This is documentation for the next SDK version. For up-to-date documentation, see the latest version (SDK 56).

ExposedDropdownMenuBox

一个 Jetpack Compose ExposedDropdownMenuBox 组件，用于显示带有可自定义锚点的下拉菜单。

Android

Included in Expo Go

GitHub

npm

更新日志

关于跨平台选择器，请参见 Picker —— 在 Android 上构建于 ExposedDropdownMenuBox 之上。

Expo UI ExposedDropdownMenuBox 与官方 Jetpack Compose ExposedDropdownMenuBox 保持一致。请在锚点内容（通常是只读的 TextField）上使用 menuAnchor() 修饰符，并使用 ExposedDropdownMenu 来包裹 DropdownMenuItem 子项。

安装

Terminal

- npx expo install @expo/ui

If you are installing this in an existing React Native app, make sure to install expo in your project.

用法

基础

当将未受控的 TextField 作为锚点时，请传入 key={selected}，以便在所选值更改时强制重新挂载——defaultValue 只会在挂载时读取。

BasicExposedDropdownMenuBoxExample.tsx

import {
  DropdownMenuItem,
  ExposedDropdownMenuBox,
  ExposedDropdownMenu,
  Host,
  Text,
  TextField,
} from '@expo/ui/jetpack-compose';
import { menuAnchor } from '@expo/ui/jetpack-compose/modifiers';
import { useState } from 'react';

const LANGUAGES = [
  { label: 'Java', value: 'java' },
  { label: 'JavaScript', value: 'js' },
  { label: 'TypeScript', value: 'ts' },
];

export default function BasicExposedDropdownMenuBoxExample() {
  const [selected, setSelected] = useState('java');
  const [expanded, setExpanded] = useState(false);

  const selectedLabel = LANGUAGES.find(l => l.value === selected)?.label ?? '';

  return (
    <Host matchContents>
      <ExposedDropdownMenuBox expanded={expanded} onExpandedChange={setExpanded}>
        <TextField
          defaultValue={selectedLabel}
          key={selected}
          readOnly
          modifiers={[menuAnchor()]}
        />
        <ExposedDropdownMenu expanded={expanded} onDismissRequest={() => setExpanded(false)}>
          {LANGUAGES.map(lang => (
            <DropdownMenuItem
              key={lang.value}
              onClick={() => {
                setSelected(lang.value);
                setExpanded(false);
              }}>
              <DropdownMenuItem.Text>
                <Text>{lang.label}</Text>
              </DropdownMenuItem.Text>
            </DropdownMenuItem>
          ))}
        </ExposedDropdownMenu>
      </ExposedDropdownMenuBox>
    </Host>
  );
}

API

import { ExposedDropdownMenuBox } from '@expo/ui/jetpack-compose';

Components

`ExposedDropdownMenu`

Android

Type: React.Element<ExposedDropdownMenuProps>

A Material 3 ExposedDropdownMenu that displays menu items in a dropdown.

Must be used inside an ExposedDropdownMenuBox.

Props for the ExposedDropdownMenu component.

ExposedDropdownMenuProps

`children`

Android

Optional • Type: ReactNode

Children should be DropdownMenuItem components.

`containerColor`

Android

Optional • Type: ColorValue

Background color of the dropdown menu container.

`expanded`

Android

Type: boolean

Whether the dropdown menu is expanded (visible).

`modifiers`

Android

Optional • Type: ModifierConfig[]

Modifiers for the component.

`onDismissRequest`

Android

Optional • Type: () => void

Callback fired when the menu requests to be dismissed (e.g. tapping outside, back button).

`ExposedDropdownMenuBox`

Android

Type: React.Element<ExposedDropdownMenuBoxProps>

A Material 3 ExposedDropdownMenuBox.

Use the menuAnchor() modifier on the anchor content (e.g. a TextField or Text). Use ExposedDropdownMenu to wrap DropdownMenuItem children.

Example

<ExposedDropdownMenuBox expanded={expanded} onExpandedChange={setExpanded}>
  <TextField modifiers={[menuAnchor()]} defaultValue={value} readOnly />
  <ExposedDropdownMenu expanded={expanded} onDismissRequest={() => setExpanded(false)}>
    <DropdownMenuItem onClick={() => { setSelected('a'); setExpanded(false); }}>
      <DropdownMenuItem.Text><Text>Option A</Text></DropdownMenuItem.Text>
    </DropdownMenuItem>
  </ExposedDropdownMenu>
</ExposedDropdownMenuBox>

ExposedDropdownMenuBoxProps

`children`

Android

Optional • Type: ReactNode

Children — should contain an anchor element with the menuAnchor() modifier and an ExposedDropdownMenu with DropdownMenuItem children.

`expanded`

Android

Type: boolean

Whether the dropdown menu is expanded (visible).

`modifiers`

Android

Optional • Type: ModifierConfig[]

Modifiers for the component.

`onExpandedChange`

Android

Optional • Type: (expanded: boolean) => void

Callback when the expanded state changes (for example, tapping the field or dismissing the menu).