --highlight-pressed: rgb(255 255 255 / 0.2);
      }
    }

    &[data-disabled] {
      color: var(--text-color-disabled);
    }

    .react-aria-Button:not([slot]) {
      margin-left: auto;
      background: transparent;
      border: none;
      font-size: 1.2rem;
      line-height: 1.2em;
      padding: 0.286rem 0.429rem;
      transition: background 200ms;

      &[data-hovered] {
        background: var(--highlight-hover);
      }

      &[data-pressed] {
        background: var(--highlight-pressed);
        box-shadow: none;
      }
    }
  }

  /* join selected items if :has selector is supported */
  @supports selector(:has(.foo)) {
    gap: 0;

    .react-aria-TreeItem[data-selected]:has(+ [data-selected]) {
      border-end-start-radius: 0;
      border-end-end-radius: 0;
    }

    .react-aria-TreeItem[data-selected] + [data-selected] {
      border-start-start-radius: 0;
      border-start-end-radius: 0;
    }
  }

  :where(.react-aria-TreeItem) .react-aria-Checkbox {
    --selected-color: var(--highlight-foreground);
    --selected-color-pressed: var(--highlight-foreground-pressed);
    --checkmark-color: var(--highlight-background);
    --background-color: var(--highlight-background);
  }
}
```

</details>

## Features

A tree can be built using the [&lt;ul&gt;](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/ul), [&lt;li&gt;](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/li),
 and [&lt;ol&gt;](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/ol), but is very limited in functionality especially when it comes to user interactions.
HTML lists are meant for static content, rather than hierarchies with rich interactions like focusable elements within cells, keyboard navigation, item selection, sorting, etc.
`Tree` helps achieve accessible and interactive tree components that can be styled as needed.

* **Item selection** – Single or multiple selection, with optional checkboxes, disabled items, and both `toggle` and `replace` selection behaviors.
* **Interactive children** – Tree items may include interactive elements such as buttons, menus, etc.
* **Actions** – Items support optional actions such as navigation via click, tap, double click, or <Keyboard>Enter</Keyboard> key.
* **Keyboard navigation** – Tree items and focusable children can be navigated using the arrow keys, along with page up/down, home/end, etc. Typeahead, auto scrolling, and selection modifier keys are supported as well.
* **Drag and drop** – Tree supports drag and drop to reorder, move, insert, or update items via mouse, touch, keyboard, and screen reader interactions.
* **Virtualized scrolling** – Use [Virtualizer](Virtualizer.html) to improve performance of large lists by rendering only the visible items.
* **Touch friendly** – Selection and actions adapt their behavior depending on the device. For example, selection is activated via long press on touch when item actions are present.
* **Accessible** – Follows the [ARIA treegrid pattern](https://www.w3.org/WAI/ARIA/apg/patterns/treegrid/), with additional selection announcements via an ARIA live region. Extensively tested across many devices and [assistive technologies](accessibility.html#testing) to ensure announcements and behaviors are consistent.

## Anatomy

<Anatomy role="img" aria-label="Anatomy diagram of a Tree, consisting of multiple items. Each item in the tree contains a selection checkbox, an expand toggle button, and the name of the item." />

A Tree consists of a container element, with items containing data inside. The items within a tree may contain focusable elements or plain text content. Each item may also contain a button to toggle the expandable state of that item.

If the tree supports item selection, each item can optionally include a selection checkbox.

```tsx render=false
"use client";
import {Tree, TreeItem, TreeItemContent, Button, Checkbox, SelectionIndicator} from 'react-aria-components';

<Tree>
  <TreeItem>
    <TreeItemContent>
      <Button slot="chevron" />
      <Checkbox slot="selection" /> or <SelectionIndicator />
      <Button slot="drag" />
    </TreeItemContent>
    <TreeItem>
      {/* ... */}
    </TreeItem>
  </TreeItem>
</Tree>
```

### Concepts

`Tree` makes use of the following concepts:

<section className={styles.cardGroup} data-size="small">

<ExampleCard
  url="collections.html"
  title="Collections"
  description="Defining collections of items, async loading, and updating items over time.">
  <Collections />
</ExampleCard>

<ExampleCard
  url="selection.html"
  title="Selection"
  description="Interactions and data structures to represent selection.">
  <Selection />
</ExampleCard>

<ExampleCard
  url="dnd.html"
  title="Drag and drop"
  description="Concepts and interactions for an accessible drag and drop experience.">
  <DragAndDrop />
</ExampleCard>

</section>

### Composed components

A `Tree` uses the following components, which may also be used standalone or reused in other components.

<section className={styles.cardGroup} data-size="small">

<ExampleCard
  url="Checkbox.html"
  title="Checkbox"
  description="A checkbox allows a user to select an individual option.">
  <Checkbox />
</ExampleCard>

<ExampleCard
  url="Button.html"
  title="Button"
  description="A button allows a user to perform an action.">
  <Button />
</ExampleCard>

</section>

## Examples

<ExampleList tag="tree" />

## Starter kits

To help kick-start your project, we offer starter kits that include example implementations of all React Aria components with various styling solutions. All components are fully styled, including support for dark mode, high contrast mode, and all UI states. Each starter comes with a pre-configured [Storybook](https://storybook.js.org/) that you can experiment with, or use as a starting point for your own component library.

<StarterKits component="tree" />


## Reusable wrappers

If you will use a Tree in multiple places in your app, you can wrap all of the pieces into a reusable component. This way, the DOM structure, styling code, and other logic are defined in a single place and reused everywhere to ensure consistency.

```tsx example export=true render=false
import type {TreeItemContentProps, TreeItemContentRenderProps} from 'react-aria-components';
import {Button} from 'react-aria-components';
import {GripVertical} from 'lucide-react';

function MyTreeItemContent(props: Omit<TreeItemContentProps, 'children'> & {children?: React.ReactNode}) {
  return (
    <TreeItemContent>
      {({hasChildItems, selectionBehavior, selectionMode, allowsDragging}: TreeItemContentRenderProps) => (
        <>
          {allowsDragging && <Button slot="drag"><GripVertical size={18} /></Button>}
          {selectionBehavior === 'toggle' && selectionMode !== 'none' && <MyCheckbox slot="selection" />}
          <Button slot="chevron">
            <svg viewBox="0 0 24 24">
              <path d="m8.25 4.5 7.5 7.5-7.5 7.5" />
            </svg>
          </Button>
          {props.children}
        </>
      )}
    </TreeItemContent>
  );
}
```

The `TreeItem` can also be wrapped. This example accepts a `title` prop and renders the `TreeItemContent` automatically.

```tsx example export=true render=false
import {TreeItemProps} from 'react-aria-components';

interface MyTreeItemProps extends Partial<TreeItemProps> {
  title: string
}

function MyTreeItem(props: MyTreeItemProps) {
  return (
    <TreeItem textValue={props.title} {...props}>
      <MyTreeItemContent>
        {props.title}
      </MyTreeItemContent>
      {props.children}
    </TreeItem>
  );
}
```

Now we can render a Tree using far less code.

```tsx example
<Tree aria-label="Files" style={{height: '300px'}} defaultExpandedKeys={['documents', 'photos', 'project']}>
  <MyTreeItem id="documents" title="Documents">
    <MyTreeItem id="project" title="Project">
      <MyTreeItem id="report" title="Weekly Report" />
    </MyTreeItem>
  </MyTreeItem>
  <MyTreeItem id="photos" title="Photos">
    <MyTreeItem id="one" title="Image 1" />
    <MyTreeItem id="two" title="Image 2" />
  </MyTreeItem>
</Tree>
```

## Content

So far, our examples have shown static collections where the data is hard coded.
Dynamic collections, as shown below, can be used when the tree data comes from an external data source such as an API,
or updates over time. In the example below, data for each item is provided to the tree via a render function.

