harmony 鸿蒙Touch Event

  • 2022-08-09
  • 浏览 (834)

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.

Events

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

TouchEvent

Name Type Description
type TouchType Type of the touch event.
touches Array<TouchObject> All finger information.
changedTouches Array<TouchObject> Finger information changed.
stopPropagation () => void Stops the event from bubbling upwards or downwards.
timestamp8+ number Timestamp of the event. It is the interval between the time when the event is triggered and the time when the system starts, in nanoseconds.
target8+ EventTarget Display area of the element that triggers the gesture event.
source8+ SourceType Event input device.
getHistoricalPoints10+ Array<HistoricalPoint> All historical points of the current frame (the touch event frequency of a frame varies by device, and all touch events of the current frame are referred to as historical points).

TouchObject

Name Type Description
type TouchType Type of the touch event.
id number Unique identifier of a finger.
x number X coordinate of the touch point relative to the upper left corner of the component being touched.
y number Y coordinate of the touch point relative to the upper left corner of the component being touched.
windowX10+ number X coordinate of the touch point relative to the upper left corner of the application window.
windowY10+ number Y coordinate of the touch point relative to the upper left corner of the application window.
displayX10+ number X coordinate of the touch point relative to the upper left corner of the application screen.
displayY10+ number Y coordinate of the touch point relative to the upper left corner of the application screen.
screenX(deprecated) number X coordinate of the touch point relative to the upper left corner of the application window.
This API is deprecated since API version 10. You are advised to use windowX instead.
screenY(deprecated) number Y coordinate of the touch point relative to the upper left corner of the application window.
This API is deprecated since API version 10. You are advised to use windowY instead.

HistoricalPoint10+

Name Type Description
touchObject TouchObject Basic information of the historical point.
size number Size of the contact area between the finger and screen for the historical point.
Default value: 0
force number Touch force of the historical point.
Default value: 0
Value range: [0,1]. A larger value indicates a greater touch force.
The support for this API varies by device. Currently, it is only available on tablets.
timestamp number Timestamp of the historical point. It is the interval between the time when the event is triggered and the time when the system starts, in nanoseconds.

Example

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

  build() {
    Column() {
      Button('Touch').height(40).width(100)
        .onTouch((event?: TouchEvent) => {
          if(event){
            if (event.type === TouchType.Down) {
              this.eventType = 'Down'
            }
            if (event.type === TouchType.Up) {
              this.eventType = 'Up'
            }
            if (event.type === TouchType.Move) {
              this.eventType = 'Move'
            }
            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
          }
        })
      Button('Touch').height(50).width(200).margin(20)
        .onTouch((event?: TouchEvent) => {
          if(event){
            if (event.type === TouchType.Down) {
              this.eventType = 'Down'
            }
            if (event.type === TouchType.Up) {
              this.eventType = 'Up'
            }
            if (event.type === TouchType.Move) {
              this.eventType = 'Move'
            }
            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)
    }.width('100%').padding(30)
  }
}

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