harmony 鸿蒙Gesture Binding

2023-06-24
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Gesture Binding

You can bind to each component different gesture events and design the logic for responding to these events. When a gesture is successfully recognized, the ArkUI framework notifies the component of the gesture recognition result through event callback.

gesture (Common Gesture Binding Method)

.gesture(gesture: GestureType, mask?: GestureMask)

gesture is a frequently used API for binding a gesture to a component.

For example, you can use it to bind the tap gesture to the <Text> component.

// xxx.ets
@Entry
@Component
struct Index {
  build() {
    Column() {
      Text('Gesture').fontSize(28)
        // Use the gesture API to bind the tap gesture.
        .gesture(
          TapGesture()
            .onAction(() => {
              console.info('TapGesture is onAction');
            }))
    }
    .height(200)
    .width(250)
  }
}

priorityGesture (Gesture Binding Method with Priority)

.priorityGesture(gesture: GestureType, mask?: GestureMask)

The priorityGesture API binds gestures that are preferentially recognized to a component.

By default, the child component preferentially recognizes the gesture specified by gesture, and the parent component preferentially recognizes the gesture specified by priorityGesture (if set).

In the following example, the parent component <Column> and child component <Text> are both bound to the tap gesture. As the <Column> is bound to the gesture through priorityGesture, the tap gesture recognized by the parent component is preferentially responded to.

// xxx.ets
@Entry
@Component
struct Index {
  build() {
    Column() {
      Text('Gesture').fontSize(28)
        .gesture(
          TapGesture()
            .onAction(() => {
              console.info('Text TapGesture is onAction');
            }))
    }
    .height(200)
    .width(250)
    // When the tap gesture is bound to the parent <Column> component through priorityGesture, the tap gesture event of the <Text> component is ignored when the text area is tapped, and the tap gesture event of the<Column> component is preferentially responded to.
    .priorityGesture(
      TapGesture()
        .onAction(() => {
          console.info('Column TapGesture is onAction');
        }), GestureMask.IgnoreInternal)
  }
}

parallelGesture (Parallel Gesture Binding Method)

.parallelGesture(gesture: GestureType, mask?: GestureMask)

The parallelGesture API binds to a component the gesture that can be triggered together with the child component gesture.

By default, the gesture event does not bubble up. When a parent component and a child component are bound to a same gesture, the gesture events bound to the parent component and the child component compete with each other, and a gesture event of at most one component can be responded to. When parallelGesture is set, the same gesture events can be triggered for the parent and child components, thereby implementing a bubbling effect.

// xxx.ets
@Entry
@Component
struct Index {
  build() {
    Column() {
      Text('Gesture').fontSize(28)
        .gesture(
          TapGesture()
            .onAction(() => {
              console.info('Text TapGesture is onAction');
            }))
    }
    .height(200)
    .width(250)
    // When parallelGesture is set, the tap gestures on the <Column> component and on the child <Text> component are both recognized.
    .parallelGesture(
      TapGesture()
        .onAction(() => {
          console.info('Column TapGesture is onAction');
        }), GestureMask.Normal)
  }
}

NOTE

When the parent component and the child component are bound to both the click gesture and the double-click gesture, both the parent component and the child component respond only to the click gesture.