src/com/android/launcher3/LauncherStateTransitionAnimation.java

/*
 * Copyright (C) 2015 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 com.android.launcher3;

import android.animation.Animator;
import android.animation.AnimatorListenerAdapter;
import android.animation.AnimatorSet;
import android.animation.ObjectAnimator;
import android.animation.PropertyValuesHolder;
import android.animation.TimeInterpolator;
import android.content.res.Resources;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.View;
import android.view.ViewAnimationUtils;
import android.view.animation.AccelerateInterpolator;
import android.view.animation.DecelerateInterpolator;

import com.android.launcher3.util.Thunk;
import com.android.launcher3.widget.WidgetsContainerView;

import java.util.HashMap;

/**
 * TODO: figure out what kind of tests we can write for this
 *
 * Things to test when changing the following class.
 *   - Home from workspace
 *          - from center screen
 *          - from other screens
 *   - Home from all apps
 *          - from center screen
 *          - from other screens
 *   - Back from all apps
 *          - from center screen
 *          - from other screens
 *   - Launch app from workspace and quit
 *          - with back
 *          - with home
 *   - Launch app from all apps and quit
 *          - with back
 *          - with home
 *   - Go to a screen that's not the default, then all
 *     apps, and launch and app, and go back
 *          - with back
 *          -with home
 *   - On workspace, long press power and go back
 *          - with back
 *          - with home
 *   - On all apps, long press power and go back
 *          - with back
 *          - with home
 *   - On workspace, power off
 *   - On all apps, power off
 *   - Launch an app and turn off the screen while in that app
 *          - Go back with home key
 *          - Go back with back key  TODO: make this not go to workspace
 *          - From all apps
 *          - From workspace
 *   - Enter and exit car mode (becuase it causes an extra configuration changed)
 *          - From all apps
 *          - From the center workspace
 *          - From another workspace
 */
public class LauncherStateTransitionAnimation {

    /**
     * Callbacks made during the state transition
     */
    interface Callbacks {
        public void onStateTransitionHideSearchBar();
    }

    /**
     * Private callbacks made during transition setup.
     */
    static abstract class PrivateTransitionCallbacks {
        void onRevealViewVisible(View revealView, View contentView, View allAppsButtonView) {}
        void onAnimationComplete(View revealView, View contentView, View allAppsButtonView) {}
        float getMaterialRevealViewFinalAlpha(View revealView) {
            return 0;
        }
        float getMaterialRevealViewFinalXDrift(View revealView) {
            return 0;
        }
        float getMaterialRevealViewFinalYDrift(View revealView) {
            return 0;
        }
        float getMaterialRevealViewStartFinalRadius() {
            return 0;
        }
        AnimatorListenerAdapter getMaterialRevealViewAnimatorListener(View revealView,
                View allAppsButtonView) {
            return null;
        }
    }

    public static final String TAG = "LauncherStateTransitionAnimation";

    // Flags to determine how to set the layers on views before the transition animation
    public static final int BUILD_LAYER = 0;
    public static final int BUILD_AND_SET_LAYER = 1;
    public static final int SINGLE_FRAME_DELAY = 16;

    @Thunk Launcher mLauncher;
    @Thunk Callbacks mCb;
    @Thunk AnimatorSet mStateAnimation;

    public LauncherStateTransitionAnimation(Launcher l, Callbacks cb) {
        mLauncher = l;
        mCb = cb;
    }

    /**
     * Starts an animation to the apps view.
     */
    public void startAnimationToAllApps(final boolean animated) {
        final AppsContainerView toView = mLauncher.getAppsView();
        PrivateTransitionCallbacks cb = new PrivateTransitionCallbacks() {
            private int[] mAllAppsToPanelDelta;

