/*
 * Copyright (C) 2008 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 android.view;

import android.content.Context;
import android.os.Handler;
import android.os.Message;

Detects various gestures and events using the supplied MotionEvents. The OnGestureListener callback will notify users when a particular motion event has occurred. This class should only be used with MotionEvents reported via touch (don't use for trackball events). To use this class: 

 
Create an instance of the GestureDetector for your View 
In the View.onTouchEvent(MotionEvent) method ensure you call onTouchEvent(MotionEvent). The methods defined in your callback will be executed when the events occur. 
If listening for OnContextClickListener.onContextClick(MotionEvent) you must call onGenericMotionEvent(MotionEvent) in View.onGenericMotionEvent(MotionEvent). 
/**
 * Detects various gestures and events using the supplied {@link MotionEvent}s.
 * The {@link OnGestureListener} callback will notify users when a particular
 * motion event has occurred. This class should only be used with {@link MotionEvent}s
 * reported via touch (don't use for trackball events).
 *
 * To use this class:
 * <ul>
 *  <li>Create an instance of the {@code GestureDetector} 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.
 *  <li>If listening for {@link OnContextClickListener#onContextClick(MotionEvent)}
 *          you must call {@link #onGenericMotionEvent(MotionEvent)}
 *          in {@link View#onGenericMotionEvent(MotionEvent)}.
 * </ul>
 */
public class GestureDetector {
    
The listener that is used to notify 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 SimpleOnGestureListener. /**
     * The listener that is used to notify 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 SimpleOnGestureListener}.
     */
    public interface OnGestureListener {

        
Notified when a tap occurs with the down MotionEvent that triggered it. This will be triggered immediately for every down event. All other events should be preceded by this. 
Params:
e – The down motion event./**
         * Notified when a tap occurs with the down {@link MotionEvent}
         * that triggered it. This will be triggered immediately for
         * every down event. All other events should be preceded by this.
         *
         * @param e The down motion event.
         */
        boolean onDown(MotionEvent e);

        
The user has performed a down MotionEvent and not performed a move or up yet. This event is commonly used to provide visual feedback to the user to let them know that their action has been recognized i.e. highlight an element. 
Params:
e – The down motion event/**
         * The user has performed a down {@link MotionEvent} and not performed
         * a move or up yet. This event is commonly used to provide visual
         * feedback to the user to let them know that their action has been
         * recognized i.e. highlight an element.
         *
         * @param e The down motion event
         */
        void onShowPress(MotionEvent e);

        
Notified when a tap occurs with the up MotionEvent that triggered it. 
Params:
e – The up motion event that completed the first tap
Returns:
true if the event is consumed, else false/**
         * Notified when a tap occurs with the up {@link MotionEvent}
         * that triggered it.
         *
         * @param e The up motion event that completed the first tap
         * @return true if the event is consumed, else false
         */
        boolean onSingleTapUp(MotionEvent e);

        
Notified when a scroll occurs with the initial on down MotionEvent and the current move MotionEvent. The distance in x and y is also supplied for convenience. 
Params:
e1 – The first down motion event that started the scrolling.
e2 – The move motion event that triggered the current onScroll.
distanceX – The distance along the X axis that has been scrolled since the last call to onScroll. This is NOT the distance between e1 and e2.
distanceY – The distance along the Y axis that has been scrolled since the last call to onScroll. This is NOT the distance between e1 and e2.
Returns:
true if the event is consumed, else false/**
         * Notified when a scroll occurs with the initial on down {@link MotionEvent} and the
         * current move {@link MotionEvent}. The distance in x and y is also supplied for
         * convenience.
         *
         * @param e1 The first down motion event that started the scrolling.
         * @param e2 The move motion event that triggered the current onScroll.
         * @param distanceX The distance along the X axis that has been scrolled since the last
         *              call to onScroll. This is NOT the distance between {@code e1}
         *              and {@code e2}.
         * @param distanceY The distance along the Y axis that has been scrolled since the last
         *              call to onScroll. This is NOT the distance between {@code e1}
         *              and {@code e2}.
         * @return true if the event is consumed, else false
         */
        boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY);

