1 /*
2  * Copyright (C) 2014 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 package com.android.internal.widget;
18 
19 import android.animation.TimeInterpolator;
20 import android.app.Activity;
21 import android.content.Context;
22 import android.util.AttributeSet;
23 import android.util.Log;
24 import android.view.MotionEvent;
25 import android.view.VelocityTracker;
26 import android.view.View;
27 import android.view.ViewConfiguration;
28 import android.view.ViewGroup;
29 import android.view.ViewTreeObserver;
30 import android.view.animation.AccelerateInterpolator;
31 import android.view.animation.DecelerateInterpolator;
32 import android.widget.FrameLayout;
33 
34 /**
35  * Special layout that finishes its activity when swiped away.
36  */
37 public class SwipeDismissLayout extends FrameLayout {
38     private static final String TAG = "SwipeDismissLayout";
39 
40     private static final float DISMISS_MIN_DRAG_WIDTH_RATIO = .33f;
41 
42     public interface OnDismissedListener {
onDismissed(SwipeDismissLayout layout)43         void onDismissed(SwipeDismissLayout layout);
44     }
45 
46     public interface OnSwipeProgressChangedListener {
47         /**
48          * Called when the layout has been swiped and the position of the window should change.
49          *
50          * @param progress A number in [0, 1] representing how far to the
51          * right the window has been swiped
52          * @param translate A number in [0, w], where w is the width of the
53          * layout. This is equivalent to progress * layout.getWidth().
54          */
onSwipeProgressChanged(SwipeDismissLayout layout, float progress, float translate)55         void onSwipeProgressChanged(SwipeDismissLayout layout, float progress, float translate);
56 
onSwipeCancelled(SwipeDismissLayout layout)57         void onSwipeCancelled(SwipeDismissLayout layout);
58     }
59 
60     // Cached ViewConfiguration and system-wide constant values
61     private int mSlop;
62     private int mMinFlingVelocity;
63     private int mMaxFlingVelocity;
64     private long mAnimationTime;
65     private TimeInterpolator mCancelInterpolator;
66     private TimeInterpolator mDismissInterpolator;
67 
68     // Transient properties
69     private int mActiveTouchId;
70     private float mDownX;
71     private float mDownY;
72     private boolean mSwiping;
73     private boolean mDismissed;
74     private boolean mDiscardIntercept;
75     private VelocityTracker mVelocityTracker;
76     private float mTranslationX;
77 
78     private OnDismissedListener mDismissedListener;
79     private OnSwipeProgressChangedListener mProgressListener;
80     private ViewTreeObserver.OnEnterAnimationCompleteListener mOnEnterAnimationCompleteListener =
81             new ViewTreeObserver.OnEnterAnimationCompleteListener() {
82                 @Override
83                 public void onEnterAnimationComplete() {
84                     // SwipeDismissLayout assumes that the host Activity is translucent
85                     // and temporarily disables translucency when it is fully visible.
86                     // As soon as the user starts swiping, we will re-enable
87                     // translucency.
