src/com/android/mail/ui/SwipeHelper.java - platform/packages/apps/UnifiedEmail - Git at Google

 /*
  * Copyright (C) 2012 Google Inc.
  * Licensed to 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 com.android.mail.ui;

 import android.animation.Animator;
 import android.animation.AnimatorListenerAdapter;
 import android.animation.ObjectAnimator;
 import android.animation.ValueAnimator;
 import android.animation.ValueAnimator.AnimatorUpdateListener;
 import android.content.Context;
 import android.content.res.Resources;
 import android.graphics.RectF;
 import android.view.MotionEvent;
 import android.view.VelocityTracker;
 import android.view.View;
 import android.view.animation.DecelerateInterpolator;

 import com.android.mail.R;
 import com.android.mail.utils.LogUtils;
 import com.android.mail.utils.Utils;

 public class SwipeHelper {
     static final String TAG = "com.android.systemui.SwipeHelper";
     private static final boolean DEBUG_INVALIDATE = false;
     private static final boolean CONSTRAIN_SWIPE = true;
     private static final boolean FADE_OUT_DURING_SWIPE = true;
     private static final boolean DISMISS_IF_SWIPED_FAR_ENOUGH = true;
     // Turn on for debugging only during development.
     private static final boolean LOG_SWIPE_DISMISS_VELOCITY = false;

     public static final int X = 0;
     public static final int Y = 1;

     private static DecelerateInterpolator sDecelerateInterpolator =
                                                         new DecelerateInterpolator(1.0f);

     private static int SWIPE_ESCAPE_VELOCITY = -1;
     private static int DEFAULT_ESCAPE_ANIMATION_DURATION;
     private static int MAX_ESCAPE_ANIMATION_DURATION;
     private static int MAX_DISMISS_VELOCITY;
     private static int SNAP_ANIM_LEN;
     private static float MIN_SWIPE;

     public static float ALPHA_FADE_START = 0f; // fraction of thumbnail width
                                                  // where fade starts
     public static float ALPHA_TEXT_FADE_START = 0.4f;
     static final float ALPHA_FADE_END = 0.7f; // fraction of thumbnail width
                                               // beyond which alpha->0
     private static final float FACTOR = 1.2f;

     /* Dead region where swipe cannot be initiated. */
     private final static int DEAD_REGION_FOR_SWIPE = 56;

     private float mPagingTouchSlop;
     private final Callback mCallback;
     private final int mSwipeDirection;
     private final VelocityTracker mVelocityTracker;

     private float mInitialTouchPosX;
     private boolean mDragging;
     private SwipeableItemView mCurrView;
     private View mCurrAnimView;
     private boolean mCanCurrViewBeDimissed;
     private float mDensityScale;
     private float mLastY;
     private float mInitialTouchPosY;
     private LeaveBehindItem mPrevView;

     public SwipeHelper(Context context, int swipeDirection, Callback callback, float densityScale,
             float pagingTouchSlop) {
         mCallback = callback;
         mSwipeDirection = swipeDirection;
         mVelocityTracker = VelocityTracker.obtain();
         mDensityScale = densityScale;
         mPagingTouchSlop = pagingTouchSlop;
         if (SWIPE_ESCAPE_VELOCITY == -1) {
             Resources res = context.getResources();
             SWIPE_ESCAPE_VELOCITY = res.getInteger(R.integer.swipe_escape_velocity);
             DEFAULT_ESCAPE_ANIMATION_DURATION = res.getInteger(R.integer.escape_animation_duration);
             MAX_ESCAPE_ANIMATION_DURATION = res.getInteger(R.integer.max_escape_animation_duration);
             MAX_DISMISS_VELOCITY = res.getInteger(R.integer.max_dismiss_velocity);
             SNAP_ANIM_LEN = res.getInteger(R.integer.snap_animation_duration);
             MIN_SWIPE = res.getDimension(R.dimen.min_swipe);
         }
     }

     public void setDensityScale(float densityScale) {
         mDensityScale = densityScale;
     }

     public void setPagingTouchSlop(float pagingTouchSlop) {
         mPagingTouchSlop = pagingTouchSlop;
     }

     private float getVelocity(VelocityTracker vt) {
         return mSwipeDirection == X ? vt.getXVelocity() :
                 vt.getYVelocity();
     }

     private ObjectAnimator createTranslationAnimation(View v, float newPos) {
         ObjectAnimator anim = ObjectAnimator.ofFloat(v,
                 mSwipeDirection == X ? "translationX" : "translationY", newPos);
         return anim;
     }

