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.view.ViewGroup;
19
20/**
21 * Extend <code>TransitionPropagation</code> to customize start delays for Animators created
22 * in {@link android.transition.Transition#createAnimator(ViewGroup,
23 * TransitionValues, TransitionValues)}. A Transition such as {@link android.transition.Explode}
24 * defaults to using {@link android.transition.CircularPropagation} and Views closer to the
25 * epicenter will move out of the scene later and into the scene sooner than Views farther
26 * from the epicenter, giving the appearance of inertia. With no TransitionPropagation, all
27 * Views will react simultaneously to the start of the transition.
28 *
29 * @see Transition#setPropagation(TransitionPropagation)
30 * @see Transition#getEpicenter()
31 */
32public abstract class TransitionPropagation {
33    /**
34     * Called by Transition to alter the Animator start delay. All start delays will be adjusted
35     * such that the minimum becomes zero.
36     * @param sceneRoot The root of the View hierarchy running the transition.
37     * @param transition The transition that created the Animator
38     * @param startValues The values for a specific target in the start scene.
39     * @param endValues The values for the target in the end scene.
40     * @return A start delay to use with the Animator created by <code>transition</code>. The
41     * delay will be offset by the minimum delay of all <code>TransitionPropagation</code>s
42     * used in the Transition so that the smallest delay will be 0. Returned values may be
43     * negative.
44     */
45    public abstract long getStartDelay(ViewGroup sceneRoot, Transition transition,
46            TransitionValues startValues, TransitionValues endValues);
47
48    /**
49     * Captures the values in the start or end scene for the properties that this
50     * transition propagation monitors. These values are then passed as the startValues
51     * or endValues structure in a later call to
52     * {@link #getStartDelay(ViewGroup, Transition, TransitionValues, TransitionValues)}.
53     * The main concern for an implementation is what the
54     * properties are that the transition cares about and what the values are
55     * for all of those properties. The start and end values will be compared
56     * later during the
57     * {@link #getStartDelay(ViewGroup, Transition, TransitionValues, TransitionValues)}.
58     * method to determine the start delay.
59     *
60     * <p>Subclasses must implement this method. The method should only be called by the
61     * transition system; it is not intended to be called from external classes.</p>
62     *
63     * @param transitionValues The holder for any values that the Transition
64     * wishes to store. Values are stored in the <code>values</code> field
65     * of this TransitionValues object and are keyed from
66     * a String value. For example, to store a view's rotation value,
67     * a transition might call
68     * <code>transitionValues.values.put("appname:transitionname:rotation",
69     * view.getRotation())</code>. The target view will already be stored in
70     * the transitionValues structure when this method is called.
71     */
72    public abstract void captureValues(TransitionValues transitionValues);
73
74    /**
75     * Returns the set of property names stored in the {@link TransitionValues}
76     * object passed into {@link #captureValues(TransitionValues)} that
77     * this transition propagation cares about for the purposes of preventing
78     * duplicate capturing of property values.
79
80     * <p>A <code>TransitionPropagation</code> must override this method to prevent
81     * duplicate capturing of values and must contain at least one </p>
82     *
83     * @return An array of property names as described in the class documentation for
84     * {@link TransitionValues}.
85     */
86    public abstract String[] getPropagationProperties() ;
87}
88