            @Override
            public void onRevealViewVisible(View revealView, View contentView,
                    View allAppsButtonView) {
                toView.setBackground(null);
                // Get the y delta between the center of the page and the center of the all apps
                // button
                mAllAppsToPanelDelta = Utilities.getCenterDeltaInScreenSpace(revealView,
                        allAppsButtonView, null);
            }
            @Override
            public float getMaterialRevealViewFinalAlpha(View revealView) {
                return 1f;
            }
            @Override
            public float getMaterialRevealViewFinalXDrift(View revealView) {
                return mAllAppsToPanelDelta[0];
            }
            @Override
            public float getMaterialRevealViewFinalYDrift(View revealView) {
                return mAllAppsToPanelDelta[1];
            }
            @Override
            public float getMaterialRevealViewStartFinalRadius() {
                int allAppsButtonSize = LauncherAppState.getInstance().
                        getDynamicGrid().getDeviceProfile().allAppsButtonVisualSize;
                return allAppsButtonSize / 2;
            }
            @Override
            public AnimatorListenerAdapter getMaterialRevealViewAnimatorListener(
                    final View revealView, final View allAppsButtonView) {
                return new AnimatorListenerAdapter() {
                    public void onAnimationStart(Animator animation) {
                        allAppsButtonView.setVisibility(View.INVISIBLE);
                    }
                    public void onAnimationEnd(Animator animation) {
                        allAppsButtonView.setVisibility(View.VISIBLE);
                    }
                };
            }
        };
        startAnimationToOverlay(Workspace.State.NORMAL_HIDDEN, toView, toView.getContentView(),
                toView.getRevealView(), animated, false /* hideSearchBar */, cb);
    }

    /**
     * Starts an animation to the widgets view.
     */
    public void startAnimationToWidgets(final boolean animated) {
        final WidgetsContainerView toView = mLauncher.getWidgetsView();
        PrivateTransitionCallbacks cb = new PrivateTransitionCallbacks() {
            @Override
            public void onRevealViewVisible(View revealView, View contentView,
                    View allAppsButtonView) {
                revealView.setBackground(mLauncher.getDrawable(R.drawable.quantum_panel_dark));
            }
            @Override
            public float getMaterialRevealViewFinalAlpha(View revealView) {
                return 0.3f;
            }
            @Override
            public float getMaterialRevealViewFinalYDrift(View revealView) {
                return revealView.getMeasuredHeight() / 2;
            }
        };
        startAnimationToOverlay(Workspace.State.OVERVIEW_HIDDEN, toView, toView.getContentView(),
                toView.getRevealView(), animated, true /* hideSearchBar */, cb);
    }

    /**
     * Starts and animation to the workspace from the current overlay view.
     */
    public void startAnimationToWorkspace(final Launcher.State fromState,
              final Workspace.State toWorkspaceState, final boolean animated,
              final Runnable onCompleteRunnable) {
        if (toWorkspaceState != Workspace.State.NORMAL &&
                toWorkspaceState != Workspace.State.SPRING_LOADED &&
                toWorkspaceState != Workspace.State.OVERVIEW) {
            Log.e(TAG, "Unexpected call to startAnimationToWorkspace");
        }

        if (fromState == Launcher.State.APPS || fromState == Launcher.State.APPS_SPRING_LOADED) {
            startAnimationToWorkspaceFromAllApps(fromState, toWorkspaceState, animated,
                    onCompleteRunnable);
        } else {
            startAnimationToWorkspaceFromWidgets(fromState, toWorkspaceState, animated,
                    onCompleteRunnable);
        }
    }

    /**
     * Creates and starts a new animation to a particular overlay view.
     */
    private void startAnimationToOverlay(final Workspace.State toWorkspaceState, final View toView,
             final View contentView, final View revealView, final boolean animated,
             final boolean hideSearchBar, final PrivateTransitionCallbacks pCb) {
        final Resources res = mLauncher.getResources();
        final boolean material = Utilities.isLmpOrAbove();
        final int revealDuration = res.getInteger(R.integer.config_appsCustomizeRevealTime);
        final int itemsAlphaStagger =
                res.getInteger(R.integer.config_appsCustomizeItemsAlphaStagger);

        final View allAppsButtonView = mLauncher.getAllAppsButton();
        final View fromView = mLauncher.getWorkspace();

        final HashMap<View, Integer> layerViews = new HashMap<>();

        // If for some reason our views aren't initialized, don't animate
        boolean initialized = allAppsButtonView != null;

        // Cancel the current animation
        cancelAnimation();

        // Create the workspace animation.
        // NOTE: this call apparently also sets the state for the workspace if !animated
        Animator workspaceAnim = mLauncher.getWorkspace().getChangeStateAnimation(
                toWorkspaceState, animated, layerViews);

        if (animated && initialized) {
            mStateAnimation = LauncherAnimUtils.createAnimatorSet();

