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/*
 * Copyright (C) 2013 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.transition;

import android.annotation.TestApi;
import android.content.Context;
import android.util.ArrayMap;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import android.view.ViewTreeObserver;

import java.lang.ref.WeakReference;
import java.util.ArrayList;


This class manages the set of transitions that fire when there is a change of Scene. To use the manager, add scenes along with transition objects with calls to setTransition(Scene, Transition) or setTransition(Scene, Scene, Transition). Setting specific transitions for scene changes is not required; by default, a Scene change will use AutoTransition to do something reasonable for most situations. Specifying other transitions for particular scene changes is only necessary if the application wants different transition behavior in these situations. 
TransitionManagers can be declared in XML resource files inside the
res/transition directory. TransitionManager resources consist of
the transitionManagertag name, containing one or more
transition tags, each of which describe the relationship of
that transition to the from/to scene information in that tag.
For example, here is a resource file that declares several scene
transitions:

{@sample development/samples/ApiDemos/res/transition/transitions_mgr.xml TransitionManager}

For each of the fromScene and toScene attributes, there is a reference to a standard XML layout file. This is equivalent to creating a scene from a layout in code by calling Scene.getSceneForLayout(ViewGroup, int, Context). For the transition attribute, there is a reference to a resource
file in the res/transition directory which describes that
transition.
 Information on XML resource descriptions for transitions can be found for Transition.Transition, TransitionSet.TransitionSet, TransitionTarget.TransitionTarget, Fade.Fade, and TransitionManager.TransitionManager. 
/**
 * This class manages the set of transitions that fire when there is a
 * change of {@link Scene}. To use the manager, add scenes along with
 * transition objects with calls to {@link #setTransition(Scene, Transition)}
 * or {@link #setTransition(Scene, Scene, Transition)}. Setting specific
 * transitions for scene changes is not required; by default, a Scene change
 * will use {@link AutoTransition} to do something reasonable for most
 * situations. Specifying other transitions for particular scene changes is
 * only necessary if the application wants different transition behavior
 * in these situations.
 *
 * <p>TransitionManagers can be declared in XML resource files inside the
 * <code>res/transition</code> directory. TransitionManager resources consist of
 * the <code>transitionManager</code>tag name, containing one or more
 * <code>transition</code> tags, each of which describe the relationship of
 * that transition to the from/to scene information in that tag.
 * For example, here is a resource file that declares several scene
 * transitions:</p>
 *
 * {@sample development/samples/ApiDemos/res/transition/transitions_mgr.xml TransitionManager}
 *
 * <p>For each of the <code>fromScene</code> and <code>toScene</code> attributes,
 * there is a reference to a standard XML layout file. This is equivalent to
 * creating a scene from a layout in code by calling
 * {@link Scene#getSceneForLayout(ViewGroup, int, Context)}. For the
 * <code>transition</code> attribute, there is a reference to a resource
 * file in the <code>res/transition</code> directory which describes that
 * transition.</p>
 *
 * Information on XML resource descriptions for transitions can be found for
 * {@link android.R.styleable#Transition}, {@link android.R.styleable#TransitionSet},
 * {@link android.R.styleable#TransitionTarget}, {@link android.R.styleable#Fade},
 * and {@link android.R.styleable#TransitionManager}.
 */
public class TransitionManager {
    // TODO: how to handle enter/exit?

    private static String LOG_TAG = "TransitionManager";

    private static Transition sDefaultTransition = new AutoTransition();

    private static final String[] EMPTY_STRINGS = new String[0];

    ArrayMap<Scene, Transition> mSceneTransitions = new ArrayMap<Scene, Transition>();
    ArrayMap<Scene, ArrayMap<Scene, Transition>> mScenePairTransitions =
            new ArrayMap<Scene, ArrayMap<Scene, Transition>>();
    private static ThreadLocal<WeakReference<ArrayMap<ViewGroup, ArrayList<Transition>>>>
            sRunningTransitions =
            new ThreadLocal<WeakReference<ArrayMap<ViewGroup, ArrayList<Transition>>>>();
    private static ArrayList<ViewGroup> sPendingTransitions = new ArrayList<ViewGroup>();


