ForEach数组发生改变。UI没刷新

import router from '@ohos.router';  
  
class cs {  
  lable: string  
  value: string  
  
  constructor(lable: string, value: string) {  
    this.lable = lable;  
    this.value = value;  
  }  
}  
  
  
@Entry  
@Component  
struct ForEachTest {  
  @State message: string = 'Hello World';  
  @State arr: cs[] = []  
  num = 0  
  
  aboutToAppear(): void {  
    this.arr.push(new cs('name1', 'value1'))  
    this.arr.push(new cs('name2', 'value2'))  
    this.arr.push(new cs('name3', 'value3'))  
    console.log('arr',JSON.stringify(this.arr))  
  }  
  
  onPageShow(): void {  
    if (this.num != 0) {  
      this.arr = []  
      this.arr.push(new cs('name1', 'value1' + this.num))  
      this.arr.push(new cs('name2', 'value2' + this.num))  
      this.arr.push(new cs('name3', 'value3' + this.num))  
    }  
    this.num++  
  }  
  
  build() {  
    Column() {  
      ForEach(this.arr, (item: cs) => {  
        Row() {  
          Text(item.lable)  
          Blank()  
          Text(item.value)  
        }.width('100%').onClick(() => {  
          router.pushUrl({  
            url: "pages/Cs",  
          })  
        })  
      })  
    }  
    .height('100%')  
  }  
}