Drag Event

A drag event is triggered when a component is dragged.

NOTE

The APIs of this module are supported since API version 8. Updates will be marked with a superscript to indicate their earliest API version.

Events

DragItemInfo

extraParams

Provides additional information required for dragging an item.

extraParams is a string converted from a JSON object. You can obtain the following attributes using the JSON object converted from Json.parse.

DragEvent

Example

Example 1

@Observed
class ClassA {
  public name: string
  public bol: boolean

  constructor(name: string, bol: boolean) {
    this.name = name
    this.bol = bol
  }
}

@Extend(Text) function textStyle() {
  .width('25%')
  .height(35)
  .fontSize(16)
  .textAlign(TextAlign.Center)
  .backgroundColor(0xAFEEEE)
}

@Entry
@Component
struct DragExample {
  @State arr: ClassA[] = [new ClassA('A', true), new ClassA('B', true), new ClassA('C', true)]
  @State dragIndex: number = 0

  changeIndex(index1: number, index2: number) {// Exchange the array position.
    [this.arr[index1], this.arr[index2]] = [this.arr[index2], this.arr[index1]];
  }

  build() {
    Column() {
      Row({ space: 15 }) {
        List({ space: 20 }) {
          ForEach(this.arr, (item, index) => {
            ListItem() {
              Column() {
                Child({ a: this.arr[index] })
              }
              .onTouch((event: TouchEvent) => {
                if (event.type === TouchType.Down) {
                  this.dragIndex = index // Obtain the index of the current dragged child component.
                  console.info('onTouch' + this.dragIndex)
                }
              })
            }
          })
        }
        .listDirection(Axis.Horizontal)
        .onDrop((event: DragEvent, extraParams: string) => { // The component bound to this event can be used as the drop target. When the dragging stops within the component scope, the callback is triggered.
          let jsonString = JSON.parse(extraParams);
          this.changeIndex(this.dragIndex, jsonString.insertIndex)
        })
      }.padding({ top: 10, bottom: 10 }).margin(10)

    }.width('100%').height('100%').padding({ top: 20 }).margin({ top: 20 })
  }
}

@Component
struct Child {
  @ObjectLink a: ClassA

  @Builder pixelMapBuilder() {
    Column() {
      Text(this.a.name)
        .width('50%')
        .height(60)
        .fontSize(16)
        .borderRadius(10)
        .textAlign(TextAlign.Center)
        .backgroundColor(Color.Yellow)
    }
  }

  build() {
    Column() {
      Text(this.a.name)
        .textStyle()
        .visibility(this.a.bol ? Visibility.Visible : Visibility.None)
        .onDragStart(() => { // The callback is triggered when the component bound to this event is dragged for the first time.
          this.a.bol = false // Control the visibility.
          return this.pixelMapBuilder() // Set the image displayed during dragging.
        })
        .onTouch((event: TouchEvent) => {
          if (event.type === TouchType.Up) {
            this.a.bol = true
          }
        })
      Text('')
        .width('25%')
        .height(35)
        .fontSize(16)
        .textAlign(TextAlign.Center)
        .border({ width: 5, color: 'red' })
        .visibility(!this.a.bol ? Visibility.Visible : Visibility.None)
    }
  }
}

Example 2

// xxx.ets
@Extend(Text) function textStyle () {
  .width('25%')
  .height(35)
  .fontSize(16)
  .textAlign(TextAlign.Center)
  .backgroundColor(0xAFEEEE)
}

@Entry
@Component
struct DragExample {
  @State numbers: string[] = ['one', 'two', 'three', 'four', 'five', 'six']
  @State text: string = ''
  @State bool: boolean = true
  @State eventType: string = ''
  @State appleVisible: Visibility = Visibility.Visible
  @State orangeVisible: Visibility = Visibility.Visible
  @State bananaVisible: Visibility = Visibility.Visible
  private dragList: string[] = ['apple', 'orange', 'banana']
  @State fruitVisible: Visibility[] = [Visibility.Visible, Visibility.Visible, Visibility.Visible]
  @State idx: number = 0

  // Customize the content displayed during dragging.
  @Builder pixelMapBuilder() {
    Column() {
      Text(this.text)
        .width('50%')
        .height(60)
        .fontSize(16)
        .borderRadius(10)
        .textAlign(TextAlign.Center)
        .backgroundColor(Color.Yellow)
    }
  }

  build() {
    Column() {
      Text('There are three Text elements here')
        .fontSize(12)
        .fontColor(0xCCCCCC)
        .width('90%')
        .textAlign(TextAlign.Start)
        .margin(5)
      Row({ space: 15 }) {
        ForEach(this.dragList, (item, index) => {
          Text(item)
            .textStyle()
            .visibility(this.fruitVisible[index])
            .onDragStart(() => {
              this.bool = true
              this.text = item
              this.fruitVisible[index] = Visibility.None
              return this.pixelMapBuilder
            })
            .onTouch((event: TouchEvent) => {
              if (event.type === TouchType.Down) {
                this.eventType = 'Down'
                this.idx = index
              }
              if (event.type === TouchType.Up) {
                this.eventType = 'Up'
                if (this.bool) {
                  this.fruitVisible[index] = Visibility.Visible
                }
              }
            })
        })
      }.padding({ top: 10, bottom: 10 }).margin(10)

      Text('This is a List element')
        .fontSize(12)
        .fontColor(0xCCCCCC)
        .width('90%')
        .textAlign(TextAlign.Start)
        .margin(15)
      List({ space: 20 }) {
        ForEach(this.numbers, (item) => {
          ListItem() {
            Text(item)
              .width('100%')
              .height(80)
              .fontSize(16)
              .borderRadius(10)
              .textAlign(TextAlign.Center)
              .backgroundColor(0xAFEEEE)
          }
        }, item => item)
      }
      .editMode(true)
      .height('50%')
      .width('90%')
      .border({ width: 1 })
      .padding(15)
      .divider({ strokeWidth: 2, color: 0xFFFFFF, startMargin: 20, endMargin: 20 })
      .onDragEnter((event: DragEvent, extraParams: string) => {
        console.log('List onDragEnter, ' + extraParams + 'X:' + event.getX() + 'Y:' + event.getY())
      })
      .onDragMove((event: DragEvent, extraParams: string) => {
        console.log('List onDragMove, ' + extraParams + 'X:' + event.getX() + 'Y:' + event.getY())
      })
      .onDragLeave((event: DragEvent, extraParams: string) => {
        console.log('List onDragLeave, ' + extraParams + 'X:' + event.getX() + 'Y:' + event.getY())
      })
      .onDrop((event: DragEvent, extraParams: string) => {
        let jsonString = JSON.parse(extraParams);
        if (this.bool) {
          // Insert an element using the splice method.
          this.numbers.splice(jsonString.insertIndex, 0, this.text)
          this.bool = false
        }
        this.fruitVisible[this.idx] = Visibility.None
      })
    }.width('100%').height('100%').padding({ top: 20 }).margin({ top: 20 })
  }
}