SwipeDismissLayout.java revision 11b1469144d73ad0280ef9d0c2e478d180f17074 
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.content.Context;
21import android.util.AttributeSet;
22import android.util.Log;
23import android.view.MotionEvent;
24import android.view.VelocityTracker;
25import android.view.View;
26import android.view.ViewConfiguration;
27import android.view.ViewGroup;
28import android.view.animation.AccelerateInterpolator;
29import android.view.animation.DecelerateInterpolator;
30import android.widget.FrameLayout;
31
32/**
33 * Special layout that finishes its activity when swiped away.
34 */
35public class SwipeDismissLayout extends FrameLayout {
36    private static final String TAG = "SwipeDismissLayout";
37
38    private static final float DISMISS_MIN_PROGRESS = 0.6f;
39
40    public interface OnDismissedListener {
41        void onDismissed(SwipeDismissLayout layout);
42    }
43
44    public interface OnSwipeProgressChangedListener {
45        /**
46         * Called when the layout has been swiped and the position of the window should change.
47         *
48         * @param progress A number in [-1, 1] representing how far to the left
49         * or right the window has been swiped. Negative values are swipes
50         * left, and positives are right.
51         * @param translate A number in [-w, w], where w is the width of the
52         * layout. This is equivalent to progress * layout.getWidth().
53         */
54        void onSwipeProgressChanged(SwipeDismissLayout layout, float progress, float translate);
55
56        void onSwipeCancelled(SwipeDismissLayout layout);
57    }
58
59    // Cached ViewConfiguration and system-wide constant values
60    private int mSlop;
61    private int mMinFlingVelocity;
62    private int mMaxFlingVelocity;
63    private long mAnimationTime;
64    private TimeInterpolator mCancelInterpolator;
65    private TimeInterpolator mDismissInterpolator;
66
67    // Transient properties
68    private int mActiveTouchId;
69    private float mDownX;
70    private float mDownY;
71    private boolean mSwiping;
72    private boolean mDismissed;
73    private boolean mDiscardIntercept;
74    private VelocityTracker mVelocityTracker;
75    private float mTranslationX;
76
77    private OnDismissedListener mDismissedListener;
78    private OnSwipeProgressChangedListener mProgressListener;
79
80    private float mLastX;
81
82    public SwipeDismissLayout(Context context) {
83        super(context);
84        init(context);
85    }
86
87    public SwipeDismissLayout(Context context, AttributeSet attrs) {
88        super(context, attrs);
89        init(context);
90    }
91
92    public SwipeDismissLayout(Context context, AttributeSet attrs, int defStyle) {
93        super(context, attrs, defStyle);
94        init(context);
95    }
96
97    private void init(Context context) {
98        ViewConfiguration vc = ViewConfiguration.get(getContext());
99        mSlop = vc.getScaledTouchSlop();
100        mMinFlingVelocity = vc.getScaledMinimumFlingVelocity();
101        mMaxFlingVelocity = vc.getScaledMaximumFlingVelocity();
102        mAnimationTime = getContext().getResources().getInteger(
103                android.R.integer.config_shortAnimTime);
104        mCancelInterpolator = new DecelerateInterpolator(1.5f);
105        mDismissInterpolator = new AccelerateInterpolator(1.5f);
106    }
107
108    public void setOnDismissedListener(OnDismissedListener listener) {
109        mDismissedListener = listener;
110    }
111
112    public void setOnSwipeProgressChangedListener(OnSwipeProgressChangedListener listener) {
113        mProgressListener = listener;
114    }
115
116    @Override
117    public boolean onInterceptTouchEvent(MotionEvent ev) {
118        // offset because the view is translated during swipe
119        ev.offsetLocation(mTranslationX, 0);
120
121        switch (ev.getActionMasked()) {
122            case MotionEvent.ACTION_DOWN:
123                resetMembers();
124                mDownX = ev.getRawX();
125                mDownY = ev.getRawY();
126                mActiveTouchId = ev.getPointerId(0);
127                mVelocityTracker = VelocityTracker.obtain();
128                mVelocityTracker.addMovement(ev);
129                break;
130
131            case MotionEvent.ACTION_POINTER_DOWN:
132                int actionIndex = ev.getActionIndex();
133                mActiveTouchId = ev.getPointerId(actionIndex);
134                break;
135            case MotionEvent.ACTION_POINTER_UP:
136                actionIndex = ev.getActionIndex();
137                int pointerId = ev.getPointerId(actionIndex);
138                if (pointerId == mActiveTouchId) {
139                    // This was our active pointer going up. Choose a new active pointer.
