Tabs 出现/消失转场动画效果

@Entry  
@Component  
struct TabsDemo {  
  @State currentIndex: number = 0  
  pageInfos: NavPathStack = new NavPathStack()  
  
  build() {  
    Navigation(this.pageInfos) {  
      Stack({ alignContent: Alignment.TopStart }){  
        Flex({ direction: FlexDirection.Column }){  
          Tabs({ index: this.currentIndex }) {  
            TabContent() {  
              Column().width('100%').height('100%').backgroundColor('#00CB87')  
            }  
            TabContent() {  
              Column().width('100%').height('100%').backgroundColor('#007DFF')  
            }  
            TabContent() {  
              Column().width('100%').height('100%').backgroundColor('#FFBF00')  
            }  
          }  
          .barHeight(0)  
          .scrollable(false)  
          .onChange((index) => {  
            this.currentIndex = index;  
          })  
          Flex({  
            direction: FlexDirection.Row,  
            alignItems: ItemAlign.Center,  
            justifyContent: FlexAlign.SpaceAround  
          }) {  
            Column({space:5}){  
              Text('0')  
                .fontSize(14).fontColor('#4f4f4f')  
            }.onClick(() => {  
              this.currentIndex = 0  
            })  
            Column({space:5}){  
              Text('1')  
                .fontSize(14).fontColor('#4f4f4f')  
            }.onClick(() => {  
              this.currentIndex = 1  
            })  
            Column({space:5}){  
              Text('2')  
                .fontSize(14).fontColor('#4f4f4f')  
            }.onClick(() => {  
              this.currentIndex = 2  
            })  
          }.height(36)  
        }  
        .width('100%')  
        .height('100%')  
      }  
    }.hideTitleBar(true)  
    .mode(NavigationMode.Stack)  
    .expandSafeArea([SafeAreaType.SYSTEM], [SafeAreaEdge.TOP, SafeAreaEdge.BOTTOM])  
  }  
}