```tsx example export=true
import type {TreeProps} from 'react-aria-components';
import {MyCheckbox} from './Checkbox';

let items = [
  {id: '1', title: 'Documents', type: 'directory', children: [
    {id: '2', title: 'Project', type: 'directory', children: [
      {id: '3', title: 'Weekly Report', type: 'file', children: []},
      {id: '4', title: 'Budget', type: 'file', children: []}
    ]}
  ]},
  {id: '5', title: 'Photos', type: 'directory', children: [
    {id: '6', title: 'Image 1', type: 'file', children: []},
    {id: '7', title: 'Image 2', type: 'file', children: []}
  ]}
];

interface FileType {
  id: string,
  title: string,
  type: 'directory' | 'file',
  children: FileType[]
}

function FileTree(props: TreeProps<FileType>) {
  return (
    <Tree
      aria-label="Files"
      defaultExpandedKeys={['1']}
      /*- begin highlight -*/
      items={items}
      /*- end highlight -*/
      selectionMode="multiple"
      {...props}>
      {/*- begin highlight -*/}
      {function renderItem(item) {
        ///- end highlight -///
        return (
          <TreeItem textValue={item.title}>
            <MyTreeItemContent>
              {item.title}
              <Button
                aria-label="Info"
                onPress={() => alert(`Info for ${item.title}...`)}>
                ⓘ
              </Button>
            </MyTreeItemContent>
            <Collection items={item.children}>
              {/*- begin highlight -*/}
              {/* recursively render children */}
              {renderItem}
              {/*- end highlight -*/}
            </Collection>
          </TreeItem>
        );
      }}
    </Tree>
  )
}

```

## Selection

### Single selection

By default, `Tree` doesn't allow item selection but this can be enabled using the `selectionMode` prop. Use `defaultSelectedKeys` to provide a default set of selected items.
Note that the value of the selected keys must match the `id` prop of the item.

The example below enables single selection mode and uses `defaultSelectedKeys` to select the item with id equal to `2`.
A user can click on a different item to change the selection or click on the same item again to deselect it entirely.

```tsx example
// Using the example above
<FileTree selectionMode="single" defaultSelectedKeys={['2']} defaultExpandedKeys={['1']} />
```

### Multiple selection

Multiple selection can be enabled by setting `selectionMode` to `multiple`.

```tsx example
// Using the example above
<FileTree selectionMode="multiple" defaultSelectedKeys={['2', '4']} defaultExpandedKeys={['1', '2']} />
```

### Disallow empty selection

Tree also supports a `disallowEmptySelection` prop which forces the user to have at least one item in the Tree selected at all times.
In this mode, if a single item is selected and the user presses it, it will not be deselected.

```tsx example
// Using the example above
<FileTree selectionMode="single" defaultSelectedKeys={['2']} defaultExpandedKeys={['1']} disallowEmptySelection />
```


### Controlled selection

To programmatically control item selection, use the `selectedKeys` prop paired with the `onSelectionChange` callback. The `id` prop from the selected items will
be passed into the callback when the item is pressed, allowing you to update state accordingly.

```tsx example export=true
import type {Selection} from 'react-aria-components';

interface Pokemon {
  id: number,
  name: string,
  children?: Pokemon[]
}

interface PokemonEvolutionTreeProps<T> extends TreeProps<T> {
  items?: T[],
  renderEmptyState?: () => string
}

function PokemonEvolutionTree(
  props: PokemonEvolutionTreeProps<Pokemon>
) {
  let items: Pokemon[] = props.items ?? [
    {id: 1, name: 'Bulbasaur', children: [
      {id: 2, name: 'Ivysaur', children: [
        {id: 3, name: 'Venusaur'}
      ]}
    ]},
    {id: 4, name: 'Charmander', children: [
      {id: 5, name: 'Charmeleon', children: [
        {id: 6, name: 'Charizard'}
      ]}
    ]},
    {id: 7, name: 'Squirtle', children: [
      {id: 8, name: 'Wartortle', children: [
        {id: 9, name: 'Blastoise'}
      ]}
    ]}
  ];

  ///- begin highlight -///
  let [selectedKeys, setSelectedKeys] =
    React.useState<Selection>(new Set());
  ///- end highlight -///

  return (
    <Tree
      aria-label="Pokemon evolution tree"
      style={{height: '300px'}}
      items={items}
      defaultExpandedKeys={[1, 2]}
      /*- begin highlight -*/
      selectedKeys={selectedKeys}
      onSelectionChange={setSelectedKeys}
      /*- end highlight -*/
      {...props}
    >
      {function renderItem(item) {
        return (
          <MyTreeItem title={item.name}>
            <Collection items={item.children}>
              {renderItem}
            </Collection>
          </MyTreeItem>
        );
      }}
    </Tree>
  );
}

<PokemonEvolutionTree selectionMode="multiple" />
```

### Selection behavior

By default, `Tree` uses the `"toggle"` selection behavior, which behaves like a checkbox group: clicking, tapping, or pressing the <Keyboard>Space</Keyboard> or <Keyboard>Enter</Keyboard> keys toggles selection for the focused item. Using the arrow keys moves focus but does not change selection. The `"toggle"` selection mode is often paired with checkboxes in each item as an explicit affordance for selection.

When the `selectionBehavior` prop is set to `"replace"`, clicking an item with the mouse _replaces_ the selection with only that item. Using the arrow keys moves both focus and selection. To select multiple items, modifier keys such as <Keyboard>Ctrl</Keyboard>, <Keyboard>Cmd</Keyboard>, and <Keyboard>Shift</Keyboard> can be used. To move focus without moving selection, the <Keyboard>Ctrl</Keyboard> key on Windows or the <Keyboard>Option</Keyboard> key on macOS can be held while pressing the arrow keys. Holding this modifier while pressing the <Keyboard>Space</Keyboard> key toggles selection for the focused item, which allows multiple selection of non-contiguous items. On touch screen devices, selection always behaves as toggle since modifier keys may not be available. This behavior emulates native platforms such as macOS and Windows and is often used when checkboxes in each item are not desired.

```tsx example
<PokemonEvolutionTree selectionMode="multiple" selectionBehavior="replace" />
```

## Item actions

`Tree` supports item actions via the `onAction` prop, which is useful for functionality such as navigation. In the default `"toggle"` selection behavior, when nothing is selected, clicking or tapping the item triggers the item action.
When at least one item is selected, the tree is in selection mode, and clicking or tapping an item toggles the selection. Actions may also be triggered via the <Keyboard>Enter</Keyboard> key, and selection using the <Keyboard>Space</Keyboard> key.

This behavior is slightly different in the `"replace"` selection behavior, where single clicking selects the item and actions are performed via double click. On touch devices, the action becomes the primary tap interaction,
and a long press enters into selection mode, which temporarily swaps the selection behavior to `"toggle"` to perform selection (you may wish to display checkboxes when this happens). Deselecting all items exits selection mode
and reverts the selection behavior back to `"replace"`. Keyboard behaviors are unaffected.

```tsx example
<div style={{display: 'flex', flexWrap: 'wrap', gap: '24px'}}>
  <PokemonEvolutionTree
    aria-label="Pokemon tree with item actions and toggle selection behavior"
    ///- begin highlight -///
    onAction={key => alert(`Opening item ${key}...`)}
    ///- end highlight -///
    selectionMode="multiple" />
  <PokemonEvolutionTree
    aria-label="Pokemon tree with item actions and replace selection behavior"
    ///- begin highlight -///
    onAction={key => alert(`Opening item ${key}...`)}
    selectionBehavior="replace"
    ///- end highlight -///
    selectionMode="multiple" />
</div>
```

Items may also have an action specified by directly applying `onAction` on the `TreeItem` itself. This may be especially convenient in static collections. If `onAction` is also provided to the `Tree`, both the tree's and the item's `onAction` are called.

```tsx example
<Tree aria-label="Tree with onAction applied on the items directly" style={{height: '300px'}} defaultExpandedKeys={['bulbasaur', 'ivysaur']}>
  <MyTreeItem
    /*- begin highlight -*/
    onAction={() => alert(`Opening Bulbasaur...`)}
    /*- end highlight -*/
    id="bulbasaur"
    title="Bulbasaur">
    <MyTreeItem
      onAction={() => alert(`Opening Ivysaur...`)}
      id="ivysaur"
      title="Ivysaur">
      <MyTreeItem
        onAction={() => alert(`Opening Venusaur...`)}
        id="venusaur"
        title="Venusaur" />
    </MyTreeItem>
  </MyTreeItem>
</Tree>
```


### Links

Tree items may also be links to another page or website. This can be achieved by passing the `href` prop to the `<TreeItem>` component. Links behave the same way as described above for item actions depending on the `selectionMode` and `selectionBehavior`.

