折叠屏和平板等大屏的瀑布流布局通过手势捏合改变列数

// xxx.ets 
import { WaterFlowDataSource } from './WaterFlowDataSource' 
  
@Entry 
@Component 
struct ScrollBarExample { 
  @State minSize: number = 80 
  @State maxSize: number = 180 
  @State fontSize: number = 24 
  @State colors: number[] = [0xFFC0CB, 0xDA70D6, 0x6B8E23, 0x6A5ACD, 0x00FFFF, 0x00FF7F] 
  scroller: Scroller = new Scroller() 
  datasource: WaterFlowDataSource = new WaterFlowDataSource() 
  private itemWidthArray: number[] = [] 
  private itemHeightArray: number[] = [] 
  private list: number[] = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15] 
  private  imageArr: string[] = [] 
  @State isScalable: boolean = false 
  @State canScale: boolean = false 
  @State scaleValue: number = 0 
  @State isScrollable: boolean = false 
  @State pinchValue: number = 2 
  @State columnTemplate: string = '1fr 1fr' 
  
  // 计算flow item宽/高 
  getSize() { 
    let ret = Math.floor(Math.random() * this.maxSize) 
    return (ret > this.minSize ? ret : this.minSize) 
  } 
  
  // 保存flow item宽/高 
  getItemSizeArray() { 
    for (let i = 0; i < 100; i++) { 
      this.itemWidthArray.push(this.getSize()) 
      this.itemHeightArray.push(this.getSize()) 
    } 
  } 
  
  aboutToAppear() { 
    this.getItemSizeArray() 
  } 
  
  @Builder itemFoot () { 
    Column() { 
      Text() 
    } 
    .height(50) 
    .width('100%') 
    .backgroundColor(Color.Pink) 
  } 
  
  
  @Styles Fancy () { 
    .gesture( 
      PinchGesture({ fingers: 2 }) 
        .onActionStart((event?: GestureEvent) => { 
          console.info('start') 
          this.isScrollable = true 
          this.canScale = true 
        }) 
        .onActionUpdate((event?: GestureEvent) => { 
          if (event) { 
            console.log(`${event.scale}`, 5555) 
            this.scaleValue = Number((this.pinchValue * event.scale).toFixed(2)) 
            if (this.scaleValue < 1) { 
              this.columnTemplate = '1fr 1fr 1fr' 
            } 
            if (this.scaleValue > 1 && this.scaleValue < 3) { 
              this.columnTemplate = '1fr 1fr' 
            } 
            if (this.scaleValue > 3) { 
              this.columnTemplate = '1fr' 
            } 
            // console.log(`${this.scaleValue}`, 6666) 
          } 
        }) 
        .onActionEnd(() => { 
          console.log('end') 
          // this.pinchValue = this.scaleValue 
          // setTimeout(() => { 
          this.canScale = false 
          this.isScrollable = false 
          // }, 0) 
        }) 
    ) 
  } 
  
  build() { 
    Column() { 
      WaterFlow() { 
        LazyForEach(this.datasource, (item: number) => { 
          FlowItem() { 
            Column() { 
              Text("N" + item).fontSize(12).height('16') 
              Image('res/waterFlowTest(' + item % 5 + ').jpg') 
                .objectFit(ImageFit.Fill) 
                .width('100%') 
                .layoutWeight(1) 
            } 
          } 
          .onAppear(() => { 
          }) 
          .width('100%') 
          .height(this.itemHeightArray[item % 100]) 
          .backgroundColor(this.colors[item % 5]) 
        }, (item: string) => item) 
      } 
      // .columnsTemplate(this.columnsTemplateStr) 
      .columnsGap(5) 
      .rowsGap(5) 
      .width("100%") 
      .enableScrollInteraction(!this.isScrollable) 
      .columnsTemplate(this.columnTemplate) 
      .Fancy() 
    } 
  } 
} 
  
// WaterFlowDataSource.ets 
  
// 实现IDataSource接口的对象，用于瀑布流组件加载数据 
export class WaterFlowDataSource implements IDataSource { 
  private dataArray: number[] = [] 
  private listeners: DataChangeListener[] = [] 
  
  constructor() { 
    for (let i = 0; i < 25; i++) { 
      this.dataArray.push(i) 
    } 
  } 
  
  // 获取索引对应的数据 
  public getData(index: number): number { 
    return this.dataArray[index] 
  } 
  
  // 通知控制器数据重新加载 
  notifyDataReload(): void { 
    this.listeners.forEach(listener => { 
      listener.onDataReloaded() 
    }) 
  } 
  
  // 通知控制器数据增加 
  notifyDataAdd(index: number): void { 
    this.listeners.forEach(listener => { 
      listener.onDataAdded(index) 
    }) 
  } 
  
  // 通知控制器数据变化 
  notifyDataChange(index: number): void { 
    this.listeners.forEach(listener => { 
      listener.onDataChanged(index) 
    }) 
  } 
  
  // 通知控制器数据删除 
  notifyDataDelete(index: number): void { 
    this.listeners.forEach(listener => { 
      listener.onDataDeleted(index) 
    }) 
  } 
  
  // 通知控制器数据位置变化 
  notifyDataMove(from: number, to: number): void { 
    this.listeners.forEach(listener => { 
      listener.onDataMoved(from, to) 
    }) 
  } 
  
  // 获取数据总数 
  public totalCount(): number { 
    return this.dataArray.length 
  } 
  
  // 注册改变数据的控制器 
  registerDataChangeListener(listener: DataChangeListener): void { 
    if (this.listeners.indexOf(listener) < 0) { 
      this.listeners.push(listener) 
    } 
  } 
  
  // 注销改变数据的控制器 
  unregisterDataChangeListener(listener: DataChangeListener): void { 
    const pos = this.listeners.indexOf(listener) 
    if (pos >= 0) { 
      this.listeners.splice(pos, 1) 
    } 
  } 
  
  // 增加数据 
  public Add1stItem(): void { 
    this.dataArray.splice(0, 0, this.dataArray.length) 
    this.notifyDataAdd(0) 
  } 
  
  // 在数据尾部增加一个元素 
  public AddLastItem(): void { 
    this.dataArray.splice(this.dataArray.length, 0, this.dataArray.length) 
    this.notifyDataAdd(this.dataArray.length - 1) 
  } 
  
  // 在指定索引位置增加一个元素 
  public AddItem(index: number): void { 
    this.dataArray.splice(index, 0, this.dataArray.length) 
    this.notifyDataAdd(index) 
  } 
  
  // 删除第一个元素 
  public Delete1stItem(): void { 
    this.dataArray.splice(0, 1) 
    this.notifyDataDelete(0) 
  } 
  
  // 删除第二个元素 
  public Delete2ndItem(): void { 
    this.dataArray.splice(1, 1) 
    this.notifyDataDelete(1) 
  } 
  
  // 删除最后一个元素 
  public DeleteLastItem(): void { 
    this.dataArray.splice(-1, 1) 
    this.notifyDataDelete(this.dataArray.length) 
  } 
  
  // 重新加载数据 
  public Reload(): void { 
    this.dataArray.splice(1, 1) 
    this.dataArray.splice(3, 2) 
    this.notifyDataReload() 
  } 
}