88                     if (getContext() instanceof Activity) {
89                         ((Activity) getContext()).convertFromTranslucent();
90                     }
91                 }
92             };
93 
94     private float mLastX;
95 
SwipeDismissLayout(Context context)96     public SwipeDismissLayout(Context context) {
97         super(context);
98         init(context);
99     }
100 
SwipeDismissLayout(Context context, AttributeSet attrs)101     public SwipeDismissLayout(Context context, AttributeSet attrs) {
102         super(context, attrs);
103         init(context);
104     }
105 
SwipeDismissLayout(Context context, AttributeSet attrs, int defStyle)106     public SwipeDismissLayout(Context context, AttributeSet attrs, int defStyle) {
107         super(context, attrs, defStyle);
108         init(context);
109     }
110 
init(Context context)111     private void init(Context context) {
112         ViewConfiguration vc = ViewConfiguration.get(getContext());
113         mSlop = vc.getScaledTouchSlop();
114         mMinFlingVelocity = vc.getScaledMinimumFlingVelocity();
115         mMaxFlingVelocity = vc.getScaledMaximumFlingVelocity();
116         mAnimationTime = getContext().getResources().getInteger(
117                 android.R.integer.config_shortAnimTime);
118         mCancelInterpolator = new DecelerateInterpolator(1.5f);
119         mDismissInterpolator = new AccelerateInterpolator(1.5f);
120     }
121 
setOnDismissedListener(OnDismissedListener listener)122     public void setOnDismissedListener(OnDismissedListener listener) {
123         mDismissedListener = listener;
124     }
125 
setOnSwipeProgressChangedListener(OnSwipeProgressChangedListener listener)126     public void setOnSwipeProgressChangedListener(OnSwipeProgressChangedListener listener) {
127         mProgressListener = listener;
128     }
129 
130     @Override
onAttachedToWindow()131     protected void onAttachedToWindow() {
132         super.onAttachedToWindow();
133         if (getContext() instanceof Activity) {
134             getViewTreeObserver().addOnEnterAnimationCompleteListener(
135                     mOnEnterAnimationCompleteListener);
136         }
137     }
138 
139     @Override
onDetachedFromWindow()140     protected void onDetachedFromWindow() {
141         super.onDetachedFromWindow();
142         if (getContext() instanceof Activity) {
143             getViewTreeObserver().removeOnEnterAnimationCompleteListener(
144                     mOnEnterAnimationCompleteListener);
145         }
146     }
147 
148     @Override
onInterceptTouchEvent(MotionEvent ev)149     public boolean onInterceptTouchEvent(MotionEvent ev) {
150         // offset because the view is translated during swipe
151         ev.offsetLocation(mTranslationX, 0);
152 
153         switch (ev.getActionMasked()) {
154             case MotionEvent.ACTION_DOWN:
155                 resetMembers();
156                 mDownX = ev.getRawX();
157                 mDownY = ev.getRawY();
158                 mActiveTouchId = ev.getPointerId(0);
159                 mVelocityTracker = VelocityTracker.obtain();
160                 mVelocityTracker.addMovement(ev);
161                 break;
162 
163             case MotionEvent.ACTION_POINTER_DOWN:
164                 int actionIndex = ev.getActionIndex();
165                 mActiveTouchId = ev.getPointerId(actionIndex);
166                 break;
167             case MotionEvent.ACTION_POINTER_UP:
168                 actionIndex = ev.getActionIndex();
169                 int pointerId = ev.getPointerId(actionIndex);
170                 if (pointerId == mActiveTouchId) {
171                     // This was our active pointer going up. Choose a new active pointer.
172                     int newActionIndex = actionIndex == 0 ? 1 : 0;
173                     mActiveTouchId = ev.getPointerId(newActionIndex);
174                 }
175                 break;
176 
177             case MotionEvent.ACTION_CANCEL:
178             case MotionEvent.ACTION_UP:
179                 resetMembers();
180                 break;
181 
182             case MotionEvent.ACTION_MOVE:
183                 if (mVelocityTracker == null || mDiscardIntercept) {
184                     break;
185                 }
186 
187                 int pointerIndex = ev.findPointerIndex(mActiveTouchId);
188                 if (pointerIndex == -1) {
189                     Log.e(TAG, "Invalid pointer index: ignoring.");
190                     mDiscardIntercept = true;
191                     break;
192                 }
193                 float dx = ev.getRawX() - mDownX;
194                 float x = ev.getX(pointerIndex);
195                 float y = ev.getY(pointerIndex);
196                 if (dx != 0 && canScroll(this, false, dx, x, y)) {
197                     mDiscardIntercept = true;
198                     break;
199                 }
200                 updateSwiping(ev);
201                 break;
202         }
203 
204         return !mDiscardIntercept && mSwiping;
205     }
206 
207     @Override
onTouchEvent(MotionEvent ev)208     public boolean onTouchEvent(MotionEvent ev) {
209         if (mVelocityTracker == null) {
210             return super.onTouchEvent(ev);
211         }
212         switch (ev.getActionMasked()) {
213             case MotionEvent.ACTION_UP:
214                 updateDismiss(ev);
215                 if (mDismissed) {
216                     dismiss();
217                 } else if (mSwiping) {
218                     cancel();
219                 }
220                 resetMembers();
221                 break;
222 
223             case MotionEvent.ACTION_CANCEL:
224                 cancel();
225                 resetMembers();
226                 break;
227 
228             case MotionEvent.ACTION_MOVE:
229                 mVelocityTracker.addMovement(ev);
230                 mLastX = ev.getRawX();
231                 updateSwiping(ev);
232                 if (mSwiping) {
233                     if (getContext() instanceof Activity) {
234                         ((Activity) getContext()).convertToTranslucent(null, null);
235                     }
236                     setProgress(ev.getRawX() - mDownX);
237                     break;
238                 }
239         }
240         return true;
241     }
242 
setProgress(float deltaX)243     private void setProgress(float deltaX) {
244         mTranslationX = deltaX;
245         if (mProgressListener != null && deltaX >= 0)  {
246             mProgressListener.onSwipeProgressChanged(this, deltaX / getWidth(), deltaX);
247         }
248     }
249 
dismiss()250     private void dismiss() {
251         if (mDismissedListener != null) {
252             mDismissedListener.onDismissed(this);
253         }
254     }
255 
cancel()256     protected void cancel() {
257         if (getContext() instanceof Activity) {
258             ((Activity) getContext()).convertFromTranslucent();
259         }
260         if (mProgressListener != null) {
261             mProgressListener.onSwipeCancelled(this);
262         }
263     }
264 
265     /**
266      * Resets internal members when canceling.