        
Notified when a long press occurs with the initial on down MotionEvent that trigged it. 
Params:
e – The initial on down motion event that started the longpress./**
         * Notified when a long press occurs with the initial on down {@link MotionEvent}
         * that trigged it.
         *
         * @param e The initial on down motion event that started the longpress.
         */
        void onLongPress(MotionEvent e);

        
Notified of a fling event when it occurs with the initial on down MotionEvent and the matching up MotionEvent. The calculated velocity is supplied along the x and y axis in pixels per second. 
Params:
e1 – The first down motion event that started the fling.
e2 – The move motion event that triggered the current onFling.
velocityX – The velocity of this fling measured in pixels per second
             along the x axis.
velocityY – The velocity of this fling measured in pixels per second
             along the y axis.
Returns:
true if the event is consumed, else false/**
         * Notified of a fling event when it occurs with the initial on down {@link MotionEvent}
         * and the matching up {@link MotionEvent}. The calculated velocity is supplied along
         * the x and y axis in pixels per second.
         *
         * @param e1 The first down motion event that started the fling.
         * @param e2 The move motion event that triggered the current onFling.
         * @param velocityX The velocity of this fling measured in pixels per second
         *              along the x axis.
         * @param velocityY The velocity of this fling measured in pixels per second
         *              along the y axis.
         * @return true if the event is consumed, else false
         */
        boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY);
    }

    
The listener that is used to notify when a double-tap or a confirmed
single-tap occur.
/**
     * The listener that is used to notify when a double-tap or a confirmed
     * single-tap occur.
     */
    public interface OnDoubleTapListener {
        
Notified when a single-tap occurs.
 Unlike OnGestureListener.onSingleTapUp(MotionEvent), this will only be called after the detector is confident that the user's first tap is not followed by a second tap leading to a double-tap gesture. 
Params:
e – The down motion event of the single-tap.
Returns:
true if the event is consumed, else false/**
         * Notified when a single-tap occurs.
         * <p>
         * Unlike {@link OnGestureListener#onSingleTapUp(MotionEvent)}, this
         * will only be called after the detector is confident that the user's
         * first tap is not followed by a second tap leading to a double-tap
         * gesture.
         *
         * @param e The down motion event of the single-tap.
         * @return true if the event is consumed, else false
         */
        boolean onSingleTapConfirmed(MotionEvent e);
 
        
Notified when a double-tap occurs.
Params:
e – The down motion event of the first tap of the double-tap.
Returns:
true if the event is consumed, else false/**
         * Notified when a double-tap occurs.
         *
         * @param e The down motion event of the first tap of the double-tap.
         * @return true if the event is consumed, else false
         */
        boolean onDoubleTap(MotionEvent e);

        
Notified when an event within a double-tap gesture occurs, including
the down, move, and up events.
Params:
e – The motion event that occurred during the double-tap gesture.
Returns:
true if the event is consumed, else false/**
         * Notified when an event within a double-tap gesture occurs, including
         * the down, move, and up events.
         *
         * @param e The motion event that occurred during the double-tap gesture.
         * @return true if the event is consumed, else false
         */
        boolean onDoubleTapEvent(MotionEvent e);
    }

    
The listener that is used to notify when a context click occurs. When listening for a context click ensure that you call GestureDetector.onGenericMotionEvent(MotionEvent) in View.onGenericMotionEvent(MotionEvent). /**
     * The listener that is used to notify when a context click occurs. When listening for a
     * context click ensure that you call {@link #onGenericMotionEvent(MotionEvent)} in
     * {@link View#onGenericMotionEvent(MotionEvent)}.
     */
    public interface OnContextClickListener {
        
Notified when a context click occurs.
Params:
e – The motion event that occurred during the context click.
Returns:
true if the event is consumed, else false/**
         * Notified when a context click occurs.
         *
         * @param e The motion event that occurred during the context click.
         * @return true if the event is consumed, else false
         */
        boolean onContextClick(MotionEvent e);
    }

