Touch Event

A touch event is triggered when a finger is pressed, slides, or is lifted from a component.

NOTE

This event is supported since API version 7. Updates will be marked with a superscript to indicate their earliest API version.

Required Permissions

None

Events

Name Bubbling Supported Description
onTouch(callback: (event?: TouchEvent) => void) Yes Invoked when a touch action is triggered. For details about event, see TouchEvent.

TouchEvent

  • Attributes
Name Type Description
type TouchType Type of the touch event.
touches Array<TouchObject> All finger information.
changedTouches Array<TouchObject> Finger information changed.
timestamp number Timestamp of the event.
target8+ EventTarget Target of the event.
  • APIs
Name Description
stopPropagation(): void Stops the event from bubbling upwards or downwards.

TouchObject

Name Type Description
type TouchType Type of the touch event.
id number Unique identifier of a finger.
screenX number X-coordinate of the touch point relative to the left edge of the screen.
screenY number Y-coordinate of the touch point relative to the upper edge of the device screen.
x number X-coordinate of the touch point relative to the left edge of the element being touched.
y number Y-coordinate of the touch point relative to the upper edge of the element being touched.

TouchType Enums

Name Description
Down A finger is pressed.
Up A finger is lifted.
Move A finger moves on the screen in pressed state.
Cancel A touch event is canceled.

Example

// xxx.ets
@Entry
@Component
struct TouchExample {
  @State text: string = ''
  @State eventType: string = ''

  build() {
    Flex({ direction: FlexDirection.Column, alignItems: ItemAlign.Center, justifyContent: FlexAlign.SpaceBetween }) {
      Button('Touch').backgroundColor(0x2788D9).height(40).width(80)
        .onTouch((event: TouchEvent) => {
          if (event.type === TouchType.Down) {
            this.eventType = 'Down'
          }
          if (event.type === TouchType.Up) {
            this.eventType = 'Up'
          }
          if (event.type === TouchType.Move) {
            this.eventType = 'Move'
          }
          console.info(this.text = 'TouchType:' + this.eventType + '\nDistance between touch point and touch element:\nx: '
          + event.touches[0].x + '\n' + 'y: ' + event.touches[0].y + '\ncomponent globalPos:('
          + event.target.area.globalPosition.x + ',' + event.target.area.globalPosition.y + ')\nwidth:'
          + event.target.area.width + '\nheight:' + event.target.area.height)
        })
      Text(this.text)
    }.height(200).width(350).padding({ left: 35, right: 35, top: 35 })
  }
}

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