     private ObjectAnimator createDismissAnimation(View v, float newPos, int duration) {
         ObjectAnimator anim = createTranslationAnimation(v, newPos);
         anim.setInterpolator(sDecelerateInterpolator);
         anim.setDuration(duration);
         return anim;
     }

     private float getPerpendicularVelocity(VelocityTracker vt) {
         return mSwipeDirection == X ? vt.getYVelocity() :
                 vt.getXVelocity();
     }

     private void setTranslation(View v, float translate) {
         if (mSwipeDirection == X) {
             v.setTranslationX(translate);
         } else {
             v.setTranslationY(translate);
         }
     }

     private float getSize(View v) {
         return mSwipeDirection == X ? v.getMeasuredWidth() :
                 v.getMeasuredHeight();
     }

     private float getAlphaForOffset(View view) {
         float viewSize = getSize(view);
         final float fadeSize = ALPHA_FADE_END * viewSize;
         float result = 1.0f;
         float pos = view.getTranslationX();
         if (pos >= viewSize * ALPHA_FADE_START) {
             result = 1.0f - (pos - viewSize * ALPHA_FADE_START) / fadeSize;
         } else if (pos < viewSize * (1.0f - ALPHA_FADE_START)) {
             result = 1.0f + (viewSize * ALPHA_FADE_START + pos) / fadeSize;
         }
         float minAlpha = 0.5f;
         return Math.max(minAlpha, result);
     }

     private float getTextAlphaForOffset(View view) {
         float viewSize = getSize(view);
         final float fadeSize = ALPHA_TEXT_FADE_START * viewSize;
         float result = 1.0f;
         float pos = view.getTranslationX();
         if (pos >= 0) {
             result = 1.0f - pos / fadeSize;
         } else if (pos < 0) {
             result = 1.0f + pos / fadeSize;
         }
         return Math.max(0, result);
     }

     // invalidate the view's own bounds all the way up the view hierarchy
     public static void invalidateGlobalRegion(View view) {
         invalidateGlobalRegion(
             view,
             new RectF(view.getLeft(), view.getTop(), view.getRight(), view.getBottom()));
     }

     // invalidate a rectangle relative to the view's coordinate system all the way up the view
     // hierarchy
     public static void invalidateGlobalRegion(View view, RectF childBounds) {
         //childBounds.offset(view.getTranslationX(), view.getTranslationY());
         if (DEBUG_INVALIDATE)
             LogUtils.v(TAG, "-------------");
         while (view.getParent() != null && view.getParent() instanceof View) {
             view = (View) view.getParent();
             view.getMatrix().mapRect(childBounds);
             view.invalidate((int) Math.floor(childBounds.left),
                             (int) Math.floor(childBounds.top),
                             (int) Math.ceil(childBounds.right),
                             (int) Math.ceil(childBounds.bottom));
             if (DEBUG_INVALIDATE) {
                 LogUtils.v(TAG, "INVALIDATE(" + (int) Math.floor(childBounds.left)
                         + "," + (int) Math.floor(childBounds.top)
                         + "," + (int) Math.ceil(childBounds.right)
                         + "," + (int) Math.ceil(childBounds.bottom));
             }
         }
     }

     public boolean onInterceptTouchEvent(MotionEvent ev) {
         final int action = ev.getAction();
         switch (action) {
             case MotionEvent.ACTION_DOWN:
                 mLastY = ev.getY();
                 mDragging = false;
                 View view = mCallback.getChildAtPosition(ev);
                 if (view instanceof SwipeableItemView) {
                     mCurrView = (SwipeableItemView) view;
                 }
                 mVelocityTracker.clear();
                 if (mCurrView != null) {
                     mCurrAnimView = mCurrView.getSwipeableView().getView();
                     mCanCurrViewBeDimissed = mCallback.canChildBeDismissed(mCurrView);
                     mVelocityTracker.addMovement(ev);
                     mInitialTouchPosX = ev.getX();
                     mInitialTouchPosY = ev.getY();
                 }
                 mCallback.cancelDismissCounter();
                 break;
             case MotionEvent.ACTION_MOVE:
                 if (mCurrView != null) {
                     // Check the movement direction.
                     if (mLastY >= 0 && !mDragging) {
                         float currY = ev.getY();
                         float currX = ev.getX();
                         float deltaY = Math.abs(currY - mInitialTouchPosY);
                         float deltaX = Math.abs(currX - mInitialTouchPosX);
                         if (deltaY > mCurrView.getMinAllowScrollDistance()
                                 && deltaY > (FACTOR * deltaX)) {
                             mLastY = ev.getY();
                             mCallback.onScroll();
                             return false;
                         }
                     }
                     mVelocityTracker.addMovement(ev);
                     float pos = ev.getX();
                     float delta = pos - mInitialTouchPosX;
                     if (Math.abs(delta) > mPagingTouchSlop) {
                         mCallback.onBeginDrag(mCurrView.getSwipeableView().getView());
                         mPrevView = mCallback.getLastSwipedItem();
                         mDragging = true;
                         mInitialTouchPosX = ev.getX() - mCurrAnimView.getTranslationX();
                         mInitialTouchPosY = ev.getY();
                     }
                 }
                 mLastY = ev.getY();
                 break;
             case MotionEvent.ACTION_UP:
             case MotionEvent.ACTION_CANCEL:
                 mDragging = false;
                 mCurrView = null;
                 mCurrAnimView = null;
                 mLastY = -1;
                 break;
         }
         return mDragging;
     }

