SwipeDismissLayout.java revision 3f8dd14451521d728fba548c7655d8fe531ed2ef 
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        ((Activity) context).convertFromTranslucent();
111    }
112
113    public void setOnDismissedListener(OnDismissedListener listener) {
114        mDismissedListener = listener;
115    }
116
117    public void setOnSwipeProgressChangedListener(OnSwipeProgressChangedListener listener) {
118        mProgressListener = listener;
119    }
120
121    @Override
122    public boolean onInterceptTouchEvent(MotionEvent ev) {
123        // offset because the view is translated during swipe
124        ev.offsetLocation(mTranslationX, 0);
125
126        switch (ev.getActionMasked()) {
127            case MotionEvent.ACTION_DOWN:
128                resetMembers();
129                mDownX = ev.getRawX();
130                mDownY = ev.getRawY();
131                mActiveTouchId = ev.getPointerId(0);
132                mVelocityTracker = VelocityTracker.obtain();
133                mVelocityTracker.addMovement(ev);
134                break;
135
136            case MotionEvent.ACTION_POINTER_DOWN:
137                int actionIndex = ev.getActionIndex();
138                mActiveTouchId = ev.getPointerId(actionIndex);
139                break;
140            case MotionEvent.ACTION_POINTER_UP:
141                actionIndex = ev.getActionIndex();
142                int pointerId = ev.getPointerId(actionIndex);
143                if (pointerId == mActiveTouchId) {
144                    // This was our active pointer going up. Choose a new active pointer.
145                    int newActionIndex = actionIndex == 0 ? 1 : 0;
146                    mActiveTouchId = ev.getPointerId(newActionIndex);
147                }
148                break;
149
150            case MotionEvent.ACTION_CANCEL:
151            case MotionEvent.ACTION_UP:
152                resetMembers();
153                break;
154
155            case MotionEvent.ACTION_MOVE:
156                if (mVelocityTracker == null || mDiscardIntercept) {
157                    break;
158                }
159
160                int pointerIndex = ev.findPointerIndex(mActiveTouchId);
161                if (pointerIndex == -1) {
162                    Log.e(TAG, "Invalid pointer index: ignoring.");
163                    mDiscardIntercept = true;
164                    break;
165                }
166                float dx = ev.getRawX() - mDownX;
167                float x = ev.getX(pointerIndex);
168                float y = ev.getY(pointerIndex);
169                if (dx != 0 && canScroll(this, false, dx, x, y)) {
170                    mDiscardIntercept = true;
171                    break;
172                }
173                updateSwiping(ev);
174                break;
175        }
176
177        return !mDiscardIntercept && mSwiping;
178    }
179
180    @Override
181    public boolean onTouchEvent(MotionEvent ev) {
182        if (mVelocityTracker == null) {
183            return super.onTouchEvent(ev);
184        }
185        switch (ev.getActionMasked()) {
186            case MotionEvent.ACTION_UP:
187                updateDismiss(ev);
188                if (mDismissed) {
189                    dismiss();
190                } else if (mSwiping) {
191                    cancel();
192                }
193                resetMembers();
194                break;
195
196            case MotionEvent.ACTION_CANCEL:
197                cancel();
198                resetMembers();
199                break;
200
201            case MotionEvent.ACTION_MOVE:
202                mVelocityTracker.addMovement(ev);
203                mLastX = ev.getRawX();
204                updateSwiping(ev);
205                if (mSwiping) {
206                    ((Activity) getContext()).convertToTranslucent(null, null);
207                    setProgress(ev.getRawX() - mDownX);
208                    break;
209                }
210        }
211        return true;
212    }
213
214    private void setProgress(float deltaX) {
215        mTranslationX = deltaX;
216        if (mProgressListener != null && deltaX >= 0)  {
217            mProgressListener.onSwipeProgressChanged(this, deltaX / getWidth(), deltaX);
218        }
219    }
220
221    private void dismiss() {
222        if (mDismissedListener != null) {
223            mDismissedListener.onDismissed(this);
224        }
225    }
226
227    protected void cancel() {
228        ((Activity) getContext()).convertFromTranslucent();
229        if (mProgressListener != null) {
230            mProgressListener.onSwipeCancelled(this);
231        }
232    }
233
234    /**
235     * Resets internal members when canceling.
236     */
237    private void resetMembers() {
238        if (mVelocityTracker != null) {
239            mVelocityTracker.recycle();
240        }
241        mVelocityTracker = null;
242        mTranslationX = 0;
243        mDownX = 0;
244        mDownY = 0;
245        mSwiping = false;
246        mDismissed = false;
247        mDiscardIntercept = false;
248    }
249
250    private void updateSwiping(MotionEvent ev) {
251        if (!mSwiping) {
252            float deltaX = ev.getRawX() - mDownX;
253            float deltaY = ev.getRawY() - mDownY;
254            if ((deltaX * deltaX) + (deltaY * deltaY) > mSlop * mSlop) {
255                mSwiping = deltaX > mSlop * 2 && Math.abs(deltaY) < mSlop * 2;
256            } else {
257                mSwiping = false;
258            }
259        }
260    }
261
262    private void updateDismiss(MotionEvent ev) {
263        float deltaX = ev.getRawX() - mDownX;
264        if (!mDismissed) {
265            mVelocityTracker.addMovement(ev);
266            mVelocityTracker.computeCurrentVelocity(1000);
267
268            if (deltaX > (getWidth() * DISMISS_MIN_DRAG_WIDTH_RATIO) &&
269                    ev.getRawX() >= mLastX) {
270                mDismissed = true;
271            }
272        }
273        // Check if the user tried to undo this.
274        if (mDismissed && mSwiping) {
275            // Check if the user's finger is actually back
276            if (deltaX < (getWidth() * DISMISS_MIN_DRAG_WIDTH_RATIO)) {
277                mDismissed = false;
278            }
279        }
280    }
281
282    /**
283     * Tests scrollability within child views of v in the direction of dx.
284     *
285     * @param v View to test for horizontal scrollability
286     * @param checkV Whether the view v passed should itself be checked for scrollability (true),
287     *               or just its children (false).
288     * @param dx Delta scrolled in pixels. Only the sign of this is used.
289     * @param x X coordinate of the active touch point
290     * @param y Y coordinate of the active touch point
291     * @return true if child views of v can be scrolled by delta of dx.
292     */
293    protected boolean canScroll(View v, boolean checkV, float dx, float x, float y) {
294        if (v instanceof ViewGroup) {
295            final ViewGroup group = (ViewGroup) v;
296            final int scrollX = v.getScrollX();
297            final int scrollY = v.getScrollY();
298            final int count = group.getChildCount();
299            for (int i = count - 1; i >= 0; i--) {
300                final View child = group.getChildAt(i);
301                if (x + scrollX >= child.getLeft() && x + scrollX < child.getRight() &&
302                        y + scrollY >= child.getTop() && y + scrollY < child.getBottom() &&
303                        canScroll(child, true, dx, x + scrollX - child.getLeft(),
304                                y + scrollY - child.getTop())) {
305                    return true;
306                }
307            }
308        }
309
310        return checkV && v.canScrollHorizontally((int) -dx);
311    }
312}
313