背景色透明度问题解决方案

// xxx.ets  
@Entry  
@Component  
struct ScrollExample {  
  scroller: Scroller = new Scroller()  
  private arr: number[] = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]  
  @State alpha: string = ''  
  
  build() {  
    Column() {  
      Row() {  
        Text('测试内容')  
      }  
      .width('100%')  
      // .height(100)  
      .backgroundColor(this.alpha)  
      Scroll(this.scroller) {  
        Column() {  
          ForEach(this.arr, (item) => {  
            Text(item.toString())  
              .width('90%')  
              .height(150)  
              .backgroundColor(0xFFFFFF)  
              .borderRadius(15)  
              .fontSize(16)  
              .textAlign(TextAlign.Center)  
              .margin({ top: 10 })  
          }, item => item)  
        }.width('100%')  
      }  
      .width('100%')  
      // .height('100%')  
      .onScroll((xOffset: number, yOffset: number) => {  
        let offset = this.scroller.currentOffset().yOffset  
        if (offset >= 150) {  
          this.alpha = 'rgba(255,0,0,0.8)'  
        } else if (offset <= 0) {  
          this.alpha = 'rgba(255,0,0,0.6)'  
        }  
        else {  
          this.alpha ='rgba(255,0,0,0.3)'  
        }  
      })  
    }  
  }  
}