Gesture Controller

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A GestureController is an InputProcessor that handles input events and detects any gesture related events and emits them as a new event.

Detecting Gestures

Using a GestureController is as simple as using an InputProcessor except that it expects a GestureProcessor as an input to handle gesture events. Gesture events can be seen as anything related to touching the screen such as pinch zooming, panning. fling scrolling, etc.

GestureProcessor

The GestureProcessor is an interface that handles gesture events. The interface itself:

interface GestureProcessor {

    fun touchDown(screenX: Float, screenY: Float, pointer: Pointer): Boolean = false

    fun tap(screenX: Float, screenY: Float, count: Int, pointer: Pointer): Boolean = false

    fun longPress(screenX: Float, screenY: Float): Boolean = false

    fun fling(velocityX: Float, velocityY: Float, pointer: Pointer): Boolean = false

    fun pan(screenX: Float, screenY: Float, dx: Float, dy: Float): Boolean = false

    fun panStop(screenX: Float, screenY: Float, pointer: Pointer): Boolean = false

    fun zoom(initialDistance: Float, distance: Float): Boolean = false

    fun pinch(initialPos1: Vec2f, initialPos2: Vec2f, pos1: Vec2f, pos2: Vec2f): Boolean = false

    fun pinchStop() = Unit
}

Events:

  • touchDown: triggered when a pointer touches the screen.
  • tap: triggered when a “tap” occurs. A tap is when a pointer touches the screen and lets go of the same area of the screen without moving outsize the tap zone. A tap zone is a rectangular area around the initial tap position.
  • longPress: triggered when a touch is pressed for a certain duration.
  • fling: triggered when a pointer “flings” the screen by dragging and lifting the pointer. Repeats the velocity in pixels per second.
  • pan: triggered when a pointer is dragged over the screen.
  • panStop: triggered when panning finishes.
  • zoom triggered when two pointers perform a pinch zoom gesture.
  • pinch: triggered when two pointers perform a pinch gesture.
  • pinchStop: triggered when pinching is finished.

Creating a GestureController

There is a handy extension method that allows us to create a GestureController and GestureProcessor and add it to the curernt contexts input all in one go.

class MyGame(context: Context) : ContextListener(context) {

    // override any of the methods in InputProcessor that we want to actually make use of.
    override suspend fun Context.start() {
        val processor = input.gestureController {
            // creates a new GestureController and a new GestureProcessor and adds the processor to the controller as well as adding the controller to the current context.
            onTap { screenX, screenY, count, pointer ->
                println("Pointer ${pointer.index} is tapping at $screenX,$screenY for a total of $count taps.")
            }
            onLongPress { screenX, screenY ->
                input.vibrate(100.milliseconds)
            }
        }

        onRelease {
            removeInputProcessor(processor) // we don't have to do this if we are closing the application
        }
    }
}
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