/*
* Copyright (C) 2010 The Android Open Source Project
*
* 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.
*/
package sofia.view;
import android.content.Context;
import android.util.DisplayMetrics;
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 OnRotateGestureListener}
* 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 RotateGestureDetector} 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>
*/
public class RotateGestureDetector
{
/**
* The listener for receiving notifications when gestures occur.
* If you want to listen for all the different gestures then implement
* this interface. If you only want to listen for a subset it might
* be easier to extend {@link SimpleOnRotateGestureListener}.
*
* An application will receive events in the following order:
* <ul>
* <li>One {@link OnRotateGestureListener#onRotateBegin(RotateGestureDetector)}
* <li>Zero or more {@link OnRotateGestureListener#onRotate(RotateGestureDetector)}
* <li>One {@link OnRotateGestureListener#onRotateEnd(RotateGestureDetector)}
* </ul>
*/
public interface OnRotateGestureListener {
/**
* Responds to rotation events for a gesture in progress.
* Reported by pointer motion.
*
* @param detector The detector reporting the event - use this to
* retrieve extended info about event state.
* @return Whether or not the detector should consider this event
* as handled. If an event was not handled, the detector
* will continue to accumulate movement until an event is
* handled. This can be useful if an application, for example,
* only wants to update rotation factors if the change is
* greater than 0.01.
*/
public boolean onRotate(RotateGestureDetector detector);
/**
* Responds to the beginning of a rotation gesture. Reported by
* new pointers going down.
*
* @param detector The detector reporting the event - use this to
* retrieve extended info about event state.
* @return Whether or not the detector should continue recognizing
* this gesture. For example, if a gesture is beginning
* with a focal point outside of a region where it makes
* sense, onRotateBegin() may return false to ignore the
* rest of the gesture.
*/
public boolean onRotateBegin(RotateGestureDetector detector);
/**
* Responds to the end of a rotation gesture. Reported by existing
* pointers going up.
*
* Once a rotation has ended, {@link RotateGestureDetector#getFocusX()}
* and {@link RotateGestureDetector#getFocusY()} will return the location
* of the pointer remaining on the screen.
*
* @param detector The detector reporting the event - use this to
* retrieve extended info about event state.
*/
public void onRotateEnd(RotateGestureDetector detector);
}
/**
* A convenience class to extend when you only want to listen for a subset
* of rotation-related events. This implements all methods in
* {@link OnRotateGestureListener} but does nothing.
* {@link OnRotateGestureListener#onRotate(RotateGestureDetector)} returns
* {@code false} so that a subclass can retrieve the accumulated rotation
* factor in an overridden onRotateEnd.
* {@link OnRotateGestureListener#onRotateBegin(RotateGestureDetector)} returns
* {@code true}.
*/
public static class SimpleOnRotateGestureListener implements OnRotateGestureListener {
public boolean onRotate(RotateGestureDetector detector) {
return false;
}
public boolean onRotateBegin(RotateGestureDetector detector) {
return true;
}
public void onRotateEnd(RotateGestureDetector detector) {
// Intentionally empty
}
}
/**
* This value is the threshold ratio between our previous combined pressure
* and the current combined pressure. We will only fire an onRotate 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 Context mContext;
private final OnRotateGestureListener 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 mCurrSlope;
private float mPrevSlope;
private float mRotation;
private float mCurrPressure;
private float mPrevPressure;
private long mTimeDelta;
private final float mEdgeSlop;
private float mRightSlopEdge;
private float mBottomSlopEdge;
private boolean mSloppyGesture;
public RotateGestureDetector(Context context, OnRotateGestureListener listener) {
ViewConfiguration config = ViewConfiguration.get(context);
mContext = context;
mListener = listener;
mEdgeSlop = config.getScaledEdgeSlop();
}
public boolean onTouchEvent(MotionEvent event) {
final int action = event.getAction();
boolean handled = true;
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 = mContext.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);
final float y1 = getRawY(event, 1);
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.onRotateBegin(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);
final float y1 = getRawY(event, 1);
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.onRotateBegin(this);
}
}
break;
case MotionEvent.ACTION_POINTER_UP:
if (mSloppyGesture) {
// Set focus point to the remaining finger
int id = (((action & MotionEvent.ACTION_POINTER_INDEX_MASK)
>> MotionEvent.ACTION_POINTER_INDEX_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_INDEX_MASK)
>> MotionEvent.ACTION_POINTER_INDEX_SHIFT) == 0) ? 1 : 0;
mFocusX = event.getX(id);
mFocusY = event.getY(id);
if (!mSloppyGesture) {
mListener.onRotateEnd(this);
}
reset();
break;
case MotionEvent.ACTION_CANCEL:
if (!mSloppyGesture) {
mListener.onRotateEnd(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.onRotate(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) {
float offset = event.getRawX() - event.getX();
return event.getX(pointerIndex) + offset;
}
/**
* MotionEvent has no getRawY(int) method; simulate it pending future API approval.
*/
private static float getRawY(MotionEvent event, int pointerIndex) {
float offset = event.getRawY() - event.getY();
return event.getY(pointerIndex) + offset;
}
private void setContext(MotionEvent curr) {
if (mCurrEvent != null) {
mCurrEvent.recycle();
}
mCurrEvent = MotionEvent.obtain(curr);
mCurrSlope = -1;
mPrevSlope = -1;
mRotation = -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 rotate gesture is in progress.
* @return {@code true} if a rotate 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 getCurrentSlope() {
if (mCurrSlope == -1) {
mCurrSlope = mCurrFingerDiffY / mCurrFingerDiffX;
}
return mCurrSlope;
}
/**
* Return the previous distance between the two pointers forming the
* gesture in progress.
*
* @return Previous distance between pointers in pixels.
*/
public float getPreviousSlope() {
if (mPrevSlope == -1) {
mPrevSlope = mPrevFingerDiffY / mPrevFingerDiffX;
}
return mPrevSlope;
}
/**
* Return the rotation factor from the previous rotation event to the current
* event. This value is defined as
* ({@link #getCurrentAngle()} / {@link #getPreviousAngle()}).
*
* @return The current rotation factor.
*/
public float getRotation() {
if (mRotation == -1) {
float prevAngle =
(float) Math.atan2(mPrevFingerDiffY, mPrevFingerDiffX);
float currAngle =
(float) Math.atan2(mCurrFingerDiffY, mCurrFingerDiffX);
mRotation = (float) ((currAngle - prevAngle) * 180 / Math.PI);
}
return mRotation;
}
/**
* Return the time difference in milliseconds between the previous
* accepted rotation event and the current rotation event.
*
* @return Time difference since the last rotation 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();
}
}