【每日学点HarmonyOS Next知识】图片拖动、动画放大、列表高度、返回键监听、分割线颜色

1、HarmonyOS image 组件的图片可以随意拖动？

mage组件默认拖拽效果，draggable设置为true时，组件可拖拽，参考以下文档：https://developer.huawei.com/consumer/cn/doc/harmonyos-references-V5/image-V5

HarmonyOS中Image组件默认支持长按触发拖拽事件。具体来说，Image组件的拖拽能力是通过设置组件的draggable属性来实现的。通常情况下，Text、TextInput、TextArea、Hyperlink、Image和RichEditor组件的draggable属性是默认为true的，这意味着这些组件可以被长按并拖拽。可以通过自定义image相关组件，实现部分把draggable关了

2、HarmonyOS 换成model后动画放大实现不了？

listitem内容为object，不能直接用 ==判断当前item，可以改用index确定当前点击的item，修改如下：（其他案例参考：https://gitee.com/harmonyos-cases/cases/tree/master/CommonAppDevelopment/feature/listexchange)

import curves from '@ohos.curves';
@Entry
@Component
struct model {
  @State private arr: titleStrModel[] = []
  @State dragItem: titleStrModel = new titleStrModel()
  @State scaleItem: titleStrModel = new titleStrModel()
  @State neighborItem: titleStrModel = new titleStrModel()
  @State selectedIndex:number = -1
  @State neighborScale: number = -1
  private dragRefOffset: number = 0
  @State offsetX: number = 0
  @State offsetY: number = 0
  private ITEM_INTV: number = 120
  aboutToAppear(): void {
    const d = new titleStrModel()
    d.name = 'wewewe'
    const b = new titleStrModel()
    b.name = 'adadad'
    const h = new titleStrModel()
    h.name = 'dfdfdf'
    this.arr.push(d)
    this.arr.push(b)
    this.arr.push(h)
  }

  //根据当前index确定item是否缩放
  scaleSelect(item: titleStrModel):void {
    this.selectedIndex = this.arr.indexOf(item)
    this.arr[this.selectedIndex].scale = 1.05
  }
  itemMove(index: number, newIndex: number): void {
    let tmp = this.arr.splice(index, 1)
    this.arr.splice(newIndex, 0, tmp[0])
  }
  build() {
    Stack() {
      List({ space: 20, initialIndex: 0 }) {
        ForEach(this.arr, (item: titleStrModel) => {
          ListItem() {
            Row() {
              Text('' + item.name)
                .width('100%')
                .height(100)
                .fontSize(16)
                .textAlign(TextAlign.Center)
                .borderRadius(10)
                .backgroundColor(0xFFFFFF)
              Image($r('app.media.app_icon'))
                .width(100)
                .height(100)
            }
            .shadow(this.scaleItem.name == item.name ? { radius: 70, color:Color.Blue, offsetX: 0, offsetY: 0 } :
              { radius: 0, color: Color.Blue, offsetX: 0, offsetY: 0 })
            .animation({ curve: Curve.Sharp, duration: 300 })
          }
          .margin({ left: 12, right: 12 })
          .scale({ x: item.scale, y: item.scale })
          .zIndex(this.dragItem.name == item.name ? 1 : 0)
          .translate(this.dragItem.name == item.name ? { y: this.offsetY } : { y: 0 })
          .gesture(

            //以下组合手势为顺序识别，当长按手势事件未正常触发时则不会触发拖动手势事件
            GestureGroup(GestureMode.Sequence,
              LongPressGesture({ repeat: true })
                .onAction((event?: GestureEvent) => {
                  animateTo({ curve: Curve.Friction, duration: 300 }, () => {
                    this.scaleItem = item
                    this.scaleSelect(item)
                  })
                })
                .onActionEnd(() => {
                  animateTo({ curve: Curve.Friction, duration: 300 }, () => {
                    this.scaleItem = new titleStrModel()
                  })
                }),
              PanGesture({ fingers: 1, direction: null, distance: 0 })
                .onActionStart(() => {
                  this.dragItem = item
                  this.dragRefOffset = 0
                })
                .onActionUpdate((event: GestureEvent) => {
                  this.offsetY = event.offsetY - this.dragRefOffset
                  // console.log('Y:' + this.offsetY.toString())
                  this.neighborItem = new titleStrModel()
                  let index = this.arr.indexOf(item)
                  let curveValue = curves.initCurve(Curve.Sharp)
                  let value: number = 0
                  //根据位移计算相邻项的缩放
                  if (this.offsetY < 0) {
                    value = curveValue.interpolate(-this.offsetY / this.ITEM_INTV)
                    this.neighborItem = this.arr[index-1]
                    this.neighborScale = 1 - value / 20;
                    console.log('neighborScale:' + this.neighborScale.toString())
                  } else if (this.offsetY > 0) {
                    value = curveValue.interpolate(this.offsetY / this.ITEM_INTV)
                    this.neighborItem = this.arr[index+1]
                    this.neighborScale = 1 - value / 20;
                  }
                  //根据位移交换排序
                  if (this.offsetY > this.ITEM_INTV / 2) {
                    animateTo({ curve: curves.interpolatingSpring(0, 1, 400, 38) }, () => {
                      this.offsetY -= this.ITEM_INTV
                      this.dragRefOffset += this.ITEM_INTV
                      this.itemMove(index, index + 1)
                    })
                  } else if (this.offsetY < -this.ITEM_INTV / 2) {
                    animateTo({ curve: curves.interpolatingSpring(0, 1, 400, 38) }, () => {
                      this.offsetY += this.ITEM_INTV
                      this.dragRefOffset -= this.ITEM_INTV
                      this.itemMove(index, index - 1)
                    })
                  }
                })
                .onActionEnd((event: GestureEvent) => {
                  animateTo({ curve: curves.interpolatingSpring(0, 1, 400, 38) }, () => {
                    this.dragItem = new titleStrModel()
                    this.neighborItem = new titleStrModel()
                    //动画结束将缩放还原
                    this.arr[this.arr.indexOf(this.scaleItem)].scale = 1
                  })
                  animateTo({
                    curve: curves.interpolatingSpring(14, 1, 170, 17), delay: 150
                  }, () => {
                    this.scaleItem = new titleStrModel()
                  })
                })
            )
              .onCancel(() => {
                animateTo({ curve: curves.interpolatingSpring(0, 1, 400, 38) }, () => {
                  this.dragItem = new titleStrModel()
                  this.neighborItem = new titleStrModel()
                })
                animateTo({
                  curve: curves.interpolatingSpring(14, 1, 170, 17), delay: 150
                }, () => {
                  this.scaleItem = new titleStrModel()
                })
              })
          )
        })
      }
    }.width('100%').height('100%').backgroundColor(0xDCDCDC).padding({ top: 5 })
  }
}
class titleStrModel {
  name:string = ''
  scale:number = 1 //增加scale属性, 每个item都有对应的scale值
}