    
Sets the transition to be used for any scene change for which no other transition is explicitly set. The initial value is an AutoTransition instance. 
Params:
  • transition – The default transition to be used for scene changes.
@hidepending later changes
/**
     * Sets the transition to be used for any scene change for which no
     * other transition is explicitly set. The initial value is
     * an {@link AutoTransition} instance.
     *
     * @param transition The default transition to be used for scene changes.
     *
     * @hide pending later changes
     */
    public void setDefaultTransition(Transition transition) {
        sDefaultTransition = transition;
    }

    
Gets the current default transition. The initial value is an AutoTransition instance. 
See Also:
Returns:The current default transition.
@hidepending later changes
/**
     * Gets the current default transition. The initial value is an {@link
     * AutoTransition} instance.
     *
     * @return The current default transition.
     * @see #setDefaultTransition(Transition)
     *
     * @hide pending later changes
     */
    public static Transition getDefaultTransition() {
        return sDefaultTransition;
    }

    
Sets a specific transition to occur when the given scene is entered.

Params:
  • scene – The scene which, when applied, will cause the given
transition to run.
  • transition – The transition that will play when the given scene is
entered. A value of null will result in the default behavior of
using the default transition instead.
/**
     * Sets a specific transition to occur when the given scene is entered.
     *
     * @param scene The scene which, when applied, will cause the given
     * transition to run.
     * @param transition The transition that will play when the given scene is
     * entered. A value of null will result in the default behavior of
     * using the default transition instead.
     */
    public void setTransition(Scene scene, Transition transition) {
        mSceneTransitions.put(scene, transition);
    }

    
Sets a specific transition to occur when the given pair of scenes is
exited/entered.

Params:
  • fromScene – The scene being exited when the given transition will
be run
  • toScene – The scene being entered when the given transition will
be run
  • transition – The transition that will play when the given scene is
entered. A value of null will result in the default behavior of
using the default transition instead.
/**
     * Sets a specific transition to occur when the given pair of scenes is
     * exited/entered.
     *
     * @param fromScene The scene being exited when the given transition will
     * be run
     * @param toScene The scene being entered when the given transition will
     * be run
     * @param transition The transition that will play when the given scene is
     * entered. A value of null will result in the default behavior of
     * using the default transition instead.
     */
    public void setTransition(Scene fromScene, Scene toScene, Transition transition) {
        ArrayMap<Scene, Transition> sceneTransitionMap = mScenePairTransitions.get(toScene);
        if (sceneTransitionMap == null) {
            sceneTransitionMap = new ArrayMap<Scene, Transition>();
            mScenePairTransitions.put(toScene, sceneTransitionMap);
        }
        sceneTransitionMap.put(fromScene, transition);
    }

    
Returns the Transition for the given scene being entered. The result depends not only on the given scene, but also the scene which the sceneRoot of the Scene is currently in. 
Params:
  • scene – The scene being entered
Returns:The Transition to be used for the given scene change. If no
Transition was specified for this scene change, the default transition
will be used instead.
@hide
/**
     * Returns the Transition for the given scene being entered. The result
     * depends not only on the given scene, but also the scene which the
     * {@link Scene#getSceneRoot() sceneRoot} of the Scene is currently in.
     *
     * @param scene The scene being entered
     * @return The Transition to be used for the given scene change. If no
     * Transition was specified for this scene change, the default transition
     * will be used instead.
     * @hide
     */
    @TestApi
    public Transition getTransition(Scene scene) {
        Transition transition = null;
        ViewGroup sceneRoot = scene.getSceneRoot();
        if (sceneRoot != null) {
            // TODO: cached in Scene instead? long-term, cache in View itself
            Scene currScene = Scene.getCurrentScene(sceneRoot);
            if (currScene != null) {
                ArrayMap<Scene, Transition> sceneTransitionMap = mScenePairTransitions.get(scene);
                if (sceneTransitionMap != null) {
                    transition = sceneTransitionMap.get(currScene);
                    if (transition != null) {
                        return transition;
                    }
                }
            }
        }
        transition = mSceneTransitions.get(scene);
        return (transition != null) ? transition : sDefaultTransition;
    }

    
This is where all of the work of a transition/scene-change is
orchestrated. This method captures the start values for the given
transition, exits the current Scene, enters the new scene, captures
the end values for the transition, and finally plays the
resulting values-populated transition.

