services/core/java/com/android/server/wm/AnimatingAppWindowTokenRegistry.java

/*
 * Copyright (C) 2018 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.server.wm;

import android.util.ArrayMap;
import android.util.ArraySet;

import java.util.ArrayList;

/**
 * Keeps track of all {@link AppWindowToken} that are animating and makes sure all animations are
 * finished at the same time such that we don't run into issues with z-ordering: An activity A
 * that has a shorter animation that is above another activity B with a longer animation in the same
 * task, the animation layer would put the B on top of A, but from the hierarchy, A needs to be on
 * top of B. Thus, we defer reparenting A to the original hierarchy such that it stays on top of B
 * until B finishes animating.
 */
class AnimatingAppWindowTokenRegistry {

    private ArraySet<AppWindowToken> mAnimatingTokens = new ArraySet<>();
    private ArrayMap<AppWindowToken, Runnable> mFinishedTokens = new ArrayMap<>();

    private ArrayList<Runnable> mTmpRunnableList = new ArrayList<>();

    /**
     * Notifies that an {@link AppWindowToken} has started animating.
     */
    void notifyStarting(AppWindowToken token) {
        mAnimatingTokens.add(token);
    }

    /**
     * Notifies that an {@link AppWindowToken} has finished animating.
     */
    void notifyFinished(AppWindowToken token) {
        mAnimatingTokens.remove(token);
        mFinishedTokens.remove(token);
    }

    /**
     * Called when an {@link AppWindowToken} is about to finish animating.
     *
     * @param endDeferFinishCallback Callback to run when defer finish should be ended.
     * @return {@code true} if finishing the animation should be deferred, {@code false} otherwise.
     */
    boolean notifyAboutToFinish(AppWindowToken token, Runnable endDeferFinishCallback) {
        final boolean removed = mAnimatingTokens.remove(token);
        if (!removed) {
            return false;
        }

        if (mAnimatingTokens.isEmpty()) {

            // If no animations are animating anymore, finish all others.
            endDeferringFinished();
            return false;
        } else {

            // Otherwise let's put it into the pending list of to be finished animations.
            mFinishedTokens.put(token, endDeferFinishCallback);
            return true;
        }
    }

    private void endDeferringFinished() {
        // Copy it into a separate temp list to avoid modifying the collection while iterating as
        // calling the callback may call back into notifyFinished.
        for (int i = mFinishedTokens.size() - 1; i >= 0; i--) {
            mTmpRunnableList.add(mFinishedTokens.valueAt(i));
        }
        mFinishedTokens.clear();
        for (int i = mTmpRunnableList.size() - 1; i >= 0; i--) {
            mTmpRunnableList.get(i).run();
        }
        mTmpRunnableList.clear();
    }
}