```tsx example
<Tree aria-label="Tree with href" style={{height: '200px'}} defaultExpandedKeys={['bulbasaur', 'ivysaur']}>
  <MyTreeItem
    /*- begin highlight -*/
    href="https://pokemondb.net/pokedex/bulbasaur"
    target="_blank"
    /*- end highlight -*/
    id="bulbasaur"
    title="Bulbasaur">
    <MyTreeItem
      id="ivysaur"
      title="Ivysaur"
      href="https://pokemondb.net/pokedex/ivysaur"
      target="_blank">
      <MyTreeItem
        id="venusaur"
        title="Venusaur"
        href="https://pokemondb.net/pokedex/venusaur"
        target="_blank" />
    </MyTreeItem>
  </MyTreeItem>
</Tree>
```

```css hidden
.react-aria-TreeItem[data-href] {
  cursor: pointer;
}
```

#### Client side routing

The `<TreeItem>` component works with frameworks and client side routers like [Next.js](https://nextjs.org/) and [React Router](https://reactrouter.com/en/main). As with other React Aria components that support links, this works via the <TypeLink links={docs.links} type={docs.exports.RouterProvider} /> component at the root of your app. See the [client side routing guide](routing.html) to learn how to set this up.

## Keyboard navigation

Navigation within the tree and within individual item actions share two keyboard keys.

The "expand" key (<Keyboard>→</Keyboard> in LTR, <Keyboard>←</Keyboard> in RTL) expands a collapsed item, and the "collapse" key (<Keyboard>←</Keyboard> in LTR, <Keyboard>→</Keyboard> in RTL) collapses an item, or navigates to its parent if the item is already collapsed.

The same keys are used to navigate between the actions within tree items. When an item has actions and is not expandable, pressing the expand key navigates to the next action, and pressing the collapse key navigates to the previous action. When focus returns to the tree item itself, pressing the collapse key again collapses the item.

## Disabled items

A `TreeItem` can be disabled with the `isDisabled` prop. This will disable all interactions on the item
unless the `disabledBehavior` prop on `Tree` is used to change this behavior.
Note that you are responsible for the styling of disabled items, however, the selection checkbox will be automatically disabled.

```tsx example
<Tree aria-label="Tree with disabled items" style={{height: '100px'}} defaultExpandedKeys={['bulbasaur']}>
  <MyTreeItem id="bulbasaur" title="Bulbasaur">
    {/*- begin highlight -*/}
    <MyTreeItem id="ivysaur" title="Ivysaur" isDisabled>
    {/*- end highlight -*/}
      <MyTreeItem id="venusaur" title="Venusaur" />
    </MyTreeItem>
  </MyTreeItem>
</Tree>
```

When `disabledBehavior` is set to `selection`, interactions such as focus, dragging, or actions can still be performed on disabled rows.

```tsx example
<Tree
  aria-label="Tree with disabled items"
  style={{height: '100px'}}
  selectionMode="multiple"
  defaultExpandedKeys={['bulbasaur']}
  /*- begin highlight -*/
  disabledBehavior="selection"
  /*- end highlight -*/
>
  <MyTreeItem id="bulbasaur" title="Bulbasaur">
    {/*- begin highlight -*/}
    <MyTreeItem id="ivysaur" title="Ivysaur" isDisabled>
    {/*- end highlight -*/}
      <MyTreeItem id="venusaur" title="Venusaur" />
    </MyTreeItem>
  </MyTreeItem>
</Tree>
```

In dynamic collections, it may be more convenient to use the `disabledKeys` prop at the `Tree` level instead of `isDisabled` on individual items.
This accepts a list of item ids that are disabled. An item is considered disabled if its key exists in `disabledKeys` or if it has `isDisabled`.

```tsx example
// Using the same tree as above
<PokemonEvolutionTree selectionMode="multiple" disabledKeys={[3]} />
```

## Asynchronous loading

This example uses the [useAsyncList](../react-stately/useAsyncList.html) hook to handle asynchronous loading
of data from a server. Use the [renderEmptyState](#empty-state) prop to display a spinner during initial load.
To enable infinite scrolling, render a `<TreeLoadMoreItem>` element at the end of the tree or an arbitrary Tree row's last item.

```tsx example
import {useAsyncList} from '@react-stately/data';

interface StarWarsCharacter {
  name: string,
  height: number,
  mass: number,
  birth_year: number
}

interface Pokemon {
  name: string
}

function AsyncTree() {
  let starWarsList = useAsyncList<StarWarsCharacter>({
    async load({signal, cursor}) {
      if (cursor) {
        cursor = cursor.replace(/^http:\/\//i, 'https://');
      }

      let res = await fetch(cursor || 'https://swapi.py4e.com/api/people/?search=', {signal});
      let json = await res.json();

      return {
        items: json.results,
        cursor: json.next
      };
    }
  });

  let pokemonList = useAsyncList<Pokemon>({
    async load({signal, cursor, filterText}) {
      let res = await fetch(
        cursor || `https://pokeapi.co/api/v2/pokemon`,
        {signal}
      );
      let json = await res.json();

      return {
        items: json.results,
        cursor: json.next
      };
    }
  });

  return (
    <Tree
      aria-label="async loading tree"
      style={{ height: '300px' }}>
      <MyTreeItem id="pokemon" title="Pokemon">
        {/*- begin highlight -*/}
        <Collection items={pokemonList.items}>
          {(item: Pokemon) => (
            <MyTreeItem id={item.name} title={item.name} />
          )}
        </Collection>
        <MyTreeLoader isLoading={pokemonList.isLoading} onLoadMore={pokemonList.loadMore} />
        {/*- end highlight -*/}
      </MyTreeItem>
      <MyTreeItem id="starwars" title="Star Wars">
        {/*- begin highlight -*/}
        <Collection items={starWarsList.items}>
          {(item: StarWarsCharacter) => (
            <MyTreeItem id={item.name} title={item.name} />
          )}
        </Collection>
        <MyTreeLoader isLoading={starWarsList.isLoading} onLoadMore={starWarsList.loadMore} />
        {/*- end highlight -*/}
      </MyTreeItem>
    </Tree>
  );
}
```

<details>
  <summary style={{fontWeight: 'bold'}}><ChevronRight size="S" />TreeLoader</summary>

```tsx example export=true render=false
import {TreeLoadMoreItem} from 'react-aria-components';

export function MyTreeLoader(props) {
  return (
    <TreeLoadMoreItem
      {...props}>
      {({level}) => {
        return (
          <MyProgressCircle
            aria-label="Loading more..."
            isIndeterminate />
        );
      }}
    </TreeLoadMoreItem>
  );
}
```

</details>

<details>
  <summary style={{fontWeight: 'bold'}}><ChevronRight size="S" /> MyProgressCircle</summary>

```tsx example export=true render=false
import {ProgressBar} from 'react-aria-components';
import type {ProgressBarProps} from 'react-aria-components';

export function MyProgressCircle(props: ProgressBarProps) {
  return (
    <ProgressBar {...props}>
      <svg width="100%" height="24" viewBox="0 0 24 24" style={{display: 'block'}}>
        <path fill="currentColor" d="M12,1A11,11,0,1,0,23,12,11,11,0,0,0,12,1Zm0,19a8,8,0,1,1,8-8A8,8,0,0,1,12,20Z" opacity=".25" />
        <path fill="currentColor" d="M10.14,1.16a11,11,0,0,0-9,8.92A1.59,1.59,0,0,0,2.46,12,1.52,1.52,0,0,0,4.11,10.7a8,8,0,0,1,6.66-6.61A1.42,1.42,0,0,0,12,2.69h0A1.57,1.57,0,0,0,10.14,1.16Z">
          <animateTransform attributeName="transform" type="rotate" dur="0.75s" values="0 12 12;360 12 12" repeatCount="indefinite"/>
        </path>
      </svg>
    </ProgressBar>
  );
}
```

</details>

## Empty state

Use the `renderEmptyState` prop to customize what the `Tree` will display if there are no items.

