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.View;
22import android.view.ViewGroup;
23
24/**
25 * A propagation that varies with the distance to the epicenter of the Transition
26 * or center of the scene if no epicenter exists. When a View is visible in the
27 * start of the transition, Views farther from the epicenter will transition
28 * sooner than Views closer to the epicenter. When a View is not in the start
29 * of the transition or is not visible at the start of the transition, it will
30 * transition sooner when closer to the epicenter and later when farther from
31 * the epicenter. This is the default TransitionPropagation used with
32 * {@link android.transition.Explode}.
33 */
34public class CircularPropagation extends VisibilityPropagation {
35    private static final String TAG = "CircularPropagation";
36
37    private float mPropagationSpeed = 3.0f;
38
39    /**
40     * Sets the speed at which transition propagation happens, relative to the duration of the
41     * Transition. A <code>propagationSpeed</code> of 1 means that a View centered farthest from
42     * the epicenter and View centered at the epicenter will have a difference
43     * in start delay of approximately the duration of the Transition. A speed of 2 means the
44     * start delay difference will be approximately half of the duration of the transition. A
45     * value of 0 is illegal, but negative values will invert the propagation.
46     *
47     * @param propagationSpeed The speed at which propagation occurs, relative to the duration
48     *                         of the transition. A speed of 4 means it works 4 times as fast
49     *                         as the duration of the transition. May not be 0.
50     */
51    public void setPropagationSpeed(float propagationSpeed) {
52        if (propagationSpeed == 0) {
53            throw new IllegalArgumentException("propagationSpeed may not be 0");
54        }
55        mPropagationSpeed = propagationSpeed;
56    }
57
58    @Override
59    public long getStartDelay(ViewGroup sceneRoot, Transition transition,
60            TransitionValues startValues, TransitionValues endValues) {
61        if (startValues == null && endValues == null) {
62            return 0;
63        }
64        int directionMultiplier = 1;
65        TransitionValues positionValues;
66        if (endValues == null || getViewVisibility(startValues) == View.VISIBLE) {
67            positionValues = startValues;
68            directionMultiplier = -1;
69        } else {
70            positionValues = endValues;
71        }
72
73        int viewCenterX = getViewX(positionValues);
74        int viewCenterY = getViewY(positionValues);
75
76        Rect epicenter = transition.getEpicenter();
77        int epicenterX;
78        int epicenterY;
79        if (epicenter != null) {
80            epicenterX = epicenter.centerX();
81            epicenterY = epicenter.centerY();
82        } else {
83            int[] loc = new int[2];
84            sceneRoot.getLocationOnScreen(loc);
85            epicenterX = Math.round(loc[0] + (sceneRoot.getWidth() / 2)
86                    + sceneRoot.getTranslationX());
87            epicenterY = Math.round(loc[1] + (sceneRoot.getHeight() / 2)
88                    + sceneRoot.getTranslationY());
89        }
90        float distance = distance(viewCenterX, viewCenterY, epicenterX, epicenterY);
91        float maxDistance = distance(0, 0, sceneRoot.getWidth(), sceneRoot.getHeight());
92        float distanceFraction = distance/maxDistance;
93
94        long duration = transition.getDuration();
95        if (duration < 0) {
96            duration = 300;
97        }
98
99        return Math.round(duration * directionMultiplier / mPropagationSpeed * distanceFraction);
100    }
101
102    private static float distance(float x1, float y1, float x2, float y2) {
103        float x = x2 - x1;
104        float y = y2 - y1;
105        return FloatMath.sqrt((x * x) + (y * y));
106    }
107}
108