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【每日学点鸿蒙知识】节点析构问题、区分手机和pad、 Navigation路由问题、Tabs组件宽度、如何监听Map

article 2025/1/1 22:24:08

1、HarmonyOS 只调用根节点的dispose,是否其下的子节点都能析构掉还是需要遍历子节点，都执行dispose才能正常析构？

前端持有引用关系的需要dispose，new出来的builderNode和FrameNode也需要dispose。只调用根节点的dispose,无法保证其下的子节点能够正常释放

2、HarmonyOS 如何在Web UserAgent中区分手机设备与pad设备？

参考：https://developer.huawei.com/consumer/cn/doc/harmonyos-guides-V5/multi-faq-V5#ZH-CN_TOPIC_0000001884757262__%E5%A6%82%E4%BD%95%E6%9F%A5%E8%AF%A2%E8%AE%BE%E5%A4%87%E7%B1%BB%E5%9E%8B

通过命令行的方式查询设备类型。
通过命令行查询指定系统参数（const.product.devicetype）进而确定设备类型

 # 方法一
 hdc shell param get "const.product.devicetype"
 # 方法二
 hdc shell cat /etc/param/ohos.para | grep const.product.devicetype

在应用开发过程中查询设备类型。

 import { deviceInfo } from'@kit.BasicServicesKit'

 @Entry
 @Component
 struct GetDeviceTypeSample {
   @State deviceType:string='unknown'

   aboutToAppear() {
     this.deviceType= deviceInfo.deviceType
   }

   build() {
     Column() {
       Text(this.deviceType).fontSize(24)
     }
     .width('100%')
     .height('100%')
   }
}

3、HarmonyOS Navigation路由问题？

在Index页面跳转PageOne页面的同时隐藏了导航页（hideNavBar），但是在PageOne页面返回上一页时，为什么会出现白屏的情况？

// Index.ets
@Entry
@Component
struct Index {
  @State hideNavBar: boolean = false
  private pageStack: NavPathStack = new NavPathStack()

  build() {
    Navigation(this.pageStack) {
      Column() {
        Button('跳转PageOne,隐藏NavBar')
          .onClick(() => {
            this.hideNavBar = true
            this.pageStack.replacePath({
              name: 'PageOne'
            })
          })
      }
      .height('100%')
      .justifyContent(FlexAlign.Center)
    }
    .hideNavBar(this.hideNavBar)
    .hideTitleBar(true)
    .hideBackButton(true)
  }
}


// PageOne.ets
@Builder
function PageOneBuilder() {
  PageOne()
}

@Component
export struct PageOne {
  pageStack: NavPathStack | null = null
  build() {
    NavDestination() {
      Column() {
        Button('返回上一页')
          .onClick(() => {
            // 这里返回上一页
            this.pageStack?.pop?.()
          })
      }.height('100%')
    }
    .hideTitleBar(true)
    .onReady((ctx: NavDestinationContext) => {
      this.pageStack = ctx.pathStack
    })
  }
}

api介绍：https://developer.huawei.com/consumer/cn/doc/harmonyos-guides-V5/arkts-navigation-navigation-V5

白屏的情况是隐藏了导航页Navigation导致 hideNavBar(true)，设置为false回去就能看到上一个界面的导航页按钮。可以在Navigation上加一个button组件，在返回即使隐藏了Navigation也能看到button组件。具体使用再参考下api文档。

4、HarmonyOS Tabs组件宽度问题？

文档显示Tabs组件的指示器和视图的宽度一样，app首页的会有很多栏目，在栏目的右边会有一个半透明的遮盖条和一个按钮，在这里有办法分开写吗？或者有其他的组件可以替代，这个会影响操作，最后的一两个栏目可能会点不到。

参考以下demo:

@Entry
@Component
struct tabTest {
  @State tabArray: Array<number> = [0, 1, 2, 3,4]
  @State focusIndex: number = 0
  @State pre: number = 0
  @State index: number = 0
  private controller: TabsController = new TabsController()
  @State test: boolean = false
  @State animationDuration: number = 300
  @State indicatorLeftMargin: number = 0
  @State indicatorWidth: number = 0
  private tabsWidth: number = 0
  private tabWidth: number = 0;
  private scrollerForScroll: Scroller = new Scroller()

  // 单独的页签
  @Builder
  Tab(tabName: string, tabItem: number, tabIndex: number) {
    Row({ space: 20 }) {
      Text(tabName)
        .fontSize(18)
        .fontColor(tabIndex === this.focusIndex ? Color.Blue :Color.Black)
        .id(tabIndex.toString())
        .onAreaChange((oldValue: Area,newValue: Area) => {
          if (this.focusIndex === tabIndex && (this.indicatorLeftMargin === 0 || this.indicatorWidth === 0)){
            if (newValue.position.x != undefined) {
              let positionX = Number.parseFloat(newValue.position.x.toString())
              this.indicatorLeftMargin = Number.isNaN(positionX) ? 0 : positionX
            }
            let width = Number.parseFloat(newValue.width.toString())
            this.tabWidth = Number.isNaN(width) ? 0 : width
            this.indicatorWidth = this.tabWidth
          }
        })
    }
    .justifyContent(FlexAlign.Center)
    .constraintSize({ minWidth: 35 })
    .width(100)
    .height(30)
    .onClick(() => {
      this.controller.changeIndex(tabIndex)
      this.focusIndex = tabIndex
    })
    .backgroundColor("#ffb7b7b7")
  }

