Java tutorial
/* * Copyright (C) 2011 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 android.view; import static android.view.DisplayEventReceiver.VSYNC_SOURCE_APP; import static android.view.DisplayEventReceiver.VSYNC_SOURCE_SURFACE_FLINGER; import android.annotation.TestApi; import android.annotation.UnsupportedAppUsage; import android.hardware.display.DisplayManagerGlobal; import android.os.Build; import android.os.Handler; import android.os.Looper; import android.os.Message; import android.os.SystemClock; import android.os.SystemProperties; import android.os.Trace; import android.util.Log; import android.util.TimeUtils; import android.view.animation.AnimationUtils; import java.io.PrintWriter; /** * Coordinates the timing of animations, input and drawing. * <p> * The choreographer receives timing pulses (such as vertical synchronization) * from the display subsystem then schedules work to occur as part of rendering * the next display frame. * </p><p> * Applications typically interact with the choreographer indirectly using * higher level abstractions in the animation framework or the view hierarchy. * Here are some examples of things you can do using the higher-level APIs. * </p> * <ul> * <li>To post an animation to be processed on a regular time basis synchronized with * display frame rendering, use {@link android.animation.ValueAnimator#start}.</li> * <li>To post a {@link Runnable} to be invoked once at the beginning of the next display * frame, use {@link View#postOnAnimation}.</li> * <li>To post a {@link Runnable} to be invoked once at the beginning of the next display * frame after a delay, use {@link View#postOnAnimationDelayed}.</li> * <li>To post a call to {@link View#invalidate()} to occur once at the beginning of the * next display frame, use {@link View#postInvalidateOnAnimation()} or * {@link View#postInvalidateOnAnimation(int, int, int, int)}.</li> * <li>To ensure that the contents of a {@link View} scroll smoothly and are drawn in * sync with display frame rendering, do nothing. This already happens automatically. * {@link View#onDraw} will be called at the appropriate time.</li> * </ul> * <p> * However, there are a few cases where you might want to use the functions of the * choreographer directly in your application. Here are some examples. * </p> * <ul> * <li>If your application does its rendering in a different thread, possibly using GL, * or does not use the animation framework or view hierarchy at all * and you want to ensure that it is appropriately synchronized with the display, then use * {@link Choreographer#postFrameCallback}.</li> * <li>... and that's about it.</li> * </ul> * <p> * Each {@link Looper} thread has its own choreographer. Other threads can * post callbacks to run on the choreographer but they will run on the {@link Looper} * to which the choreographer belongs. * </p> */ public final class Choreographer { private static final String TAG = "Choreographer"; // Prints debug messages about jank which was detected (low volume). private static final boolean DEBUG_JANK = false; // Prints debug messages about every frame and callback registered (high volume). private static final boolean DEBUG_FRAMES = false; // The default amount of time in ms between animation frames. // When vsync is not enabled, we want to have some idea of how long we should // wait before posting the next animation message. It is important that the // default value be less than the true inter-frame delay on all devices to avoid // situations where we might skip frames by waiting too long (we must compensate // for jitter and hardware variations). Regardless of this value, the animation // and display loop is ultimately rate-limited by how fast new graphics buffers can // be dequeued. private static final long DEFAULT_FRAME_DELAY = 10; // The number of milliseconds between animation frames. private static volatile long sFrameDelay = DEFAULT_FRAME_DELAY; // Thread local storage for the choreographer. private static final ThreadLocal<Choreographer> sThreadInstance = new ThreadLocal<Choreographer>() { @Override protected Choreographer initialValue() { Looper looper = Looper.myLooper(); if (looper == null) { throw new IllegalStateException("The current thread must have a looper!"); } Choreographer choreographer = new Choreographer(looper, VSYNC_SOURCE_APP); if (looper == Looper.getMainLooper()) { mMainInstance = choreographer; } return choreographer; } }; private static volatile Choreographer mMainInstance; // Thread local storage for the SF choreographer. private static final ThreadLocal<Choreographer> sSfThreadInstance = new ThreadLocal<Choreographer>() { @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, VSYNC_SOURCE_SURFACE_FLINGER); } }; // Enable/disable