SwipeDismissLayout.java revision 625ec4849118f061a99558ad558b16020435a88d 
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.animation.AccelerateInterpolator;
30import android.view.animation.DecelerateInterpolator;
31import android.widget.FrameLayout;
32
33/**
34 * Special layout that finishes its activity when swiped away.
35 */
36public class SwipeDismissLayout extends FrameLayout {
37    private static final String TAG = "SwipeDismissLayout";
38
39    private static final float DISMISS_MIN_DRAG_WIDTH_RATIO = .33f;
40
41    public interface OnDismissedListener {
42        void onDismissed(SwipeDismissLayout layout);
43    }
44
45    public interface OnSwipeProgressChangedListener {
46        /**
47         * Called when the layout has been swiped and the position of the window should change.
48         *
49         * @param progress A number in [0, 1] representing how far to the
50         * right the window has been swiped
51         * @param translate A number in [0, 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        // SwipeDismissLayout assumes that the host Activity is translucent
107        // and temporarily disables translucency when it is fully visible.
108        // As soon as the user starts swiping, we will re-enable
109        // translucency.
110        if (context instanceof Activity) {
111            ((Activity) context).convertFromTranslucent();
112        }
113    }
114
115    public void setOnDismissedListener(OnDismissedListener listener) {
116        mDismissedListener = listener;
117    }
118
119    public void setOnSwipeProgressChangedListener(OnSwipeProgressChangedListener listener) {
120        mProgressListener = listener;
121    }
122
123    @Override
124    public boolean onInterceptTouchEvent(MotionEvent ev) {
125        // offset because the view is translated during swipe
126        ev.offsetLocation(mTranslationX, 0);
127
128        switch (ev.getActionMasked()) {
129            case MotionEvent.ACTION_DOWN:
130                resetMembers();
131                mDownX = ev.getRawX();
132                mDownY = ev.getRawY();
133                mActiveTouchId = ev.getPointerId(0);
134                mVelocityTracker = VelocityTracker.obtain();
135                mVelocityTracker.addMovement(ev);
136                break;
137
138            case MotionEvent.ACTION_POINTER_DOWN:
139                int actionIndex = ev.getActionIndex();
140                mActiveTouchId = ev.getPointerId(actionIndex);
141                break;
142            case MotionEvent.ACTION_POINTER_UP:
143                actionIndex = ev.getActionIndex();
144                int pointerId = ev.getPointerId(actionIndex);
145                if (pointerId == mActiveTouchId) {
146                    // This was our active pointer going up. Choose a new active pointer.
147                    int newActionIndex = actionIndex == 0 ? 1 : 0;
148                    mActiveTouchId = ev.getPointerId(newActionIndex);
149                }
150                break;
151
152            case MotionEvent.ACTION_CANCEL:
153            case MotionEvent.ACTION_UP:
154                resetMembers();
155                break;
156
157            case MotionEvent.ACTION_MOVE:
158                if (mVelocityTracker == null || mDiscardIntercept) {
159                    break;
160                }
161
162                int pointerIndex = ev.findPointerIndex(mActiveTouchId);
163                if (pointerIndex == -1) {
164                    Log.e(TAG, "Invalid pointer index: ignoring.");
165                    mDiscardIntercept = true;
166                    break;
167                }
168                float dx = ev.getRawX() - mDownX;
169                float x = ev.getX(pointerIndex);
170                float y = ev.getY(pointerIndex);
171                if (dx != 0 && canScroll(this, false, dx, x, y)) {
172                    mDiscardIntercept = true;
173                    break;
174                }
175                updateSwiping(ev);
176                break;
177        }
178
179        return !mDiscardIntercept && mSwiping;
180    }
181
182    @Override
183    public boolean onTouchEvent(MotionEvent ev) {
184        if (mVelocityTracker == null) {
185            return super.onTouchEvent(ev);
186        }
187        switch (ev.getActionMasked()) {
188            case MotionEvent.ACTION_UP:
189                updateDismiss(ev);
190                if (mDismissed) {
191                    dismiss();
192                } else if (mSwiping) {
193                    cancel();
194                }
195                resetMembers();
196                break;
197
198            case MotionEvent.ACTION_CANCEL:
199                cancel();
200                resetMembers();
201                break;
202
203            case MotionEvent.ACTION_MOVE:
204                mVelocityTracker.addMovement(ev);
205                mLastX = ev.getRawX();
206                updateSwiping(ev);
207                if (mSwiping) {
208                    if (getContext() instanceof Activity) {
209                        ((Activity) getContext()).convertToTranslucent(null, null);
210                    }
211                    setProgress(ev.getRawX() - mDownX);
212                    break;
213                }
214        }
215        return true;
216    }
217
218    private void setProgress(float deltaX) {
219        mTranslationX = deltaX;
220        if (mProgressListener != null && deltaX >= 0)  {
221            mProgressListener.onSwipeProgressChanged(this, deltaX / getWidth(), deltaX);
222        }
223    }
224
225    private void dismiss() {
226        if (mDismissedListener != null) {
227            mDismissedListener.onDismissed(this);
228        }
229    }
230
231    protected void cancel() {
232        if (getContext() instanceof Activity) {
233            ((Activity) getContext()).convertFromTranslucent();
234        }
235        if (mProgressListener != null) {
236            mProgressListener.onSwipeCancelled(this);
237        }
238    }
239
240    /**
241     * Resets internal members when canceling.