3、HarmonyOS 为什么List的高度设置100% 还是显示不全？

问题是解决了（方法：子控件Column，List都加上layoutWeight(1)），有点疑惑，想请教一下：

1. 为什么外部用了layoutWeight(1) 内部所有的Column与List也要用layoutWeight(1) 想知道原理
2. 外部我已经计算高度了（TNAppUIData.getPageHeight()）为什么Tabs我不用layoutWeight(1)还是占满屏幕的剩余高度，我计算给的高度不起作用？

问题1：父容器尺寸确定时，设置了layoutWeight属性的子元素与兄弟元素占主轴尺寸按照权重进行分配，前提是父容器尺寸确定。比如共有三个元素且都用了layoutWeight(1)，它们按照“1:1:1”的比例均分父容器主轴方向的空间。与.width(‘33%’)、.width(‘34%’)、.width(‘33%’)效果相同。

问题2：tabs是默认占满屏幕的

4、HarmonyOS 物理返回键监听？

customdialog弹窗打开时，按物理返回键，希望不关闭弹窗
可以使用onBackPress当用户点击返回按钮时触发，仅@Entry装饰的自定义组件生效。返回true表示页面自己处理返回逻辑，不进行页面路由；返回false表示使用默认的路由返回逻辑，不设置返回值按照false处理。参考文档：https://developer.huawei.com/consumer/cn/doc/harmonyos-references-V5/ts-custom-component-lifecycle-V5#onbackpress

onBackPress?(): void | boolean

当用户点击返回按钮时触发，仅@Entry装饰的自定义组件生效。返回true表示页面自己处理返回逻辑，不进行页面路由；返回false表示使用默认的路由返回逻辑，不设置返回值按照false处理。

// xxx.ets
@Entry
@Component
struct IndexComponent {
  @State textColor: Color = Color.Black;

  onPageShow() {
    this.textColor = Color.Blue;
    console.info('IndexComponent onPageShow');
  }

  onPageHide() {
    this.textColor = Color.Transparent;
    console.info('IndexComponent onPageHide');
  }

  onBackPress() {
    this.textColor = Color.Red;
    console.info('IndexComponent onBackPress');
  }

  build() {
    Column() {
      Text('Hello World')
        .fontColor(this.textColor)
        .fontSize(30)
        .margin(30)
    }.width('100%')
  }
}

5、HarmonyOS list divider中startmargin前面的颜色怎么和listitem保持一致？

目前使用list的divider属性并不能满足你想实现的效果，可以自定义实现分隔线效果，参考如下代码：

build() {

  Row(){
    List(){
      ListItem(){
        Flex({direction:FlexDirection.Column,justifyContent:FlexAlign.SpaceBetween}){
          Text('test')
          Divider()
            .color(Color.Red)
              // .height(15)
            .strokeWidth(5)
            .margin({left:50})
        }
      }.backgroundColor(Color.Blue)
      .height(100)
      ListItem(){
        Flex({direction:FlexDirection.Column,justifyContent:FlexAlign.SpaceBetween}){
          Text('test')
          Divider()
            .color(Color.Red)
            .strokeWidth(5)
            .margin({left:50,bottom:0})
        }


      }.backgroundColor(Color.Orange)
      .height(100)
      ListItem(){
        Flex({direction:FlexDirection.Column,justifyContent:FlexAlign.SpaceBetween}){
          Text('test')
          Divider()
            .color(Color.Red)
            .strokeWidth(5)
            .margin({left:50})
        }


      }.backgroundColor(Color.Yellow)
      .height(100)
    }

    // .divider({strokeWidth:5,color:Color.Red,startMargin:50})
    .width('100%').height('100%')
    .backgroundColor(Color.Gray)
  }
}