vsync for animations and drawing. @UnsupportedAppUsage private static final boolean USE_VSYNC = SystemProperties.getBoolean("debug.choreographer.vsync", true); // Enable/disable using the frame time instead of returning now. private static final boolean USE_FRAME_TIME = SystemProperties.getBoolean("debug.choreographer.frametime", true); // Set a limit to warn about skipped frames. // Skipped frames imply jank. private static final int SKIPPED_FRAME_WARNING_LIMIT = SystemProperties .getInt("debug.choreographer.skipwarning", 30); private static final int MSG_DO_FRAME = 0; private static final int MSG_DO_SCHEDULE_VSYNC = 1; private static final int MSG_DO_SCHEDULE_CALLBACK = 2; // All frame callbacks posted by applications have this token. private static final Object FRAME_CALLBACK_TOKEN = new Object() { public String toString() { return "FRAME_CALLBACK_TOKEN"; } }; @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.P, trackingBug = 115609023) private final Object mLock = new Object(); private final Looper mLooper; private final FrameHandler mHandler; // The display event receiver can only be accessed by the looper thread to which // it is attached. We take care to ensure that we post message to the looper // if appropriate when interacting with the display event receiver. @UnsupportedAppUsage private final FrameDisplayEventReceiver mDisplayEventReceiver; private CallbackRecord mCallbackPool; @UnsupportedAppUsage private final CallbackQueue[] mCallbackQueues; private boolean mFrameScheduled; private boolean mCallbacksRunning; @UnsupportedAppUsage private long mLastFrameTimeNanos; @UnsupportedAppUsage private long mFrameIntervalNanos; private boolean mDebugPrintNextFrameTimeDelta; private int mFPSDivisor = 1; /** * Contains information about the current frame for jank-tracking, * mainly timings of key events along with a bit of metadata about * view tree state * * TODO: Is there a better home for this? Currently Choreographer * is the only one with CALLBACK_ANIMATION start time, hence why this * resides here. * * @hide */ FrameInfo mFrameInfo = new FrameInfo(); /** * Must be kept in sync with CALLBACK_* ints below, used to index into this array. * @hide */ private static final String[] CALLBACK_TRACE_TITLES = { "input", "animation", "traversal", "commit" }; /** * Callback type: Input callback. Runs first. * @hide */ public static final int CALLBACK_INPUT = 0; /** * Callback type: Animation callback. Runs before traversals. * @hide */ @TestApi public static final int CALLBACK_ANIMATION = 1; /** * Callback type: Traversal callback. Handles layout and draw. Runs * after all other asynchronous messages have been handled. * @hide */ public static final int CALLBACK_TRAVERSAL = 2; /** * Callback type: Commit callback. Handles post-draw operations for the frame. * Runs after traversal completes. The {@link #getFrameTime() frame time} reported * during this callback may be updated to reflect delays that occurred while * traversals were in progress in case heavy layout operations caused some frames * to be skipped. The frame time reported during this callback provides a better * estimate of the start time of the frame in which animations (and other updates * to the view hierarchy state) actually took effect. * @hide */ public static final int CALLBACK_COMMIT = 3; private static final int CALLBACK_LAST = CALLBACK_COMMIT; private Choreographer(Looper looper, int vsyncSource) { mLooper = looper; mHandler = new FrameHandler(looper); mDisplayEventReceiver = USE_VSYNC ? new FrameDisplayEventReceiver(looper, vsyncSource) : null; mLastFrameTimeNanos = Long.MIN_VALUE; mFrameIntervalNanos = (long) (1000000000 / getRefreshRate()); mCallbackQueues = new CallbackQueue[CALLBACK_LAST + 1]; for (int i = 0; i <= CALLBACK_LAST; i++) { mCallbackQueues[i] = new CallbackQueue(); } // b/68769804: For low FPS experiments. setFPSDivisor(SystemProperties.getInt(ThreadedRenderer.DEBUG_FPS_DIVISOR, 1)); } private static float getRefreshRate() { DisplayInfo di = DisplayManagerGlobal.getInstance().getDisplayInfo(Display.DEFAULT_DISPLAY); return di.getMode().getRefreshRate(); } /** * Gets the choreographer for the calling thread. Must be called from * a thread that already has a {@link android.os.Looper} associated with it. * * @return The choreographer for this thread. * @throws IllegalStateException if the thread does not have a looper. */ public static Choreographer getInstance() { return sThreadInstance.get(); } /** * @hide */ @UnsupportedAppUsage public static Choreographer getSfInstance() { return sSfThreadInstance.get(); } /** * @return The Choreographer of the main thread, if it