Android界面显示_视图Choreographer控制

GPU/CPU生产帧率和屏幕消费帧率的生产者消费者模式
掉帧，双缓存，三缓存
SurfaceFlinger进程发出vsync信号
Choreographer(ThreadLocal持有，即ui线程持有)负责获取Vsync同步信号并控制App线程(主线程)完成图像绘制的类
主线程中初始化变量时，创建Choreographer对象，绑定主线程Looper
Choreographer通过DisplayEventReceiver通过JNI调用，利用Binder机制接收surfaceflinger进程底层Vsync信号，请求帧画面显示控制。在需要绘制时，发起请求。底层初始化(nativeInit)，发起请求(scheduleVsync)，实现回调(dispatchVsync)

DisplayEventReceiver收到底层各种类型的信号，在doFrame()方法中处理doCallbacks(int callbackType, long frameTimeNanos)

void doFrame(long frameTimeNanos, int frame) {         ...try {                   Trace.traceBegin(Trace.TRACE_TAG_VIEW, "Choreographer#doFrame");            AnimationUtils.lockAnimationClock(frameTimeNanos / TimeUtils.NANOS_PER_MS);            mFrameInfo.markInputHandlingStart();            doCallbacks(Choreographer.CALLBACK_INPUT, frameTimeNanos);            mFrameInfo.markAnimationsStart();            doCallbacks(Choreographer.CALLBACK_ANIMATION, frameTimeNanos);            doCallbacks(Choreographer.CALLBACK_INSETS_ANIMATION, frameTimeNanos);            mFrameInfo.markPerformTraversalsStart();            doCallbacks(Choreographer.CALLBACK_TRAVERSAL, frameTimeNanos);            doCallbacks(Choreographer.CALLBACK_COMMIT, frameTimeNanos);        } finally {                   AnimationUtils.unlockAnimationClock();            Trace.traceEnd(Trace.TRACE_TAG_VIEW);        }  ...}

callbackType类型:
- Choreographer.CALLBACK_INPUT(控制同步处理输入Input)
- Choreographer.CALLBACK_ANIMATION(控制同步动画Animation)
- Choreographer.CALLBACK_TRAVERSAL(触发ViewRootImpl的doTraversal方法，实现一次遍历绘制)
- Choreographer.CALLBACK_INSETS_ANIMATION
- Choreographer.CALLBACK_COMMIT(遍历完成的提交操作，用来修正动画启动时间)

自定义doFrame监听每一帧渲染时间，获取设备当前帧率(开源项目:Tiny Dancer)

Choreographer.getInstance().postFrameCallback(new FPSFrameCallback());public class FPSFrameCallback implements Choreographer.FrameCallback{       @Override  public void doFrame(long frameTimeNanos){             //do something  }

doCallbacks代码如下:

void doCallbacks(int callbackType, long frameTimeNanos) {               CallbackRecord callbacks;        synchronized (mLock) {                   // We use "now" to determine when callbacks become due because it's possible            // for earlier processing phases in a frame to post callbacks that should run            // in a following phase, such as an input event that causes an animation to start.            final long now = System.nanoTime();            callbacks = mCallbackQueues[callbackType].extractDueCallbacksLocked(                    now / TimeUtils.NANOS_PER_MS);            if (callbacks == null) {                       return;            }            mCallbacksRunning = true;            // Update the frame time if necessary when committing the frame.            // We only update the frame time if we are more than 2 frames late reaching            // the commit phase.  This ensures that the frame time which is observed by the            // callbacks will always increase from one frame to the next and never repeat.            // We never want the next frame's starting frame time to end up being less than            // or equal to the previous frame's commit frame time.  Keep in mind that the            // next frame has most likely already been scheduled by now so we play it            // safe by ensuring the commit time is always at least one frame behind.            if (callbackType == Choreographer.CALLBACK_COMMIT) {                       final long jitterNanos = now - frameTimeNanos;                Trace.traceCounter(Trace.TRACE_TAG_VIEW, "jitterNanos", (int) jitterNanos);                if (jitterNanos >= 2 * mFrameIntervalNanos) {                           final long lastFrameOffset = jitterNanos % mFrameIntervalNanos                            + mFrameIntervalNanos;                    if (DEBUG_JANK) {                               Log.d(TAG, "Commit callback delayed by " + (jitterNanos * 0.000001f)                                + " ms which is more than twice the frame interval of "                                + (mFrameIntervalNanos * 0.000001f) + " ms!  "                                + "Setting frame time to " + (lastFrameOffset * 0.000001f)                                + " ms in the past.");                        mDebugPrintNextFrameTimeDelta = true;                    }                    frameTimeNanos = now - lastFrameOffset;                    mLastFrameTimeNanos = frameTimeNanos;                }            }        }        try {                   Trace.traceBegin(Trace.TRACE_TAG_VIEW, CALLBACK_TRACE_TITLES[callbackType]);            for (CallbackRecord c = callbacks; c != null; c = c.next) {                       if (DEBUG_FRAMES) {                           Log.d(TAG, "RunCallback: type=" + callbackType                            + ", action=" + c.action + ", token=" + c.token                            + ", latencyMillis=" + (SystemClock.uptimeMillis() - c.dueTime));                }                c.run(frameTimeNanos);            }        } finally {                   synchronized (mLock) {                       mCallbacksRunning = false;                do {                           final CallbackRecord next = callbacks.next;                    recycleCallbackLocked(callbacks);                    callbacks = next;                } while (callbacks != null);            }            Trace.traceEnd(Trace.TRACE_TAG_VIEW);        }    }

从mCallbackQueues中取出CallbackRecord，for循环遍历执行c.run(frameTimeNanos);

CallbackRecord代码如下：

    private static final class CallbackRecord {               public CallbackRecord next;        public long dueTime;        public Object action; // Runnable or FrameCallback        public Object token;        @UnsupportedAppUsage        public void run(long frameTimeNanos) {                   if (token == FRAME_CALLBACK_TOKEN) {                       ((FrameCallback)action).doFrame(frameTimeNanos);            } else {                       ((Runnable)action).run();            }        }    }

CallbackRecord的run方法中((Runnable)action).run();

CallbackRecord对象中的(Runnable)action是我们在ViewRootImpl类当中的InvalidateOnAnimationRunnable、mConsumedBatchedInputRunnable、mTraversalRunnable添加到Choreographer中来的。那么回到View的流程中，比如收到Vsync信号后，就会回调mTraversalRunnable的run()方法，再次发起一次measure、layout、draw流程，那么也就和Vsync信号对接上了

Android界面显示_视图Choreographer控制

Android界面显示_视图Choreographer控制

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