    
A convenience class to extend when you only want to listen for a subset of all the gestures. This implements all methods in the OnGestureListener, OnDoubleTapListener, and OnContextClickListener but does nothing and return false for all applicable methods. /**
     * A convenience class to extend when you only want to listen for a subset
     * of all the gestures. This implements all methods in the
     * {@link OnGestureListener}, {@link OnDoubleTapListener}, and {@link OnContextClickListener}
     * but does nothing and return {@code false} for all applicable methods.
     */
    public static class SimpleOnGestureListener implements OnGestureListener, OnDoubleTapListener,
            OnContextClickListener {

        public boolean onSingleTapUp(MotionEvent e) {
            return false;
        }

        public void onLongPress(MotionEvent e) {
        }

        public boolean onScroll(MotionEvent e1, MotionEvent e2,
                float distanceX, float distanceY) {
            return false;
        }

        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
                float velocityY) {
            return false;
        }

        public void onShowPress(MotionEvent e) {
        }

        public boolean onDown(MotionEvent e) {
            return false;
        }

        public boolean onDoubleTap(MotionEvent e) {
            return false;
        }

        public boolean onDoubleTapEvent(MotionEvent e) {
            return false;
        }

        public boolean onSingleTapConfirmed(MotionEvent e) {
            return false;
        }

        public boolean onContextClick(MotionEvent e) {
            return false;
        }
    }

    private int mTouchSlopSquare;
    private int mDoubleTapTouchSlopSquare;
    private int mDoubleTapSlopSquare;
    private int mMinimumFlingVelocity;
    private int mMaximumFlingVelocity;

    private static final int LONGPRESS_TIMEOUT = ViewConfiguration.getLongPressTimeout();
    private static final int TAP_TIMEOUT = ViewConfiguration.getTapTimeout();
    private static final int DOUBLE_TAP_TIMEOUT = ViewConfiguration.getDoubleTapTimeout();
    private static final int DOUBLE_TAP_MIN_TIME = ViewConfiguration.getDoubleTapMinTime();

    // constants for Message.what used by GestureHandler below
    private static final int SHOW_PRESS = 1;
    private static final int LONG_PRESS = 2;
    private static final int TAP = 3;

    private final Handler mHandler;
    private final OnGestureListener mListener;
    private OnDoubleTapListener mDoubleTapListener;
    private OnContextClickListener mContextClickListener;

    private boolean mStillDown;
    private boolean mDeferConfirmSingleTap;
    private boolean mInLongPress;
    private boolean mInContextClick;
    private boolean mAlwaysInTapRegion;
    private boolean mAlwaysInBiggerTapRegion;
    private boolean mIgnoreNextUpEvent;

    private MotionEvent mCurrentDownEvent;
    private MotionEvent mPreviousUpEvent;

    
True when the user is still touching for the second tap (down, move, and
up events). Can only be true if there is a double tap listener attached.
/**
     * True when the user is still touching for the second tap (down, move, and
     * up events). Can only be true if there is a double tap listener attached.
     */
    private boolean mIsDoubleTapping;

    private float mLastFocusX;
    private float mLastFocusY;
    private float mDownFocusX;
    private float mDownFocusY;

    private boolean mIsLongpressEnabled;

    
Determines speed during touch scrolling
/**
     * Determines speed during touch scrolling
     */
    private VelocityTracker mVelocityTracker;

    
Consistency verifier for debugging purposes.
/**
     * Consistency verifier for debugging purposes.
     */
    private final InputEventConsistencyVerifier mInputEventConsistencyVerifier =
            InputEventConsistencyVerifier.isInstrumentationEnabled() ?
                    new InputEventConsistencyVerifier(this, 0) : null;

    private class GestureHandler extends Handler {
        GestureHandler() {
            super();
        }

        GestureHandler(Handler handler) {
            super(handler.getLooper());
        }

        @Override
        public void handleMessage(Message msg) {
            switch (msg.what) {
            case SHOW_PRESS:
                mListener.onShowPress(mCurrentDownEvent);
                break;
                
            case LONG_PRESS:
                dispatchLongPress();
                break;
                
            case TAP:
                // If the user's finger is still down, do not count it as a tap
                if (mDoubleTapListener != null) {
                    if (!mStillDown) {
                        mDoubleTapListener.onSingleTapConfirmed(mCurrentDownEvent);
                    } else {
                        mDeferConfirmSingleTap = true;
                    }
                }
                break;

            default:
                throw new RuntimeException("Unknown message " + msg); //never
            }
        }
    }