Params:
  • scene – The scene being entered
  • transition – The transition to play for this scene change
/**
     * This is where all of the work of a transition/scene-change is
     * orchestrated. This method captures the start values for the given
     * transition, exits the current Scene, enters the new scene, captures
     * the end values for the transition, and finally plays the
     * resulting values-populated transition.
     *
     * @param scene The scene being entered
     * @param transition The transition to play for this scene change
     */
    private static void changeScene(Scene scene, Transition transition) {

        final ViewGroup sceneRoot = scene.getSceneRoot();
        if (!sPendingTransitions.contains(sceneRoot)) {
            if (transition == null) {
                scene.enter();
            } else {
                sPendingTransitions.add(sceneRoot);

                Transition transitionClone = transition.clone();
                transitionClone.setSceneRoot(sceneRoot);

                Scene oldScene = Scene.getCurrentScene(sceneRoot);
                if (oldScene != null && oldScene.isCreatedFromLayoutResource()) {
                    transitionClone.setCanRemoveViews(true);
                }

                sceneChangeSetup(sceneRoot, transitionClone);

                scene.enter();

                sceneChangeRunTransition(sceneRoot, transitionClone);
            }
        }
    }

    private static ArrayMap<ViewGroup, ArrayList<Transition>> getRunningTransitions() {
        WeakReference<ArrayMap<ViewGroup, ArrayList<Transition>>> runningTransitions =
                sRunningTransitions.get();
        if (runningTransitions == null || runningTransitions.get() == null) {
            ArrayMap<ViewGroup, ArrayList<Transition>> transitions =
                    new ArrayMap<ViewGroup, ArrayList<Transition>>();
            runningTransitions = new WeakReference<ArrayMap<ViewGroup, ArrayList<Transition>>>(
                    transitions);
            sRunningTransitions.set(runningTransitions);
        }
        return runningTransitions.get();
    }

    private static void sceneChangeRunTransition(final ViewGroup sceneRoot,
            final Transition transition) {
        if (transition != null && sceneRoot != null) {
            MultiListener listener = new MultiListener(transition, sceneRoot);
            sceneRoot.addOnAttachStateChangeListener(listener);
            sceneRoot.getViewTreeObserver().addOnPreDrawListener(listener);
        }
    }

    
This private utility class is used to listen for both OnPreDraw and
OnAttachStateChange events. OnPreDraw events are the main ones we care
about since that's what triggers the transition to take place.
OnAttachStateChange events are also important in case the view is removed
from the hierarchy before the OnPreDraw event takes place; it's used to
clean up things since the OnPreDraw listener didn't get called in time.

/**
     * This private utility class is used to listen for both OnPreDraw and
     * OnAttachStateChange events. OnPreDraw events are the main ones we care
     * about since that's what triggers the transition to take place.
     * OnAttachStateChange events are also important in case the view is removed
     * from the hierarchy before the OnPreDraw event takes place; it's used to
     * clean up things since the OnPreDraw listener didn't get called in time.
     */
    private static class MultiListener implements ViewTreeObserver.OnPreDrawListener,
            View.OnAttachStateChangeListener {

        Transition mTransition;
        ViewGroup mSceneRoot;
        final ViewTreeObserver mViewTreeObserver;

        MultiListener(Transition transition, ViewGroup sceneRoot) {
            mTransition = transition;
            mSceneRoot = sceneRoot;
            mViewTreeObserver = mSceneRoot.getViewTreeObserver();
        }

        private void removeListeners() {
            if (mViewTreeObserver.isAlive()) {
                mViewTreeObserver.removeOnPreDrawListener(this);
            } else {
                mSceneRoot.getViewTreeObserver().removeOnPreDrawListener(this);
            }
            mSceneRoot.removeOnAttachStateChangeListener(this);
        }