     /**
      * @param view The view to be dismissed
      * @param velocity The desired pixels/second speed at which the view should
      *            move
      */
     private void dismissChild(final SwipeableItemView view, float velocity) {
         final View animView = mCurrView.getSwipeableView().getView();
         final boolean canAnimViewBeDismissed = mCallback.canChildBeDismissed(view);
         float newPos = determinePos(animView, velocity);
         int duration = determineDuration(animView, newPos, velocity);

         Utils.enableHardwareLayer(animView);
         ObjectAnimator anim = createDismissAnimation(animView, newPos, duration);
         anim.addListener(new AnimatorListenerAdapter() {
             @Override
             public void onAnimationEnd(Animator animation) {
                 mCallback.onChildDismissed(mCurrView);
                 animView.setLayerType(View.LAYER_TYPE_NONE, null);
             }
         });
         anim.addUpdateListener(new AnimatorUpdateListener() {
             @Override
             public void onAnimationUpdate(ValueAnimator animation) {
                 if (FADE_OUT_DURING_SWIPE && canAnimViewBeDismissed) {
                     animView.setAlpha(getAlphaForOffset(animView));
                 }
                 invalidateGlobalRegion(animView);
             }
         });
         anim.start();
     }

     private static int determineDuration(View animView, float newPos, float velocity) {
         int duration = MAX_ESCAPE_ANIMATION_DURATION;
         if (velocity != 0) {
             duration = Math
                     .min(duration,
                             (int) (Math.abs(newPos - animView.getTranslationX()) * 1000f / Math
                                     .abs(velocity)));
         } else {
             duration = DEFAULT_ESCAPE_ANIMATION_DURATION;
         }
         return duration;
     }

     private float determinePos(View animView, float velocity) {
         final float newPos;
         if (velocity < 0 || (velocity == 0 && animView.getTranslationX() < 0)
         // if we use the Menu to dismiss an item in landscape, animate up
                 || (velocity == 0 && animView.getTranslationX() == 0 && mSwipeDirection == Y)) {
             newPos = -getSize(animView);
         } else {
             newPos = getSize(animView);
         }
         return newPos;
     }

     public void snapChild(final SwipeableItemView view) {
         final View animView = view.getSwipeableView().getView();
         final boolean canAnimViewBeDismissed = mCallback.canChildBeDismissed(view);
         final ObjectAnimator anim = createTranslationAnimation(animView, 0);
         final int duration = SNAP_ANIM_LEN;
         anim.setDuration(duration);
         anim.addUpdateListener(new AnimatorUpdateListener() {
             @Override
             public void onAnimationUpdate(ValueAnimator animation) {
                 if (FADE_OUT_DURING_SWIPE && canAnimViewBeDismissed) {
                     animView.setAlpha(getAlphaForOffset(animView));
                 }
                 invalidateGlobalRegion(animView);
             }
         });
         anim.addListener(new Animator.AnimatorListener() {
             @Override
             public void onAnimationStart(Animator animation) {
             }
             @Override
             public void onAnimationEnd(Animator animation) {
                 animView.setAlpha(1.0f);
                 mCallback.onDragCancelled(mCurrView);
             }
             @Override
             public void onAnimationCancel(Animator animation) {
             }
             @Override
             public void onAnimationRepeat(Animator animation) {
             }
         });
         anim.start();
     }

