Android6.0 WMS(六) WMS动画管理.doc

Android6.0 WMS（六） WMS动画管理Android的应用启动时，或者切换Activity时都会以动画的方式显示前后两屏的切换过程。动画的原理很简单，把一帧一帧的图像按一定时间间隔显示出来就完成了。动画的绘制需要定时驱动，通常的做法是启动一个定时消息，每隔一定时间发一个消息，收到消息后输出一帧画面。Android支持VSync信号后，动画的驱动就有VSync信号承担了。窗口动画的基本元素是窗口Surface中保存的图像，通过对窗口的Surface设置不同的变换矩阵和透明度，然后强制Surface刷新，就能在屏幕上显示出窗口的变化过程。Choreographer对象初始化我们先来看WMS中的mChoreographer 变量cpp view plain copy 在CODE上查看代码片派生到我的代码片final Choreographer mChoreographer = Choreographer.getInstance(); 该变量是一个线程局部存储变量，在它的initialValue中创建了Choreographer对象并返回。这里使用线程局部存储的目录就是保证在线程中只有一个Choreographer对象。cpp view plain copy 在CODE上查看代码片派生到我的代码片public static Choreographer getInstance() return sThreadInstance.get(); cpp view plain copy 在CODE上查看代码片派生到我的代码片private static final ThreadLocal sThreadInstance = new ThreadLocal() Override protected Choreographer initialValue() Looper looper = Looper.myLooper(); if (looper = null) throw new IllegalStateException(The current thread must have a looper!); return new Choreographer(looper); ; 再来看下Choreographer的构造函数，这里主要是创建了FrameDisplayEventReceiver用来接受VSync信号的对象。cpp view plain copy 在CODE上查看代码片派生到我的代码片private Choreographer(Looper looper) mLooper = looper; mHandler = new FrameHandler(looper); mDisplayEventReceiver = USE_VSYNC ? new FrameDisplayEventReceiver(looper) : null;/接受VSync信号对象 mLastFrameTimeNanos = Long.MIN_VALUE; mFrameIntervalNanos = (long)(1000000000 / getRefreshRate();/计算刷新的时间间隔 mCallbackQueues = new CallbackQueueCALLBACK_LAST + 1; for (int i = 0; i now) Log.w(TAG, Frame time is + (timestampNanos - now) * 0.000001f) + ms in the future! Check that graphics HAL is generating vsync + timestamps using the correct timebase.); timestampNanos = now; if (mHavePendingVsync) Log.w(TAG, Already have a pending vsync event. There should only be + one at a time.); else mHavePendingVsync = true; mTimestampNanos = timestampNanos; mFrame = frame; Message msg = Message.obtain(mHandler, this); msg.setAsynchronous(true); mHandler.sendMessageAtTime(msg, timestampNanos / TimeUtils.NANOS_PER_MS); 这主要是发送了一个信号，而是是Runnable的那种消息。因此我们主要看下这个类的run函数，这里就是调用了Choreographer的doFrame函数。cpp view plain copy 在CODE上查看代码片派生到我的代码片Override public void run() mHavePendingVsync = false; doFrame(mTimestampNanos, mFrame); doFrame函数doFrame函数主要有一些VSync时间逻辑处理如果抛弃该VSync信号的话会调用scheduleVsyncLocked函数让SurfaceFlinger发送一个VSync信号，如果正常会调用4个doCallBacks函数。cpp view plain copy 在CODE上查看代码片派生到我的代码片void doFrame(long frameTimeNanos, int frame) final long startNanos; synchronized (mLock) . long intendedFrameTimeNanos = frameTimeNanos; startNanos = System.nanoTime(); final long jitterNanos = startNanos - frameTimeNanos; if (jitterNanos = mFrameIntervalNanos) final long skippedFrames = jitterNanos / mFrameIntervalNanos; final long lastFrameOffset = jitterNanos % mFrameIntervalNanos; frameTimeNanos = startNanos - lastFrameOffset; if (frameTimeNanos = 2 * mFrameIntervalNanos) final long lastFrameOffset = jitterNanos % mFrameIntervalNanos + mFrameIntervalNanos; if (DEBUG_JANK) mDebugPrintNextFrameTimeDelta = true; frameTimeNanos = now - lastFrameOffset; mLastFrameTimeNanos = frameTimeNanos; try for (CallbackRecord c = callbacks; c != null; c = c.next) c.run(frameTimeNanos);/调用回调run函数 . 这也就意味着当你没有CallBackType对应的回调，每次VSync信号过来到doFrame函数再到doCallBacks函数都是没有意义的。WMS启动动画那我们下面看在哪里把CallBackType对应的回调加入了，这里我们只关注动画相关的。上面我们说到VSync会不断的发送，每秒60多次，但是动画不会不停的播放，就是这个CallBackType对应的回调没有。哪动画的启动和结束也就是受这个影响，而就是在WMS中调用scheduleAnimationLocked函数发起的动画启动。cpp view plain copy 在CODE上查看代码片派生到我的代码片void scheduleAnimationLocked() if (!mAnimationScheduled) mAnimationScheduled = true; mChoreographer.postFrameCallback(mAnimator.mAnimationFrameCallback); 这里就是调用Choreographer设置CallBackType，相关的回调。