Lock movement with PanResponder in react native

Question

Using react native PanResponder, how can I block the movement when the screen touch coordinates are outside of a certain range of values?

For example, how can I prevent users from moving a component below a certain y position on the screen?

The PanResponder uses the Gesture Responder System.

I am carefully reading the documentation, but I cannot find the answer.

Any help is greatly appreciated.

Answer 1

Looking at the PanResponder documentation page you provided (https://facebook.github.io/react-native/docs/panresponder.html), I think you could modify the example to meet your needs.

The function responsible for taking action in response to a gesture is a property of PanResponder called onPanResponderMove, in the example code from the documentation this looks like:

_handlePanResponderMove: function(e: Object, gestureState: Object) {
    this._circleStyles.style.left = this._previousLeft + gestureState.dx;
    this._circleStyles.style.top = this._previousTop + gestureState.dy;
    this._updateNativeStyles();
},

Where the gestureState object looks like this:

stateID - ID of the gestureState- persisted as long as there at least one touch on screen
moveX - the latest screen coordinates of the recently-moved touch
moveY - the latest screen coordinates of the recently-moved touch
x0 - the screen coordinates of the responder grant
y0 - the screen coordinates of the responder grant
dx - accumulated distance of the gesture since the touch started
dy - accumulated distance of the gesture since the touch started
vx - current velocity of the gesture
vy - current velocity of the gesture
numberActiveTouches - Number of touches currently on screen

You might add a conditional check in _handlePanResponderMove to determine if the gestureState.y0 is below some threshold, and only apply a change if so

Answer 2

I solved it using interpolate

transform: [
  {
    translateX: this._translateX.interpolate({
      inputRange: [0, 100],
      outputRange: [0, 100],
      extrapolate: 'clamp',
    }),
  },
],