     public boolean onTouchEvent(MotionEvent ev) {
         if (!mDragging) {
             return false;
         }
         mVelocityTracker.addMovement(ev);
         final int action = ev.getAction();
         switch (action) {
             case MotionEvent.ACTION_OUTSIDE:
             case MotionEvent.ACTION_MOVE:
                 if (mCurrView != null) {
                     float deltaX = ev.getX() - mInitialTouchPosX;
                     // If the swipe started in the dead region, ignore it.
                     if (mInitialTouchPosX <= (DEAD_REGION_FOR_SWIPE * mDensityScale)){
                             return true;
                     }
                     // If the user has gone vertical and not gone horizontalish AT
                     // LEAST minBeforeLock, switch to scroll. Otherwise, cancel
                     // the swipe.
                     float minDistance = MIN_SWIPE;
                     if (Math.abs(deltaX) < minDistance) {
                         // Don't start the drag until at least X distance has
                         // occurred.
                         return true;
                     }
                     // don't let items that can't be dismissed be dragged more
                     // than maxScrollDistance
                     if (CONSTRAIN_SWIPE && !mCallback.canChildBeDismissed(mCurrView)) {
                         float size = getSize(mCurrAnimView);
                         float maxScrollDistance = 0.15f * size;
                         if (Math.abs(deltaX) >= size) {
                             deltaX = deltaX > 0 ? maxScrollDistance : -maxScrollDistance;
                         } else {
                             deltaX = maxScrollDistance
                                     * (float) Math.sin((deltaX / size) * (Math.PI / 2));
                         }
                     }
                     setTranslation(mCurrAnimView, deltaX);
                     if (FADE_OUT_DURING_SWIPE && mCanCurrViewBeDimissed) {
                         mCurrAnimView.setAlpha(getAlphaForOffset(mCurrAnimView));
                         if (mPrevView != null) {
                             // Base how much the text of the prev item is faded
                             // on how far the current item has moved.
                             mPrevView.setTextAlpha(getTextAlphaForOffset(mCurrAnimView));
                         }
                     }
                     invalidateGlobalRegion(mCurrView.getSwipeableView().getView());
                 }
                 break;
             case MotionEvent.ACTION_UP:
             case MotionEvent.ACTION_CANCEL:
                 if (mCurrView != null) {
                     float maxVelocity = MAX_DISMISS_VELOCITY * mDensityScale;
                     mVelocityTracker.computeCurrentVelocity(1000 /* px/sec */, maxVelocity);
                     float escapeVelocity = SWIPE_ESCAPE_VELOCITY * mDensityScale;
                     float velocity = getVelocity(mVelocityTracker);
                     float perpendicularVelocity = getPerpendicularVelocity(mVelocityTracker);

                     // Decide whether to dismiss the current view
                     // Tweak constants below as required to prevent erroneous
                     // swipe/dismiss
                     float translation = Math.abs(mCurrAnimView.getTranslationX());
                     float currAnimViewSize = getSize(mCurrAnimView);
                     // Long swipe = translation of .4 * width
                     boolean childSwipedFarEnough = DISMISS_IF_SWIPED_FAR_ENOUGH
                             && translation > 0.4 * currAnimViewSize;
                     // Fast swipe = > escapeVelocity and translation of .1 *
                     // width
                     boolean childSwipedFastEnough = (Math.abs(velocity) > escapeVelocity)
                             && (Math.abs(velocity) > Math.abs(perpendicularVelocity))
                             && (velocity > 0) == (mCurrAnimView.getTranslationX() > 0)
                             && translation > 0.05 * currAnimViewSize;
                     if (LOG_SWIPE_DISMISS_VELOCITY) {
                         LogUtils.v(TAG, "Swipe/Dismiss: " + velocity + "/" + escapeVelocity + "/"
                                 + perpendicularVelocity + ", x: " + translation + "/"
                                 + currAnimViewSize);
                     }

                     boolean dismissChild = mCallback.canChildBeDismissed(mCurrView)
                             && (childSwipedFastEnough || childSwipedFarEnough);

                     if (dismissChild) {
                         dismissChild(mCurrView, childSwipedFastEnough ? velocity : 0f);
                     } else {
                         snapChild(mCurrView);
                     }
                 }
                 break;
         }
         return true;
     }

     public interface Callback {
         View getChildAtPosition(MotionEvent ev);

         void cancelDismissCounter();

         void onScroll();

         boolean canChildBeDismissed(SwipeableItemView v);

         void onBeginDrag(View v);

         void onChildDismissed(SwipeableItemView v);

         void onDragCancelled(SwipeableItemView v);

