SwipeDismissLayout.java revision 6eafa902cbc15fa35f8f0dfb5e559673fa67f637 
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
17package com.android.internal.widget;
18
19import android.animation.TimeInterpolator;
20import android.app.Activity;
21import android.content.Context;
22import android.util.AttributeSet;
23import android.util.Log;
24import android.view.MotionEvent;
25import android.view.VelocityTracker;
26import android.view.View;
27import android.view.ViewConfiguration;
28import android.view.ViewGroup;
29import android.view.ViewTreeObserver;
30import android.view.animation.AccelerateInterpolator;
31import android.view.animation.DecelerateInterpolator;
32import android.widget.FrameLayout;
33
34/**
35 * Special layout that finishes its activity when swiped away.
36 */
37public 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 {
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         */
55        void onSwipeProgressChanged(SwipeDismissLayout layout, float progress, float translate);
56
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
96    public SwipeDismissLayout(Context context) {
97        super(context);
98        init(context);
99    }
100
101    public SwipeDismissLayout(Context context, AttributeSet attrs) {
102        super(context, attrs);
103        init(context);
104    }
105
106    public SwipeDismissLayout(Context context, AttributeSet attrs, int defStyle) {
107        super(context, attrs, defStyle);
108        init(context);
109    }
110
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
122    public void setOnDismissedListener(OnDismissedListener listener) {
123        mDismissedListener = listener;
124    }
125
126    public void setOnSwipeProgressChangedListener(OnSwipeProgressChangedListener listener) {
127        mProgressListener = listener;
128    }
129
130    @Override
131    protected void onAttachedToWindow() {
132        super.onAttachedToWindow();
133        if (getContext() instanceof Activity) {
134            getViewTreeObserver().addOnEnterAnimationCompleteListener(
135                    mOnEnterAnimationCompleteListener);
136        }
137    }
138
139    @Override
140    protected void onDetachedFromWindow() {
141        super.onDetachedFromWindow();
142        if (getContext() instanceof Activity) {
143            getViewTreeObserver().removeOnEnterAnimationCompleteListener(
144                    mOnEnterAnimationCompleteListener);
145        }
146    }
147
148    @Override
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
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
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
250    private void dismiss() {
251        if (mDismissedListener != null) {
252            mDismissedListener.onDismissed(this);
253        }
254    }
255
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     */
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
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