Java tutorial
/* * Copyright (C) 2017 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 io.codetail.animation; import android.os.SystemClock; import android.support.v4.util.SimpleArrayMap; import android.view.Choreographer; import java.util.ArrayList; /** * This custom, static handler handles the timing pulse that is shared by all active * ValueAnimators. This approach ensures that the setting of animation values will happen on the * same thread that animations start on, and that all animations will share the same times for * calculating their values, which makes synchronizing animations possible. * * The handler uses the Choreographer by default for doing periodic callbacks. A custom * AnimationFrameCallbackProvider can be set on the handler to provide timing pulse that * may be independent of UI frame update. This could be useful in testing. * * @hide */ class AnimationHandler { /** * Callbacks that receives notifications for animation timing */ interface AnimationFrameCallback { /** * Run animation based on the frame time. * * @param frameTime The frame start time */ boolean doAnimationFrame(long frameTime); } /** * Internal per-thread collections used to avoid set collisions as animations start and end * while being processed. * * @hide */ private final SimpleArrayMap<AnimationFrameCallback, Long> mDelayedCallbackStartTime = new SimpleArrayMap<>(); public static final ThreadLocal<AnimationHandler> sAnimatorHandler = new ThreadLocal<>(); private final ArrayList<AnimationFrameCallback> mAnimationCallbacks = new ArrayList<>(); private AnimationFrameCallbackProvider mProvider; private long mCurrentFrameTime = 0; private final Choreographer.FrameCallback mFrameCallback = new Choreographer.FrameCallback() { @Override public void doFrame(long frameTimeNanos) { mCurrentFrameTime = System.currentTimeMillis(); doAnimationFrame(mCurrentFrameTime); if (mAnimationCallbacks.size() > 0) { getProvider().postFrameCallback(this); } } }; private boolean mListDirty = false; public static AnimationHandler getInstance() { if (sAnimatorHandler.get() == null) { sAnimatorHandler.set(new AnimationHandler()); } return sAnimatorHandler.get(); } public static long getFrameTime() { if (sAnimatorHandler.get() == null) { return 0; } return sAnimatorHandler.get().mCurrentFrameTime; } /** * By default, the Choreographer is used to provide timing for frame callbacks. A custom * provider can be used here to provide different timing pulse. */ public void setProvider(AnimationFrameCallbackProvider provider) { if (provider == null) { mProvider = new MyFrameCallbackProvider(); } else { mProvider = provider; } } private AnimationFrameCallbackProvider getProvider() { if (mProvider == null) { mProvider = new MyFrameCallbackProvider(); } return mProvider; } /** * Register to get a callback on the next frame after the delay. */ public void addAnimationFrameCallback(final AnimationFrameCallback callback, long delay) { if (mAnimationCallbacks.size() == 0) { getProvider().postFrameCallback(mFrameCallback); } if (!mAnimationCallbacks.contains(callback)) { mAnimationCallbacks.add(callback); } if (delay > 0) { mDelayedCallbackStartTime.put(callback, (SystemClock.uptimeMillis() + delay)); } } /** * Removes the given callback from the list, so it will no longer be called for frame related * timing. */ public void removeCallback(AnimationFrameCallback callback) { mDelayedCallbackStartTime.remove(callback); int id = mAnimationCallbacks.indexOf(callback); if (id >= 0) { mAnimationCallbacks.set(id, null); mListDirty = true; } } private void doAnimationFrame(long frameTime) { long currentTime = SystemClock.uptimeMillis(); for (int i = 0; i < mAnimationCallbacks.size(); i++) { final AnimationFrameCallback callback = mAnimationCallbacks.get(i); if (callback == null) { continue; } if (isCallbackDue(callback, currentTime)) { callback.doAnimationFrame(frameTime); } } cleanUpList(); } /** * Remove the callbacks from mDelayedCallbackStartTime once they have passed the initial delay * so that they can start getting frame callbacks. * * @return true if they have passed the initial delay or have no delay, false otherwise. */ private boolean isCallbackDue(AnimationFrameCallback callback, long currentTime) { Long startTime = mDelayedCallbackStartTime.get(callback); if (startTime == null) { return true; } if (startTime < currentTime) { mDelayedCallbackStartTime.remove(callback); return true; } return false; } private void cleanUpList() { if (mListDirty) { for (int i = mAnimationCallbacks.size() - 1; i >= 0; i--) { if (mAnimationCallbacks.get(i) == null) { mAnimationCallbacks.remove(i); } } mListDirty = false; } } private int getCallbackSize() { int count = 0; int size = mAnimationCallbacks.size(); for (int i = size - 1; i >= 0; i--) { if (mAnimationCallbacks.get(i) != null) { count++; } } return count; } /** * Default provider of timing pulse that uses Choreographer for frame callbacks. */ private class MyFrameCallbackProvider implements AnimationFrameCallbackProvider { final Choreographer mChoreographer = Choreographer.getInstance(); @Override public void postFrameCallback(Choreographer.FrameCallback callback) { mChoreographer.postFrameCallback(callback); } } /** * The intention for having this interface is to increase the testability of ValueAnimator. * Specifically, we can have a custom implementation of the interface below and provide * timing pulse without using Choreographer. That way we could use any arbitrary interval for * our timing pulse in the tests. * * @hide */ public interface AnimationFrameCallbackProvider { void postFrameCallback(Choreographer.FrameCallback callback); } }