         ConversationSelectionSet getSelectionSet();

         LeaveBehindItem getLastSwipedItem();
     }
 }
	/*
	* Copyright (C) 2012 Google Inc.
	* Licensed to 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 com.android.mail.ui;

	import android.animation.Animator;
	import android.animation.AnimatorListenerAdapter;
	import android.animation.ObjectAnimator;
	import android.animation.ValueAnimator;
	import android.animation.ValueAnimator.AnimatorUpdateListener;
	import android.content.Context;
	import android.content.res.Resources;
	import android.graphics.RectF;
	import android.view.MotionEvent;
	import android.view.VelocityTracker;
	import android.view.View;
	import android.view.animation.DecelerateInterpolator;

	import com.android.mail.R;
	import com.android.mail.utils.LogUtils;
	import com.android.mail.utils.Utils;

	public class SwipeHelper {
	static final String TAG = "com.android.systemui.SwipeHelper";
	private static final boolean DEBUG_INVALIDATE = false;
	private static final boolean CONSTRAIN_SWIPE = true;
	private static final boolean FADE_OUT_DURING_SWIPE = true;
	private static final boolean DISMISS_IF_SWIPED_FAR_ENOUGH = true;
	// Turn on for debugging only during development.
	private static final boolean LOG_SWIPE_DISMISS_VELOCITY = false;

	public static final int X = 0;
	public static final int Y = 1;

	private static DecelerateInterpolator sDecelerateInterpolator =
	new DecelerateInterpolator(1.0f);

	private static int SWIPE_ESCAPE_VELOCITY = -1;
	private static int DEFAULT_ESCAPE_ANIMATION_DURATION;
	private static int MAX_ESCAPE_ANIMATION_DURATION;
	private static int MAX_DISMISS_VELOCITY;
	private static int SNAP_ANIM_LEN;
	private static float MIN_SWIPE;

	public static float ALPHA_FADE_START = 0f; // fraction of thumbnail width
	// where fade starts
	public static float ALPHA_TEXT_FADE_START = 0.4f;
	static final float ALPHA_FADE_END = 0.7f; // fraction of thumbnail width
	// beyond which alpha->0
	private static final float FACTOR = 1.2f;

	/* Dead region where swipe cannot be initiated. */
	private final static int DEAD_REGION_FOR_SWIPE = 56;

	private float mPagingTouchSlop;
	private final Callback mCallback;
	private final int mSwipeDirection;
	private final VelocityTracker mVelocityTracker;

	private float mInitialTouchPosX;
	private boolean mDragging;
	private SwipeableItemView mCurrView;
	private View mCurrAnimView;
	private boolean mCanCurrViewBeDimissed;
	private float mDensityScale;
	private float mLastY;
	private float mInitialTouchPosY;
	private LeaveBehindItem mPrevView;

	public SwipeHelper(Context context, int swipeDirection, Callback callback, float densityScale,
	float pagingTouchSlop) {
	mCallback = callback;
	mSwipeDirection = swipeDirection;
	mVelocityTracker = VelocityTracker.obtain();
	mDensityScale = densityScale;
	mPagingTouchSlop = pagingTouchSlop;
	if (SWIPE_ESCAPE_VELOCITY == -1) {
	Resources res = context.getResources();
	SWIPE_ESCAPE_VELOCITY = res.getInteger(R.integer.swipe_escape_velocity);
	DEFAULT_ESCAPE_ANIMATION_DURATION = res.getInteger(R.integer.escape_animation_duration);
	MAX_ESCAPE_ANIMATION_DURATION = res.getInteger(R.integer.max_escape_animation_duration);
	MAX_DISMISS_VELOCITY = res.getInteger(R.integer.max_dismiss_velocity);
	SNAP_ANIM_LEN = res.getInteger(R.integer.snap_animation_duration);
	MIN_SWIPE = res.getDimension(R.dimen.min_swipe);
	}
	}

	public void setDensityScale(float densityScale) {
	mDensityScale = densityScale;
	}

	public void setPagingTouchSlop(float pagingTouchSlop) {
	mPagingTouchSlop = pagingTouchSlop;
	}

	private float getVelocity(VelocityTracker vt) {
	return mSwipeDirection == X ? vt.getXVelocity() :
	vt.getYVelocity();
	}

