札记：翻译-使用Scene和Transition实现【场景切换】动画效果

Scene mScene;

// Obtain the scene root element
mSceneRoot = (ViewGroup) mSomeLayoutElement;

// Obtain the view hierarchy to add as a child of
// the scene root when this scene is entered
mViewHierarchy = (ViewGroup) someOtherLayoutElement;

// Create a scene
mScene = new Scene(mSceneRoot, mViewHierarchy);

/**
 * Returns a Scene described by the resource file associated with the given
 * <code>layoutId</code> parameter. If such a Scene has already been created for
 * the given <code>sceneRoot</code>, that same Scene will be returned.
 * This caching of layoutId-based scenes enables sharing of common scenes
 * between those created in code and those referenced by {@link TransitionManager}
 * XML resource files.
 *
 * @param sceneRoot The root of the hierarchy in which scene changes
 * and transitions will take place.
 * @param layoutId The id of a standard layout resource file.
 * @param context The context used in the process of inflating
 * the layout resource.
 * @return The scene for the given root and layout id
 */
public static Scene getSceneForLayout(ViewGroup sceneRoot, int layoutId, Context context);

<fade xmlns:android="http://schemas.android.com/apk/res/android" />

Transition mFadeTransition =
        TransitionInflater.from(this).
        inflateTransition(R.transition.fade_transition);

/**
  * Convenience method to simply change to the given scene using
  * the given transition.
  *
  * <p>Passing in <code>null</code> for the transition parameter will
  * result in the scene changing without any transition running, and is
  * equivalent to calling {@link Scene#exit()} on the scene root's
  * current scene, followed by {@link Scene#enter()} on the scene
  * specified by the <code>scene</code> parameter.</p>
  *
  * @param scene The Scene to change to
  * @param transition The transition to use for this scene change. A
  * value of null causes the scene change to happen with no transition.
  */
 public static void go(Scene scene, Transition transition)

<transitionSet xmlns:android="http://schemas.android.com/apk/res/android"
    android:transitionOrdering="sequential">
    <fade android:fadingMode="fade_out" />
    <changeBounds />
    <fade android:fadingMode="fade_in" />
</transitionSet>

// Start recording changes to the view hierarchy
TransitionManager.beginDelayedTransition(mRootView, mFade);

// Add the new TextView to the view hierarchy
mRootView.addView(mLabelText);

// When the system redraws the screen to show this update,
// the framework will animate the addition as a fade in

public class CustomTransition extends Transition {

    @Override
    public void captureStartValues(TransitionValues values) {}

    @Override
    public void captureEndValues(TransitionValues values) {}

    @Override
    public Animator createAnimator(ViewGroup sceneRoot,
                                   TransitionValues startValues,
                                   TransitionValues endValues) {}
}

public class CustomTransition extends Transition {

    // Define a key for storing a property value in
    // TransitionValues.values with the syntax
    // package_name:transition_class:property_name to avoid collisions
    private static final String PROPNAME_BACKGROUND =
            "com.example.android.customtransition:CustomTransition:background";

    @Override
    public void captureStartValues(TransitionValues transitionValues) {
        // Call the convenience method captureValues
        captureValues(transitionValues);
    }


    // For the view in transitionValues.view, get the values you
    // want and put them in transitionValues.values
    private void captureValues(TransitionValues transitionValues) {
        // Get a reference to the view
        View view = transitionValues.view;
        // Store its background property in the values map
        transitionValues.values.put(PROPNAME_BACKGROUND, view.getBackground());
    }
    ...
}

public class ChangeColor extends Transition {

    /** Key to store a color value in TransitionValues object */
    private static final String PROPNAME_BACKGROUND = "customtransition:change_color:background";

    // BEGIN_INCLUDE (capture_values)
    /**
     * Convenience method: Add the background Drawable property value
     * to the TransitionsValues.value Map for a target.
     */
    private void captureValues(TransitionValues values) {
        // Capture the property values of views for later use
        values.values.put(PROPNAME_BACKGROUND, values.view.getBackground());
    }

    @Override
    public void captureStartValues(TransitionValues transitionValues) {
        captureValues(transitionValues);
    }

    // Capture the value of the background drawable property for a target in the ending Scene.
    @Override
    public void captureEndValues(TransitionValues transitionValues) {
        captureValues(transitionValues);
    }
    // END_INCLUDE (capture_values)

    // BEGIN_INCLUDE (create_animator)
    // Create an animation for each target that is in both the starting and ending Scene. For each
    // pair of targets, if their background property value is a color (rather than a graphic),
    // create a ValueAnimator based on an ArgbEvaluator that interpolates between the starting and
    // ending color. Also create an update listener that sets the View background color for each
    // animation frame
    @Override
    public Animator createAnimator(ViewGroup sceneRoot,
                                   TransitionValues startValues, TransitionValues endValues) {
        // This transition can only be applied to views that are on both starting and ending scenes.
        if (null == startValues || null == endValues) {
            return null;
        }
        // Store a convenient reference to the target. Both the starting and ending layout have the
        // same target.
        final View view = endValues.view;
        // Store the object containing the background property for both the starting and ending
        // layouts.
        Drawable startBackground = (Drawable) startValues.values.get(PROPNAME_BACKGROUND);
        Drawable endBackground = (Drawable) endValues.values.get(PROPNAME_BACKGROUND);
        // This transition changes background colors for a target. It doesn't animate any other
        // background changes. If the property isn't a ColorDrawable, ignore the target.
        if (startBackground instanceof ColorDrawable && endBackground instanceof ColorDrawable) {
            ColorDrawable startColor = (ColorDrawable) startBackground;
            ColorDrawable endColor = (ColorDrawable) endBackground;
            // If the background color for the target in the starting and ending layouts is
            // different, create an animation.
            if (startColor.getColor() != endColor.getColor()) {
                // Create a new Animator object to apply to the targets as the transitions framework
                // changes from the starting to the ending layout. Use the class ValueAnimator,
                // which provides a timing pulse to change property values provided to it. The
                // animation runs on the UI thread. The Evaluator controls what type of
                // interpolation is done. In this case, an ArgbEvaluator interpolates between two
                // #argb values, which are specified as the 2nd and 3rd input arguments.
                ValueAnimator animator = ValueAnimator.ofObject(new ArgbEvaluator(),
                        startColor.getColor(), endColor.getColor());
                // Add an update listener to the Animator object.
                animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
                    @Override
                    public void onAnimationUpdate(ValueAnimator animation) {
                        Object value = animation.getAnimatedValue();
                        // Each time the ValueAnimator produces a new frame in the animation, change
                        // the background color of the target. Ensure that the value isn't null.
                        if (null != value) {
                            view.setBackgroundColor((Integer) value);
                        }
                    }
                });
                // Return the Animator object to the transitions framework. As the framework changes
                // between the starting and ending layouts, it applies the animation you've created.
                return animator;
            }
        }
        // For non-ColorDrawable backgrounds, we just return null, and no animation will take place.
        return null;
    }
    // END_INCLUDE (create_animator)

}