ChangeColor.java

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/*
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 * Copyright (C) 2014 The Android Open Source Project
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 *
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 * Licensed under the Apache License, Version 2.0 (the "License");
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 * you may not use this file except in compliance with the License.
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 * You may obtain a copy of the License at
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 *
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 *      http://www.apache.org/licenses/LICENSE-2.0
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 *
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 * Unless required by applicable law or agreed to in writing, software
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 * distributed under the License is distributed on an "AS IS" BASIS,
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 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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 * See the License for the specific language governing permissions and
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 * limitations under the License.
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 */
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package com.example.android.customtransition;
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import android.animation.Animator;
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import android.animation.ArgbEvaluator;
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import android.animation.ObjectAnimator;
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import android.animation.PropertyValuesHolder;
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import android.animation.ValueAnimator;
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import android.graphics.drawable.ColorDrawable;
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import android.graphics.drawable.Drawable;
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import android.graphics.drawable.TransitionDrawable;
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import android.transition.ChangeBounds;
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import android.transition.Transition;
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import android.transition.TransitionValues;
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import android.view.View;
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import android.view.ViewGroup;
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import android.view.ViewPropertyAnimator;
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public class ChangeColor extends Transition {
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    /** Key to store a color value in TransitionValues object */
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    private static final String PROPNAME_BACKGROUND = "customtransition:change_color:background";
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    /**
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     * Convenience method: Add the background Drawable property value
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     * to the TransitionsValues.value Map for a target.
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     */
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    private void captureValues(TransitionValues values) {
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        // Capture the property values of views for later use
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        values.values.put(PROPNAME_BACKGROUND, values.view.getBackground());
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    }
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   @Override
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    public void captureStartValues(TransitionValues transitionValues) {
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        captureValues(transitionValues);
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    }
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    // Capture the value of the background drawable property for a target in the ending Scene.
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    @Override
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    public void captureEndValues(TransitionValues transitionValues) {
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        captureValues(transitionValues);
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    }
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    // Create an animation for each target that is in both the starting and ending Scene. For each
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    // pair of targets, if their background property value is a color (rather than a graphic),
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    // create a ValueAnimator based on an ArgbEvaluator that interpolates between the starting and
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    // ending color. Also create an update listener that sets the View background color for each
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    // animation frame
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    @Override
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    public Animator createAnimator(ViewGroup sceneRoot,
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                                   TransitionValues startValues, TransitionValues endValues) {
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        // This transition can only be applied to views that are on both starting and ending scenes.
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        if (null == startValues || null == endValues) {
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            return null;
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        }
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        // Store a convenient reference to the target. Both the starting and ending layout have the
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        // same target.
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        final View view = endValues.view;
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        // Store the object containing the background property for both the starting and ending
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        // layouts.
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        Drawable startBackground = (Drawable) startValues.values.get(PROPNAME_BACKGROUND);
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        Drawable endBackground = (Drawable) endValues.values.get(PROPNAME_BACKGROUND);
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        // This transition changes background colors for a target. It doesn't animate any other
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        // background changes. If the property isn't a ColorDrawable, ignore the target.
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        if (startBackground instanceof ColorDrawable && endBackground instanceof ColorDrawable) {
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            ColorDrawable startColor = (ColorDrawable) startBackground;
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            ColorDrawable endColor = (ColorDrawable) endBackground;
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            // If the background color for the target in the starting and ending layouts is
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            // different, create an animation.
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            if (startColor.getColor() != endColor.getColor()) {
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                // Create a new Animator object to apply to the targets as the transitions framework
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                // changes from the starting to the ending layout. Use the class ValueAnimator,
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                // which provides a timing pulse to change property values provided to it. The
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                // animation runs on the UI thread. The Evaluator controls what type of
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                // interpolation is done. In this case, an ArgbEvaluator interpolates between two
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                // #argb values, which are specified as the 2nd and 3rd input arguments.
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                ValueAnimator animator = ValueAnimator.ofObject(new ArgbEvaluator(),
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                        startColor.getColor(), endColor.getColor());
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                // Add an update listener to the Animator object.
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                animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
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                    @Override
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                    public void onAnimationUpdate(ValueAnimator animation) {
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                        Object value = animation.getAnimatedValue();
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                        // Each time the ValueAnimator produces a new frame in the animation, change
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                        // the background color of the target. Ensure that the value isn't null.
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                        if (null != value) {
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                            view.setBackgroundColor((Integer) value);
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                        }
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                    }
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                });
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                // Return the Animator object to the transitions framework. As the framework changes
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                // between the starting and ending layouts, it applies the animation you've created.
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                return animator;
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            }
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        }
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        // For non-ColorDrawable backgrounds, we just return null, and no animation will take place.
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        return null;
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    }
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}