	private ObjectAnimator createTranslationAnimation(View v, float newPos) {
	ObjectAnimator anim = ObjectAnimator.ofFloat(v,
	mSwipeDirection == X ? "translationX" : "translationY", newPos);
	return anim;
	}

	private ObjectAnimator createDismissAnimation(View v, float newPos, int duration) {
	ObjectAnimator anim = createTranslationAnimation(v, newPos);
	anim.setInterpolator(sDecelerateInterpolator);
	anim.setDuration(duration);
	return anim;
	}

	private float getPerpendicularVelocity(VelocityTracker vt) {
	return mSwipeDirection == X ? vt.getYVelocity() :
	vt.getXVelocity();
	}

	private void setTranslation(View v, float translate) {
	if (mSwipeDirection == X) {
	v.setTranslationX(translate);
	} else {
	v.setTranslationY(translate);
	}
	}

	private float getSize(View v) {
	return mSwipeDirection == X ? v.getMeasuredWidth() :
	v.getMeasuredHeight();
	}

	private float getAlphaForOffset(View view) {
	float viewSize = getSize(view);
	final float fadeSize = ALPHA_FADE_END * viewSize;
	float result = 1.0f;
	float pos = view.getTranslationX();
	if (pos >= viewSize * ALPHA_FADE_START) {
	result = 1.0f - (pos - viewSize * ALPHA_FADE_START) / fadeSize;
	} else if (pos < viewSize * (1.0f - ALPHA_FADE_START)) {
	result = 1.0f + (viewSize * ALPHA_FADE_START + pos) / fadeSize;
	}
	float minAlpha = 0.5f;
	return Math.max(minAlpha, result);
	}

	private float getTextAlphaForOffset(View view) {
	float viewSize = getSize(view);
	final float fadeSize = ALPHA_TEXT_FADE_START * viewSize;
	float result = 1.0f;
	float pos = view.getTranslationX();
	if (pos >= 0) {
	result = 1.0f - pos / fadeSize;
	} else if (pos < 0) {
	result = 1.0f + pos / fadeSize;
	}
	return Math.max(0, result);
	}

	// invalidate the view's own bounds all the way up the view hierarchy
	public static void invalidateGlobalRegion(View view) {
	invalidateGlobalRegion(
	view,
	new RectF(view.getLeft(), view.getTop(), view.getRight(), view.getBottom()));
	}

	// invalidate a rectangle relative to the view's coordinate system all the way up the view
	// hierarchy
	public static void invalidateGlobalRegion(View view, RectF childBounds) {
	//childBounds.offset(view.getTranslationX(), view.getTranslationY());
	if (DEBUG_INVALIDATE)
	LogUtils.v(TAG, "-------------");
	while (view.getParent() != null && view.getParent() instanceof View) {
	view = (View) view.getParent();
	view.getMatrix().mapRect(childBounds);
	view.invalidate((int) Math.floor(childBounds.left),
	(int) Math.floor(childBounds.top),
	(int) Math.ceil(childBounds.right),
	(int) Math.ceil(childBounds.bottom));
	if (DEBUG_INVALIDATE) {
	LogUtils.v(TAG, "INVALIDATE(" + (int) Math.floor(childBounds.left)
	+ "," + (int) Math.floor(childBounds.top)
	+ "," + (int) Math.ceil(childBounds.right)
	+ "," + (int) Math.ceil(childBounds.bottom));
	}
	}
	}

	public boolean onInterceptTouchEvent(MotionEvent ev) {
	final int action = ev.getAction();
	switch (action) {
	case MotionEvent.ACTION_DOWN:
	mLastY = ev.getY();
	mDragging = false;
	View view = mCallback.getChildAtPosition(ev);
	if (view instanceof SwipeableItemView) {
	mCurrView = (SwipeableItemView) view;
	}
	mVelocityTracker.clear();
	if (mCurrView != null) {
	mCurrAnimView = mCurrView.getSwipeableView().getView();
	mCanCurrViewBeDimissed = mCallback.canChildBeDismissed(mCurrView);
	mVelocityTracker.addMovement(ev);
	mInitialTouchPosX = ev.getX();
	mInitialTouchPosY = ev.getY();
	}
	mCallback.cancelDismissCounter();
	break;
	case MotionEvent.ACTION_MOVE:
	if (mCurrView != null) {
	// Check the movement direction.
	if (mLastY >= 0 && !mDragging) {
	float currY = ev.getY();
	float currX = ev.getX();
	float deltaY = Math.abs(currY - mInitialTouchPosY);
	float deltaX = Math.abs(currX - mInitialTouchPosX);
	if (deltaY > mCurrView.getMinAllowScrollDistance()
	&& deltaY > (FACTOR * deltaX)) {
	mLastY = ev.getY();
	mCallback.onScroll();
	return false;
	}
	}
	mVelocityTracker.addMovement(ev);
	float pos = ev.getX();
	float delta = pos - mInitialTouchPosX;
	if (Math.abs(delta) > mPagingTouchSlop) {
	mCallback.onBeginDrag(mCurrView.getSwipeableView().getView());
	mPrevView = mCallback.getLastSwipedItem();
	mDragging = true;
	mInitialTouchPosX = ev.getX() - mCurrAnimView.getTranslationX();
	mInitialTouchPosY = ev.getY();
	}
	}
	mLastY = ev.getY();
	break;
	case MotionEvent.ACTION_UP:
	case MotionEvent.ACTION_CANCEL:
	mDragging = false;
	mCurrView = null;
	mCurrAnimView = null;
	mLastY = -1;
	break;
	}
	return mDragging;
	}

