harmony 鸿蒙@ohos.mediaquery (Media Query)

2022-08-09
浏览 (887)

@ohos.mediaquery (Media Query)

The mediaquery module provides different styles for different media types.

NOTE

The APIs of this module are supported since API version 7. Updates will be marked with a superscript to indicate their earliest API version.

This module cannot be used in the file declaration of the UIAbility. In other words, the APIs of this module can be used only after a component instance is created; they cannot be called in the lifecycle of the UIAbility.

The functionality of this module depends on UI context. This means that the APIs of this module cannot be used where the UI context is unclear. For details, see UIContext.

Since API version 10, you can use the getMediaQuery API in UIContext to obtain the MediaQuery object associated with the current UI context.

Modules to Import

import mediaquery from '@ohos.mediaquery'

mediaquery.matchMediaSync

matchMediaSync(condition: string): MediaQueryListener

Sets the media query condition. This API returns the corresponding media query listener.

System capability: SystemCapability.ArkUI.ArkUI.Full

Parameters

Name	Type	Mandatory	Description
condition	string	Yes	Media query condition. For details, see Syntax.

Return value

Type	Description
MediaQueryListener	Media query listener, which is used to register or deregister the listening callback.

Example

import mediaquery from '@ohos.mediaquery'
let listener:mediaquery.MediaQueryListener = mediaquery.matchMediaSync('(orientation: landscape)'); // Listen for landscape events.

MediaQueryListener

Implements the media query listener, including the first query result when the listener is applied for.

System capability: SystemCapability.ArkUI.ArkUI.Full

Attributes

Name	Type	Readable	Writable	Description
matches	boolean	Yes	No	Whether the media query condition is met.
media	string	Yes	No	Media query condition.

on

on(type: ‘change’, callback: Callback<MediaQueryResult>): void

Registers the media query listener. The callback is triggered when the media attributes change.

System capability: SystemCapability.ArkUI.ArkUI.Full

Parameters

Name	Type	Mandatory	Description
type	string	Yes	Listener type. The value is fixed at ‘change’.
callback	Callback<MediaQueryResult>	Yes	Callback registered with media query.

Example

For details, see off Example.

off

off(type: ‘change’, callback?: Callback<MediaQueryResult>): void

Deregisters the media query listener, so that no callback is triggered when the media attributes change.

System capability: SystemCapability.ArkUI.ArkUI.Full

Parameters

Name	Type	Mandatory	Description
type	string	Yes	Listener type. The value is fixed at ‘change’.
callback	Callback<MediaQueryResult>	No	Callback to be deregistered. If the default value is used, all callbacks of the handle are deregistered.

Example

    import mediaquery from '@ohos.mediaquery'
    
    let listener = mediaquery.matchMediaSync('(orientation: landscape)'); // Listen for landscape events.
    function onPortrait(mediaQueryResult:mediaquery.MediaQueryResult) {
        if (mediaQueryResult.matches) {
            // do something here
        } else {
            // do something here
        }
    }
    listener.on('change', onPortrait) // Register the media query listener.
    listener.off('change', onPortrait) // Deregister the media query listener.

MediaQueryResult

Provides the media query result.

System capability: SystemCapability.ArkUI.ArkUI.Full

Attributes

Name	Type	Readable	Writable	Description
matches	boolean	Yes	No	Whether the media query condition is met.
media	string	Yes	No	Media query condition.

Example

import mediaquery from '@ohos.mediaquery'


@Entry
@Component
struct MediaQueryExample {
  @State color: string = '#DB7093'
  @State text: string = 'Portrait'
  listener = mediaquery.matchMediaSync('(orientation: landscape)')

  onPortrait(mediaQueryResult:mediaquery.MediaQueryResult) {
    if (mediaQueryResult.matches) {
      this.color = '#FFD700'
      this.text = 'Landscape'
    } else {
      this.color = '#DB7093'
      this.text = 'Portrait'
    }
  }

  aboutToAppear() {
    let portraitFunc = (mediaQueryResult:mediaquery.MediaQueryResult):void=>this.onPortrait(mediaQueryResult)  // bind current js instance
    this.listener.on('change', portraitFunc)
  }

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {
      Text(this.text).fontSize(24).fontColor(this.color)
    }
    .width('100%').height('100%')
  }
}