SidePropagation.java revision 2db3bf5c49ebcd56f02f10145aa40b2445f6be06 
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 */
16package android.transition;
17
18import android.graphics.Rect;
19import android.util.FloatMath;
20import android.util.Log;
21import android.view.Gravity;
22import android.view.View;
23import android.view.ViewGroup;
24
25/**
26 * A <code>TransitionPropagation</code> that propagates based on the distance to the side
27 * and, orthogonally, the distance to epicenter. If the transitioning View is visible in
28 * the start of the transition, then it will transition sooner when closer to the side and
29 * later when farther. If the view is not visible in the start of the transition, then
30 * it will transition later when closer to the side and sooner when farther from the edge.
31 * This is the default TransitionPropagation used with {@link android.transition.Slide}.
32 */
33public class SidePropagation extends VisibilityPropagation {
34    private static final String TAG = "SlidePropagation";
35
36    private float mPropagationSpeed = 3.0f;
37    private int mSide = Gravity.BOTTOM;
38
39    /**
40     * Sets the side that is used to calculate the transition propagation. If the transitioning
41     * View is visible in the start of the transition, then it will transition sooner when
42     * closer to the side and later when farther. If the view is not visible in the start of
43     * the transition, then it will transition later when closer to the side and sooner when
44     * farther from the edge. The default is {@link Gravity#BOTTOM}.
45     *
46     * @param side The side that is used to calculate the transition propagation. Must be one of
47     *             {@link Gravity#LEFT}, {@link Gravity#TOP}, {@link Gravity#RIGHT},
48     *             {@link Gravity#BOTTOM}, {@link Gravity#START}, or {@link Gravity#END}.
49     */
50    public void setSide(int side) {
51        mSide = side;
52    }
53
54    /**
55     * Sets the speed at which transition propagation happens, relative to the duration of the
56     * Transition. A <code>propagationSpeed</code> of 1 means that a View centered at the side
57     * set in {@link #setSide(int)} and View centered at the opposite edge will have a difference
58     * in start delay of approximately the duration of the Transition. A speed of 2 means the
59     * start delay difference will be approximately half of the duration of the transition. A
60     * value of 0 is illegal, but negative values will invert the propagation.
61     *
62     * @param propagationSpeed The speed at which propagation occurs, relative to the duration
63     *                         of the transition. A speed of 4 means it works 4 times as fast
64     *                         as the duration of the transition. May not be 0.
65     */
66    public void setPropagationSpeed(float propagationSpeed) {
67        if (propagationSpeed == 0) {
68            throw new IllegalArgumentException("propagationSpeed may not be 0");
69        }
70        mPropagationSpeed = propagationSpeed;
71    }
72
73    @Override
74    public long getStartDelay(ViewGroup sceneRoot, Transition transition,
75            TransitionValues startValues, TransitionValues endValues) {
76        if (startValues == null && endValues == null) {
77            return 0;
78        }
79        int directionMultiplier = 1;
80        Rect epicenter = transition.getEpicenter();
81        TransitionValues positionValues;
82        if (endValues == null || getViewVisibility(startValues) == View.VISIBLE) {
83            positionValues = startValues;
84            directionMultiplier = -1;
85        } else {
86            positionValues = endValues;
87        }
88
89        int viewCenterX = getViewX(positionValues);
90        int viewCenterY = getViewY(positionValues);
91
92        int[] loc = new int[2];
93        sceneRoot.getLocationOnScreen(loc);
94        int left = loc[0] + Math.round(sceneRoot.getTranslationX());
95        int top = loc[1] + Math.round(sceneRoot.getTranslationY());
96        int right = left + sceneRoot.getWidth();
97        int bottom = top + sceneRoot.getHeight();
98
99        int epicenterX;
100        int epicenterY;
101        if (epicenter != null) {
102            epicenterX = epicenter.centerX();
103            epicenterY = epicenter.centerY();
104        } else {
105            epicenterX = (left + right) / 2;
106            epicenterY = (top + bottom) / 2;
107        }
108
109        float distance = distance(sceneRoot, viewCenterX, viewCenterY, epicenterX, epicenterY,
110                left, top, right, bottom);
111        float maxDistance = getMaxDistance(sceneRoot);
112        float distanceFraction = distance/maxDistance;
113
114        long duration = transition.getDuration();
115        if (duration < 0) {
116            duration = 300;
117        }
118
119        return Math.round(duration * directionMultiplier / mPropagationSpeed * distanceFraction);
120    }
121
122    private int distance(View sceneRoot, int viewX, int viewY, int epicenterX, int epicenterY,
123            int left, int top, int right, int bottom) {
124        final int side;
125        if (mSide == Gravity.START) {
126            final boolean isRtl = sceneRoot.getLayoutDirection() == View.LAYOUT_DIRECTION_RTL;
127            side = isRtl ? Gravity.RIGHT : Gravity.LEFT;
128        } else if (mSide == Gravity.END) {
129            final boolean isRtl = sceneRoot.getLayoutDirection() == View.LAYOUT_DIRECTION_RTL;
130            side = isRtl ? Gravity.LEFT : Gravity.RIGHT;
131        } else {
132            side = mSide;
133        }
134        int distance = 0;
135        switch (side) {
136            case Gravity.LEFT:
137                distance = right - viewX + Math.abs(epicenterY - viewY);
138                break;
139            case Gravity.TOP:
140                distance = bottom - viewY + Math.abs(epicenterX - viewX);
141                break;
142            case Gravity.RIGHT:
143                distance = viewX - left + Math.abs(epicenterY - viewY);
144                break;
145            case Gravity.BOTTOM:
146                distance = viewY - top + Math.abs(epicenterX - viewX);
147                break;
148        }
149        return distance;
150    }
151
152    private int getMaxDistance(ViewGroup sceneRoot) {
153        switch (mSide) {
154            case Gravity.LEFT:
155            case Gravity.RIGHT:
156            case Gravity.START:
157            case Gravity.END:
158                return sceneRoot.getWidth();
159            default:
160                return sceneRoot.getHeight();
161        }
162    }
163}
164