	/**
	* @param view The view to be dismissed
	* @param velocity The desired pixels/second speed at which the view should
	* move
	*/
	private void dismissChild(final SwipeableItemView view, float velocity) {
	final View animView = mCurrView.getSwipeableView().getView();
	final boolean canAnimViewBeDismissed = mCallback.canChildBeDismissed(view);
	float newPos = determinePos(animView, velocity);
	int duration = determineDuration(animView, newPos, velocity);

	Utils.enableHardwareLayer(animView);
	ObjectAnimator anim = createDismissAnimation(animView, newPos, duration);
	anim.addListener(new AnimatorListenerAdapter() {
	@Override
	public void onAnimationEnd(Animator animation) {
	mCallback.onChildDismissed(mCurrView);
	animView.setLayerType(View.LAYER_TYPE_NONE, null);
	}
	});
	anim.addUpdateListener(new AnimatorUpdateListener() {
	@Override
	public void onAnimationUpdate(ValueAnimator animation) {
	if (FADE_OUT_DURING_SWIPE && canAnimViewBeDismissed) {
	animView.setAlpha(getAlphaForOffset(animView));
	}
	invalidateGlobalRegion(animView);
	}
	});
	anim.start();
	}

	private static int determineDuration(View animView, float newPos, float velocity) {
	int duration = MAX_ESCAPE_ANIMATION_DURATION;
	if (velocity != 0) {
	duration = Math
	.min(duration,
	(int) (Math.abs(newPos - animView.getTranslationX()) * 1000f / Math
	.abs(velocity)));
	} else {
	duration = DEFAULT_ESCAPE_ANIMATION_DURATION;
	}
	return duration;
	}

	private float determinePos(View animView, float velocity) {
	final float newPos;
	if (velocity < 0 \|\| (velocity == 0 && animView.getTranslationX() < 0)
	// if we use the Menu to dismiss an item in landscape, animate up
	\|\| (velocity == 0 && animView.getTranslationX() == 0 && mSwipeDirection == Y)) {
	newPos = -getSize(animView);
	} else {
	newPos = getSize(animView);
	}
	return newPos;
	}

	public void snapChild(final SwipeableItemView view) {
	final View animView = view.getSwipeableView().getView();
	final boolean canAnimViewBeDismissed = mCallback.canChildBeDismissed(view);
	final ObjectAnimator anim = createTranslationAnimation(animView, 0);
	final int duration = SNAP_ANIM_LEN;
	anim.setDuration(duration);
	anim.addUpdateListener(new AnimatorUpdateListener() {
	@Override
	public void onAnimationUpdate(ValueAnimator animation) {
	if (FADE_OUT_DURING_SWIPE && canAnimViewBeDismissed) {
	animView.setAlpha(getAlphaForOffset(animView));
	}
	invalidateGlobalRegion(animView);
	}
	});
	anim.addListener(new Animator.AnimatorListener() {
	@Override
	public void onAnimationStart(Animator animation) {
	}
	@Override
	public void onAnimationEnd(Animator animation) {
	animView.setAlpha(1.0f);
	mCallback.onDragCancelled(mCurrView);
	}
	@Override
	public void onAnimationCancel(Animator animation) {
	}
	@Override
	public void onAnimationRepeat(Animator animation) {
	}
	});
	anim.start();
	}