exists, or {@code null} otherwise. * @hide */ public static Choreographer getMainThreadInstance() { return mMainInstance; } /** Destroys the calling thread's choreographer * @hide */ public static void releaseInstance() { Choreographer old = sThreadInstance.get(); sThreadInstance.remove(); old.dispose(); } private void dispose() { mDisplayEventReceiver.dispose(); } /** * The amount of time, in milliseconds, between each frame of the animation. * <p> * This is a requested time that the animation will attempt to honor, but the actual delay * between frames may be different, depending on system load and capabilities. This is a static * function because the same delay will be applied to all animations, since they are all * run off of a single timing loop. * </p><p> * The frame delay may be ignored when the animation system uses an external timing * source, such as the display refresh rate (vsync), to govern animations. * </p> * * @return the requested time between frames, in milliseconds * @hide */ @TestApi public static long getFrameDelay() { return sFrameDelay; } /** * The amount of time, in milliseconds, between each frame of the animation. * <p> * This is a requested time that the animation will attempt to honor, but the actual delay * between frames may be different, depending on system load and capabilities. This is a static * function because the same delay will be applied to all animations, since they are all * run off of a single timing loop. * </p><p> * The frame delay may be ignored when the animation system uses an external timing * source, such as the display refresh rate (vsync), to govern animations. * </p> * * @param frameDelay the requested time between frames, in milliseconds * @hide */ @TestApi public static void setFrameDelay(long frameDelay) { sFrameDelay = frameDelay; } /** * Subtracts typical frame delay time from a delay interval in milliseconds. * <p> * This method can be used to compensate for animation delay times that have baked * in assumptions about the frame delay. For example, it's quite common for code to * assume a 60Hz frame time and bake in a 16ms delay. When we call * {@link #postAnimationCallbackDelayed} we want to know how long to wait before * posting the animation callback but let the animation timer take care of the remaining * frame delay time. * </p><p> * This method is somewhat conservative about how much of the frame delay it * subtracts. It uses the same value returned by {@link #getFrameDelay} which by * default is 10ms even though many parts of the system assume 16ms. Consequently, * we might still wait 6ms before posting an animation callback that we want to run * on the next frame, but this is much better than waiting a whole 16ms and likely * missing the deadline. * </p> * * @param delayMillis The original delay time including an assumed frame delay. * @return The adjusted delay time with the assumed frame delay subtracted out. * @hide */ public static long subtractFrameDelay(long delayMillis) { final long frameDelay = sFrameDelay; return delayMillis <= frameDelay ? 0 : delayMillis - frameDelay; } /** * @return The refresh rate as the nanoseconds between frames * @hide */ public long getFrameIntervalNanos() { return mFrameIntervalNanos; } void dump(String prefix, PrintWriter writer) { String innerPrefix = prefix + " "; writer.print(prefix); writer.println("Choreographer:"); writer.print(innerPrefix); writer.print("mFrameScheduled="); writer.println(mFrameScheduled); writer.print(innerPrefix); writer.print("mLastFrameTime="); writer.println(TimeUtils.formatUptime(mLastFrameTimeNanos / 1000000)); } /** * Posts a callback to run on the next frame. * <p> * The callback runs once then is automatically removed. * </p> * * @param callbackType The callback type. * @param action The callback action to run during the next frame. * @param token The callback token, or null if none. * * @see #removeCallbacks * @hide */ @TestApi public void postCallback(int callbackType, Runnable action, Object token) { postCallbackDelayed(callbackType, action, token, 0); } /** * Posts a callback to run on the next frame after the specified delay. * <p> * The callback runs once then is automatically removed. * </p> * * @param callbackType The callback type. * @param action The callback action to run during the next frame after the specified delay. * @param token The callback token, or null if none. * @param delayMillis The delay time in milliseconds. * * @see #removeCallback * @hide */ @TestApi public void postCallbackDelayed(int callbackType, Runnable action, Object token, long delayMillis) { if (action == null) { throw new IllegalArgumentException("action must not be null"); } if (callbackType < 0 || callbackType > CALLBACK_LAST) { throw new IllegalArgumentException("callbackType is invalid"); } postCallbackDelayedInternal(callbackType, action, token, delayMillis); } private void postCallbackDelayedInternal(int callbackType, Object action, Object token, long delayMillis) { if (DEBUG_FRAMES) { Log.d(TAG, "PostCallback: type=" + callbackType + ", action=" + action + ", token=" + token + ", delayMillis=" + delayMillis); } synchronized (mLock) { final long now = SystemClock.uptimeMillis(); final long dueTime = now + delayMillis; mCallbackQueues[callbackType].