package com.qhm123.slide;
import android.content.Context;
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>
*/
public class ScaleGestureDetector {
public static final String TAG = ScaleGestureDetector.class.getSimpleName();
/**
* 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 SimpleOnScaleGestureListener}.
*
* An application will receive events in the following order:
* <ul>
* <li>One {@link OnScaleGestureListener#onScaleBegin(ScaleGestureDetector)}
* <li>Zero or more
* {@link OnScaleGestureListener#onScale(ScaleGestureDetector)}
* <li>One {@link OnScaleGestureListener#onScaleEnd(ScaleGestureDetector)}
* </ul>
*/
public interface OnScaleGestureListener {
/**
* Responds to scaling 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 scaling factors if the change is greater than 0.01.
*/
public boolean onScale(ScaleGestureDetector detector, float mx, float my);
/**
* Responds to the beginning of a scaling 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,
* onScaleBegin() may return false to ignore the rest of the
* gesture.
*/
public boolean onScaleBegin(ScaleGestureDetector detector);
/**
* Responds to the end of a scale gesture. Reported by existing pointers
* going up.
*
* Once a scale has ended, {@link ScaleGestureDetector#getFocusX()} and
* {@link ScaleGestureDetector#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 onScaleEnd(ScaleGestureDetector detector);
}
/**
* A convenience class to extend when you only want to listen for a subset
* of scaling-related events. This implements all methods in
* {@link OnScaleGestureListener} but does nothing.
* {@link OnScaleGestureListener#onScale(ScaleGestureDetector)} returns
* {@code false} so that a subclass can retrieve the accumulated scale
* factor in an overridden onScaleEnd.
* {@link OnScaleGestureListener#onScaleBegin(ScaleGestureDetector)} returns
* {@code true}.
*/
public static class SimpleOnScaleGestureListener implements
OnScaleGestureListener {
public boolean onScale(ScaleGestureDetector detector, float mx, float my) {
return false;
}
public boolean onScaleBegin(ScaleGestureDetector detector) {
return true;
}
public void onScaleEnd(ScaleGestureDetector detector) {
// Intentionally empty
}
}
/**
* 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 Context mContext;
private final OnScaleGestureListener mListener;
private boolean mGestureInProgress;
private MotionEvent mPrevEvent;
private MotionEvent mCurrEvent;
private float mMiddleX;
private float mMiddleY;
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 ScaleGestureDetector(Context context, OnScaleGestureListener 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) {
mSloppyGesture = true;
} else if (p0sloppy) {
mSloppyGesture = true;
} else if (p1sloppy) {
mSloppyGesture = true;
} else {
mGestureInProgress = mListener.onScaleBegin(this);
}
}
break;
case MotionEvent.ACTION_MOVE:
try {
if (mSloppyGesture) {
// Logger.d(TAG, "scale gesture move 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) {
} else if (p0sloppy) {
} else if (p1sloppy) {
} else {
mSloppyGesture = false;
mGestureInProgress = mListener.onScaleBegin(this);
}
}
} catch (Exception e) {
e.printStackTrace();
}
break;
case MotionEvent.ACTION_POINTER_UP:
if (mSloppyGesture) {
}
break;
}
} else {
// Transform gesture in progress - attempt to handle it
switch (action & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_POINTER_UP:
// Gesture ended
setContext(event);
if (!mSloppyGesture) {
mListener.onScaleEnd(this);
}
reset();
break;
case MotionEvent.ACTION_CANCEL:
if (!mSloppyGesture) {
mListener.onScaleEnd(this);
}
reset();
break;
case MotionEvent.ACTION_MOVE:
// Logger.d(TAG, "scale gesture move");
try {
setContext(event);
mMiddleX = (event.getX(0) + event.getX(1)) / 2;
mMiddleY = (event.getY(0) + event.getY(1)) / 2;
// 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,
mMiddleX, mMiddleY);
if (updatePrevious) {
mPrevEvent.recycle();
mPrevEvent = MotionEvent.obtain(event);
}
}
} catch (Exception e) {
e.printStackTrace();
}
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);
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;
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;
}
public float getMiddleX() {
return mMiddleX;
}
public float getMiddleY() {
return mMiddleY;
}
/**
* 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();
}
}