    
Creates a GestureDetector with the supplied listener.
This variant of the constructor should be used from a non-UI thread 
(as it allows specifying the Handler).
Params:
listener – the listener invoked for all the callbacks, this must
not be null.
handler – the handler to use
Throws:
NullPointerException – if either listener or handler is null.
Deprecated:
Use GestureDetector(Context, OnGestureListener, Handler) instead./**
     * Creates a GestureDetector with the supplied listener.
     * This variant of the constructor should be used from a non-UI thread 
     * (as it allows specifying the Handler).
     * 
     * @param listener the listener invoked for all the callbacks, this must
     * not be null.
     * @param handler the handler to use
     *
     * @throws NullPointerException if either {@code listener} or
     * {@code handler} is null.
     *
     * @deprecated Use {@link #GestureDetector(android.content.Context,
     *      android.view.GestureDetector.OnGestureListener, android.os.Handler)} instead.
     */
    @Deprecated
    public GestureDetector(OnGestureListener listener, Handler handler) {
        this(null, listener, handler);
    }

    
Creates a GestureDetector with the supplied listener.
You may only use this constructor from a UI thread (this is the usual situation).
Params:
listener – the listener invoked for all the callbacks, this must
not be null.
Throws:
NullPointerException – if listener is null.
See Also:
Handler.Handler()
Deprecated:
Use GestureDetector(Context, OnGestureListener) instead./**
     * Creates a GestureDetector with the supplied listener.
     * You may only use this constructor from a UI thread (this is the usual situation).
     * @see android.os.Handler#Handler()
     * 
     * @param listener the listener invoked for all the callbacks, this must
     * not be null.
     * 
     * @throws NullPointerException if {@code listener} is null.
     *
     * @deprecated Use {@link #GestureDetector(android.content.Context,
     *      android.view.GestureDetector.OnGestureListener)} instead.
     */
    @Deprecated
    public GestureDetector(OnGestureListener listener) {
        this(null, listener, null);
    }

    
Creates a GestureDetector with the supplied listener. You may only use this constructor from a Looper thread. 
Params:
context – the application's context
listener – the listener invoked for all the callbacks, this must
not be null.
Throws:
NullPointerException – if listener is null.
See Also:
Handler()/**
     * Creates a GestureDetector with the supplied listener.
     * You may only use this constructor from a {@link android.os.Looper} thread.
     * @see android.os.Handler#Handler()
     *
     * @param context the application's context
     * @param listener the listener invoked for all the callbacks, this must
     * not be null.
     *
     * @throws NullPointerException if {@code listener} is null.
     */
    public GestureDetector(Context context, OnGestureListener listener) {
        this(context, listener, null);
    }

    
Creates a GestureDetector with the supplied listener that runs deferred events on the thread associated with the supplied Handler. 
Params:
context – the application's context
listener – the listener invoked for all the callbacks, this must
not be null.
handler – the handler to use for running deferred listener events.
Throws:
NullPointerException – if listener is null.
See Also:
Handler()/**
     * Creates a GestureDetector with the supplied listener that runs deferred events on the
     * thread associated with the supplied {@link android.os.Handler}.
     * @see android.os.Handler#Handler()
     *
     * @param context the application's context
     * @param listener the listener invoked for all the callbacks, this must
     * not be null.
     * @param handler the handler to use for running deferred listener events.
     *
     * @throws NullPointerException if {@code listener} is null.
     */
    public GestureDetector(Context context, OnGestureListener listener, Handler handler) {
        if (handler != null) {
            mHandler = new GestureHandler(handler);
        } else {
            mHandler = new GestureHandler();
        }
        mListener = listener;
        if (listener instanceof OnDoubleTapListener) {
            setOnDoubleTapListener((OnDoubleTapListener) listener);
        }
        if (listener instanceof OnContextClickListener) {
            setContextClickListener((OnContextClickListener) listener);
        }
        init(context);
    }
    
