Android Open Source - PinchToClose Multi Finger Gesture Detector

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License

The source code is released under:

Apache License

Java Source Code

package lt.marius.pinchtoclose;
//  w  ww .j a  va  2 s . c  o m
import android.view.MotionEvent;

public class MultiFingerGestureDetector {
  
  private static float POINTER_ERROR_THRESHOLD = 10.f;  //10 pixels here and there
  private int fingerCount;
  private float[] posX, posY;
  private float[] startX, startY;
  private float[] dx, dy;
  private boolean moving;
  private int[] mappings;
  private float lastArea = -1;
  
  private MultiFingerGestureListener listener;
  
  /**
   * 
   * @param fingerCount maximum number of fingers to register
   */
  public MultiFingerGestureDetector(int fingerCount, MultiFingerGestureListener l) {
    this.listener = l;
    this.fingerCount = fingerCount;
    posX = new float[fingerCount];
    posY = new float[fingerCount];
    dx = new float[fingerCount];
    dy = new float[fingerCount];
    startX = new float[fingerCount];
    startY = new float[fingerCount];
    moving = false;
  }
  
  public void setListener(MultiFingerGestureListener listener) {
    this.listener = listener;
  }
  
  private int pointerCount;
  
  public boolean onTouchEvent(MotionEvent event) {
    if (listener == null) return false;
    pointerCount = Math.min(event.getPointerCount(), fingerCount);
      
//      int index = event.getActionIndex();
      //for secondary pointer events
    switch (event.getActionMasked()) {
    case MotionEvent.ACTION_POINTER_DOWN:
      listener.onDown(pointerCount);
      break;
    case MotionEvent.ACTION_POINTER_UP:
      listener.onUp(pointerCount);
      break;
    default:
      break;
    }
      
    switch (event.getAction()) {
      case MotionEvent.ACTION_DOWN:
        listener.onDown(pointerCount);
        break;
      case MotionEvent.ACTION_UP:
        listener.onUp(pointerCount);
        break;
      case MotionEvent.ACTION_CANCEL:
        moving = false;
        break;
      case MotionEvent.ACTION_MOVE:
        posX = new float[fingerCount];
        posY = new float[fingerCount];
        gatherXY(event, posX, posY, pointerCount);
        dx = substract(posX, startX, pointerCount);
        dy = substract(posY, startY, pointerCount);
        listener.onDeltaMove(dx, dy);
        listener.onMove(copy(startX, pointerCount), copy(startY, pointerCount),
            copy(posX, pointerCount), copy(posY, pointerCount));
        copyValues(posX, startX);
        copyValues(posY, startY);
        
        break;
      }

    return true;
  }
  
  
  
  private float[] copy(float[] array) {
    return copy(array, array.length);
  }
  
  private float[] copy(float[] array, int length) {
    float[] dst = new float[length];
    System.arraycopy(array, 0, dst, 0, length);
    return dst;
  }
  
  private void copyValues(float[] src, float[] dst) {
    int n = Math.min(src.length, dst.length);
    for (int i = 0; i < n; i++) {
      dst[i] = src[i];
    }
  }
  
  private float[] substract(float[] a, float[] b) {
    return substract(a, b, a.length);
  }
  
  private float[] substract(float a[], float b[], int length) {
    float[] c = new float[length];
    for (int i = 0; i < length; i++) {
      c[i] = a[i] - b[i];
    }
    return c;
  }
  
  private void gatherXY(MotionEvent event, float x[], float y[], int pointerCount) {
    for (int pointerIndex = 0; pointerIndex < pointerCount; pointerIndex++ ) {
      int pointerId = event.getPointerId(pointerIndex);
      if (pointerId >= 0) {
        x[pointerIndex] = event.getX(pointerIndex);
        y[pointerIndex] = event.getY(pointerIndex);
      }
    }
  }
  
}

Java Source Code List

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