```tsx example
<Tree aria-label="Search results" renderEmptyState={() => 'No results found.'} style={{height: '100px'}}>
  {[]}
</Tree>
```

<details>
  <summary style={{fontWeight: 'bold'}}><ChevronRight size="S" /> Show CSS</summary>

```css
.react-aria-Tree {
  &[data-empty] {
    display: flex;
    align-items: center;
    justify-content: center;
    font-style: italic;
  }
}
```

</details>

## Drag and drop <VersionBadge version="rc" style={{marginLeft: 4, verticalAlign: 'bottom'}} />

Tree supports drag and drop interactions when the `dragAndDropHooks` prop is provided using the <TypeLink links={docs.links} type={docs.exports.useDragAndDrop} /> hook. Users can drop data on the tree as a whole, on individual items, insert new items between existing ones, or move items within the tree hierarchy.

React Aria supports traditional mouse and touch based drag and drop, but also implements keyboard and screen reader friendly interactions. Users can press <Keyboard>Enter</Keyboard> on a draggable element to enter drag and drop mode. Then, they can press <Keyboard>Tab</Keyboard> to navigate between drop targets. A droppable collection is treated as a single drop target, so that users can easily tab past it to get to the next drop target. Within a droppable tree, keys such as <Keyboard>ArrowDown</Keyboard> and <Keyboard>ArrowUp</Keyboard> can be used to select a _drop position_, such as on an item, or between items.

Items with children can be expanded or collapsed during keyboard drag and drop mode by using the <Keyboard>ArrowRight</Keyboard> and <Keyboard>ArrowLeft</Keyboard> keys, or the <Keyboard>Option</Keyboard> (<Keyboard>Alt</Keyboard> on Windows) + <Keyboard>Enter</Keyboard> keys. Screen reader users can expand and collapse items with children by navigating to and activating a visually hidden button that gets announced.

Draggable tree items must include a focusable drag handle using a `<Button slot="drag">`. This enables keyboard and screen reader users to initiate drag and drop. The `MyTreeItemContent` component defined in the [reusable wrappers](#reusable-wrappers) section above can be extended to include this automatically when the tree allows dragging.

See the [drag and drop introduction](dnd.html) to learn more.

### Moving between levels

The `onMove` event handler allows reordering items within a level, as well as moving items to a different level. It supports dropping both on and between items. The `getItems` function must also be implemented for items to become draggable. [See below](#drag-data) for more details.

This uses [useTreeData](../react-stately/useTreeData.html) from React Stately to manage the tree data. Note that `useTreeData` is a convenience hook, not a requirement. You can manage your state however you wish.

```tsx example
function Example() {
  let tree = useTreeData({
    initialItems: items
  });

  let {dragAndDropHooks} = useDragAndDrop({
    getItems: (keys) => [...keys].map(key => ({
      'text/plain': tree.getItem(key).value.title
    })),
    ///- begin highlight -///
    onMove(e) {
      if (e.target.dropPosition === 'before') {
        tree.moveBefore(e.target.key, e.keys);
      } else if (e.target.dropPosition === 'after') {
        tree.moveAfter(e.target.key, e.keys);
      } else if (e.target.dropPosition === 'on') {
        // Move items to become children of the target
        let targetNode = tree.getItem(e.target.key);
        if (targetNode) {
          let targetIndex = targetNode.children ? targetNode.children.length : 0;
          let keyArray = Array.from(e.keys);
          for (let i = 0; i < keyArray.length; i++) {
            tree.move(keyArray[i], e.target.key, targetIndex + i);
          }
        }
      }
    }
    ///- end highlight -///
  });

  return (
    <Tree
      aria-label="Tree with hierarchical drag and drop"
      selectionMode="multiple"
      items={tree.items}
      dragAndDropHooks={dragAndDropHooks}
    >
      {function renderItem(item) {
        return (
          <MyTreeItem title={item.value.title}>
            <Collection items={item.children}>
              {renderItem}
            </Collection>
          </MyTreeItem>
        )
      }}
    </Tree>
  );
}
```

### Reordering within a level

The `onReorder` event handler allows reordering items within the same level. Unlike `onMove` it does not allow moving items to a different level.

```tsx example
import {useTreeData} from '@react-stately/data';
import {useDragAndDrop, Button} from 'react-aria-components';

function Example() {
  let tree = useTreeData({
    initialItems: items
  });

  ///- begin highlight -///
  let {dragAndDropHooks} = useDragAndDrop({
    getItems: (keys) => [...keys].map(key => ({
      'text/plain': tree.getItem(key).value.title
    })),
    onReorder(e) {
      if (e.target.dropPosition === 'before') {
        tree.moveBefore(e.target.key, e.keys);
      } else if (e.target.dropPosition === 'after') {
        tree.moveAfter(e.target.key, e.keys);
      }
    }
  });
  ///- end highlight -///

  return (
    <Tree
      aria-label="Reorderable tree"
      selectionMode="multiple"
      items={tree.items}
      ///- begin highlight -///
      dragAndDropHooks={dragAndDropHooks}
      ///- end highlight -///
    >
      {function renderItem(item) {
        return (
          <MyTreeItem title={item.value.title}>
            <Collection items={item.children}>
              {renderItem}
            </Collection>
          </MyTreeItem>
        )
      }}
    </Tree>
  );
}
```

<details>
  <summary style={{fontWeight: 'bold'}}><ChevronRight size="S" /> Show CSS</summary>

```css
.react-aria-TreeItem {
  &[data-allows-dragging] {
    padding-left: 4px;
  }

  &[data-dragging] {
    opacity: 0.6;
  }

  &[data-drop-target] {
    outline: 2px solid var(--highlight-background);
    background: var(--highlight-overlay);
  }

  [slot=drag] {
    all: unset;
    width: 15px;
    text-align: center;

    &[data-focus-visible] {
      border-radius: 4px;
      outline: 2px solid var(--focus-ring-color);
    }
  }
}

.react-aria-Tree {
  &[data-selection-mode=multiple] {
    --checkbox-width: 28px;
  }

  &[data-allows-dragging] {
    --drag-button-width: 23px;
  }

  .react-aria-DropIndicator {
    &[data-drop-target] {
      outline: 1px solid var(--highlight-background);
      margin-left: calc(8px + var(--checkbox-width, 0px) + var(--drag-button-width, 0px) + 26px + (var(--tree-item-level) - 1) * 16px);
    }
  }
}
```

</details>

### Custom drag preview

By default, the drag preview shown under the user's pointer or finger is a copy of the original element that started the drag. A custom preview can be rendered by implementing the `renderDragPreview` function, passed to `useDragAndDrop`. This receives the dragged data that was returned by `getItems`, and returns a rendered preview for those items.

This example renders a custom drag preview which shows the number of items being dragged.

```tsx example
function Example() {
  let tree = useTreeData({
    initialItems: items
  });

  let {dragAndDropHooks} = useDragAndDrop({
    getItems: (keys) => [...keys].map(key => ({
      'text/plain': tree.getItem(key).value.title
    })),
    ///- begin highlight -///
    renderDragPreview(items) {
      return (
        <div className="drag-preview">
          {items[0]['text/plain']}
          <span className="badge">{items.length}</span>
        </div>
      );
    }
    ///- end highlight -///
  });

  return (
    <Tree
      aria-label="Tree with custom drag preview"
      selectionMode="multiple"
      items={tree.items}
      dragAndDropHooks={dragAndDropHooks}
    >
      {function renderItem(item) {
        return (
          <MyTreeItem title={item.value.title}>
            <Collection items={item.children}>
              {renderItem}
            </Collection>
          </MyTreeItem>
        )
      }}
    </Tree>
  );
}
```

<details>
  <summary style={{fontWeight: 'bold'}}><ChevronRight size="S" /> Show CSS</summary>

```css
.drag-preview {
  padding: 4px 8px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  background: var(--highlight-background);
  color: var(--highlight-foreground);
  border-radius: 4px;

  .badge {
    background: var(--highlight-foreground);
    color: var(--highlight-background);
    padding: 0 8px;
    border-radius: 4px;
  }
}
```

</details>

### Drag data

Data for draggable items can be provided in multiple formats at once. This allows drop targets to choose data in a format that they understand. For example, you could serialize a complex object as JSON in a custom format for use within your own application, and also provide plain text and/or rich HTML fallbacks that can be used when a user drops data in an external application (e.g. an email message).

This can be done by returning multiple keys for an item from the `getItems` function. Types can either be a standard [mime type](https://developer.mozilla.org/en-US/docs/Web/HTTP/Basics_of_HTTP/MIME_types/Common_types) for interoperability with external applications, or a custom string for use within your own app.

This example provides representations of each item as plain text, HTML, and a custom app-specific data format. Dropping on the drop targets in this page will use the custom data format to render formatted items. If you drop in an external application supporting rich text, the HTML representation will be used. Dropping in a text editor will use the plain text format.