    
Creates a GestureDetector with the supplied listener that runs deferred events on the thread associated with the supplied Handler. 
Params:
context – the application's context
listener – the listener invoked for all the callbacks, this must
not be null.
handler – the handler to use for running deferred listener events.
unused – currently not used.
Throws:
NullPointerException – if listener is null.
See Also:
Handler()/**
     * Creates a GestureDetector with the supplied listener that runs deferred events on the
     * thread associated with the supplied {@link android.os.Handler}.
     * @see android.os.Handler#Handler()
     *
     * @param context the application's context
     * @param listener the listener invoked for all the callbacks, this must
     * not be null.
     * @param handler the handler to use for running deferred listener events.
     * @param unused currently not used.
     *
     * @throws NullPointerException if {@code listener} is null.
     */
    public GestureDetector(Context context, OnGestureListener listener, Handler handler,
            boolean unused) {
        this(context, listener, handler);
    }

    private void init(Context context) {
        if (mListener == null) {
            throw new NullPointerException("OnGestureListener must not be null");
        }
        mIsLongpressEnabled = true;

        // Fallback to support pre-donuts releases
        int touchSlop, doubleTapSlop, doubleTapTouchSlop;
        if (context == null) {
            //noinspection deprecation
            touchSlop = ViewConfiguration.getTouchSlop();
            doubleTapTouchSlop = touchSlop; // Hack rather than adding a hiden method for this
            doubleTapSlop = ViewConfiguration.getDoubleTapSlop();
            //noinspection deprecation
            mMinimumFlingVelocity = ViewConfiguration.getMinimumFlingVelocity();
            mMaximumFlingVelocity = ViewConfiguration.getMaximumFlingVelocity();
        } else {
            final ViewConfiguration configuration = ViewConfiguration.get(context);
            touchSlop = configuration.getScaledTouchSlop();
            doubleTapTouchSlop = configuration.getScaledDoubleTapTouchSlop();
            doubleTapSlop = configuration.getScaledDoubleTapSlop();
            mMinimumFlingVelocity = configuration.getScaledMinimumFlingVelocity();
            mMaximumFlingVelocity = configuration.getScaledMaximumFlingVelocity();
        }
        mTouchSlopSquare = touchSlop * touchSlop;
        mDoubleTapTouchSlopSquare = doubleTapTouchSlop * doubleTapTouchSlop;
        mDoubleTapSlopSquare = doubleTapSlop * doubleTapSlop;
    }

    
Sets the listener which will be called for double-tap and related
gestures.
Params:
onDoubleTapListener – the listener invoked for all the callbacks, or
       null to stop listening for double-tap gestures./**
     * Sets the listener which will be called for double-tap and related
     * gestures.
     * 
     * @param onDoubleTapListener the listener invoked for all the callbacks, or
     *        null to stop listening for double-tap gestures.
     */
    public void setOnDoubleTapListener(OnDoubleTapListener onDoubleTapListener) {
        mDoubleTapListener = onDoubleTapListener;
    }

    
Sets the listener which will be called for context clicks.
Params:
onContextClickListener – the listener invoked for all the callbacks, or null to stop
           listening for context clicks./**
     * Sets the listener which will be called for context clicks.
     *
     * @param onContextClickListener the listener invoked for all the callbacks, or null to stop
     *            listening for context clicks.
     */
    public void setContextClickListener(OnContextClickListener onContextClickListener) {
        mContextClickListener = onContextClickListener;
    }

    
Set whether longpress is enabled, if this is enabled when a user
presses and holds down you get a longpress event and nothing further.
If it's disabled the user can press and hold down and then later
moved their finger and you will get scroll events. By default
longpress is enabled.
Params:
isLongpressEnabled – whether longpress should be enabled./**
     * Set whether longpress is enabled, if this is enabled when a user
     * presses and holds down you get a longpress event and nothing further.
     * If it's disabled the user can press and hold down and then later
     * moved their finger and you will get scroll events. By default
     * longpress is enabled.
     *
     * @param isLongpressEnabled whether longpress should be enabled.
     */
    public void setIsLongpressEnabled(boolean isLongpressEnabled) {
        mIsLongpressEnabled = isLongpressEnabled;
    }

    
Returns:
true if longpress is enabled, else false./**
     * @return true if longpress is enabled, else false.
     */
    public boolean isLongpressEnabled() {
        return mIsLongpressEnabled;
    }