  @Builder
  textTest(textName:string){
    Row({ space: 20 }) {
      Text(textName).fontSize(18)
    }
    .justifyContent(FlexAlign.Center)
    .constraintSize({ minWidth: 35 })
    .height(30)
    .backgroundColor("#ffb7b7b7")
  }

  build() {
    Column() {
      Stack({ alignContent: Alignment.TopStart }) {
        Column() {
          // 页签
          Row({ space: 8 }) {
            List({ space: 20, initialIndex: 0, scroller: this.scrollerForScroll }) {
              ForEach(this.tabArray, (item: number, index: number) => {
                ListItem() {
                  this.Tab("页签 " + item, item, index)
                }
              }, (item: string) => item)
            }
            .listDirection(Axis.Horizontal)
            .height(30)
            .width('80%')
            .friction(0.6)
            .alignListItem(ListItemAlign.Start)
            .scrollBar(BarState.Off)
            .width('80%')
            .backgroundColor("#ffb7b7b7")
            .onScroll((xOffset: number, yOffset: number) => {
              this.indicatorLeftMargin -= xOffset
            })
            this.textTest('更多')

          }
          .alignItems(VerticalAlign.Bottom)
          .width('100%')
          .backgroundColor("#ffb7b7b7")

        }
        .alignItems(HorizontalAlign.Start)
        .width('100%')

        Column()
          .height(2)
          .width(this.indicatorWidth)
          .margin({ left: this.indicatorLeftMargin, top:30})
          .backgroundColor(Color.Blue)
        Column()
          .height(10)
          .width("20%")
          .margin({ left: '80%', top:28})
          .backgroundColor("#ffb7b7b7")
      }
      .height(40)
      .width('100%')
      .backgroundColor("#ffb7b7b7")
      //tabs
      Tabs({ barPosition: BarPosition.Start, controller: this.controller }) {
        ForEach(this.tabArray, (item: number, index: number) => {
          TabContent() {
            Text('我是页面 ' + item + " 的内容")
              .height(300)
              .width('100%')
              .fontSize(30)
          }
          .backgroundColor(Color.White)
        }, (item: string) => item)
      }
      .onAreaChange((oldValue: Area,newValue: Area)=> {
        let width = Number.parseFloat(newValue.width.toString())
        this.tabsWidth = Number.isNaN(width) ? 0 : width
      })
      .width('100%')
      .barHeight(0)
      .animationDuration(100)
      .onChange((index: number) => {
        console.log('foo change')
        this.focusIndex = index
        this.scrollerForScroll.scrollToIndex(index-1,true)
      })
      .onAnimationStart((index: number, targetIndex: number, event: TabsAnimationEvent) => {
        // 切换动画开始时触发该回调。下划线跟着页面一起滑动
        this.focusIndex = targetIndex
        let targetIndexInfo = this.getTextInfo(targetIndex)
        this.startAnimateTo(this.animationDuration, targetIndexInfo.left, targetIndexInfo.width)
      })
      .onAnimationEnd((index: number,event: TabsAnimationEvent) => {
        // 切换动画结束时触发该回调。下划线动画停止。
        let currentIndicatorInfo = this.getCurrentIndicatorInfo(index,event)
        this.startAnimateTo(0,currentIndicatorInfo.left,currentIndicatorInfo.width)
      })
      .onGestureSwipe((index: number,event: TabsAnimationEvent) => {
        // 在页面跟手滑动过程中，逐帧触发该回调。
        let currentIndicatorInfo = this.getCurrentIndicatorInfo(index,event)
        this.focusIndex = currentIndicatorInfo.index
        this.indicatorLeftMargin = currentIndicatorInfo.left
        this.tabWidth = currentIndicatorInfo.width
        this.indicatorWidth = currentIndicatorInfo.width
      })
    }
    .height('100%')
  }

  private getTextInfo(index: number): Record<string, number> {
    let strJson = getInspectorByKey(index.toString())
    try {
      let obj: Record<string, string> = JSON.parse(strJson)
      let rectInfo: number[][] = JSON.parse('[' + obj.$rect + ']')
      return { 'left': px2vp(rectInfo[0][0]), 'width': px2vp(rectInfo[1][0] - rectInfo[0][0]) }
    } catch (error) {
      return { 'left': 0, 'width': 0 }
    }
  }
  private getCurrentIndicatorInfo(index: number, event: TabsAnimationEvent): Record<string, number> {
    let nextIndex = index
    if (index > 0 && event.currentOffset > 0) {
      nextIndex--
    } else if (index < 4 && event.currentOffset < 0) {
      nextIndex++
    }
    let indexInfo = this.getTextInfo(index)
    let nextIndexInfo = this.getTextInfo(nextIndex)
    let swipeRatio = Math.abs(event.currentOffset / this.tabsWidth)
    let currentIndex = swipeRatio > 0.5 ? nextIndex : index  // 页面滑动超过一半，tabBar切换到下一页。
    let currentLeft = indexInfo.left + (nextIndexInfo.left - indexInfo.left) * swipeRatio
    let currentWidth = indexInfo.width + (nextIndexInfo.width - indexInfo.width) * swipeRatio
    return { 'index': currentIndex, 'left': currentLeft, 'width': currentWidth }
  }

  private startAnimateTo(duration: number, leftMargin: number, width: number) {
    animateTo({
      duration: duration, // 动画时长
      curve: Curve.Linear, // 动画曲线
      iterations: 1, // 播放次数
      playMode: PlayMode.Normal, // 动画模式
      onFinish: () => {
        console.info('play end')
      }
    }, () => {
      this.indicatorLeftMargin = leftMargin
      this.tabWidth = width
      this.indicatorWidth = width
    })
  }
}