harmony 鸿蒙Touch Event

2022-08-09
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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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