            // Setup the reveal view animation
            int width = revealView.getMeasuredWidth();
            int height = revealView.getMeasuredHeight();
            float revealRadius = (float) Math.sqrt((width * width) / 4 + (height * height) / 4);
            revealView.setVisibility(View.VISIBLE);
            revealView.setAlpha(0f);
            revealView.setTranslationY(0f);
            revealView.setTranslationX(0f);
            pCb.onRevealViewVisible(revealView, contentView, allAppsButtonView);

            // Calculate the final animation values
            final float revealViewToAlpha;
            final float revealViewToXDrift;
            final float revealViewToYDrift;
            if (material) {
                revealViewToAlpha = pCb.getMaterialRevealViewFinalAlpha(revealView);
                revealViewToYDrift = pCb.getMaterialRevealViewFinalYDrift(revealView);
                revealViewToXDrift = pCb.getMaterialRevealViewFinalXDrift(revealView);
            } else {
                revealViewToAlpha = 0f;
                revealViewToYDrift = 2 * height / 3;
                revealViewToXDrift = 0;
            }

            // Create the animators
            PropertyValuesHolder panelAlpha =
                    PropertyValuesHolder.ofFloat("alpha", revealViewToAlpha, 1f);
            PropertyValuesHolder panelDriftY =
                    PropertyValuesHolder.ofFloat("translationY", revealViewToYDrift, 0);
            PropertyValuesHolder panelDriftX =
                    PropertyValuesHolder.ofFloat("translationX", revealViewToXDrift, 0);
            ObjectAnimator panelAlphaAndDrift = ObjectAnimator.ofPropertyValuesHolder(revealView,
                    panelAlpha, panelDriftY, panelDriftX);
            panelAlphaAndDrift.setDuration(revealDuration);
            panelAlphaAndDrift.setInterpolator(new LogDecelerateInterpolator(100, 0));

            // Play the animation
            layerViews.put(revealView, BUILD_AND_SET_LAYER);
            mStateAnimation.play(panelAlphaAndDrift);

            // Setup the animation for the content view
            contentView.setVisibility(View.VISIBLE);
            contentView.setAlpha(0f);
            contentView.setTranslationY(revealViewToYDrift);
            layerViews.put(contentView, BUILD_AND_SET_LAYER);

            // Create the individual animators
            ObjectAnimator pageDrift = ObjectAnimator.ofFloat(contentView, "translationY",
                    revealViewToYDrift, 0);
            pageDrift.setDuration(revealDuration);
            pageDrift.setInterpolator(new LogDecelerateInterpolator(100, 0));
            pageDrift.setStartDelay(itemsAlphaStagger);
            mStateAnimation.play(pageDrift);

            ObjectAnimator itemsAlpha = ObjectAnimator.ofFloat(contentView, "alpha", 0f, 1f);
            itemsAlpha.setDuration(revealDuration);
            itemsAlpha.setInterpolator(new AccelerateInterpolator(1.5f));
            itemsAlpha.setStartDelay(itemsAlphaStagger);
            mStateAnimation.play(itemsAlpha);

            if (material) {
                // Animate the all apps button
                float startRadius = pCb.getMaterialRevealViewStartFinalRadius();
                AnimatorListenerAdapter listener = pCb.getMaterialRevealViewAnimatorListener(
                        revealView, allAppsButtonView);
                Animator reveal = ViewAnimationUtils.createCircularReveal(revealView, width / 2,
                        height / 2, startRadius, revealRadius);
                reveal.setDuration(revealDuration);
                reveal.setInterpolator(new LogDecelerateInterpolator(100, 0));
                if (listener != null) {
                    reveal.addListener(listener);
                }
                mStateAnimation.play(reveal);
            }

            mStateAnimation.addListener(new AnimatorListenerAdapter() {
                @Override
                public void onAnimationEnd(Animator animation) {
                    dispatchOnLauncherTransitionEnd(fromView, animated, false);
                    dispatchOnLauncherTransitionEnd(toView, animated, false);

                    // Hide the reveal view
                    revealView.setVisibility(View.INVISIBLE);
                    pCb.onAnimationComplete(revealView, contentView, allAppsButtonView);