```tsx example export=true
function DraggableTree() {
  let tree = useTreeData({
    initialItems: items
  });

  let {dragAndDropHooks} = useDragAndDrop({
    ///- begin highlight -///
    getItems(keys) {
      return [...keys].map(key => {
        let item = tree.getItem(key).value;
        return {
          'text/plain': `${item.title}`,
          'text/html': `<strong>${item.title}</strong>`,
          'custom-app-type': JSON.stringify(item)
        };
      });
    },
    ///- end highlight -///
    renderDragPreview(items) {
      return (
        <div className="drag-preview">
          {items[0]['text/plain']}
          <span className="badge">{items.length}</span>
        </div>
      );
    }
  });

  return (
    <Tree
      aria-label="Draggable tree"
      selectionMode="multiple"
      items={tree.items}
      dragAndDropHooks={dragAndDropHooks}
    >
      {function renderItem(item) {
        return (
          <MyTreeItem title={item.value.title}>
            <Collection items={item.children}>
              {renderItem}
            </Collection>
          </MyTreeItem>
        )
      }}
    </Tree>
  );
}

<div style={{display: 'flex', gap: 12, flexWrap: 'wrap'}}>
  <DraggableTree />
  {/* see below */}
  <DroppableTree />
</div>
```

### Dropping on the collection

Dropping on the Tree as a whole can be enabled using the `onRootDrop` event. When a valid drag hovers over the Tree, it receives the `isDropTarget` state and can be styled using the `[data-drop-target]` CSS selector.

```tsx example
import {isTextDropItem} from 'react-aria-components';

interface DroppableItem {
  id: string | number;
  title: string;
  children?: DroppableItem[];
}

function Example() {
  let [items, setItems] = React.useState<any[]>([]);

  let {dragAndDropHooks} = useDragAndDrop({
    /*- begin highlight -*/
    async onRootDrop(e) {
      let items = await Promise.all(
        e.items
          .filter(isTextDropItem)
          .map(async item => JSON.parse(await item.getText('custom-app-type')))
      );
      setItems(items);
    }
    /*- end highlight -*/
  });

  return (
    <div style={{display: 'flex', gap: 12, flexWrap: 'wrap'}}>
      <DraggableTree />
      <Tree
        aria-label="Drop target tree"
        items={items}
        dragAndDropHooks={dragAndDropHooks}
        renderEmptyState={() => 'Drop items here'}
      >
        {function renderItem(item: DroppableItem) {
          return (
            <MyTreeItem title={item.title}>
              <Collection items={item.children}>
                {renderItem}
              </Collection>
            </MyTreeItem>
          )
        }}
      </Tree>
    </div>
  );
}
```

<details>
  <summary style={{fontWeight: 'bold'}}><ChevronRight size="S" /> Show CSS</summary>

```css
.react-aria-Tree[data-drop-target] {
  outline: 2px solid var(--highlight-background);
  outline-offset: -1px;
  background: var(--highlight-overlay);
}
```

</details>

### Dropping on items

Dropping on items can be enabled using the `onItemDrop` event. When a valid drag hovers over an item, it receives the `isDropTarget` state and can be styled using the `[data-drop-target]` CSS selector.

```tsx example export=true
const droppableItems = [
  {id: '8', title: 'Videos', type: 'directory', children: [
    {id: '9', title: 'Movie.mp4', type: 'file'}
  ]},
  // ...
  ///- begin collapse -///
  {id: '10', title: 'Music', type: 'directory', children: [
    {id: '11', title: 'Song.mp3', type: 'file'},
    {id: '12', title: 'Album', type: 'directory', children: [
      {id: '13', title: 'Track1.mp3', type: 'file'}
    ]}
  ]}
  ///- end collapse -///
];

function DroppableTreeExample() {
  let tree = useTreeData({
    initialItems: droppableItems
  });

  let serializeItem = (nodeItem) => ({
    ...nodeItem,
    children: nodeItem.children.map(serializeItem),
    // Assign a unique ID to avoid duplicates when the same item is dropped multiple times.
    id: Math.random().toString(36).slice(2)
  });

  let {dragAndDropHooks} = useDragAndDrop({
    ///- begin highlight -///
    async onItemDrop(e) {
      let items = await Promise.all(
        e.items
          .filter(isTextDropItem)
          .map(async item => {
            let parsed = JSON.parse(await item.getText('custom-app-type'));
            return serializeItem(parsed);
          })
      );

      tree.insert(e.target.key, 0, ...items);
    }
    ///- end highlight -///
  });

  return (
    <div style={{display: 'flex', gap: 12, flexWrap: 'wrap'}}>
      <DraggableTree />
      <Tree
        aria-label="Tree with item drop targets"
        items={tree.items}
        dragAndDropHooks={dragAndDropHooks}>
        {function renderItem(item) {
          return (
            <MyTreeItem title={item.value.title}>
              <Collection items={item.children}>
                {renderItem}
              </Collection>
            </MyTreeItem>
          )
        }}
      </Tree>
    </div>
  );
}
```

### Dropping between items

Dropping between items can be enabled using the `onInsert` event. Tree renders a <TypeLink links={docs.links} type={docs.exports.DropIndicator} /> between items to indicate the insertion position, which can be styled using the `.react-aria-DropIndicator` selector. When it is active, it receives the `[data-drop-target]` state.

```tsx example
import {isTextDropItem} from 'react-aria-components';

function Example() {
  let tree = useTreeData({
    initialItems: droppableItems
  });

  let serializeItem = (nodeItem) => ({
    ...nodeItem,
    children: nodeItem.children.map(serializeItem),
    // Assign a unique ID to avoid duplicates when the same item is dropped multiple times.
    id: Math.random().toString(36).slice(2)
  });

  let {dragAndDropHooks} = useDragAndDrop({
    ///- begin highlight -///
    async onInsert(e) {
      let items = await Promise.all(
        e.items
          .filter(isTextDropItem)
          .map(async item => {
            let parsed = JSON.parse(await item.getText('custom-app-type'));
            return serializeItem(parsed);
          })
      );

      if (e.target.dropPosition === 'before') {
        tree.insertBefore(e.target.key, ...items);
      } else if (e.target.dropPosition === 'after') {
        tree.insertAfter(e.target.key, ...items);
      }
    }
    ///- end highlight -///
  });

  return (
    <div style={{display: 'flex', gap: 12, flexWrap: 'wrap'}}>
      <DraggableTree />
      <Tree
        aria-label="Tree with insertion"
        items={tree.items}
        dragAndDropHooks={dragAndDropHooks}>
        {function renderItem(item) {
          return (
            <MyTreeItem title={item.value.title}>
              <Collection items={item.children}>
                {renderItem}
              </Collection>
            </MyTreeItem>
          )
        }}
      </Tree>
    </div>
  );
}
```

### Drop data

`Tree` allows users to drop one or more **drag items**, each of which contains data to be transferred from the drag source to drop target. There are three kinds of drag items:

* `text` – represents data inline as a string in one or more formats
* `file` – references a file on the user's device
* `directory` – references the contents of a directory

#### Text

A <TypeLink links={sharedDocs.links} type={sharedDocs.links[sharedDocs.exports.TextDropItem.id]} /> represents textual data in one or more different formats. These may be either standard [mime types](https://developer.mozilla.org/en-US/docs/Web/HTTP/Basics_of_HTTP/MIME_types/Common_types) or custom app-specific formats. Representing data in multiple formats allows drop targets both within and outside an application to choose data in a format that they understand. For example, a complex object may be serialized in a custom format for use within an application, with fallbacks in plain text and/or rich HTML that can be used when a user drops data from an external application.

The example below uses the `acceptedDragTypes` prop to accept items that include a custom app-specific type, which is retrieved using the item's `getText` method. The same draggable component as used in the above example is used here, but rather than displaying the plain text representation, the custom format is used instead. When `acceptedDragTypes` is specified, the dropped items are filtered to include only items that include the accepted types.

