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 
17 package com.example.android.customtransition;
18 
19 import android.animation.Animator;
20 import android.animation.ArgbEvaluator;
21 import android.animation.ObjectAnimator;
22 import android.animation.PropertyValuesHolder;
23 import android.animation.ValueAnimator;
24 import android.graphics.drawable.ColorDrawable;
25 import android.graphics.drawable.Drawable;
26 import android.graphics.drawable.TransitionDrawable;
27 import android.transition.ChangeBounds;
28 import android.transition.Transition;
29 import android.transition.TransitionValues;
30 import android.view.View;
31 import android.view.ViewGroup;
32 import android.view.ViewPropertyAnimator;
33 
34 public class ChangeColor extends Transition {
35 
36     /** Key to store a color value in TransitionValues object */
37     private static final String PROPNAME_BACKGROUND = "customtransition:change_color:background";
38 
39     // BEGIN_INCLUDE (capture_values)
40     /**
41      * Convenience method: Add the background Drawable property value
42      * to the TransitionsValues.value Map for a target.
43      */
captureValues(TransitionValues values)44     private void captureValues(TransitionValues values) {
45         // Capture the property values of views for later use
46         values.values.put(PROPNAME_BACKGROUND, values.view.getBackground());
47     }
48 
49     @Override
captureStartValues(TransitionValues transitionValues)50     public void captureStartValues(TransitionValues transitionValues) {
51         captureValues(transitionValues);
52     }
53 
54     // Capture the value of the background drawable property for a target in the ending Scene.
55     @Override
captureEndValues(TransitionValues transitionValues)56     public void captureEndValues(TransitionValues transitionValues) {
57         captureValues(transitionValues);
58     }
59     // END_INCLUDE (capture_values)
60 
61     // BEGIN_INCLUDE (create_animator)
62     // Create an animation for each target that is in both the starting and ending Scene. For each
63     // pair of targets, if their background property value is a color (rather than a graphic),
64     // create a ValueAnimator based on an ArgbEvaluator that interpolates between the starting and
65     // ending color. Also create an update listener that sets the View background color for each
66     // animation frame
67     @Override
createAnimator(ViewGroup sceneRoot, TransitionValues startValues, TransitionValues endValues)68     public Animator createAnimator(ViewGroup sceneRoot,
69                                    TransitionValues startValues, TransitionValues endValues) {
70         // This transition can only be applied to views that are on both starting and ending scenes.
71         if (null == startValues || null == endValues) {
72             return null;
73         }
74         // Store a convenient reference to the target. Both the starting and ending layout have the
75         // same target.
76         final View view = endValues.view;
77         // Store the object containing the background property for both the starting and ending
78         // layouts.
79         Drawable startBackground = (Drawable) startValues.values.get(PROPNAME_BACKGROUND);
80         Drawable endBackground = (Drawable) endValues.values.get(PROPNAME_BACKGROUND);
81         // This transition changes background colors for a target. It doesn't animate any other
82         // background changes. If the property isn't a ColorDrawable, ignore the target.
83         if (startBackground instanceof ColorDrawable && endBackground instanceof ColorDrawable) {
84             ColorDrawable startColor = (ColorDrawable) startBackground;
85             ColorDrawable endColor = (ColorDrawable) endBackground;
86             // If the background color for the target in the starting and ending layouts is
87             // different, create an animation.
88             if (startColor.getColor() != endColor.getColor()) {
89                 // Create a new Animator object to apply to the targets as the transitions framework
90                 // changes from the starting to the ending layout. Use the class ValueAnimator,
91                 // which provides a timing pulse to change property values provided to it. The
92                 // animation runs on the UI thread. The Evaluator controls what type of
93                 // interpolation is done. In this case, an ArgbEvaluator interpolates between two
94                 // #argb values, which are specified as the 2nd and 3rd input arguments.
95                 ValueAnimator animator = ValueAnimator.ofObject(new ArgbEvaluator(),
96                         startColor.getColor(), endColor.getColor());
97                 // Add an update listener to the Animator object.
98                 animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
99                     @Override
100                     public void onAnimationUpdate(ValueAnimator animation) {
101                         Object value = animation.getAnimatedValue();
102                         // Each time the ValueAnimator produces a new frame in the animation, change
103                         // the background color of the target. Ensure that the value isn't null.
104                         if (null != value) {
105                             view.setBackgroundColor((Integer) value);
106                         }
107                     }
108                 });
109                 // Return the Animator object to the transitions framework. As the framework changes
110                 // between the starting and ending layouts, it applies the animation you've created.
111                 return animator;
112             }
113         }
114         // For non-ColorDrawable backgrounds, we just return null, and no animation will take place.
115         return null;
116     }
117     // END_INCLUDE (create_animator)
118 
119 }
120