                    // Disable all necessary layers
                    for (View v : layerViews.keySet()) {
                        if (layerViews.get(v) == BUILD_AND_SET_LAYER) {
                            v.setLayerType(View.LAYER_TYPE_NONE, null);
                        }
                    }

                    if (hideSearchBar) {
                        mCb.onStateTransitionHideSearchBar();
                    }

                    // This can hold unnecessary references to views.
                    mStateAnimation = null;
                }

            });

            // Play the workspace animation
            if (workspaceAnim != null) {
                mStateAnimation.play(workspaceAnim);
            }

            // Dispatch the prepare transition signal
            dispatchOnLauncherTransitionPrepare(fromView, animated, false);
            dispatchOnLauncherTransitionPrepare(toView, animated, false);


            final AnimatorSet stateAnimation = mStateAnimation;
            final Runnable startAnimRunnable = new Runnable() {
                public void run() {
                    // Check that mStateAnimation hasn't changed while
                    // we waited for a layout/draw pass
                    if (mStateAnimation != stateAnimation)
                        return;
                    dispatchOnLauncherTransitionStart(fromView, animated, false);
                    dispatchOnLauncherTransitionStart(toView, animated, false);

                    // Enable all necessary layers
                    for (View v : layerViews.keySet()) {
                        if (layerViews.get(v) == BUILD_AND_SET_LAYER) {
                            v.setLayerType(View.LAYER_TYPE_HARDWARE, null);
                        }
                        if (Utilities.isViewAttachedToWindow(v)) {
                            v.buildLayer();
                        }
                    }

                    // Focus the new view
                    toView.requestFocus();

                    mStateAnimation.start();
                }
            };

            toView.bringToFront();
            toView.setVisibility(View.VISIBLE);
            toView.post(startAnimRunnable);
        } else {
            toView.setTranslationX(0.0f);
            toView.setTranslationY(0.0f);
            toView.setScaleX(1.0f);
            toView.setScaleY(1.0f);
            toView.setVisibility(View.VISIBLE);
            toView.bringToFront();

            // Show the content view
            contentView.setVisibility(View.VISIBLE);

            if (hideSearchBar) {
                mCb.onStateTransitionHideSearchBar();
            }

            dispatchOnLauncherTransitionPrepare(fromView, animated, false);
            dispatchOnLauncherTransitionStart(fromView, animated, false);
            dispatchOnLauncherTransitionEnd(fromView, animated, false);
            dispatchOnLauncherTransitionPrepare(toView, animated, false);
            dispatchOnLauncherTransitionStart(toView, animated, false);
            dispatchOnLauncherTransitionEnd(toView, animated, false);
        }
    }

    /**
     * Starts and animation to the workspace from the apps view.
     */
    private void startAnimationToWorkspaceFromAllApps(final Launcher.State fromState,
              final Workspace.State toWorkspaceState, final boolean animated,
              final Runnable onCompleteRunnable) {
        AppsContainerView appsView = mLauncher.getAppsView();
        PrivateTransitionCallbacks cb = new PrivateTransitionCallbacks() {
            int[] mAllAppsToPanelDelta;

            @Override
            public void onRevealViewVisible(View revealView, View contentView,
                                            View allAppsButtonView) {
                // Get the y delta between the center of the page and the center of the all apps
                // button
                mAllAppsToPanelDelta = Utilities.getCenterDeltaInScreenSpace(revealView,
                        allAppsButtonView, null);
            }
            @Override
            public float getMaterialRevealViewFinalXDrift(View revealView) {
                return mAllAppsToPanelDelta[0];
            }
            @Override
            public float getMaterialRevealViewFinalYDrift(View revealView) {
                return mAllAppsToPanelDelta[1];
            }
            @Override
            float getMaterialRevealViewFinalAlpha(View revealView) {
                // No alpha anim from all apps
                return 1f;
            }
            @Override
            float getMaterialRevealViewStartFinalRadius() {
                int allAppsButtonSize = LauncherAppState.getInstance().
                        getDynamicGrid().getDeviceProfile().allAppsButtonVisualSize;
                return allAppsButtonSize / 2;
            }
            @Override
            public AnimatorListenerAdapter getMaterialRevealViewAnimatorListener(
                    final View revealView, final View allAppsButtonView) {
                return new AnimatorListenerAdapter() {
                    public void onAnimationStart(Animator animation) {
                        // We set the alpha instead of visibility to ensure that the focus does not
                        // get taken from the all apps view
                        allAppsButtonView.setVisibility(View.VISIBLE);
                        allAppsButtonView.setAlpha(0f);
                    }
                    public void onAnimationEnd(Animator animation) {
                        // Hide the reveal view
                        revealView.setVisibility(View.INVISIBLE);