	public boolean onTouchEvent(MotionEvent ev) {
	if (!mDragging) {
	return false;
	}
	mVelocityTracker.addMovement(ev);
	final int action = ev.getAction();
	switch (action) {
	case MotionEvent.ACTION_OUTSIDE:
	case MotionEvent.ACTION_MOVE:
	if (mCurrView != null) {
	float deltaX = ev.getX() - mInitialTouchPosX;
	// If the swipe started in the dead region, ignore it.
	if (mInitialTouchPosX <= (DEAD_REGION_FOR_SWIPE * mDensityScale)){
	return true;
	}
	// If the user has gone vertical and not gone horizontalish AT
	// LEAST minBeforeLock, switch to scroll. Otherwise, cancel
	// the swipe.
	float minDistance = MIN_SWIPE;
	if (Math.abs(deltaX) < minDistance) {
	// Don't start the drag until at least X distance has
	// occurred.
	return true;
	}
	// don't let items that can't be dismissed be dragged more
	// than maxScrollDistance
	if (CONSTRAIN_SWIPE && !mCallback.canChildBeDismissed(mCurrView)) {
	float size = getSize(mCurrAnimView);
	float maxScrollDistance = 0.15f * size;
	if (Math.abs(deltaX) >= size) {
	deltaX = deltaX > 0 ? maxScrollDistance : -maxScrollDistance;
	} else {
	deltaX = maxScrollDistance
	* (float) Math.sin((deltaX / size) * (Math.PI / 2));
	}
	}
	setTranslation(mCurrAnimView, deltaX);
	if (FADE_OUT_DURING_SWIPE && mCanCurrViewBeDimissed) {
	mCurrAnimView.setAlpha(getAlphaForOffset(mCurrAnimView));
	if (mPrevView != null) {
	// Base how much the text of the prev item is faded
	// on how far the current item has moved.
	mPrevView.setTextAlpha(getTextAlphaForOffset(mCurrAnimView));
	}
	}
	invalidateGlobalRegion(mCurrView.getSwipeableView().getView());
	}
	break;
	case MotionEvent.ACTION_UP:
	case MotionEvent.ACTION_CANCEL:
	if (mCurrView != null) {
	float maxVelocity = MAX_DISMISS_VELOCITY * mDensityScale;
	mVelocityTracker.computeCurrentVelocity(1000 /* px/sec */, maxVelocity);
	float escapeVelocity = SWIPE_ESCAPE_VELOCITY * mDensityScale;
	float velocity = getVelocity(mVelocityTracker);
	float perpendicularVelocity = getPerpendicularVelocity(mVelocityTracker);

	// Decide whether to dismiss the current view
	// Tweak constants below as required to prevent erroneous
	// swipe/dismiss
	float translation = Math.abs(mCurrAnimView.getTranslationX());
	float currAnimViewSize = getSize(mCurrAnimView);
	// Long swipe = translation of .4 * width
	boolean childSwipedFarEnough = DISMISS_IF_SWIPED_FAR_ENOUGH
	&& translation > 0.4 * currAnimViewSize;
	// Fast swipe = > escapeVelocity and translation of .1 *
	// width
	boolean childSwipedFastEnough = (Math.abs(velocity) > escapeVelocity)
	&& (Math.abs(velocity) > Math.abs(perpendicularVelocity))
	&& (velocity > 0) == (mCurrAnimView.getTranslationX() > 0)
	&& translation > 0.05 * currAnimViewSize;
	if (LOG_SWIPE_DISMISS_VELOCITY) {
	LogUtils.v(TAG, "Swipe/Dismiss: " + velocity + "/" + escapeVelocity + "/"
	+ perpendicularVelocity + ", x: " + translation + "/"
	+ currAnimViewSize);
	}

	boolean dismissChild = mCallback.canChildBeDismissed(mCurrView)
	&& (childSwipedFastEnough \|\| childSwipedFarEnough);

	if (dismissChild) {
	dismissChild(mCurrView, childSwipedFastEnough ? velocity : 0f);
	} else {
	snapChild(mCurrView);
	}
	}
	break;
	}
	return true;
	}

	public interface Callback {
	View getChildAtPosition(MotionEvent ev);

	void cancelDismissCounter();

	void onScroll();

	boolean canChildBeDismissed(SwipeableItemView v);

	void onBeginDrag(View v);

	void onChildDismissed(SwipeableItemView v);

	void onDragCancelled(SwipeableItemView v);

	ConversationSelectionSet getSelectionSet();

	LeaveBehindItem getLastSwipedItem();
	}
	}