/*
* Copyright (C) 2010 Google Inc. All rights reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
// BACKPORTED FROM ANDROID PUBLIC REPOSITORY
package com.google.android.apps.tvremote.backport;
import android.annotation.SuppressLint;
import android.graphics.Rect;
import android.util.DisplayMetrics;
import android.util.FloatMath;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewConfiguration;
/**
* Detects transformation gestures involving more than one pointer
* ("multitouch") using the supplied {@link MotionEvent}s. The
* {@link OnScaleGestureListener} callback will notify users when a particular
* gesture event has occurred. This class should only be used with
* {@link MotionEvent}s reported via touch.
*
* To use this class:
* <ul>
* <li>Create an instance of the {@code ScaleGestureDetector} for your
* {@link View}
* <li>In the {@link View#onTouchEvent(MotionEvent)} method ensure you call
* {@link #onTouchEvent(MotionEvent)}. The methods defined in your callback will
* be executed when the events occur.
* </ul>
*
*/
@SuppressLint("FloatMath")
public class ScaleGestureDetectorImpl implements ScaleGestureDetector {
/**
* This value is the threshold ratio between our previous combined pressure
* and the current combined pressure. We will only fire an onScale event if
* the computed ratio between the current and previous event pressures is
* greater than this value. When pressure decreases rapidly between events the
* position values can often be imprecise, as it usually indicates that the
* user is in the process of lifting a pointer off of the device. Its value
* was tuned experimentally.
*/
private static final float PRESSURE_THRESHOLD = 0.67f;
private final View mView;
private final OnScaleGestureListener mListener;
private boolean mGestureInProgress;
private MotionEvent mPrevEvent;
private MotionEvent mCurrEvent;
private float mFocusX;
private float mFocusY;
private float mPrevFingerDiffX;
private float mPrevFingerDiffY;
private float mCurrFingerDiffX;
private float mCurrFingerDiffY;
private float mCurrLen;
private float mPrevLen;
private float mScaleFactor;
private float mCurrPressure;
private float mPrevPressure;
private long mTimeDelta;
private final float mEdgeSlop;
private float mRightSlopEdge;
private float mBottomSlopEdge;
private boolean mSloppyGesture;
public ScaleGestureDetectorImpl(View view, OnScaleGestureListener listener) {
ViewConfiguration config = ViewConfiguration.get(view.getContext());
mView = view;
mListener = listener;
mEdgeSlop = config.getScaledEdgeSlop();
}
@SuppressWarnings("deprecation")
public boolean onTouchEvent(MotionEvent event) {
final int action = event.getAction();
boolean handled = true;
Rect rect = new Rect();
if (!mView.getGlobalVisibleRect(rect)) {
return false;
}
if (!mGestureInProgress) {
switch (action & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_POINTER_DOWN: {
// We have a new multi-finger gesture
// as orientation can change, query the metrics in touch down
DisplayMetrics metrics =
mView.getContext().getResources().getDisplayMetrics();
mRightSlopEdge = metrics.widthPixels - mEdgeSlop;
mBottomSlopEdge = metrics.heightPixels - mEdgeSlop;
// Be paranoid in case we missed an event
reset();
mPrevEvent = MotionEvent.obtain(event);
mTimeDelta = 0;
setContext(event);
// Check if we have a sloppy gesture. If so, delay
// the beginning of the gesture until we're sure that's
// what the user wanted. Sloppy gestures can happen if the
// edge of the user's hand is touching the screen, for example.