        @Override
        public void onViewAttachedToWindow(View v) {
        }

        @Override
        public void onViewDetachedFromWindow(View v) {
            removeListeners();

            sPendingTransitions.remove(mSceneRoot);
            ArrayList<Transition> runningTransitions = getRunningTransitions().get(mSceneRoot);
            if (runningTransitions != null && runningTransitions.size() > 0) {
                for (Transition runningTransition : runningTransitions) {
                    runningTransition.resume(mSceneRoot);
                }
            }
            mTransition.clearValues(true);
        }

        @Override
        public boolean onPreDraw() {
            removeListeners();

            // Don't start the transition if it's no longer pending.
            if (!sPendingTransitions.remove(mSceneRoot)) {
                return true;
            }

            // Add to running list, handle end to remove it
            final ArrayMap<ViewGroup, ArrayList<Transition>> runningTransitions =
                    getRunningTransitions();
            ArrayList<Transition> currentTransitions = runningTransitions.get(mSceneRoot);
            ArrayList<Transition> previousRunningTransitions = null;
            if (currentTransitions == null) {
                currentTransitions = new ArrayList<Transition>();
                runningTransitions.put(mSceneRoot, currentTransitions);
            } else if (currentTransitions.size() > 0) {
                previousRunningTransitions = new ArrayList<Transition>(currentTransitions);
            }
            currentTransitions.add(mTransition);
            mTransition.addListener(new TransitionListenerAdapter() {
                @Override
                public void onTransitionEnd(Transition transition) {
                    ArrayList<Transition> currentTransitions =
                            runningTransitions.get(mSceneRoot);
                    currentTransitions.remove(transition);
                }
            });
            mTransition.captureValues(mSceneRoot, false);
            if (previousRunningTransitions != null) {
                for (Transition runningTransition : previousRunningTransitions) {
                    runningTransition.resume(mSceneRoot);
                }
            }
            mTransition.playTransition(mSceneRoot);

            return true;
        }
    };

    private static void sceneChangeSetup(ViewGroup sceneRoot, Transition transition) {

        // Capture current values
        ArrayList<Transition> runningTransitions = getRunningTransitions().get(sceneRoot);

        if (runningTransitions != null && runningTransitions.size() > 0) {
            for (Transition runningTransition : runningTransitions) {
                runningTransition.pause(sceneRoot);
            }
        }

        if (transition != null) {
            transition.captureValues(sceneRoot, true);
        }

        // Notify previous scene that it is being exited
        Scene previousScene = Scene.getCurrentScene(sceneRoot);
        if (previousScene != null) {
            previousScene.exit();
        }
    }

    
Change to the given scene, using the
appropriate transition for this particular scene change
(as specified to the TransitionManager, or the default
if no such transition exists).

Params:
  • scene – The Scene to change to
/**
     * Change to the given scene, using the
     * appropriate transition for this particular scene change
     * (as specified to the TransitionManager, or the default
     * if no such transition exists).
     *
     * @param scene The Scene to change to
     */
    public void transitionTo(Scene scene) {
        // Auto transition if there is no transition declared for the Scene, but there is
        // a root or parent view
        changeScene(scene, getTransition(scene));
    }

    
Convenience method to simply change to the given scene using
the default transition for TransitionManager.

Params:
  • scene – The Scene to change to
/**
     * Convenience method to simply change to the given scene using
     * the default transition for TransitionManager.
     *
     * @param scene The Scene to change to
     */
    public static void go(Scene scene) {
        changeScene(scene, sDefaultTransition);
    }

    
Convenience method to simply change to the given scene using
the given transition.

Passing in null for the transition parameter will result in the scene changing without any transition running, and is equivalent to calling Scene.exit() on the scene root's current scene, followed by Scene.enter() on the scene specified by the scene parameter.


Params:
  • scene – The Scene to change to
  • transition – The transition to use for this scene change. A
value of null causes the scene change to happen with no 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) {
        changeScene(scene, transition);
    }

    
Convenience method to animate, using the default transition, to a new scene defined by all changes within the given scene root between calling this method and the next rendering frame. Equivalent to calling beginDelayedTransition(ViewGroup, Transition) with a value of null for the transition parameter.