140                    int newActionIndex = actionIndex == 0 ? 1 : 0;
141                    mActiveTouchId = ev.getPointerId(newActionIndex);
142                }
143                break;
144
145            case MotionEvent.ACTION_CANCEL:
146            case MotionEvent.ACTION_UP:
147                resetMembers();
148                break;
149
150            case MotionEvent.ACTION_MOVE:
151                if (mVelocityTracker == null || mDiscardIntercept) {
152                    break;
153                }
154
155                int pointerIndex = ev.findPointerIndex(mActiveTouchId);
156                if (pointerIndex == -1) {
157                    Log.e(TAG, "Invalid pointer index: ignoring.");
158                    mDiscardIntercept = true;
159                    break;
160                }
161                float dx = ev.getRawX() - mDownX;
162                float x = ev.getX(pointerIndex);
163                float y = ev.getY(pointerIndex);
164                if (dx != 0 && canScroll(this, false, dx, x, y)) {
165                    mDiscardIntercept = true;
166                    break;
167                }
168                updateSwiping(ev);
169                break;
170        }
171
172        return !mDiscardIntercept && mSwiping;
173    }
174
175    @Override
176    public boolean onTouchEvent(MotionEvent ev) {
177        if (mVelocityTracker == null) {
178            return super.onTouchEvent(ev);
179        }
180        switch (ev.getActionMasked()) {
181            case MotionEvent.ACTION_UP:
182                updateDismiss(ev);
183                if (mDismissed) {
184                    dismiss();
185                } else if (mSwiping) {
186                    cancel();
187                }
188                resetMembers();
189                break;
190
191            case MotionEvent.ACTION_CANCEL:
192                cancel();
193                resetMembers();
194                break;
195
196            case MotionEvent.ACTION_MOVE:
197                mVelocityTracker.addMovement(ev);
198                mLastX = ev.getRawX();
199                updateSwiping(ev);
200                if (mSwiping) {
201                    setProgress(ev.getRawX() - mDownX);
202                    break;
203                }
204        }
205        return true;
206    }
207
208    private void setProgress(float deltaX) {
209        mTranslationX = deltaX;
210        if (mProgressListener != null) {
211            mProgressListener.onSwipeProgressChanged(this, deltaX / getWidth(), deltaX);
212        }
213    }
214
215    private void dismiss() {
216        if (mDismissedListener != null) {
217            mDismissedListener.onDismissed(this);
218        }
219    }
220
221    protected void cancel() {
222        if (mProgressListener != null) {
223            mProgressListener.onSwipeCancelled(this);
224        }
225    }
226
227    /**
228     * Resets internal members when canceling.
229     */
230    private void resetMembers() {
231        if (mVelocityTracker != null) {
232            mVelocityTracker.recycle();
233        }
234        mVelocityTracker = null;
235        mTranslationX = 0;
236        mDownX = 0;
237        mDownY = 0;
238        mSwiping = false;
239        mDismissed = false;
240        mDiscardIntercept = false;
241    }
242
243    private void updateSwiping(MotionEvent ev) {
244        if (!mSwiping) {
245            float deltaX = ev.getRawX() - mDownX;
246            float deltaY = ev.getRawY() - mDownY;
247            mSwiping = deltaX > mSlop * 2 && Math.abs(deltaY) < mSlop * 2;
248        }
249    }
250
251    private void updateDismiss(MotionEvent ev) {
252        float deltaX = ev.getRawX() - mDownX;
253        if (!mDismissed) {
254            mVelocityTracker.addMovement(ev);
255            mVelocityTracker.computeCurrentVelocity(1000);
256
257            float velocityX = mVelocityTracker.getXVelocity();
258            float absVelocityX = Math.abs(velocityX);
259            float absVelocityY = Math.abs(mVelocityTracker.getYVelocity());
260
261            if (deltaX > (getWidth() * DISMISS_MIN_PROGRESS) &&
262                    absVelocityX < mMinFlingVelocity &&
263                    ev.getRawX() >= mLastX) {
264                mDismissed = true;
265            }
266        }
267        // Check if the user tried to undo this.
268        if (mDismissed && mSwiping) {
269            // Check if the user's finger is actually back
270            if (deltaX < (getWidth() * DISMISS_MIN_PROGRESS)) {
271                mDismissed = false;
272            }
273        }
274    }
275
276    /**
277     * Tests scrollability within child views of v in the direction of dx.
278     *
279     * @param v View to test for horizontal scrollability
280     * @param checkV Whether the view v passed should itself be checked for scrollability (true),
281     *               or just its children (false).
282     * @param dx Delta scrolled in pixels. Only the sign of this is used.
283     * @param x X coordinate of the active touch point
284     * @param y Y coordinate of the active touch point
285     * @return true if child views of v can be scrolled by delta of dx.
286     */
287    protected boolean canScroll(View v, boolean checkV, float dx, float x, float y) {
288        if (v instanceof ViewGroup) {
289            final ViewGroup group = (ViewGroup) v;
290            final int scrollX = v.getScrollX();
291            final int scrollY = v.getScrollY();
292            final int count = group.getChildCount();
293            for (int i = count - 1; i >= 0; i--) {
294                final View child = group.getChildAt(i);
295                if (x + scrollX >= child.getLeft() && x + scrollX < child.getRight() &&
296                        y + scrollY >= child.getTop() && y + scrollY < child.getBottom() &&
297                        canScroll(child, true, dx, x + scrollX - child.getLeft(),
298                                y + scrollY - child.getTop())) {
299                    return true;
300                }
301            }
302        }
303
304        return checkV && v.canScrollHorizontally((int) -dx);
305    }
306}
307