State Variables, Common Pages, Visible Area Change Callbacks, Parameter Reception, Drag-and-Drop Sorting Controls

[Daily HarmonyOS Next Knowledge] State Variables, Common Pages, Visible Area Change Callbacks, Parameter Reception, Drag-and-Drop Sorting Controls

1. Can @state-decorated variables in HarmonyOS be updated in a timer to refresh the UI?

Wrapping the function in a proper closure allows UI updates:

@Entry
@Component
struct Index {
  @State acSetValve: number = 0;

  aboutToAppear(): void {
    setInterval(() => {
      this.acSetValve += 200;
      console.log('hahhah' + this.acSetValve)
    }, 100)
  }

  build() {
    Row() {
      Column() {
        Text(this.acSetValve.toString())
          .fontSize(50)
          .fontWeight(FontWeight.Bold)
      }
      .width('100%')
    }
    .height('100%')
  }
}

2. How to create a common page in HarmonyOS for other pages to inherit and process shared logic?

Demo reference:

// Main page: FirstTest.ets
import { FirstTest2 } from "./FirstTest2"

@Entry
@Component
struct FirstTest {
  @State message1: string = 'Hello World';

  build() {
    Column() {
      Text("FirstTest：" + this.message1)
        .fontSize(25)
        .fontWeight(FontWeight.Bold)
      FirstTest2({ message2: this.message1 });
    }
  }
}

// Reusable component: FirstTest2.ets
@Component
export struct FirstTest2 {
  @State test: string = "FirstTest2"
  @Link message2: string;

  build() {
    Row() {
      Column() {
        Text("FirstTest2:" + this.test)
          .fontSize(25)
          .fontWeight(FontWeight.Bold)
        Text("FirstTest2:" + this.message2)
          .fontSize(25)
          .fontWeight(FontWeight.Bold)
      }
      .width('100%')
    }
    .height('100%')
  }
}

3. Why isn't the onVisibleAreaChange event triggered in HarmonyOS?

The onVisibleAreaChange event does not monitor component area changes caused by offset adjustments. For screen switching monitoring, use the Swiper component.

Documentation: https://developer.huawei.com/consumer/cn/doc/harmonyos-references-V5/ts-container-swiper-V5

4. How to receive parameters passed via router.pushNamedRoute in HarmonyOS?

Use router.getParams() to receive parameters.

API link: https://developer.huawei.com/consumer/cn/doc/harmonyos-references-V5/js-apis-router-V5#ZH-CN_TOPIC_0000001884917590__routergetparams

Demo reference:

import router from '@ohos.router';
class innerParams {
  array: number[]
  constructor(tuple: number[]) {
    this.array = tuple
  }
}

class routerParams {
  text: string
  data: innerParams
  constructor(str: string, tuple: number[]) {
    this.text = str
    this.data = new innerParams(tuple)
  }
}

@Entry
@Component
struct Router1 {
  build() {
    Column() {
      Column() {
        Text("I am Page 1").fontSize(50)
      }
      Column() {
        Button("Jump")
          .onClick(() => {
            router.pushUrl({
              url: 'pages/Router11',
              params: new routerParams('message', [123, 456, 789])
            })
          })
      }
    }
    .width('100%')
    .height('100%')
  }
}

import router from '@ohos.router';

class innerParams {
  array: number[]
  constructor(tuple: number[]) {
    this.array = tuple
  }
}

class routerParams {
  text: string
  data: innerParams
  constructor(str: string, tuple: number[]) {
    this.text = str
    this.data = new innerParams(tuple)
  }
}

@Entry
@Component
struct Router11 {
  aboutToAppear(): void {
    let s: number[] = ((router.getParams() as routerParams).data as innerParams).array
    console.log("*********:" + s);
  }
  build() {
    Column() {
      Text("123").fontSize(50)
      Row() {
        Text("33333").fontSize(50)
      }
    }
    .width('100%')
    .height('100%')
    .opacity(0.5)
    .backgroundColor(Color.Pink)
  }
}

5. Are there utility classes for drag-and-drop sorting and control translation effects in HarmonyOS when current control data limits are insufficient?

For animation effects, refer to the following demo:

@Entry
@Component
struct AnimationPage {
  @Provide desX: number = 0;
  @Provide desY: number = 0;

  @Builder
  TabBar(index: number) {
    Column() {
      Image($r("app.media.icon"))
        .width(38)
        .height(38)
      Text(index == 1 ? "Classification" : index.toString())
    }
    .onAreaChange((oldValue: Area, newValue: Area) => {
      if (index == 1) {
        this.desX = newValue.globalPosition.x as number
        this.desY = newValue.globalPosition.y as number
      }
    })
  }

  build() {
    Column() {
      Category()
      Column() {
        Image($r("app.media.icon"))
          .width(38)
          .height(38)
      }
      .onAreaChange((oldValue: Area, newValue: Area) => {
        this.desX = newValue.globalPosition.x as number
        this.desY = newValue.globalPosition.y as number
      })
    }
    .width("100%")
    .height("100%")
  }
}

@Component
struct Category {
  @State dataList: number[] = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]

  build() {
    Column() {
      Flex({ direction: FlexDirection.Row, justifyContent: FlexAlign.SpaceBetween, wrap: FlexWrap.Wrap }) {
        ForEach(this.dataList, (item: number) => {
          ListItemComponent()
        })
      }
      .width('100%')
      .height('80%')
      .backgroundColor(Color.White)
    }
  }
}

@Observed
class AnimationBean {
  animationAppear: Boolean = false;
  id: number = -1;
}

@Component
struct ListItemComponent {
  @State animationList: AnimationBean[] = []
  static index: number = 0;
  @Consume desX: number;
  @Consume desY: number;
  @Provide orgX: number = 0;
  @Provide orgY: number = 0;

  @Builder
  BuildAnimationItem() {
    Image($r("app.media.app_icon"))
      .width(41)
      .height(41)
      .id("test")
      .onClick(() => {
        this.startAnimation();
      })
      .onAreaChange((oldValue: Area, newValue: Area) => {
        this.orgX = newValue.globalPosition.x as number
        this.orgY = newValue.globalPosition.y as number
      })
  }

  startAnimation() {
    const animation = new AnimationBean();
    animation.id = ListItemComponent.index++
    this.animationList.push(animation)
    animateTo({
      duration: 800,
      curve: Curve.FastOutLinearIn,
      onFinish: () => {
        animation.animationAppear = false;
        this.animationList = this.animationList.filter((item: AnimationBean) => {
          return item.animationAppear
        })
      }
    }, () => {
      animation.animationAppear = true;
    })
  }

  @Builder
  BuildItem() {
    Row() {
      Stack() {
        this.BuildAnimationItem()
        ForEach(this.animationList, (item: AnimationBean) => {
          AnimationChild({ item: item, AnimationView: this.BuildAnimationItem })
        }, (item: AnimationBean, index: number) => {
          return item.id.toLocaleString()
        })
      }
    }
    .width("20%")
    .height(60)
  }

  build() {
    this.BuildItem()
  }
}

@Component
struct AnimationChild {
  @ObjectLink item: AnimationBean;
  @Consume desX: number;
  @Consume desY: number;
  @Consume orgX: number;
  @Consume orgY: number;
  @BuilderParam
  AnimationView: () => void;

  build() {
    Row() {
      this.AnimationView()
    }
    .zIndex(5)
    .translate(this.item.animationAppear ? { x: (this.desX - this.orgX - 20), y: (this.desY - this.orgY) } : { x: 0 })
  }
}