```tsx example export=true
import {isTextDropItem} from 'react-aria-components';

interface DroppableItem {
  id: string | number;
  title: string;
  children?: DroppableItem[];
}

function DroppableTree() {
  let [items, setItems] = React.useState<any[]>([]);

  let serializeItem = (nodeItem) => ({
    ...nodeItem,
    children: nodeItem.children.map(serializeItem),
    // Assign a unique ID to avoid duplicates when the same item is dropped multiple times.
    id: Math.random().toString(36).slice(2)
  });

  let {dragAndDropHooks} = useDragAndDrop({
    /*- begin highlight -*/
    acceptedDragTypes: ['custom-app-type'],
    async onRootDrop(e) {
      let items = await Promise.all(
        e.items
          .filter(isTextDropItem)
          .map(async item => {
            let parsed = JSON.parse(await item.getText('custom-app-type'));
            return serializeItem(parsed);
          })
      );
      setItems(items);
    }
    /*- end highlight -*/
  });

  return (
    <Tree
      aria-label="Droppable tree"
      items={items}
      dragAndDropHooks={dragAndDropHooks}
      renderEmptyState={() => 'Drop items here'}
    >
      {function renderItem(item: DroppableItem) {
        return (
          <MyTreeItem title={item.title}>
            <Collection items={item.children}>
              {renderItem}
            </Collection>
          </MyTreeItem>
        )
      }}
    </Tree>
  );
}

<div style={{display: 'flex', gap: 12, flexWrap: 'wrap'}}>
  <DraggableTree />
  <DroppableTree />
</div>
```

#### Files

A <TypeLink links={sharedDocs.links} type={sharedDocs.links[sharedDocs.exports.FileDropItem.id]} /> references a file on the user's device. It includes the name and mime type of the file, and methods to read the contents as plain text, or retrieve a native [File](https://developer.mozilla.org/en-US/docs/Web/API/File) object which can be attached to form data for uploading.

This example accepts JPEG and PNG image files, and renders them in a tree structure by creating a local [object URL](https://developer.mozilla.org/en-US/docs/Web/API/URL/createObjectURL). When the tree is empty, you can drop on the whole collection, and otherwise items can be inserted.

```tsx example
import {isFileDropItem} from 'react-aria-components';

interface ImageItem {
  id: number,
  url: string,
  name: string,
  type: string,
  lastModified: number
}

function Example() {
  let [items, setItems] = React.useState<ImageItem[]>([]);

  let {dragAndDropHooks} = useDragAndDrop({
    /*- begin highlight -*/
    acceptedDragTypes: ['image/jpeg', 'image/png'],
    async onRootDrop(e) {
      let items = await Promise.all(
        e.items.filter(isFileDropItem).map(async item => {
          let file = await item.getFile();
          return {
            id: Math.random(),
            url: URL.createObjectURL(file),
            name: item.name,
            type: file.type,
            lastModified: file.lastModified
          };
        })
      );
      setItems(items);
    }
    /*- end highlight -*/
  });

  return (
    <Tree
      aria-label="Droppable tree"
      items={items}
      dragAndDropHooks={dragAndDropHooks}
      renderEmptyState={() => 'Drop images here'}
    >
      {(item) => (
        <TreeItem textValue={item.name}>
          <TreeItemContent>
            <img src={item.url} style={{width: 20, height: 20, marginRight: 8}} />
            {item.name}
          </TreeItemContent>
        </TreeItem>
      )}
    </Tree>
  );
}
```

#### Directories

A <TypeLink links={sharedDocs.links} type={sharedDocs.links[sharedDocs.exports.DirectoryDropItem.id]} /> references the contents of a directory on the user's device. It includes the name of the directory, as well as a method to iterate through the files and folders within the directory. The contents of any folders within the directory can be accessed recursively.

The `getEntries` method returns an [async iterable](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for-await...of) object, which can be used in a `for await...of` loop. This provides each item in the directory as either a <TypeLink links={sharedDocs.links} type={sharedDocs.links[sharedDocs.exports.FileDropItem.id]} /> or <TypeLink links={sharedDocs.links} type={sharedDocs.links[sharedDocs.exports.DirectoryDropItem.id]} />, and you can access the contents of each file as discussed above.

This example accepts directory drops over the whole collection, and renders the contents as items in the tree. `DIRECTORY_DRAG_TYPE` is imported from `react-aria-components` and included in the `acceptedDragTypes` prop to limit the accepted items to only directories.

```tsx example
import {DIRECTORY_DRAG_TYPE, isDirectoryDropItem} from 'react-aria-components';

interface DirItem {
  name: string,
  kind: string,
  type: string,
  children?: DirItem[]
}

function Example() {
  let [files, setFiles] = React.useState<DirItem[]>([]);

  let {dragAndDropHooks} = useDragAndDrop({
    /*- begin highlight -*/
    acceptedDragTypes: [DIRECTORY_DRAG_TYPE],
    async onRootDrop(e) {
      // Read entries in directory and update state with relevant info.
      let getFiles = async (dir) => {
        let files = [];
        for await (let entry of dir.getEntries()) {
          files.push({
            id: Math.random().toString(36).slice(2),
            name: entry.name,
            kind: entry.kind,
            children: entry.kind === 'directory'
              ? await getFiles(entry)
              : []
          });
        }
        return files;
      };

      let dir = e.items.find(isDirectoryDropItem)!;
      setFiles(await getFiles(dir));
    }
    /*- end highlight -*/
  });

  return (
    <Tree
      aria-label="Droppable tree"
      items={files}
      dragAndDropHooks={dragAndDropHooks}
      renderEmptyState={() => 'Drop directory here'}
    >
      {function renderItem(item) {
        return (
          <MyTreeItem title={`${item.kind === 'directory' ? '📁' : '📄'} ${item.name}`}>
            <Collection items={item.children}>
              {renderItem}
            </Collection>
          </MyTreeItem>
        )
      }}
    </Tree>
  );
}
```

### Drop operations

A <TypeLink links={sharedDocs.links} type={sharedDocs.links[sharedDocs.exports.DropOperation.id]} /> is an indication of what will happen when dragged data is dropped on a particular drop target. These are:

* `move` – indicates that the dragged data will be moved from its source location to the target location.
* `copy` – indicates that the dragged data will be copied to the target destination.
* `link` – indicates that there will be a relationship established between the source and target locations.
* `cancel` – indicates that the drag and drop operation will be canceled, resulting in no changes made to the source or target.

Many operating systems display these in the form of a cursor change, e.g. a plus sign to indicate a copy operation. The user may also be able to use a modifier key to choose which drop operation to perform, such as <Keyboard>Option</Keyboard> or <Keyboard>Alt</Keyboard> to switch from move to copy.

#### onDragEnd

The `onDragEnd` event allows the drag source to respond when a drag that it initiated ends, either because it was dropped or because it was canceled by the user. The `dropOperation` property of the event object indicates the operation that was performed. For example, when data is moved, the UI could be updated to reflect this change by removing the original dragged items.

This example removes the dragged items from the UI when a move operation is completed. Try holding the <Keyboard>Option</Keyboard> or <Keyboard>Alt</Keyboard> keys to change the operation to copy, and see how the behavior changes.

```tsx example
function Example() {
  let tree = useTreeData({
    initialItems: items
  });

  let { dragAndDropHooks } = useDragAndDrop({
    ///- begin collapse -///
    renderDragPreview(items) {
      return (
        <div className="drag-preview">
          {items[0]['text/plain']}
          <span className="badge">{items.length}</span>
        </div>
      );
    },
    getItems(keys) {
      return [...keys].map(key => {
        let item = tree.getItem(key).value;
        return {
          'text/plain': item.title,
          'custom-app-type': JSON.stringify(item)
        };
      });
    },
    ///- end collapse -///
    // ...
    /*- begin highlight -*/
    onDragEnd(e) {
      if (e.dropOperation === 'move') {
        tree.remove(...e.keys);
      }
    }
    /*- end highlight -*/
  });

  return (
    <div style={{display: 'flex', gap: 12, flexWrap: 'wrap'}}>
      <Tree aria-label="Draggable tree" selectionMode="multiple" items={tree.items} dragAndDropHooks={dragAndDropHooks}>
        {function renderItem(item) {
          return (
            <MyTreeItem title={item.value.title}>
              <Collection items={item.children}>
                {renderItem}
              </Collection>
            </MyTreeItem>
          )
        }}
      </Tree>
      <DroppableTree />
    </div>
  );
}
```

#### getAllowedDropOperations

The drag source can also control which drop operations are allowed for the data. For example, if moving data is not allowed, and only copying is supported, the `getAllowedDropOperations` function could be implemented to indicate this. When you drag the element below, the cursor now shows the copy affordance by default, and pressing a modifier to switch drop operations results in the drop being canceled.

