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package com.almeros.android.multitouch.gesturedetectors;
import android.content.Context;
import android.graphics.PointF;
import android.view.MotionEvent;
/**
* @author Almer Thie (code.almeros.com) Copyright (c) 2013, Almer Thie
* (code.almeros.com)
* <p>
* All rights reserved.
* <p>
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* <p>
* Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* <p>
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
* WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
public class MoveGestureDetector extends BaseGestureDetector {
/**
* Listener which must be implemented which is used by MoveGestureDetector
* to perform callbacks to any implementing class which is registered to a
* MoveGestureDetector via the constructor.
*
* @see MoveGestureDetector.SimpleOnMoveGestureListener
*/
public interface OnMoveGestureListener {
public boolean onMove(MoveGestureDetector detector);
public boolean onMoveBegin(MoveGestureDetector detector);
public void onMoveEnd(MoveGestureDetector detector);
}
/**
* Helper class which may be extended and where the methods may be
* implemented. This way it is not necessary to implement all methods of
* OnMoveGestureListener.
*/
public static class SimpleOnMoveGestureListener implements
OnMoveGestureListener {
public boolean onMove(MoveGestureDetector detector) {
return false;
}
public boolean onMoveBegin(MoveGestureDetector detector) {
return true;
}
public void onMoveEnd(MoveGestureDetector detector) {
// Do nothing, overridden implementation may be used
}
}
private static final PointF FOCUS_DELTA_ZERO = new PointF();
private final OnMoveGestureListener listener;
private PointF focusExternal = new PointF();
private PointF focusDeltaExternal = new PointF();
public MoveGestureDetector(Context context, OnMoveGestureListener listener) {
super(context);
this.listener = listener;
}
@Override
protected void handleStartProgressEvent(int actionCode, MotionEvent event) {
switch (actionCode) {
case MotionEvent.ACTION_DOWN:
resetState(); // In case we missed an UP/CANCEL event
prevEvent = MotionEvent.obtain(event);
timeDelta = 0;
updateStateByEvent(event);
break;
case MotionEvent.ACTION_MOVE:
gestureInProgress = listener.onMoveBegin(this);
break;
}
}
@Override
protected void handleInProgressEvent(int actionCode, MotionEvent event) {
switch (actionCode) {
case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_CANCEL:
listener.onMoveEnd(this);
resetState();
break;
case MotionEvent.ACTION_MOVE:
updateStateByEvent(event);
// Only accept the event if our relative pressure is within
// a certain limit. This can help filter shaky data as a
// finger is lifted.
if (currPressure / prevPressure > PRESSURE_THRESHOLD) {
final boolean updatePrevious = listener.onMove(this);
if (updatePrevious) {
prevEvent.recycle();
prevEvent = MotionEvent.obtain(event);
}
}
break;
}
}
protected void updateStateByEvent(MotionEvent curr) {
super.updateStateByEvent(curr);
final MotionEvent prev = prevEvent;
// Focus intenal
PointF currFocusInternal = determineFocalPoint(curr);
PointF prevFocusInternal = determineFocalPoint(prev);
// Focus external
// - Prevent skipping of focus delta when a finger is added or removed
boolean skipNextMoveEvent = prev.getPointerCount() != curr
.getPointerCount();
focusDeltaExternal = skipNextMoveEvent ? FOCUS_DELTA_ZERO
: new PointF(currFocusInternal.x - prevFocusInternal.x,
currFocusInternal.y - prevFocusInternal.y);
// - Don't directly use mFocusInternal (or skipping will occur). Add
// unskipped delta values to focusExternal instead.
focusExternal.x += focusDeltaExternal.x;
focusExternal.y += focusDeltaExternal.y;
}
/**
* Determine (multi)finger focal point (a.k.a. center point between all
* fingers)
*
* @param motionEvent a {@link MotionEvent} object.
* @return PointF focal point
*/
private PointF determineFocalPoint(MotionEvent motionEvent) {
// Number of fingers on screen
final int pCount = motionEvent.getPointerCount();
float x = 0.0f;
float y = 0.0f;
for (int i = 0; i < pCount; i++) {
x += motionEvent.getX(i);
y += motionEvent.getY(i);
}
return new PointF(x / pCount, y / pCount);
}
public float getFocusX() {
return focusExternal.x;
}
public float getFocusY() {
return focusExternal.y;
}
public PointF getFocusDelta() {
return focusDeltaExternal;
}
}
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