2.5.1 — Pointer Gestures

kotlin

val scaleGestureDetector = ScaleGestureDetector(
    this,
    object : ScaleGestureDetector.SimpleOnScaleGestureListener() {
        override fun onScale(detector: ScaleGestureDetector): Boolean {
            // Provide alternative
            return super.onScale(detector)
        }
    }
)

view.setOnTouchListener { _, event ->
    scaleGestureDetector.onTouchEvent(event)
}

kotlin

Box(
    modifier = Modifier
        .pointerInput(Unit) {
            detectTransformGestures { _, _, zoom, _ ->
                // Provide alternative
            }
        }
) {
    // Scalable Box content ...
}

swift

let gesture = UIPinchGestureRecognizer(
    target: self, 
    action: #selector(onPinch(_:))
)
addGestureRecognizer(gesture)

@objc private func onPinch(_ sender: UIPinchGestureRecognizer) {
  // Provide alternative
}

swift

@State private var scale: CGFloat = 1.0

var body: some View {
    VStack {
        Image("appt_logo")
            .scaleEffect(scale) // Apply the scale effect
        HStack {
            Button(action: {
                // Alternative way to trigger the same action
                self.scale(factor: 0.1)
            }) {
                Text("Enlarge")
            }
            
            Button(action: {
                // Alternative way to trigger the same action
                self.scale(factor: -0.1)
            }) {
                Text("Shrink")
            }
        }
    }
    .gesture(
        MagnificationGesture()
            .onChanged { value in
                self.scale = value
            }
    )

    private func scale(factor: CGFloat) {
        self.scale += factor
    }
}

dart

double _baseScaleFactor = 1;
double _scaleFactor = 1;

GestureDetector(
  onScaleStart: (details) {
    _baseScaleFactor = _scaleFactor;
  },
  onScaleUpdate: (details) {
    setState(() {
      _scaleFactor = _baseScaleFactor * details.scale;
      // Provide alternative
    });
  },
  child: ...
  ),
);

jsx

import { PinchGestureHandler, State } from 'react-native-gesture-handler'

const PinchableView = () => {
  scale = new Animated.Value(1)

  onPinchEvent = Animated.event([{
    nativeEvent: { scale: this.scale }
  }], {
      useNativeDriver: true
  })

  
  onPinchStateChange = event => {
    if (event.nativeEvent.oldState === State.ACTIVE) {
        // Provide alternative
        Animated.spring(this.scale, {
            toValue: 1,
            useNativeDriver: true
        }).start()
    }
  }

  return (
    <PinchGestureHandler
        onGestureEvent={this.onPinchEvent}
        onHandlerStateChange={this.onPinchStateChange}>
        <View style={{
            transform: [{ scale: this.scale }] 
        }} />
    </PinchGestureHandler>
  )
}

csharp

var label = new Label();

var dragGestureRecognizer = new DragGestureRecognizer();
dragGestureRecognizer.CanDrag = true;
dragGestureRecognizer.DropCompleted += DragGestureRecognizer_DropCompleted;
dragGestureRecognizer.DragStarting += DragGestureRecognizer_DragStarting;

label.GestureRecognizers.Add(dragGestureRecognizer);


var dropGestureRecognizer = new DropGestureRecognizer();
dropGestureRecognizer.AllowDrop = true;
dropGestureRecognizer.DragLeave += DropGestureRecognizer_DragLeave;
dropGestureRecognizer.DragOver += DropGestureRecognizer_DragOver;

label.GestureRecognizers.Add(dropGestureRecognizer);


var panGestureRecognizer = new PanGestureRecognizer();
panGestureRecognizer.PanUpdated += PanGestureRecognizer_PanUpdated;

label.GestureRecognizers.Add(panGestureRecognizer);


var pinchGestureRecognizer = new PinchGestureRecognizer();
pinchGestureRecognizer.PinchUpdated += PinchGestureRecognizer_PinchUpdated;

label.GestureRecognizers.Add(pinchGestureRecognizer);


var pointerGestureRecognizer = new PointerGestureRecognizer();
pointerGestureRecognizer.PointerEntered += PointerGestureRecognizer_PointerEntered;
pointerGestureRecognizer.PointerExited += PointerGestureRecognizer_PointerExited;
pointerGestureRecognizer.PointerMoved += PointerGestureRecognizer_PointerMoved;
pointerGestureRecognizer.PointerPressed += PointerGestureRecognizer_PointerPressed;

label.GestureRecognizers.Add(pointerGestureRecognizer);


var swipeGestureRecognizer = new SwipeGestureRecognizer();
swipeGestureRecognizer.Direction = SwipeDirection.Left;
swipeGestureRecognizer.Swiped += SwipeGestureRecognizer_Swiped;

label.GestureRecognizers.Add(swipeGestureRecognizer);


var tapGestureRecognizer = new TapGestureRecognizer();
tapGestureRecognizer.NumberOfTapsRequired = 2;
tapGestureRecognizer.Tapped += TapGestureRecognizer_Tapped;

label.GestureRecognizers.Add(tapGestureRecognizer);

csharp

<Label
    Text="Hello">
    <Label.GestureRecognizers>
        <DragGestureRecognizer CanDrag="True" DropCompleted="DragGestureRecognizer_DropCompleted" DragStarting="DragGestureRecognizer_DragStarting"  />
        <DropGestureRecognizer AllowDrop="True" DragLeave="DropGestureRecognizer_DragLeave" DragOver="DropGestureRecognizer_DragOver"  />
        <PanGestureRecognizer PanUpdated="PanGestureRecognizer_PanUpdated"  />
        <PinchGestureRecognizer PinchUpdated="PinchGestureRecognizer_PinchUpdated"  />
        <PointerGestureRecognizer PointerEntered="PointerGestureRecognizer_PointerEntered" PointerExited="PointerGestureRecognizer_PointerExited" PointerMoved="PointerGestureRecognizer_PointerMoved" PointerPressed="PointerGestureRecognizer_PointerPressed"  />
        <SwipeGestureRecognizer Direction="Left" Swiped="SwipeGestureRecognizer_Swiped"  />
        <TapGestureRecognizer NumberOfTapsRequired="2" Tapped="TapGestureRecognizer_Tapped"  />
    </Label.GestureRecognizers>
</Label>

csharp

var pinchGesture = new PinchGestureRecognizer();
pinchGesture.PinchUpdated += (sender, event) => {
  // Provide alternative
};
view.GestureRecognizers.Add(pinchGesture);