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); } } } /** * Removes callbacks that have the specified action and token. * * @param callbackType The callback type. * @param action The action property of the callbacks to remove, or null to remove * callbacks with any action. * @param token The token property of the callbacks to remove, or null to remove * callbacks with any token. * * @see #postCallback * @see #postCallbackDelayed * @hide */ @TestApi public void removeCallbacks(int callbackType, Runnable action, Object token) { if (callbackType < 0 || callbackType > CALLBACK_LAST) { throw new IllegalArgumentException("callbackType is invalid"); } removeCallbacksInternal(callbackType, action, token); } private void removeCallbacksInternal(int callbackType, Object action, Object token) { if (DEBUG_FRAMES) { Log.d(TAG, "RemoveCallbacks: type=" + callbackType + ", action=" + action + ", token=" + token); } synchronized (mLock) { mCallbackQueues[callbackType].removeCallbacksLocked(action, token); if (action != null && token == null) { mHandler.removeMessages(MSG_DO_SCHEDULE_CALLBACK, action); } } } /** * Posts a frame callback to run on the next frame. * <p> * The callback runs once then is automatically removed. * </p> * * @param callback The frame callback to run during the next frame. * * @see #postFrameCallbackDelayed * @see #removeFrameCallback */ public void postFrameCallback(FrameCallback callback) { postFrameCallbackDelayed(callback, 0); } /** * Posts a frame callback to run on the next frame after the specified delay. * <p> * The callback runs once then is automatically removed. * </p> * * @param callback The frame callback to run during the next frame. * @param delayMillis The delay time in milliseconds. * * @see #postFrameCallback * @see #removeFrameCallback */ 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); } /** * Removes a previously posted frame callback. * * @param callback The frame callback to remove. * * @see #postFrameCallback * @see #postFrameCallbackDelayed */ public void removeFrameCallback(FrameCallback callback) { if (callback == null) { throw new IllegalArgumentException("callback must not be null"); } removeCallbacksInternal(CALLBACK_ANIMATION, callback, FRAME_CALLBACK_TOKEN); } /** * Gets the time when the current frame started. * <p> * This method provides the time in milliseconds when the frame started being rendered. * The frame time provides a stable time base for synchronizing animations * and drawing. It should be used instead of {@link SystemClock#uptimeMillis()} * or {@link System#nanoTime()} for animations and drawing in the UI. Using the frame * time helps to reduce inter-frame jitter because the frame time is fixed at the time * the frame was scheduled to start, regardless of when the animations or drawing * callback actually runs. All callbacks that run as part of rendering a frame will * observe the same frame time so using the frame time also helps to synchronize effects * that are performed by different callbacks. * </p><p> * Please note that the framework already takes care to process animations and * drawing using the frame time as a stable time base. Most applications should * not need to use the frame time information directly. * </p><p> * This method should only be called from within a callback. * </p> * * @return The frame start time, in the {@link SystemClock#uptimeMillis()} time base. * * @throws IllegalStateException if no frame is in progress. * @hide */ @UnsupportedAppUsage public long getFrameTime() { return getFrameTimeNanos() / TimeUtils.NANOS_PER_MS; } /** * Same as {@link #getFrameTime()} but with nanosecond precision. * * @return The frame start time, in the {@link System#nanoTime()} time base. * * @throws IllegalStateException if no frame is in progress. * @hide */ @UnsupportedAppUsage public long getFrameTimeNanos() { synchronized (mLock) { if (!mCallbacksRunning) { throw new IllegalStateException( "This method must only be called as " + "part of a callback while a frame is in progress."); } return USE_FRAME_TIME ? mLastFrameTimeNanos : System.nanoTime(); } } /** * Like {@link #getLastFrameTimeNanos}, but always returns the last frame time, not matter * whether callbacks are currently running. * @return The frame start time of the last frame, in the {@link System#nanoTime()} time base. * @hide */ public long getLastFrameTimeNanos() { synchronized (mLock) { return USE_FRAME_TIME ? mLastFrameTimeNanos : System.nanoTime(); } } private void scheduleFrameLocked(long now) { if (!mFrameScheduled) { mFrameScheduled = true; if (USE_VSYNC) { if (DEBUG_FRAMES) { Log.d(TAG, "Scheduling next frame on vsync."); } // If running on the Looper thread, then schedule the vsync immediately, // otherwise post a message to schedule the vsync from the UI thread // as soon as possible. if (isRunningOnLooperThreadLocked()) { scheduleVsyncLocked(); } 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); } } } void setFPSDivisor(int divisor) { if (divisor <= 0) divisor = 1; mFPSDivisor = divisor; ThreadedRenderer.setFPSDivisor(divisor); } @UnsupportedAppUsage void doFrame(long frameTimeNanos, int frame) { final long startNanos; synchronized (mLock) { if (!mFrameScheduled) { return; // no work to do } if (DEBUG_JANK && mDebugPrintNextFrameTimeDelta) { mDebugPrintNextFrameTimeDelta = false; Log.d(TAG, "Frame time delta: " + ((frameTimeNanos - mLastFrameTimeNanos) * 0.000001f) + " ms"); } long intendedFrameTimeNanos = frameTimeNanos; startNanos = System.nanoTime(); final long jitterNanos = startNanos - frameTimeNanos; if (jitterNanos >= mFrameIntervalNanos) { final long skippedFrames = jitterNanos / mFrameIntervalNanos; if (skippedFrames >= SKIPPED_FRAME_WARNING_LIMIT) { Log.i(TAG, "Skipped " + skippedFrames + " frames! " + "The application may be doing too much work on its main thread."); } final long lastFrameOffset = jitterNanos % mFrameIntervalNanos; if (DEBUG_JANK) { Log.d(TAG, "Missed vsync by " + (jitterNanos * 0.000001f) + " ms " + "which is more than the frame interval of " + (mFrameIntervalNanos * 0.000001f) + " ms! " + "Skipping " + skippedFrames + " frames and setting frame " + "time to " + (lastFrameOffset * 0.000001f) + " ms in the past."); } frameTimeNanos = startNanos - lastFrameOffset; } if (frameTimeNanos < mLastFrameTimeNanos) { if (DEBUG_JANK) { Log.d(TAG, "Frame time appears to be going backwards. May be due to a " + "previously skipped frame. Waiting for next vsync."); } scheduleVsyncLocked(); return; } if (mFPSDivisor > 1) { long timeSinceVsync = frameTimeNanos - mLastFrameTimeNanos; if (timeSinceVsync < (mFrameIntervalNanos * mFPSDivisor) && timeSinceVsync > 0) { scheduleVsyncLocked(); return; } } mFrameInfo.setVsync(intendedFrameTimeNanos, frameTimeNanos); mFrameScheduled = false; mLastFrameTimeNanos = frameTimeNanos; } 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); mFrameInfo.markPerformTraversalsStart(); doCallbacks(Choreographer.CALLBACK_TRAVERSAL, frameTimeNanos); doCallbacks(Choreographer.CALLBACK_COMMIT, frameTimeNanos); } finally { AnimationUtils.unlockAnimationClock(); Trace.traceEnd(Trace.TRACE_TAG_VIEW); } if (DEBUG_FRAMES) { final long endNanos = System.nanoTime(); Log.d(TAG, "Frame " + frame + ": Finished, took " + (endNanos - startNanos) * 0.000001f + " ms, latency " + (startNanos - frameTimeNanos) * 0.000001f + " ms."); } } 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); } } void doScheduleVsync() { synchronized (mLock) { if (mFrameScheduled) { scheduleVsyncLocked(); } } } void doScheduleCallback(int callbackType) { synchronized (mLock) { if (!mFrameScheduled) { final long now = SystemClock.uptimeMillis(); if (mCallbackQueues[callbackType].hasDueCallbacksLocked(now)) { scheduleFrameLocked(now); } } } } @UnsupportedAppUsage private void scheduleVsyncLocked() { mDisplayEventReceiver.scheduleVsync(); } private boolean isRunningOnLooperThreadLocked() { return Looper.myLooper() == mLooper; } private CallbackRecord obtainCallbackLocked(long dueTime, Object action, Object token) { CallbackRecord callback = mCallbackPool; if (callback == null) { callback = new CallbackRecord(); } else { mCallbackPool = callback.next; callback.next = null; } callback.dueTime = dueTime; callback.action = action; callback.token = token; return callback; } private void recycleCallbackLocked(CallbackRecord callback) { callback.action = null; callback.token = null; callback.next = mCallbackPool; mCallbackPool = callback; } /** * Implement this interface to receive a callback when a new display frame is * being rendered. The callback is invoked on the {@link Looper} thread to * which the {@link Choreographer} is attached. */ public interface FrameCallback { /** * Called when a new display frame is being rendered. * <p> * This method provides the time in nanoseconds when the frame started being