242     */
243    private void resetMembers() {
244        if (mVelocityTracker != null) {
245            mVelocityTracker.recycle();
246        }
247        mVelocityTracker = null;
248        mTranslationX = 0;
249        mDownX = 0;
250        mDownY = 0;
251        mSwiping = false;
252        mDismissed = false;
253        mDiscardIntercept = false;
254    }
255
256    private void updateSwiping(MotionEvent ev) {
257        if (!mSwiping) {
258            float deltaX = ev.getRawX() - mDownX;
259            float deltaY = ev.getRawY() - mDownY;
260            if ((deltaX * deltaX) + (deltaY * deltaY) > mSlop * mSlop) {
261                mSwiping = deltaX > mSlop * 2 && Math.abs(deltaY) < mSlop * 2;
262            } else {
263                mSwiping = false;
264            }
265        }
266    }
267
268    private void updateDismiss(MotionEvent ev) {
269        float deltaX = ev.getRawX() - mDownX;
270        if (!mDismissed) {
271            mVelocityTracker.addMovement(ev);
272            mVelocityTracker.computeCurrentVelocity(1000);
273
274            if (deltaX > (getWidth() * DISMISS_MIN_DRAG_WIDTH_RATIO) &&
275                    ev.getRawX() >= mLastX) {
276                mDismissed = true;
277            }
278        }
279        // Check if the user tried to undo this.
280        if (mDismissed && mSwiping) {
281            // Check if the user's finger is actually back
282            if (deltaX < (getWidth() * DISMISS_MIN_DRAG_WIDTH_RATIO)) {
283                mDismissed = false;
284            }
285        }
286    }
287
288    /**
289     * Tests scrollability within child views of v in the direction of dx.
290     *
291     * @param v View to test for horizontal scrollability
292     * @param checkV Whether the view v passed should itself be checked for scrollability (true),
293     *               or just its children (false).
294     * @param dx Delta scrolled in pixels. Only the sign of this is used.
295     * @param x X coordinate of the active touch point
296     * @param y Y coordinate of the active touch point
297     * @return true if child views of v can be scrolled by delta of dx.
298     */
299    protected boolean canScroll(View v, boolean checkV, float dx, float x, float y) {
300        if (v instanceof ViewGroup) {
301            final ViewGroup group = (ViewGroup) v;
302            final int scrollX = v.getScrollX();
303            final int scrollY = v.getScrollY();
304            final int count = group.getChildCount();
305            for (int i = count - 1; i >= 0; i--) {
306                final View child = group.getChildAt(i);
307                if (x + scrollX >= child.getLeft() && x + scrollX < child.getRight() &&
308                        y + scrollY >= child.getTop() && y + scrollY < child.getBottom() &&
309                        canScroll(child, true, dx, x + scrollX - child.getLeft(),
310                                y + scrollY - child.getTop())) {
311                    return true;
312                }
313            }
314        }
315
316        return checkV && v.canScrollHorizontally((int) -dx);
317    }
318}
319