final float edgeSlop = mEdgeSlop;
final float rightSlop = mRightSlopEdge;
final float bottomSlop = mBottomSlopEdge;
final float x0 = event.getRawX();
final float y0 = event.getRawY();
final float x1 = getRawX(event, 1, rect);
final float y1 = getRawY(event, 1, rect);
boolean p0sloppy = x0 < edgeSlop || y0 < edgeSlop || x0 > rightSlop
|| y0 > bottomSlop;
boolean p1sloppy = x1 < edgeSlop || y1 < edgeSlop || x1 > rightSlop
|| y1 > bottomSlop;
if (p0sloppy && p1sloppy) {
mFocusX = -1;
mFocusY = -1;
mSloppyGesture = true;
} else if (p0sloppy) {
mFocusX = event.getX(1);
mFocusY = event.getY(1);
mSloppyGesture = true;
} else if (p1sloppy) {
mFocusX = event.getX(0);
mFocusY = event.getY(0);
mSloppyGesture = true;
} else {
mGestureInProgress = mListener.onScaleBegin(this);
}
}
break;
case MotionEvent.ACTION_MOVE:
if (mSloppyGesture) {
// Initiate sloppy gestures if we've moved outside of the slop area.
final float edgeSlop = mEdgeSlop;
final float rightSlop = mRightSlopEdge;
final float bottomSlop = mBottomSlopEdge;
final float x0 = event.getRawX();
final float y0 = event.getRawY();
final float x1 = getRawX(event, 1, rect);
final float y1 = getRawY(event, 1, rect);
boolean p0sloppy = x0 < edgeSlop || y0 < edgeSlop || x0 > rightSlop
|| y0 > bottomSlop;
boolean p1sloppy = x1 < edgeSlop || y1 < edgeSlop || x1 > rightSlop
|| y1 > bottomSlop;
if (p0sloppy && p1sloppy) {
mFocusX = -1;
mFocusY = -1;
} else if (p0sloppy) {
mFocusX = event.getX(1);
mFocusY = event.getY(1);
} else if (p1sloppy) {
mFocusX = event.getX(0);
mFocusY = event.getY(0);
} else {
mSloppyGesture = false;
mGestureInProgress = mListener.onScaleBegin(this);
}
}
break;
case MotionEvent.ACTION_POINTER_UP:
if (mSloppyGesture) {
// Set focus point to the remaining finger
int id =
(
((action & MotionEvent.ACTION_POINTER_ID_MASK)
>> MotionEvent.ACTION_POINTER_ID_SHIFT) == 0) ? 1 : 0;
mFocusX = event.getX(id);
mFocusY = event.getY(id);
}
break;
}
} else {
// Transform gesture in progress - attempt to handle it
switch (action & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_POINTER_UP:
// Gesture ended
setContext(event);
// Set focus point to the remaining finger
int id = (((action & MotionEvent.ACTION_POINTER_ID_MASK)
>> MotionEvent.ACTION_POINTER_ID_SHIFT) == 0) ? 1 : 0;
mFocusX = event.getX(id);
mFocusY = event.getY(id);
if (!mSloppyGesture) {
mListener.onScaleEnd(this);
}
reset();
break;
case MotionEvent.ACTION_CANCEL:
if (!mSloppyGesture) {
mListener.onScaleEnd(this);
}
reset();
break;
case MotionEvent.ACTION_MOVE:
setContext(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 (mCurrPressure / mPrevPressure > PRESSURE_THRESHOLD) {
final boolean updatePrevious = mListener.onScale(this);
if (updatePrevious) {
mPrevEvent.recycle();
mPrevEvent = MotionEvent.obtain(event);
}
}
break;
}
}
return handled;
}
/**
* MotionEvent has no getRawX(int) method; simulate it pending future API
* approval.
*/
private static float getRawX(
MotionEvent event, int pointerIndex, Rect viewRect) {
return event.getX(pointerIndex) + viewRect.left;
}
/**
* MotionEvent has no getRawY(int) method; simulate it pending future API
* approval.