这里我们的callbackType是CALLBACK_ANIMATIONcpp view plain copy 在CODE上查看代码片派生到我的代码片public void postFrameCallback(FrameCallback callback) postFrameCallbackDelayed(callback, 0); public void postFrameCallbackDelayed(FrameCallback callback, long delayMillis) if (callback = null) throw new IllegalArgumentException(callback must not be null); postCallbackDelayedInternal(CALLBACK_ANIMATION, callback, FRAME_CALLBACK_TOKEN, delayMillis); 我们最后看postCallbackDelayedInternal函数，就是在mCallBackQueues对应的CallBackType中增加相应的回调。这里也就是前面在WMS的scheduleAnimationLocked的参数mAnimator.mAnimationFrameCallback就是回调。cpp view plain copy 在CODE上查看代码片派生到我的代码片private void postCallbackDelayedInternal(int callbackType, Object action, Object token, long delayMillis) synchronized (mLock) final long now = SystemClock.uptimeMillis(); final long dueTime = now + delayMillis; mCallbackQueuescallbackType.addCallbackLocked(dueTime, action, token); if (dueTime = now) scheduleFrameLocked(now); else Message msg = mHandler.obtainMessage(MSG_DO_SCHEDULE_CALLBACK, action); msg.arg1 = callbackType; msg.setAsynchronous(true); mHandler.sendMessageAtTime(msg, dueTime); 我们来看下scheduleFrameLocked函数，我们注意mFrameScheduled这个变量，这个时候赋值为true，后面就是用这个变量来控制每次VSync信号过来调用doFrame函数的时候是否要播放动画cpp view plain copy 在CODE上查看代码片派生到我的代码片private void scheduleFrameLocked(long now) if (!mFrameScheduled) mFrameScheduled = true;/注意这个变量 if (USE_VSYNC) if (isRunningOnLooperThreadLocked() scheduleVsyncLocked();/尽快让SurfaceFlinger中的EventThread发送一个VSync信号 else Message msg = mHandler.obtainMessage(MSG_DO_SCHEDULE_VSYNC); msg.setAsynchronous(true); mHandler.sendMessageAtFrontOfQueue(msg); else final long nextFrameTime = Math.max( mLastFrameTimeNanos / TimeUtils.NANOS_PER_MS + sFrameDelay, now); if (DEBUG_FRAMES) Log.d(TAG, Scheduling next frame in + (nextFrameTime - now) + ms.); Message msg = mHandler.obtainMessage(MSG_DO_FRAME); msg.setAsynchronous(true); mHandler.sendMessageAtTime(msg, nextFrameTime); 我们再回过头来看doFrame函数，当mFrameScheduled为false时，VSync信号过来该函数直接return不会播放动画。cpp view plain copy 在CODE上查看代码片派生到我的代码片void doFrame(long frameTimeNanos, int frame) final long startNanos; synchronized (mLock) if (!mFrameScheduled) return; / no work to do 继续看postCallbackDelayedInternal函数中增加的回调，这个回调在WindowAnimator的构造函数中就新建了Choreographer.FrameCallback回调cpp view plain copy 在CODE上查看代码片派生到我的代码片WindowAnimator(final WindowManagerService service) mService = service; mContext = service.mContext; mPolicy = service.mPolicy; mAnimationFrameCallback = new Choreographer.FrameCallback() public void doFrame(long frameTimeNs) synchronized (mService.mWindowMap) mService.mAnimationScheduled = false; animateLocked(frameTimeNs); ; 我们最后看回调的run函数，如果是FRAME_CALLBACK_TOKEN，就是调用回调的doFrame函数。cpp view plain copy 在CODE上查看代码片派生到我的代码片private static final class CallbackRecord public CallbackRecord next; public long dueTime; public Object action; / Runnable or FrameCallback public Object token; public void run(long frameTimeNanos) if (token = FRAME_CALLBACK_TOKEN) (FrameCallback)action).doFrame(frameTimeNanos); else (Runnable)action).run(); 播放动画在上面doFrame函数启动动画，而动画的播放主要在WindowAnimator的animateLocked函数。