Params:
  • sceneRoot – The root of the View hierarchy to run the transition on.
/**
     * Convenience method to animate, using the default transition,
     * to a new scene defined by all changes within the given scene root between
     * calling this method and the next rendering frame.
     * Equivalent to calling {@link #beginDelayedTransition(ViewGroup, Transition)}
     * with a value of <code>null</code> for the <code>transition</code> parameter.
     *
     * @param sceneRoot The root of the View hierarchy to run the transition on.
     */
    public static void beginDelayedTransition(final ViewGroup sceneRoot) {
        beginDelayedTransition(sceneRoot, null);
    }

    
Convenience method to animate to a new scene defined by all changes within
the given scene root between calling this method and the next rendering frame.
Calling this method causes TransitionManager to capture current values in the
scene root and then post a request to run a transition on the next frame.
At that time, the new values in the scene root will be captured and changes
will be animated. There is no need to create a Scene; it is implied by
changes which take place between calling this method and the next frame when
the transition begins.

Calling this method several times before the next frame (for example, if
unrelated code also wants to make dynamic changes and run a transition on
the same scene root), only the first call will trigger capturing values
and exiting the current scene. Subsequent calls to the method with the
same scene root during the same frame will be ignored.


Passing in null for the transition parameter will
cause the TransitionManager to use its default transition.


Params:
  • sceneRoot – The root of the View hierarchy to run the transition on.
  • transition – The transition to use for this change. A
value of null causes the TransitionManager to use the default transition.
/**
     * Convenience method to animate to a new scene defined by all changes within
     * the given scene root between calling this method and the next rendering frame.
     * Calling this method causes TransitionManager to capture current values in the
     * scene root and then post a request to run a transition on the next frame.
     * At that time, the new values in the scene root will be captured and changes
     * will be animated. There is no need to create a Scene; it is implied by
     * changes which take place between calling this method and the next frame when
     * the transition begins.
     *
     * <p>Calling this method several times before the next frame (for example, if
     * unrelated code also wants to make dynamic changes and run a transition on
     * the same scene root), only the first call will trigger capturing values
     * and exiting the current scene. Subsequent calls to the method with the
     * same scene root during the same frame will be ignored.</p>
     *
     * <p>Passing in <code>null</code> for the transition parameter will
     * cause the TransitionManager to use its default transition.</p>
     *
     * @param sceneRoot The root of the View hierarchy to run the transition on.
     * @param transition The transition to use for this change. A
     * value of null causes the TransitionManager to use the default transition.
     */
    public static void beginDelayedTransition(final ViewGroup sceneRoot, Transition transition) {
        if (!sPendingTransitions.contains(sceneRoot) && sceneRoot.isLaidOut()) {
            if (Transition.DBG) {
                Log.d(LOG_TAG, "beginDelayedTransition: root, transition = " +
                        sceneRoot + ", " + transition);
            }
            sPendingTransitions.add(sceneRoot);
            if (transition == null) {
                transition = sDefaultTransition;
            }
            final Transition transitionClone = transition.clone();
            sceneChangeSetup(sceneRoot, transitionClone);
            Scene.setCurrentScene(sceneRoot, null);
            sceneChangeRunTransition(sceneRoot, transitionClone);
        }
    }

    
Ends all pending and ongoing transitions on the specified scene root.

Params:
  • sceneRoot – The root of the View hierarchy to end transitions on.
/**
     * Ends all pending and ongoing transitions on the specified scene root.
     *
     * @param sceneRoot The root of the View hierarchy to end transitions on.
     */
    public static void endTransitions(final ViewGroup sceneRoot) {
        sPendingTransitions.remove(sceneRoot);

        final ArrayList<Transition> runningTransitions = getRunningTransitions().get(sceneRoot);
        if (runningTransitions != null && !runningTransitions.isEmpty()) {
            // Make a copy in case this is called by an onTransitionEnd listener
            ArrayList<Transition> copy = new ArrayList(runningTransitions);
            for (int i = copy.size() - 1; i >= 0; i--) {
                final Transition transition = copy.get(i);
                transition.forceToEnd(sceneRoot);
            }
        }

    }
}