组件创建和重新初始化示例

@Entry
@Component
struct ParentComp {
    @State isCountDown: boolean = true
    build() {
        Column() {
            Text(this.isCountDown ? 'Count Down' : 'Stopwatch')
            if (this.isCountDown) {
                Image('countdown.png')
                TimerComponent({counter: 10, changePerSec: -1, showInColor: Color.Red})
            } else {
                Image('stopwatch.png')
                TimerComponent({counter: 0, changePerSec: +1, showInColor: Color.Black })
            }
            Button(this.isCountDown ? 'Swtich to Stopwatch' : 'Switch to Count Down')
                .onClick(() => {this.isCountDown = !this.isCountDown})
        }
    }
}

// Manage and display a count down / stop watch timer
@Component
struct TimerComponent {
    @State counter: number = 0
    private changePerSec: number = -1
    private showInColor: Color = Color.Black
    private timerId : number = -1

    build() {
        Text(`${this.counter}sec`)
            .fontColor(this.showInColor)
    }

    aboutToAppear() {
        this.timerId = setInterval(() => {this.counter += this.changePerSec}, 1000)
    }

    aboutToDisappear() {
        if (this.timerId > 0) {
            clearTimeout(this.timerId)
            this.timerId = -1
        }
    }
}