ETS开发鸿蒙Slider的划动过程中进度是一个无限循环小数是什么原因？

　　如上图：ETS开发鸿蒙 Slider的划动过程中进度是一个无限循环小数
代码如下：
@Entry

@Component

struct Index {

@State private angle: number = 0

@State private imageSize: number = 1

@State private speed: number = 5

@State private interval: number = 0

build() {

Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.Center }) {

Image ($rawfile("huaren_golden_round.png"))

.objectFit(ImageFit.Auto)

.height(150)

.width(150)

.margin({top:50, bottom:150, right:16, left:16})

.rotate({x:0, y:0, z:1, angle:this.angle})

.scale({x:this.imageSize, y:this.imageSize})

Text("速度： " + this.speed)

.margin({top: 30})

.fontSize(20)

.fontWeight(FontWeight.Bold)

Slider({

value: this.speed,

min: 1,

max: 10,

step: 1,

style: SliderStyle.OutSet

}).showTips(true)

.blockColor(Color.Gray)

.onChange((value: number, mode: SliderChangeMode) => {

// 在点击事件中赋值

console.log("vale:" + value)

this.speed = value

})

}

.width('100%')

.height('100%')

}

// 速度改变方法

private speedChange() {

var that = this

this.interval = setInterval(function(){

that.angle += that.speed

}, 16)

}

onPageShow() {

this.speedChange()

}

}