harmony 鸿蒙Hit Test Control

2022-10-28
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Hit Test Control

Hit test control allows you to configure hit testing for components. When processing a touch event, ArkUI performs hit testing on the touch points and component area before the touch event is triggered, in order to determine the component that needs to respond to the touch event, and then distributes the touch event based on the hit test result. The hitTestBehavior attribute sets how the component behaves during hit testing. The settings will affect the hit test result and thereby the subsequent touch event distribution. For details, see HitTestMode.

NOTE

The APIs of this module are supported since API version 9. Updates will be marked with a superscript to indicate their earliest API version.

When the touch areas of nodes, for example, two nodes, in the <Stack> component overlap, hit testing is performed only on the node displayed at the top layer by default. To perform hit testing on the node at the lower layer, set hitTestBehavior to HitTestMode.Transparent for the upper-layer node.

Attributes

Name	Type	Description
hitTestBehavior	HitTestMode	How the component behaves during hit testing. Default value: HitTestMode.Default

HitTestMode

Name	Description
Default	Both the node and its child node respond to the hit test of a touch event, but its sibling node is blocked from the hit test.
Block	The node responds to the hit test of a touch event, but its child node and sibling node are blocked from the hit test.
Transparent	Both the node and its child node respond to the hit test of a touch event, and its sibling node is also considered during the hit test.
None	The node does not respond to the hit test of a touch event, but its child node and sibling node are considered during the hit test.

Example

Set hitTestBehavior to HitTestMode.Transparent for the <Text> component, which means that the inner-layer <Stack> component is also considered during hit testing. Therefore, both the <Text> and <Stack> components respond to the onTouch event.

Set hitTestBehavior to HitTestMode.Block for the inner-layer <Stack> component, which means that its child nodes and sibling node <Button> are blocked from hit testing. Therefore, neither the inner-layer or out-layer <Button> components respond to the onTouch event.

// xxx.ets
@Entry
@Component
struct HitTestBehaviorExample {
  build() {
    // outer stack
    Stack() {
      Button('outer button')
        .onTouch((event) => {
          console.info('outer button touched type: ' + (event as TouchEvent).type)
        })
      // inner stack
      Stack() {
        Button('inner button')
          .onTouch((event) => {
            console.info('inner button touched type: ' + (event as TouchEvent).type)
          })
      }
      .width("100%").height("100%")
      .hitTestBehavior(HitTestMode.Block)
      .onTouch((event) => {
        console.info('stack touched type: ' + (event as TouchEvent).type)
      })

      Text('Transparent')
        .hitTestBehavior(HitTestMode.Transparent)
        .width("100%").height("100%")
        .onTouch((event) => {
          console.info('text touched type: ' + (event as TouchEvent).type)
        })
    }.width(300).height(300)
  }
}