    
Analyzes the given motion event and if applicable triggers the appropriate callbacks on the OnGestureListener supplied. 
Params:
ev – The current motion event.
Returns:
true if the OnGestureListener consumed the event, else false./**
     * Analyzes the given motion event and if applicable triggers the
     * appropriate callbacks on the {@link OnGestureListener} supplied.
     *
     * @param ev The current motion event.
     * @return true if the {@link OnGestureListener} consumed the event,
     *              else false.
     */
    public boolean onTouchEvent(MotionEvent ev) {
        if (mInputEventConsistencyVerifier != null) {
            mInputEventConsistencyVerifier.onTouchEvent(ev, 0);
        }

        final int action = ev.getAction();

        if (mVelocityTracker == null) {
            mVelocityTracker = VelocityTracker.obtain();
        }
        mVelocityTracker.addMovement(ev);

        final boolean pointerUp =
                (action & MotionEvent.ACTION_MASK) == MotionEvent.ACTION_POINTER_UP;
        final int skipIndex = pointerUp ? ev.getActionIndex() : -1;
        final boolean isGeneratedGesture =
                (ev.getFlags() & MotionEvent.FLAG_IS_GENERATED_GESTURE) != 0;

        // Determine focal point
        float sumX = 0, sumY = 0;
        final int count = ev.getPointerCount();
        for (int i = 0; i < count; i++) {
            if (skipIndex == i) continue;
            sumX += ev.getX(i);
            sumY += ev.getY(i);
        }
        final int div = pointerUp ? count - 1 : count;
        final float focusX = sumX / div;
        final float focusY = sumY / div;

        boolean handled = false;

        switch (action & MotionEvent.ACTION_MASK) {
            case MotionEvent.ACTION_POINTER_DOWN:
                mDownFocusX = mLastFocusX = focusX;
                mDownFocusY = mLastFocusY = focusY;
                // Cancel long press and taps
                cancelTaps();
                break;

            case MotionEvent.ACTION_POINTER_UP:
                mDownFocusX = mLastFocusX = focusX;
                mDownFocusY = mLastFocusY = focusY;

                // Check the dot product of current velocities.
                // If the pointer that left was opposing another velocity vector, clear.
                mVelocityTracker.computeCurrentVelocity(1000, mMaximumFlingVelocity);
                final int upIndex = ev.getActionIndex();
                final int id1 = ev.getPointerId(upIndex);
                final float x1 = mVelocityTracker.getXVelocity(id1);
                final float y1 = mVelocityTracker.getYVelocity(id1);
                for (int i = 0; i < count; i++) {
                    if (i == upIndex) continue;

                    final int id2 = ev.getPointerId(i);
                    final float x = x1 * mVelocityTracker.getXVelocity(id2);
                    final float y = y1 * mVelocityTracker.getYVelocity(id2);

                    final float dot = x + y;
                    if (dot < 0) {
                        mVelocityTracker.clear();
                        break;
                    }
                }
                break;

            case MotionEvent.ACTION_DOWN:
                if (mDoubleTapListener != null) {
                    boolean hadTapMessage = mHandler.hasMessages(TAP);
                    if (hadTapMessage) mHandler.removeMessages(TAP);
                    if ((mCurrentDownEvent != null) && (mPreviousUpEvent != null)
                            && hadTapMessage
                            && isConsideredDoubleTap(mCurrentDownEvent, mPreviousUpEvent, ev)) {
                        // This is a second tap
                        mIsDoubleTapping = true;
                        // Give a callback with the first tap of the double-tap
                        handled |= mDoubleTapListener.onDoubleTap(mCurrentDownEvent);
                        // Give a callback with down event of the double-tap
                        handled |= mDoubleTapListener.onDoubleTapEvent(ev);
                    } else {
                        // This is a first tap
                        mHandler.sendEmptyMessageDelayed(TAP, DOUBLE_TAP_TIMEOUT);
                    }
                }

                mDownFocusX = mLastFocusX = focusX;
                mDownFocusY = mLastFocusY = focusY;
                if (mCurrentDownEvent != null) {
                    mCurrentDownEvent.recycle();
                }
                mCurrentDownEvent = MotionEvent.obtain(ev);
                mAlwaysInTapRegion = true;
                mAlwaysInBiggerTapRegion = true;
                mStillDown = true;
                mInLongPress = false;
                mDeferConfirmSingleTap = false;

