DoubleGestureDetector.java

/*
   2 finger gesture detector
 
   Copyright 2013 Thincast Technologies GmbH, Author: Martin Fleisz
 
   This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0.
   If a copy of the MPL was not distributed with this file, You can obtain one at
   http://mozilla.org/MPL/2.0/.
*/
 
package com.freerdp.freerdpcore.utils;
 
import android.content.Context;
import android.os.Handler;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;
 
import com.freerdp.freerdpcore.utils.GestureDetector.OnGestureListener;
 
public class DoubleGestureDetector
{
  // timeout during that the second finger has to touch the screen before the double finger
  // detection is cancelled
  private static final long DOUBLE_TOUCH_TIMEOUT = 100;
  // timeout during that an UP event will trigger a single double touch event
  private static final long SINGLE_DOUBLE_TOUCH_TIMEOUT = 1000;
  // constants for Message.what used by GestureHandler below
  private static final int TAP = 1;
  // different detection modes
  private static final int MODE_UNKNOWN = 0;
  private static final int MODE_PINCH_ZOOM = 1;
  private static final int MODE_SCROLL = 2;
  private static final int SCROLL_SCORE_TO_REACH = 20;
  private final OnDoubleGestureListener mListener;
  private int mPointerDistanceSquare;
  private int mCurrentMode;
  private int mScrollDetectionScore;
  private ScaleGestureDetector scaleGestureDetector;
  private boolean mCancelDetection;
  private boolean mDoubleInProgress;
  private GestureHandler mHandler;
  private MotionEvent mCurrentDownEvent;
  private MotionEvent mCurrentDoubleDownEvent;
  private MotionEvent mPreviousUpEvent;
  private MotionEvent mPreviousPointerUpEvent;
  public DoubleGestureDetector(Context context, Handler handler, OnDoubleGestureListener listener)
  {
    mListener = listener;
    init(context, handler);
  }
 
  private void init(Context context, Handler handler)
  {
    if (mListener == null)
    {
      throw new NullPointerException("OnGestureListener must not be null");
    }
 
    if (handler != null)
      mHandler = new GestureHandler(handler);
    else
      mHandler = new GestureHandler();
 
    // we use 1cm distance to decide between scroll and pinch zoom
    //  - first convert cm to inches
    //  - then multiply inches by dots per inch
    float distInches = 0.5f / 2.54f;
    float distPixelsX = distInches * context.getResources().getDisplayMetrics().xdpi;
    float distPixelsY = distInches * context.getResources().getDisplayMetrics().ydpi;
 
    mPointerDistanceSquare = (int)(distPixelsX * distPixelsX + distPixelsY * distPixelsY);
  }
 
  public void setScaleGestureDetector(ScaleGestureDetector scaleGestureDetector)
  {
    this.scaleGestureDetector = scaleGestureDetector;
  }
 
  public boolean onTouchEvent(MotionEvent ev)
  {
    boolean handled = false;
    final int action = ev.getAction();
    // dumpEvent(ev);
 
    switch (action & MotionEvent.ACTION_MASK)
    {
      case MotionEvent.ACTION_DOWN:
        if (mCurrentDownEvent != null)
          mCurrentDownEvent.recycle();
 
        mCurrentMode = MODE_UNKNOWN;
        mCurrentDownEvent = MotionEvent.obtain(ev);
        mCancelDetection = false;
        mDoubleInProgress = false;
        mScrollDetectionScore = 0;
        handled = true;
        break;
 
      case MotionEvent.ACTION_POINTER_UP:
        if (mPreviousPointerUpEvent != null)
          mPreviousPointerUpEvent.recycle();
        mPreviousPointerUpEvent = MotionEvent.obtain(ev);
        break;
 
      case MotionEvent.ACTION_POINTER_DOWN:
        // more than 2 fingers down? cancel
        // 2nd finger touched too late? cancel
        if (ev.getPointerCount() > 2 ||
            (ev.getEventTime() - mCurrentDownEvent.getEventTime()) > DOUBLE_TOUCH_TIMEOUT)
        {
          cancel();
          break;
        }
 
        // detection cancelled?
        if (mCancelDetection)
          break;
 
        // double touch gesture in progress
        mDoubleInProgress = true;
        if (mCurrentDoubleDownEvent != null)
          mCurrentDoubleDownEvent.recycle();
        mCurrentDoubleDownEvent = MotionEvent.obtain(ev);
 
        // set detection mode to unknown and send a TOUCH timeout event to detect single
        // taps
        mCurrentMode = MODE_UNKNOWN;
        mHandler.sendEmptyMessageDelayed(TAP, SINGLE_DOUBLE_TOUCH_TIMEOUT);
 
        handled |= mListener.onDoubleTouchDown(ev);
        break;
 
      case MotionEvent.ACTION_MOVE:
 
        // detection cancelled or not active?
        if (mCancelDetection || !mDoubleInProgress || ev.getPointerCount() != 2)
          break;
 