                        // Show the all apps button, and focus it
                        allAppsButtonView.setAlpha(1f);
                    }
                };
            }
        };
        startAnimationToWorkspaceFromOverlay(toWorkspaceState, appsView, appsView.getContentView(),
                appsView.getRevealView(), animated, onCompleteRunnable, cb);
    }

    /**
     * Starts and animation to the workspace from the widgets view.
     */
    private void startAnimationToWorkspaceFromWidgets(final Launcher.State fromState,
              final Workspace.State toWorkspaceState, final boolean animated,
              final Runnable onCompleteRunnable) {
        WidgetsContainerView widgetsView = mLauncher.getWidgetsView();
        PrivateTransitionCallbacks cb = new PrivateTransitionCallbacks() {
            @Override
            public float getMaterialRevealViewFinalYDrift(View revealView) {
                return revealView.getMeasuredHeight() / 2;
            }
            @Override
            float getMaterialRevealViewFinalAlpha(View revealView) {
                return 0.4f;
            }
            @Override
            public AnimatorListenerAdapter getMaterialRevealViewAnimatorListener(
                    final View revealView, final View allAppsButtonView) {
                return new AnimatorListenerAdapter() {
                    public void onAnimationEnd(Animator animation) {
                        // Hide the reveal view
                        revealView.setVisibility(View.INVISIBLE);
                    }
                };
            }
        };
        startAnimationToWorkspaceFromOverlay(toWorkspaceState, widgetsView,
                widgetsView.getContentView(), widgetsView.getRevealView(), animated,
                onCompleteRunnable, cb);
    }

    /**
     * Creates and starts a new animation to the workspace.
     */
    private void startAnimationToWorkspaceFromOverlay(final Workspace.State toWorkspaceState,
              final View fromView, final View contentView, final View revealView,
              final boolean animated, final Runnable onCompleteRunnable,
              final PrivateTransitionCallbacks pCb) {
        final Resources res = mLauncher.getResources();
        final boolean material = Utilities.isLmpOrAbove();
        final int revealDuration = res.getInteger(R.integer.config_appsCustomizeRevealTime);
        final int itemsAlphaStagger =
                res.getInteger(R.integer.config_appsCustomizeItemsAlphaStagger);

        final View allAppsButtonView = mLauncher.getAllAppsButton();
        final View toView = mLauncher.getWorkspace();

        final HashMap<View, Integer> layerViews = new HashMap<>();

        // If for some reason our views aren't initialized, don't animate
        boolean initialized = allAppsButtonView != null;

        // Cancel the current animation
        cancelAnimation();

        // Create the workspace animation.
        // NOTE: this call apparently also sets the state for the workspace if !animated
        Animator workspaceAnim = mLauncher.getWorkspace().getChangeStateAnimation(
                toWorkspaceState, animated, layerViews);

        if (animated && initialized) {
            mStateAnimation = LauncherAnimUtils.createAnimatorSet();

            // Play the workspace animation
            if (workspaceAnim != null) {
                mStateAnimation.play(workspaceAnim);
            }

            // hideAppsCustomizeHelper is called in some cases when it is already hidden
            // don't perform all these no-op animations. In particularly, this was causing
            // the all-apps button to pop in and out.
            if (fromView.getVisibility() == View.VISIBLE) {
                int width = revealView.getMeasuredWidth();
                int height = revealView.getMeasuredHeight();
                float revealRadius = (float) Math.sqrt((width * width) / 4 + (height * height) / 4);
                revealView.setVisibility(View.VISIBLE);
                revealView.setAlpha(1f);
                revealView.setTranslationY(0);
                layerViews.put(revealView, BUILD_AND_SET_LAYER);
                pCb.onRevealViewVisible(revealView, contentView, allAppsButtonView);