```tsx example
function Example() {
  ///- begin collapse -///
  let tree = useTreeData({
    initialItems: items
  });
  ///- end collapse -///
  // ...

  let { dragAndDropHooks } = useDragAndDrop({
    ///- begin collapse -///
    renderDragPreview(items) {
      return (
        <div className="drag-preview">
          {items[0]['text/plain']}
          <span className="badge">{items.length}</span>
        </div>
      );
    },
    getItems(keys) {
      return [...keys].map(key => {
        let item = tree.getItem(key).value;
        return {
          'text/plain': item.title,
          'custom-app-type': JSON.stringify(item)
        };
      });
    },
    ///- end collapse -///
    // ...
    /*- begin highlight -*/
    getAllowedDropOperations: () => ['copy']
    /*- end highlight -*/
  });

  return (
    <div style={{display: 'flex', gap: 12, flexWrap: 'wrap'}}>
      <Tree aria-label="Draggable tree" selectionMode="multiple" items={tree.items} dragAndDropHooks={dragAndDropHooks}>
        {function renderItem(item) {
          return (
            <MyTreeItem title={item.value.title}>
              <Collection items={item.children}>
                {renderItem}
              </Collection>
            </MyTreeItem>
          )
        }}
      </Tree>
      <DroppableTree />
    </div>
  );
}
```

#### getDropOperation

The `getDropOperation` function passed to `useDragAndDrop` can be used to provide appropriate feedback to the user when a drag hovers over the drop target. This function receives the drop target, set of types contained in the drag, and a list of allowed drop operations as specified by the drag source. It should return one of the drop operations in `allowedOperations`, or a specific drop operation if only that drop operation is supported. It may also return `'cancel'` to reject the drop. If the returned operation is not in `allowedOperations`, then the drop target will act as if `'cancel'` was returned.

In the below example, the drop target only supports dropping PNG images. If a PNG is dragged over the target, it will be highlighted and the operating system displays a copy cursor. If another type is dragged over the target, then there is no visual feedback, indicating that a drop is not accepted there. If the user holds a modifier key such as <Keyboard>Control</Keyboard> while dragging over the drop target in order to change the drop operation, then the drop target does not accept the drop.

```tsx example
///- begin collapse -///
interface ImageItem {
  id: number,
  url: string,
  name: string
}
///- end collapse -///
function Example() {
  let [items, setItems] = React.useState<ImageItem[]>([]);

  let { dragAndDropHooks } = useDragAndDrop({
    /*- begin highlight -*/
    getDropOperation: () => 'copy',
    /*- end highlight -*/
    acceptedDragTypes: ['image/png'],
    async onRootDrop(e) {
      ///- begin collapse -///
      let items = await Promise.all(
        e.items.filter(isFileDropItem).map(async item => ({
          id: Math.random(),
          url: URL.createObjectURL(await item.getFile()),
          name: item.name
        }))
      );
      setItems(items);
      ///- end collapse -///
      // ...
    }
  });

  ///- begin collapse -///
  return (
    <Tree aria-label="Droppable tree" items={items} dragAndDropHooks={dragAndDropHooks} renderEmptyState={() => "Drop PNGs here"}>
      {item => (
        <TreeItem textValue={item.name}>
          <TreeItemContent>
            <div className="image-item">
              <img src={item.url} />
              <span>{item.name}</span>
            </div>
          </TreeItemContent>
        </TreeItem>
      )}
    </Tree>
  );
  ///- end collapse -///
  // See "Files" example above...
}
```

#### Drop events

Drop events such as `onInsert`, `onItemDrop`, etc. also include the `dropOperation`. This can be used to perform different actions accordingly, for example, when communicating with a backend API.

```tsx
let onItemDrop = async (e) => {
  let data = JSON.parse(await e.items[0].getText('my-app-file'));
  /*- begin highlight -*/
  switch (e.dropOperation) {
    case 'move':
      MyAppFileService.move(data.filePath, props.filePath);
      break;
    case 'copy':
      MyAppFileService.copy(data.filePath, props.filePath);
      break;
    case 'link':
      MyAppFileService.link(data.filePath, props.filePath);
      break;
  }
  /*- end highlight -*/
};
```

### Drag between trees

This example puts together many of the concepts described above, allowing users to drag items between trees bidirectionally. It also supports moving items within the same tree hierarchy. When a tree is empty, it accepts drops on the whole collection. `getDropOperation` ensures that items are always moved rather than copied, which avoids duplicate items.

```tsx example
import {isTextDropItem} from 'react-aria-components';

interface FileItem {
  id: string,
  title: string,
  type: string,
  children?: FileItem[]
}

interface DndTreeProps {
  initialItems: FileItem[],
  'aria-label': string
}

function DndTree(props: DndTreeProps) {
  let tree = useTreeData({
    initialItems: props.initialItems,
    getKey: item => item.id,
    getChildren: item => item.children || []
  });

  let {dragAndDropHooks} = useDragAndDrop({
    // Provide drag data in a custom format as well as plain text.
    getItems(keys) {
      return [...keys].map((key) => {
        let item = tree.getItem(key);
        let serializeItem = (nodeItem) => ({
          ...nodeItem.value,
          children: nodeItem.children ? [...nodeItem.children].map(serializeItem) : []
        });

        return {
          'custom-app-type': JSON.stringify(serializeItem(item)),
          'text/plain': item.value.title
        };
      });
    },

    // Accept drops with the custom format.
    acceptedDragTypes: ['custom-app-type'],

    // Ensure items are always moved rather than copied.
    getDropOperation: () => 'move',

    // Handle drops between items from other trees.
    async onInsert(e) {
      let processedItems = await Promise.all(
        e.items
          .filter(isTextDropItem)
          .map(async item => JSON.parse(await item.getText('custom-app-type')))
      );
      if (e.target.dropPosition === 'before') {
        tree.insertBefore(e.target.key, ...processedItems);
      } else if (e.target.dropPosition === 'after') {
        tree.insertAfter(e.target.key, ...processedItems);
      }
    },

    // Handle drops on the collection when empty.
    async onRootDrop(e) {
      let processedItems = await Promise.all(
        e.items
          .filter(isTextDropItem)
          .map(async item => JSON.parse(await item.getText('custom-app-type')))
      );
      tree.insert(null, 0, ...processedItems);
    },

    // Handle moving items within the same tree or to different levels.
    onMove(e) {
      if (e.target.dropPosition === 'before') {
        tree.moveBefore(e.target.key, e.keys);
      } else if (e.target.dropPosition === 'after') {
        tree.moveAfter(e.target.key, e.keys);
      } else if (e.target.dropPosition === 'on') {
        let targetNode = tree.getItem(e.target.key);
        if (targetNode) {
          let targetIndex = targetNode.children ? targetNode.children.length : 0;
          let keyArray = Array.from(e.keys);
          for (let i = 0; i < keyArray.length; i++) {
            tree.move(keyArray[i], e.target.key, targetIndex + i);
          }
        }
      }
    },

    // Remove the items from the source tree on drop
    // if they were moved to a different tree.
    onDragEnd(e) {
      if (e.dropOperation === 'move' && !e.isInternal) {
        tree.remove(...e.keys);
      }
    }
  });

  return (
    <Tree
      aria-label={props['aria-label']}
      selectionMode="multiple"
      items={tree.items}
      dragAndDropHooks={dragAndDropHooks}
      renderEmptyState={() => 'Drop items here'}
    >
      {function renderItem(item) {
        return (
          <MyTreeItem title={item.value.title}>
            <Collection items={item.children}>
              {renderItem}
            </Collection>
          </MyTreeItem>
        )
      }}
    </Tree>
  );
}

<div style={{display: 'flex', gap: 12, flexWrap: 'wrap'}}>
  <DndTree
    initialItems={items}
    aria-label="First Tree"
  />
  <DndTree
    initialItems={droppableItems}
    aria-label="Second Tree"
  />
</div>
```

## Props

### Tree

<PropTable component={docs.exports.Tree} links={docs.links} />

### TreeItem

<PropTable component={docs.exports.TreeItem} links={docs.links} />

### TreeItemContent

<PropTable component={docs.exports.TreeItemContent} links={docs.links} />

### TreeLoadMoreItem

A `<TreeLoadMoreItem>` defines the load more spinner within a `<Tree>`. It renders its children when `isLoading` is true, and allows you to customize the scroll distance from the bottom of the tree or tree row that should trigger another load operation.

<details>
  <summary style={{fontWeight: 'bold'}}><ChevronRight size="S" /> Show props</summary>

<PropTable component={docs.exports.TreeLoadMoreItem} links={docs.links} />

</details>

## Styling

React Aria components can be styled in many ways, including using CSS classes, inline styles, utility classes (e.g. Tailwind), CSS-in-JS (e.g. Styled Components), etc. By default, all components include a builtin `className` attribute which can be targeted using CSS selectors. These follow the `react-aria-ComponentName` naming convention.