                if (mIsLongpressEnabled) {
                    mHandler.removeMessages(LONG_PRESS);
                    mHandler.sendEmptyMessageAtTime(LONG_PRESS,
                            mCurrentDownEvent.getDownTime() + LONGPRESS_TIMEOUT);
                }
                mHandler.sendEmptyMessageAtTime(SHOW_PRESS,
                        mCurrentDownEvent.getDownTime() + TAP_TIMEOUT);
                handled |= mListener.onDown(ev);
                break;

            case MotionEvent.ACTION_MOVE:
                if (mInLongPress || mInContextClick) {
                    break;
                }
                final float scrollX = mLastFocusX - focusX;
                final float scrollY = mLastFocusY - focusY;
                if (mIsDoubleTapping) {
                    // Give the move events of the double-tap
                    handled |= mDoubleTapListener.onDoubleTapEvent(ev);
                } else if (mAlwaysInTapRegion) {
                    final int deltaX = (int) (focusX - mDownFocusX);
                    final int deltaY = (int) (focusY - mDownFocusY);
                    int distance = (deltaX * deltaX) + (deltaY * deltaY);
                    int slopSquare = isGeneratedGesture ? 0 : mTouchSlopSquare;
                    if (distance > slopSquare) {
                        handled = mListener.onScroll(mCurrentDownEvent, ev, scrollX, scrollY);
                        mLastFocusX = focusX;
                        mLastFocusY = focusY;
                        mAlwaysInTapRegion = false;
                        mHandler.removeMessages(TAP);
                        mHandler.removeMessages(SHOW_PRESS);
                        mHandler.removeMessages(LONG_PRESS);
                    }
                    int doubleTapSlopSquare = isGeneratedGesture ? 0 : mDoubleTapTouchSlopSquare;
                    if (distance > doubleTapSlopSquare) {
                        mAlwaysInBiggerTapRegion = false;
                    }
                } else if ((Math.abs(scrollX) >= 1) || (Math.abs(scrollY) >= 1)) {
                    handled = mListener.onScroll(mCurrentDownEvent, ev, scrollX, scrollY);
                    mLastFocusX = focusX;
                    mLastFocusY = focusY;
                }
                break;

            case MotionEvent.ACTION_UP:
                mStillDown = false;
                MotionEvent currentUpEvent = MotionEvent.obtain(ev);
                if (mIsDoubleTapping) {
                    // Finally, give the up event of the double-tap
                    handled |= mDoubleTapListener.onDoubleTapEvent(ev);
                } else if (mInLongPress) {
                    mHandler.removeMessages(TAP);
                    mInLongPress = false;
                } else if (mAlwaysInTapRegion && !mIgnoreNextUpEvent) {
                    handled = mListener.onSingleTapUp(ev);
                    if (mDeferConfirmSingleTap && mDoubleTapListener != null) {
                        mDoubleTapListener.onSingleTapConfirmed(ev);
                    }
                } else if (!mIgnoreNextUpEvent) {

                    // A fling must travel the minimum tap distance
                    final VelocityTracker velocityTracker = mVelocityTracker;
                    final int pointerId = ev.getPointerId(0);
                    velocityTracker.computeCurrentVelocity(1000, mMaximumFlingVelocity);
                    final float velocityY = velocityTracker.getYVelocity(pointerId);
                    final float velocityX = velocityTracker.getXVelocity(pointerId);

                    if ((Math.abs(velocityY) > mMinimumFlingVelocity)
                            || (Math.abs(velocityX) > mMinimumFlingVelocity)) {
                        handled = mListener.onFling(mCurrentDownEvent, ev, velocityX, velocityY);
                    }
                }
                if (mPreviousUpEvent != null) {
                    mPreviousUpEvent.recycle();
                }
                // Hold the event we obtained above - listeners may have changed the original.
                mPreviousUpEvent = currentUpEvent;
                if (mVelocityTracker != null) {
                    // This may have been cleared when we called out to the
                    // application above.
                    mVelocityTracker.recycle();
                    mVelocityTracker = null;
                }
                mIsDoubleTapping = false;
                mDeferConfirmSingleTap = false;
                mIgnoreNextUpEvent = false;
                mHandler.removeMessages(SHOW_PRESS);
                mHandler.removeMessages(LONG_PRESS);
                break;

            case MotionEvent.ACTION_CANCEL:
                cancel();
                break;
        }

        if (!handled && mInputEventConsistencyVerifier != null) {
            mInputEventConsistencyVerifier.onUnhandledEvent(ev, 0);
        }
        return handled;
    }

