HarmonyOS Prop的用法

以在B内部给factorChange添加一个观察者，然后在观察回调内给logoMarginTop赋值，以下为代码示例：

// xxx.ets
import image from '@ohos.multimedia.image'

@Entry
@Component
struct SelectExample {
  @State factorChange: number = 0

  build() {
    Column() {
      Text(this.factorChange + '')
        .onClick(() => {
          this.factorChange++
        })
      TopBarView({ factorChange: this.factorChange })
    }.width('100%')
  }
}

@Component
struct TopBarView {
  @Prop @Watch('factorDidChange') factorChange: number = 0
  @State logoMarginTop: number = 0

  build() {
    Column() {
      Text('TopBarView')
      Text('factorChange=' + this.factorChange)
      Text('logoMarginTop=' + this.logoMarginTop)
    }
  }

  factorDidChange() {
    this.logoMarginTop = this.factorChange * 2
  }
}