*/
private static float getRawY(
MotionEvent event, int pointerIndex, Rect viewRect) {
return event.getY(pointerIndex) + viewRect.top;
}
private void setContext(MotionEvent curr) {
if (mCurrEvent != null) {
mCurrEvent.recycle();
}
mCurrEvent = MotionEvent.obtain(curr);
mCurrLen = -1;
mPrevLen = -1;
mScaleFactor = -1;
final MotionEvent prev = mPrevEvent;
final float px0 = prev.getX(0);
final float py0 = prev.getY(0);
final float px1 = prev.getX(1);
final float py1 = prev.getY(1);
final float cx0 = curr.getX(0);
final float cy0 = curr.getY(0);
final float cx1 = curr.getX(1);
final float cy1 = curr.getY(1);
final float pvx = px1 - px0;
final float pvy = py1 - py0;
final float cvx = cx1 - cx0;
final float cvy = cy1 - cy0;
mPrevFingerDiffX = pvx;
mPrevFingerDiffY = pvy;
mCurrFingerDiffX = cvx;
mCurrFingerDiffY = cvy;
mFocusX = cx0 + cvx * 0.5f;
mFocusY = cy0 + cvy * 0.5f;
mTimeDelta = curr.getEventTime() - prev.getEventTime();
mCurrPressure = curr.getPressure(0) + curr.getPressure(1);
mPrevPressure = prev.getPressure(0) + prev.getPressure(1);
}
private void reset() {
if (mPrevEvent != null) {
mPrevEvent.recycle();
mPrevEvent = null;
}
if (mCurrEvent != null) {
mCurrEvent.recycle();
mCurrEvent = null;
}
mSloppyGesture = false;
mGestureInProgress = false;
}
/**
* Returns {@code true} if a two-finger scale gesture is in progress.
*
* @return {@code true} if a scale gesture is in progress, {@code false}
* otherwise.
*/
public boolean isInProgress() {
return mGestureInProgress;
}
/**
* Get the X coordinate of the current gesture's focal point. If a gesture is
* in progress, the focal point is directly between the two pointers forming
* the gesture. If a gesture is ending, the focal point is the location of the
* remaining pointer on the screen. If {@link #isInProgress()} would return
* false, the result of this function is undefined.
*
* @return X coordinate of the focal point in pixels.
*/
public float getFocusX() {
return mFocusX;
}
/**
* Get the Y coordinate of the current gesture's focal point. If a gesture is
* in progress, the focal point is directly between the two pointers forming
* the gesture. If a gesture is ending, the focal point is the location of the
* remaining pointer on the screen. If {@link #isInProgress()} would return
* false, the result of this function is undefined.
*
* @return Y coordinate of the focal point in pixels.
*/
public float getFocusY() {
return mFocusY;
}
/**
* Return the current distance between the two pointers forming the gesture in
* progress.
*
* @return Distance between pointers in pixels.
*/
public float getCurrentSpan() {
if (mCurrLen == -1) {
final float cvx = mCurrFingerDiffX;
final float cvy = mCurrFingerDiffY;
mCurrLen = FloatMath.sqrt(cvx * cvx + cvy * cvy);
}
return mCurrLen;
}
/**
* Return the previous distance between the two pointers forming the gesture
* in progress.
*
* @return Previous distance between pointers in pixels.
*/
public float getPreviousSpan() {
if (mPrevLen == -1) {
final float pvx = mPrevFingerDiffX;
final float pvy = mPrevFingerDiffY;
mPrevLen = FloatMath.sqrt(pvx * pvx + pvy * pvy);
}
return mPrevLen;
}
/**
* Return the scaling factor from the previous scale event to the current
* event. This value is defined as ({@link #getCurrentSpan()} /
* {@link #getPreviousSpan()}).
*
* @return The current scaling factor.
*/
public float getScaleFactor() {
if (mScaleFactor == -1) {
mScaleFactor = getCurrentSpan() / getPreviousSpan();
}
return mScaleFactor;
}
/**
* Return the time difference in milliseconds between the previous accepted
* scaling event and the current scaling event.
*
* @return Time difference since the last scaling event in milliseconds.
*/
public long getTimeDelta() {
return mTimeDelta;
}
/**
* Return the event time of the current event being processed.
*
* @return Current event time in milliseconds.
*/
public long getEventTime() {
return mCurrEvent.getEventTime();
}
}