                // Calculate the final animation values
                final float revealViewToXDrift;
                final float revealViewToYDrift;
                if (material) {
                    revealViewToYDrift = pCb.getMaterialRevealViewFinalYDrift(revealView);
                    revealViewToXDrift = pCb.getMaterialRevealViewFinalXDrift(revealView);
                } else {
                    revealViewToYDrift = 2 * height / 3;
                    revealViewToXDrift = 0;
                }

                // The vertical motion of the apps panel should be delayed by one frame
                // from the conceal animation in order to give the right feel. We correspondingly
                // shorten the duration so that the slide and conceal end at the same time.
                TimeInterpolator decelerateInterpolator = material ?
                        new LogDecelerateInterpolator(100, 0) :
                        new DecelerateInterpolator(1f);
                ObjectAnimator panelDriftY = LauncherAnimUtils.ofFloat(revealView, "translationY",
                        0, revealViewToYDrift);
                panelDriftY.setDuration(revealDuration - SINGLE_FRAME_DELAY);
                panelDriftY.setStartDelay(itemsAlphaStagger + SINGLE_FRAME_DELAY);
                panelDriftY.setInterpolator(decelerateInterpolator);
                mStateAnimation.play(panelDriftY);

                ObjectAnimator panelDriftX = LauncherAnimUtils.ofFloat(revealView, "translationX",
                        0, revealViewToXDrift);
                panelDriftX.setDuration(revealDuration - SINGLE_FRAME_DELAY);
                panelDriftX.setStartDelay(itemsAlphaStagger + SINGLE_FRAME_DELAY);
                panelDriftX.setInterpolator(decelerateInterpolator);
                mStateAnimation.play(panelDriftX);

                // Setup animation for the reveal panel alpha
                final float revealViewToAlpha = !material ? 0f :
                        pCb.getMaterialRevealViewFinalAlpha(revealView);
                if (revealViewToAlpha != 1f) {
                    ObjectAnimator panelAlpha = LauncherAnimUtils.ofFloat(revealView, "alpha",
                            1f, revealViewToAlpha);
                    panelAlpha.setDuration(material ? revealDuration : 150);
                    panelAlpha.setStartDelay(material ? 0 : itemsAlphaStagger + SINGLE_FRAME_DELAY);
                    panelAlpha.setInterpolator(decelerateInterpolator);
                    mStateAnimation.play(panelAlpha);
                }

                // Setup the animation for the content view
                layerViews.put(contentView, BUILD_AND_SET_LAYER);

                // Create the individual animators
                ObjectAnimator pageDrift = LauncherAnimUtils.ofFloat(contentView, "translationY",
                        0, revealViewToYDrift);
                contentView.setTranslationY(0);
                pageDrift.setDuration(revealDuration - SINGLE_FRAME_DELAY);
                pageDrift.setInterpolator(decelerateInterpolator);
                pageDrift.setStartDelay(itemsAlphaStagger + SINGLE_FRAME_DELAY);
                mStateAnimation.play(pageDrift);

                contentView.setAlpha(1f);
                ObjectAnimator itemsAlpha = LauncherAnimUtils.ofFloat(contentView, "alpha", 1f, 0f);
                itemsAlpha.setDuration(100);
                itemsAlpha.setInterpolator(decelerateInterpolator);
                mStateAnimation.play(itemsAlpha);

                if (material) {
                    // Animate the all apps button
                    float finalRadius = pCb.getMaterialRevealViewStartFinalRadius();
                    AnimatorListenerAdapter listener =
                            pCb.getMaterialRevealViewAnimatorListener(revealView, allAppsButtonView);
                    Animator reveal =
                            LauncherAnimUtils.createCircularReveal(revealView, width / 2,
                                    height / 2, revealRadius, finalRadius);
                    reveal.setInterpolator(new LogDecelerateInterpolator(100, 0));
                    reveal.setDuration(revealDuration);
                    reveal.setStartDelay(itemsAlphaStagger);
                    if (listener != null) {
                        reveal.addListener(listener);
                    }
                    mStateAnimation.play(reveal);
                }

                dispatchOnLauncherTransitionPrepare(fromView, animated, true);
                dispatchOnLauncherTransitionPrepare(toView, animated, true);
            }

            mStateAnimation.addListener(new AnimatorListenerAdapter() {
                @Override
                public void onAnimationEnd(Animator animation) {
                    fromView.setVisibility(View.GONE);
                    dispatchOnLauncherTransitionEnd(fromView, animated, true);
                    dispatchOnLauncherTransitionEnd(toView, animated, true);