267      */
resetMembers()268     private void resetMembers() {
269         if (mVelocityTracker != null) {
270             mVelocityTracker.recycle();
271         }
272         mVelocityTracker = null;
273         mTranslationX = 0;
274         mDownX = 0;
275         mDownY = 0;
276         mSwiping = false;
277         mDismissed = false;
278         mDiscardIntercept = false;
279     }
280 
updateSwiping(MotionEvent ev)281     private void updateSwiping(MotionEvent ev) {
282         if (!mSwiping) {
283             float deltaX = ev.getRawX() - mDownX;
284             float deltaY = ev.getRawY() - mDownY;
285             if ((deltaX * deltaX) + (deltaY * deltaY) > mSlop * mSlop) {
286                 mSwiping = deltaX > mSlop * 2 && Math.abs(deltaY) < mSlop * 2;
287             } else {
288                 mSwiping = false;
289             }
290         }
291     }
292 
293     private void updateDismiss(MotionEvent ev) {
294         float deltaX = ev.getRawX() - mDownX;
295         if (!mDismissed) {
296             mVelocityTracker.addMovement(ev);
297             mVelocityTracker.computeCurrentVelocity(1000);
298 
299             if (deltaX > (getWidth() * DISMISS_MIN_DRAG_WIDTH_RATIO) &&
300                     ev.getRawX() >= mLastX) {
301                 mDismissed = true;
302             }
303         }
304         // Check if the user tried to undo this.
305         if (mDismissed && mSwiping) {
306             // Check if the user's finger is actually back
307             if (deltaX < (getWidth() * DISMISS_MIN_DRAG_WIDTH_RATIO)) {
308                 mDismissed = false;
309             }
310         }
311     }
312 
313     /**
314      * Tests scrollability within child views of v in the direction of dx.
315      *
316      * @param v View to test for horizontal scrollability
317      * @param checkV Whether the view v passed should itself be checked for scrollability (true),
318      *               or just its children (false).
319      * @param dx Delta scrolled in pixels. Only the sign of this is used.
320      * @param x X coordinate of the active touch point
321      * @param y Y coordinate of the active touch point
322      * @return true if child views of v can be scrolled by delta of dx.
323      */
324     protected boolean canScroll(View v, boolean checkV, float dx, float x, float y) {
325         if (v instanceof ViewGroup) {
326             final ViewGroup group = (ViewGroup) v;
327             final int scrollX = v.getScrollX();
328             final int scrollY = v.getScrollY();
329             final int count = group.getChildCount();
330             for (int i = count - 1; i >= 0; i--) {
331                 final View child = group.getChildAt(i);
332                 if (x + scrollX >= child.getLeft() && x + scrollX < child.getRight() &&
333                         y + scrollY >= child.getTop() && y + scrollY < child.getBottom() &&
334                         canScroll(child, true, dx, x + scrollX - child.getLeft(),
335                                 y + scrollY - child.getTop())) {
336                     return true;
337                 }
338             }
339         }
340 
341         return checkV && v.canScrollHorizontally((int) -dx);
342     }
343 }
344