    
Analyzes the given generic motion event and if applicable triggers the appropriate callbacks on the OnGestureListener supplied. 
Params:
ev – The current motion event.
Returns:
true if the OnGestureListener consumed the event, else false./**
     * Analyzes the given generic motion event and if applicable triggers the
     * appropriate callbacks on the {@link OnGestureListener} supplied.
     *
     * @param ev The current motion event.
     * @return true if the {@link OnGestureListener} consumed the event,
     *              else false.
     */
    public boolean onGenericMotionEvent(MotionEvent ev) {
        if (mInputEventConsistencyVerifier != null) {
            mInputEventConsistencyVerifier.onGenericMotionEvent(ev, 0);
        }

        final int actionButton = ev.getActionButton();
        switch (ev.getActionMasked()) {
            case MotionEvent.ACTION_BUTTON_PRESS:
                if (mContextClickListener != null && !mInContextClick && !mInLongPress
                        && (actionButton == MotionEvent.BUTTON_STYLUS_PRIMARY
                        || actionButton == MotionEvent.BUTTON_SECONDARY)) {
                    if (mContextClickListener.onContextClick(ev)) {
                        mInContextClick = true;
                        mHandler.removeMessages(LONG_PRESS);
                        mHandler.removeMessages(TAP);
                        return true;
                    }
                }
                break;

            case MotionEvent.ACTION_BUTTON_RELEASE:
                if (mInContextClick && (actionButton == MotionEvent.BUTTON_STYLUS_PRIMARY
                        || actionButton == MotionEvent.BUTTON_SECONDARY)) {
                    mInContextClick = false;
                    mIgnoreNextUpEvent = true;
                }
                break;
        }
        return false;
    }

    private void cancel() {
        mHandler.removeMessages(SHOW_PRESS);
        mHandler.removeMessages(LONG_PRESS);
        mHandler.removeMessages(TAP);
        mVelocityTracker.recycle();
        mVelocityTracker = null;
        mIsDoubleTapping = false;
        mStillDown = false;
        mAlwaysInTapRegion = false;
        mAlwaysInBiggerTapRegion = false;
        mDeferConfirmSingleTap = false;
        mInLongPress = false;
        mInContextClick = false;
        mIgnoreNextUpEvent = false;
    }

    private void cancelTaps() {
        mHandler.removeMessages(SHOW_PRESS);
        mHandler.removeMessages(LONG_PRESS);
        mHandler.removeMessages(TAP);
        mIsDoubleTapping = false;
        mAlwaysInTapRegion = false;
        mAlwaysInBiggerTapRegion = false;
        mDeferConfirmSingleTap = false;
        mInLongPress = false;
        mInContextClick = false;
        mIgnoreNextUpEvent = false;
    }

    private boolean isConsideredDoubleTap(MotionEvent firstDown, MotionEvent firstUp,
            MotionEvent secondDown) {
        if (!mAlwaysInBiggerTapRegion) {
            return false;
        }

        final long deltaTime = secondDown.getEventTime() - firstUp.getEventTime();
        if (deltaTime > DOUBLE_TAP_TIMEOUT || deltaTime < DOUBLE_TAP_MIN_TIME) {
            return false;
        }

        int deltaX = (int) firstDown.getX() - (int) secondDown.getX();
        int deltaY = (int) firstDown.getY() - (int) secondDown.getY();
        final boolean isGeneratedGesture =
                (firstDown.getFlags() & MotionEvent.FLAG_IS_GENERATED_GESTURE) != 0;
        int slopSquare = isGeneratedGesture ? 0 : mDoubleTapSlopSquare;
        return (deltaX * deltaX + deltaY * deltaY < slopSquare);
    }

    private void dispatchLongPress() {
        mHandler.removeMessages(TAP);
        mDeferConfirmSingleTap = false;
        mInLongPress = true;
        mListener.onLongPress(mCurrentDownEvent);
    }
}