cpp view plain copy 在CODE上查看代码片派生到我的代码片private void animateLocked(long frameTimeNs) . boolean wasAnimating = mAnimating; mAnimating = false;/设置mAnimating为false mAppWindowAnimating = false; SurfaceControl.openTransaction(); SurfaceControl.setAnimationTransaction(); try final int numDisplays = mDisplayContentsAnimators.size(); for (int i = 0; i numDisplays; i+) final int displayId = mDisplayContentsAnimators.keyAt(i); updateAppWindowsLocked(displayId); . / Update animations of all applications, including those / associated with exiting/removed apps updateWindowsLocked(displayId); updateWallpaperLocked(displayId); final WindowList windows = mService.getWindowListLocked(displayId); final int N = windows.size(); for (int j = 0; j N; j+) windows.get(j).mWinAnimator.prepareSurfaceLocked(true);/输出动画帧 for (int i = 0; i = 0; i-) final WindowState win = windows.get(i); WindowStateAnimator winAnimator = win.mWinAnimator; if (winAnimator.mSurfaceControl = null) continue; final int flags = win.mAttrs.flags; if (winAnimator.mAnimating) . mAnimating = true; . 再回到animatelocked方法，当mAnimating为true是会调用WMS的scheduleAnimationLocked方法继续显示动画，否则动画显示就结束了。下面我们总结下动画的播放过程：需要播放动画时，先会调用WMS的scheduleAnimationLocked方法。调用这个方法后，才会接受并处理一次VSync信号，对VSync信号的处理，就是所有需要绘制的窗口根据各自动画的谁知重新调整窗口Surface的变化矩阵和透明度；如果还有窗口动画需要显示，继续调用scheduleAnimationLocked方法准备下一帧。准备一帧动画的时间可以跨越多个VSync信号周期，但是只有收到VSync信号才能更新窗口的Surface的属性和内容，对应用而言收到VSync信号意味着SurfaceFlinger中已经把上次设置的动画数据取走了，可以安全地设置下一帧动画的属性和内容了。窗口动画对象WindowStateAnimator窗口对象WindowState中定义了一个类型为WindowStateAnimator的成员变量mWinAnimator，用来表示窗口的动画对象。下面是一些成员变量cpp view plain copy 在CODE上查看代码片派生到我的代码片boolean mAnimating;/表示是否正在显示动画 boolean mLocalAnimating;/表示窗口动画是否已经初始化 Animation mAnimation;/表示窗口动画对象 boolean mAnimationIsEntrance;/ boolean mHasTransformation;/表示当前动画的mTransformation是否可用 boolean mHasLocalTransformation;/表示当前动画时一个窗口动画还是Activity动画 final Transformation mTransformation = new Transformation();/变换矩阵对象 当前正在显示的动画有两种类型，一种的窗口切换动画，一种是Activity切换动画，这里使用了mLocalAnimating和mHasLocalTransformation分别表示窗口动画的状态。stepAnimationLocked是WindowStateAnimator类中显示动画首先调用的方法，它会初始化WindowStateAnimator对象的一些成员变量cpp view plain copy 在CODE上查看代码片派生到我的代码片boolean stepAnimationLocked(long currentTime) final DisplayContent displayContent = mWin.getDisplayContent(); if (displayContent != null & mService.okToDisplay() if (mWin.isDrawnLw() & mAnimation != null) /窗口准备好绘制了，窗口动画对象不为空 mHasTransformation = true; mHasLocalTransformation = true; if (!mLocalAnimating) /还没有初始化窗口对象 final DisplayInfo displayInfo = displayContent.getDisplayInfo(); if (mAnimateMove) mAnimateMove = false; mAnimation.initialize(mWin.mFrame.width(), mWin.mFrame.height(),/初始化窗口对象 mAnimDw, mAnimDh); else mAnimation.initialize(mWin.mFrame.width(), mWin.mFrame.height(), displayInfo.appWidth, displayInfo.appHeight); mAnimDw = displayInfo.appWidth; mAnimDh = displayInfo.appHeight; mAnimation.setStartTime(mAnimationStartTime != -1 ? mAnimationStartTime : currentTime); mLocalAnimating = true;/ 设置为true代表已经初始化窗口对象 mAnimating = true; if (mAnimation != null) & mLocalAnimating) mLastAnimationTime = currentTime; if (stepAnimation(currentTime) /通过时间判断动画是否显示完毕 return true; mHasLocalTransformation = false; if (!mLocalAnimating | mAnimationIsEntrance) & mAppAnimator != null/没有设置窗口动画或者窗口动画结束了 & mAppAnimator.animation != null) / 如果有Activity动画，将mAnimating设为true mAnimating = true; mHasTransformation = true; mTransformation.clear(); return alse; else if (mHasTransformation) / Little trick to get through the path below to act like / we have finished an animation. mAnimating = true; else if (isAnimating() mAnimating = true; else if (mAnimation != null) mAnimating = true; if (!mAnimating & !mLocalAnimating) return false; mAnimating = false; mKeyguardGoingAwayAnimation = false; mAnimatingMove = false; mLocalAnimating = false; . mHasLocalTransformation = false; . mTransformation.clear(); . return false; 该方法的工作就是设置WindowStateAnimator对象的几个成员变量，首先调用WindowState对象的isDrawnLw来判断窗口