                    // Run any queued runnables
                    if (onCompleteRunnable != null) {
                        onCompleteRunnable.run();
                    }

                    // Animation complete callback
                    pCb.onAnimationComplete(revealView, contentView, allAppsButtonView);

                    // Disable all necessary layers
                    for (View v : layerViews.keySet()) {
                        if (layerViews.get(v) == BUILD_AND_SET_LAYER) {
                            v.setLayerType(View.LAYER_TYPE_NONE, null);
                        }
                    }

                    // Reset page transforms
                    if (contentView != null) {
                        contentView.setTranslationX(0);
                        contentView.setTranslationY(0);
                        contentView.setAlpha(1);
                    }

                    // This can hold unnecessary references to views.
                    mStateAnimation = null;
                }
            });

            final AnimatorSet stateAnimation = mStateAnimation;
            final Runnable startAnimRunnable = new Runnable() {
                public void run() {
                    // Check that mStateAnimation hasn't changed while
                    // we waited for a layout/draw pass
                    if (mStateAnimation != stateAnimation)
                        return;
                    dispatchOnLauncherTransitionStart(fromView, animated, false);
                    dispatchOnLauncherTransitionStart(toView, animated, false);

                    // Enable all necessary layers
                    for (View v : layerViews.keySet()) {
                        if (layerViews.get(v) == BUILD_AND_SET_LAYER) {
                            v.setLayerType(View.LAYER_TYPE_HARDWARE, null);
                        }
                        if (Utilities.isLmpOrAbove()) {
                            v.buildLayer();
                        }
                    }
                    mStateAnimation.start();
                }
            };
            fromView.post(startAnimRunnable);
        } else {
            fromView.setVisibility(View.GONE);
            dispatchOnLauncherTransitionPrepare(fromView, animated, true);
            dispatchOnLauncherTransitionStart(fromView, animated, true);
            dispatchOnLauncherTransitionEnd(fromView, animated, true);
            dispatchOnLauncherTransitionPrepare(toView, animated, true);
            dispatchOnLauncherTransitionStart(toView, animated, true);
            dispatchOnLauncherTransitionEnd(toView, animated, true);

            // Run any queued runnables
            if (onCompleteRunnable != null) {
                onCompleteRunnable.run();
            }
        }
    }


    /**
     * Dispatches the prepare-transition event to suitable views.
     */
    void dispatchOnLauncherTransitionPrepare(View v, boolean animated, boolean toWorkspace) {
        if (v instanceof LauncherTransitionable) {
            ((LauncherTransitionable) v).onLauncherTransitionPrepare(mLauncher, animated,
                    toWorkspace);
        }
    }

    /**
     * Dispatches the start-transition event to suitable views.
     */
    void dispatchOnLauncherTransitionStart(View v, boolean animated, boolean toWorkspace) {
        if (v instanceof LauncherTransitionable) {
            ((LauncherTransitionable) v).onLauncherTransitionStart(mLauncher, animated,
                    toWorkspace);
        }

        // Update the workspace transition step as well
        dispatchOnLauncherTransitionStep(v, 0f);
    }

    /**
     * Dispatches the step-transition event to suitable views.
     */
    void dispatchOnLauncherTransitionStep(View v, float t) {
        if (v instanceof LauncherTransitionable) {
            ((LauncherTransitionable) v).onLauncherTransitionStep(mLauncher, t);
        }
    }

    /**
     * Dispatches the end-transition event to suitable views.
     */
    void dispatchOnLauncherTransitionEnd(View v, boolean animated, boolean toWorkspace) {
        if (v instanceof LauncherTransitionable) {
            ((LauncherTransitionable) v).onLauncherTransitionEnd(mLauncher, animated,
                    toWorkspace);
        }

        // Update the workspace transition step as well
        dispatchOnLauncherTransitionStep(v, 1f);
    }

    /**
     * Cancels the current animation.
     */
    private void cancelAnimation() {
        if (mStateAnimation != null) {
            mStateAnimation.setDuration(0);
            mStateAnimation.cancel();
            mStateAnimation = null;
        }
    }
}