harmony 鸿蒙Component Area Change Event

2022-08-09
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Component Area Change Event

The area change event is triggered when the component’s size, position, or any other attribute that may affect its display area changes.

NOTE

The APIs of this module are supported since API version 8. Updates will be marked with a superscript to indicate their earliest API version.

Events

Name	Bubbling Supported	Description
onAreaChange(event: (oldValue: Area, newValue: Area) => void)	No	Triggered when the component area changes in size or position due to layout updates. This event is not triggered for render attribute changes caused by re-rendering, such as changes of translate and offset. - Area: returns the target width and height of the component and the target coordinates of the component relative to the parent component and the upper left corner of the page.

Example

// xxx.ets
@Entry
@Component
struct AreaExample {
  @State value: string = 'Text'
  @State sizeValue: string = ''

  build() {
    Column() {
      Text(this.value)
        .backgroundColor(Color.Green).margin(30).fontSize(20)
        .onClick(() => {
          this.value = this.value + 'Text'
        })
        .onAreaChange((oldValue: Area, newValue: Area) => {
          console.info(`Ace: on area change, oldValue is ${JSON.stringify(oldValue)} value is ${JSON.stringify(newValue)}`)
          this.sizeValue = JSON.stringify(newValue)
        })
      Text('new area is: \n' + this.sizeValue).margin({ right: 30, left: 30 })
    }
    .width('100%').height('100%').margin({ top: 30 })
  }
}

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