        // determine mode
        if (mCurrentMode == MODE_UNKNOWN)
        {
          // did the pointer distance change?
          if (pointerDistanceChanged(mCurrentDoubleDownEvent, ev))
          {
            handled |= scaleGestureDetector.onTouchEvent(mCurrentDownEvent);
            MotionEvent e = MotionEvent.obtain(ev);
            e.setAction(mCurrentDoubleDownEvent.getAction());
            handled |= scaleGestureDetector.onTouchEvent(e);
            mCurrentMode = MODE_PINCH_ZOOM;
            break;
          }
          else
          {
            mScrollDetectionScore++;
            if (mScrollDetectionScore >= SCROLL_SCORE_TO_REACH)
              mCurrentMode = MODE_SCROLL;
          }
        }
 
        switch (mCurrentMode)
        {
          case MODE_PINCH_ZOOM:
            if (scaleGestureDetector != null)
              handled |= scaleGestureDetector.onTouchEvent(ev);
            break;
 
          case MODE_SCROLL:
            handled = mListener.onDoubleTouchScroll(mCurrentDownEvent, ev);
            break;
 
          default:
            handled = true;
            break;
        }
 
        break;
 
      case MotionEvent.ACTION_UP:
        // fingers were not removed equally? cancel
        if (mPreviousPointerUpEvent != null &&
            (ev.getEventTime() - mPreviousPointerUpEvent.getEventTime()) >
                DOUBLE_TOUCH_TIMEOUT)
        {
          mPreviousPointerUpEvent.recycle();
          mPreviousPointerUpEvent = null;
          cancel();
          break;
        }
 
        // detection cancelled or not active?
        if (mCancelDetection || !mDoubleInProgress)
          break;
 
        boolean hasTapEvent = mHandler.hasMessages(TAP);
        MotionEvent currentUpEvent = MotionEvent.obtain(ev);
        if (mCurrentMode == MODE_UNKNOWN && hasTapEvent)
          handled = mListener.onDoubleTouchSingleTap(mCurrentDoubleDownEvent);
        else if (mCurrentMode == MODE_PINCH_ZOOM)
          handled = scaleGestureDetector.onTouchEvent(ev);
 
        if (mPreviousUpEvent != null)
          mPreviousUpEvent.recycle();
 
        // Hold the event we obtained above - listeners may have changed the original.
        mPreviousUpEvent = currentUpEvent;
        handled |= mListener.onDoubleTouchUp(ev);
        break;
 
      case MotionEvent.ACTION_CANCEL:
        cancel();
        break;
    }
 
    if ((action == MotionEvent.ACTION_MOVE) && !handled)
      handled = true;
 
    return handled;
  }
 
  private void cancel()
  {
    mHandler.removeMessages(TAP);
    mCurrentMode = MODE_UNKNOWN;
    mCancelDetection = true;
    mDoubleInProgress = false;
  }
 
  // returns true of the distance between the two pointers changed
  private boolean pointerDistanceChanged(MotionEvent oldEvent, MotionEvent newEvent)
  {
    int deltaX1 = Math.abs((int)oldEvent.getX(0) - (int)oldEvent.getX(1));
    int deltaX2 = Math.abs((int)newEvent.getX(0) - (int)newEvent.getX(1));
    int distXSquare = (deltaX2 - deltaX1) * (deltaX2 - deltaX1);
 
    int deltaY1 = Math.abs((int)oldEvent.getY(0) - (int)oldEvent.getY(1));
    int deltaY2 = Math.abs((int)newEvent.getY(0) - (int)newEvent.getY(1));
    int distYSquare = (deltaY2 - deltaY1) * (deltaY2 - deltaY1);
 
    return (distXSquare + distYSquare) > mPointerDistanceSquare;
  }
 
  public interface OnDoubleGestureListener {
 
    boolean onDoubleTouchDown(MotionEvent e);
 
    boolean onDoubleTouchUp(MotionEvent e);
 
    boolean onDoubleTouchSingleTap(MotionEvent e);
 
    boolean onDoubleTouchScroll(MotionEvent e1, MotionEvent e2);
  }
 
  /*
  private void dumpEvent(MotionEvent event) {
         String names[] = { "DOWN" , "UP" , "MOVE" , "CANCEL" , "OUTSIDE" ,
            "POINTER_DOWN" , "POINTER_UP" , "7?" , "8?" , "9?" };
         StringBuilder sb = new StringBuilder();
         int action = event.getAction();
         int actionCode = action & MotionEvent.ACTION_MASK;
         sb.append("event ACTION_" ).append(names[actionCode]);
         if (actionCode == MotionEvent.ACTION_POINTER_DOWN
               || actionCode == MotionEvent.ACTION_POINTER_UP) {
            sb.append("(pid " ).append(
            action >> MotionEvent.ACTION_POINTER_ID_SHIFT);
            sb.append(")" );
         }
         sb.append("[" );
         for (int i = 0; i < event.getPointerCount(); i++) {
            sb.append("#" ).append(i);
            sb.append("(pid " ).append(event.getPointerId(i));
            sb.append(")=" ).append((int) event.getX(i));
            sb.append("," ).append((int) event.getY(i));
            if (i + 1 < event.getPointerCount())
               sb.append(";" );
         }
         sb.append("]" );
         Log.d("DoubleDetector", sb.toString());
      }
  */
 
  private class GestureHandler extends Handler
  {
    GestureHandler()
    {
      super();
    }
 
    GestureHandler(Handler handler)
    {
      super(handler.getLooper());
    }
  }
}