```css
.react-aria-Tree {
  /* ... */
}
```

A custom `className` can also be specified on any component. This overrides the default `className` provided by React Aria with your own.

```jsx
<TreeItem className="my-tree-item">
  {/* ... */}
</TreeItem>
```

In addition, some components support multiple UI states (e.g. focused, placeholder, readonly, etc.). React Aria components expose states using data attributes, which you can target in CSS selectors. For example:

```css
.react-aria-TreeItem[data-expanded] {
  /* ... */
}

.react-aria-TreeItem[data-selected] {
  /* ... */
}
```

The `className` and `style` props also accept functions which receive states for styling. This lets you dynamically determine the classes or styles to apply, which is useful when using utility CSS libraries like [Tailwind](https://tailwindcss.com/).

```jsx
<TreeItem className={({ isSelected }) => isSelected ? 'bg-blue-400' : 'bg-gray-100'} />
```

Render props may also be used as children to alter what elements are rendered based on the current state. For example, you could render a checkbox only when selection is enabled.

```jsx
<TreeItem>
    <TreeItemContent>
      {({selectionMode}) => (
        <>
          {selectionMode !== 'none' && <Checkbox />}
          Item
        </>
      )}
    </TreeItemContent>
</TreeItem>
```

The states, selectors, and render props for each component used in a `Tree` are documented below.

### Tree

A `Tree` can be targeted with the `.react-aria-Tree` CSS selector, or by overriding with a custom `className`. It supports the following states:

<StateTable properties={docs.exports.TreeRenderProps.properties} />

### TreeItem

A `TreeItem` can be targeted with the `.react-aria-TreeItem` CSS selector, or by overriding with a custom `className`. It supports the following states:

<StateTable properties={docs.exports.TreeItemRenderProps.properties} showOptional />

TreeItem also exposes a `--tree-item-level` CSS custom property, which you can use to adjust the indentation.

```css render=false
.react-aria-TreeItem {
  padding-left: calc((var(--tree-item-level) - 1) * 20px);
}
```

### TreeItemContent

`TreeItemContent` does not render a DOM node. It supports the following render props:

<StateTable properties={docs.exports.TreeItemContentRenderProps.properties} showOptional hideSelector />

## Advanced customization

### Contexts

All React Aria Components export a corresponding context that can be used to send props to them from a parent element. This enables you to build your own compositional APIs similar to those found in React Aria Components itself. You can send any prop or ref via context that you could pass to the corresponding component. The local props and ref on the component are merged with the ones passed via context, with the local props taking precedence (following the rules documented in [mergeProps](mergeProps.html)).

<ContextTable components={['Tree']} docs={docs} />

This example shows a component that accepts a `Tree` and a [ToggleButton](ToggleButton.html) as children, and allows the user to turn selection mode for the tree on and off by pressing the button.

```tsx example render=false export=true
import type {SelectionMode} from 'react-aria-components';
import {ToggleButtonContext, TreeContext} from 'react-aria-components';

function Selectable({children}) {
  let [isSelected, onChange] = React.useState(false);
  let selectionMode: SelectionMode = isSelected ? 'multiple' : 'none';
  return (
    <ToggleButtonContext.Provider value={{isSelected, onChange}}>
      {/*- begin highlight -*/}
      <TreeContext.Provider value={{selectionMode}}>
      {/*- end highlight -*/}
        {children}
      </TreeContext.Provider>
    </ToggleButtonContext.Provider>
  );
}
```

The `Selectable` component can be reused to make the selection mode of any nested `Tree` controlled by a `ToggleButton`.

```tsx example
import {ToggleButton} from 'react-aria-components';

<Selectable>
  <ToggleButton>Select</ToggleButton>
  <PokemonEvolutionTree />
</Selectable>
```

<details>
  <summary style={{fontWeight: 'bold'}}><ChevronRight size="S" /> Show CSS</summary>

```css
.react-aria-ToggleButton {
  margin-bottom: 8px;
}
```
</details>


### Custom children

Tree passes props to its child components, such as the selection checkboxes, via their associated contexts. These contexts are exported so you can also consume them in your own custom components. This enables you to reuse existing components from your app or component library together with React Aria Components.

<ContextTable components={['Checkbox', 'Button']} docs={docs} />

This example consumes from `CheckboxContext` in an existing styled checkbox component to make it compatible with React Aria Components. The <TypeLink links={docs.links} type={docs.exports.useContextProps} /> hook merges the local props and ref with the ones provided via context by Tree. See [useCheckbox](useCheckbox.html) for more details about the hooks used in this example.

```tsx
import type {CheckboxProps, useContextProps} from 'react-aria-components';
import {CheckboxContext} from 'react-aria-components';
import {useToggleState} from 'react-stately';
import {useCheckbox} from 'react-aria';

const MyCustomCheckbox = React.forwardRef((props: CheckboxProps, ref: React.ForwardedRef<HTMLInputElement>) => {
  // Merge the local props and ref with the ones provided via context.
  ///- begin highlight -///
  [props, ref] = useContextProps(props, ref, CheckboxContext);
  ///- end highlight -///

  let state = useToggleState(props);
  let {inputProps} = useCheckbox(props, state, ref);
  return <input {...inputProps} ref={ref} />;
});
```

Now you can use `MyCustomCheckbox` within a `Tree`, in place of the builtin React Aria Components `Checkbox`.

```tsx
<Tree>
  <TreeItem>
    <TreeItemContent>
      {/*- begin highlight -*/}
      <MyCustomCheckbox slot="selection" />
      {/*- end highlight -*/}
      {/* ... */}
    </TreeItemContent>
  </TreeItem>
</Tree>
```

{/* ### Hooks
TODO: add back once hooks docs are written with new collections
If you need to customize things even further, such as accessing internal state or customizing DOM structure, you can drop down to the lower level Hook-based API. See [useTree](useTree.html) for more details. */}

## Testing

### Test utils <VersionBadge version="beta" style={{marginLeft: 4, verticalAlign: 'bottom'}} />

`@react-aria/test-utils` offers common tree interaction utilities which you may find helpful when writing tests. See [here](./testing.html#react-aria-test-utils) for more information on how to setup these utilities
in your tests. Below is the full definition of the tree tester and a sample of how you could use it in your test suite.

```ts
// Tree.test.ts
import {render, within} from '@testing-library/react';
import {User} from '@react-aria/test-utils';

let testUtilUser = new User({interactionType: 'mouse'});
// ...

it('Tree can select a item via keyboard', async function () {
  // Render your test component/app and initialize the Tree tester
  let {getByTestId} = render(
     <Tree data-testid="test-tree" selectionMode="multiple">
      ...
    </Tree>
  );
  let treeTester = testUtilUser.createTester('Tree', {root: getByTestId('test-tree'), interactionType: 'keyboard'});

  await treeTester.toggleRowSelection({row: 0});
  expect(treeTester.selectedRows).toHaveLength(1);
  expect(within(treeTester.rows[0]).getByRole('checkbox')).toBeChecked();

  await treeTester.toggleRowSelection({row: 1});
  expect(treeTester.selectedRows).toHaveLength(2);
  expect(within(treeTester.rows[1]).getByRole('checkbox')).toBeChecked();

  await treeTester.toggleRowSelection({row: 0});
  expect(treeTester.selectedRows).toHaveLength(1);
  expect(within(treeTester.rows[0]).getByRole('checkbox')).not.toBeChecked();
});
```

<ClassAPI links={treeUtils.links} class={treeUtils.exports.TreeTester} />