rendered. * The frame time provides a stable time base for synchronizing animations * and drawing. It should be used instead of {@link SystemClock#uptimeMillis()} * or {@link System#nanoTime()} for animations and drawing in the UI. Using the frame * time helps to reduce inter-frame jitter because the frame time is fixed at the time * the frame was scheduled to start, regardless of when the animations or drawing * callback actually runs. All callbacks that run as part of rendering a frame will * observe the same frame time so using the frame time also helps to synchronize effects * that are performed by different callbacks. * </p><p> * Please note that the framework already takes care to process animations and * drawing using the frame time as a stable time base. Most applications should * not need to use the frame time information directly. * </p> * * @param frameTimeNanos The time in nanoseconds when the frame started being rendered, * in the {@link System#nanoTime()} timebase. Divide this value by {@code 1000000} * to convert it to the {@link SystemClock#uptimeMillis()} time base. */ public void doFrame(long frameTimeNanos); } private final class FrameHandler extends Handler { public FrameHandler(Looper looper) { super(looper); } @Override public void handleMessage(Message msg) { switch (msg.what) { case MSG_DO_FRAME: doFrame(System.nanoTime(), 0); break; case MSG_DO_SCHEDULE_VSYNC: doScheduleVsync(); break; case MSG_DO_SCHEDULE_CALLBACK: doScheduleCallback(msg.arg1); break; } } } private final class FrameDisplayEventReceiver extends DisplayEventReceiver implements Runnable { private boolean mHavePendingVsync; private long mTimestampNanos; private int mFrame; public FrameDisplayEventReceiver(Looper looper, int vsyncSource) { super(looper, vsyncSource); } @Override public void onVsync(long timestampNanos, int builtInDisplayId, int frame) { // Ignore vsync from secondary display. // This can be problematic because the call to scheduleVsync() is a one-shot. // We need to ensure that we will still receive the vsync from the primary // display which is the one we really care about. Ideally we should schedule // vsync for a particular display. // At this time Surface Flinger won't send us vsyncs for secondary displays // but that could change in the future so let's log a message to help us remember // that we need to fix this. if (builtInDisplayId != SurfaceControl.BUILT_IN_DISPLAY_ID_MAIN) { Log.d(TAG, "Received vsync from secondary display, but we don't support " + "this case yet. Choreographer needs a way to explicitly request " + "vsync for a specific display to ensure it doesn't lose track " + "of its scheduled vsync."); scheduleVsync(); return; } // Post the vsync event to the Handler. // The idea is to prevent incoming vsync events from completely starving // the message queue. If there are no messages in the queue with timestamps // earlier than the frame time, then the vsync event will be processed immediately. // Otherwise, messages that predate the vsync event will be handled first. long now = System.nanoTime(); if (timestampNanos > 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); } @Override public void run() { mHavePendingVsync = false; doFrame(mTimestampNanos, mFrame); } } 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(); } } } private final class CallbackQueue { private CallbackRecord mHead; public boolean hasDueCallbacksLocked(long now) { return mHead != null && mHead.dueTime <= now; } public CallbackRecord extractDueCallbacksLocked(long now) { CallbackRecord callbacks = mHead; if (callbacks == null || callbacks.dueTime > now) { return null; } CallbackRecord last = callbacks; CallbackRecord next = last.next; while (next != null) { if (next.dueTime > now) { last.next = null; break; } last = next; next = next.next; } mHead = next; return callbacks; } @UnsupportedAppUsage public void addCallbackLocked(long dueTime, Object action, Object token) { CallbackRecord callback = obtainCallbackLocked(dueTime, action, token); CallbackRecord entry = mHead; if (entry == null) { mHead = callback; return; } if (dueTime < entry.dueTime) { callback.next = entry; mHead = callback; return; } while (entry.next != null) { if (dueTime < entry.next.dueTime) { callback.next = entry.next; break; } entry = entry.next; } entry.next = callback; } public void removeCallbacksLocked(Object action, Object token) { CallbackRecord predecessor = null; for (CallbackRecord callback = mHead; callback != null;) { final CallbackRecord next = callback.next; if ((action == null || callback.action == action) && (token == null || callback.token == token)) { if (predecessor != null) { predecessor.next = next; } else { mHead = next; } recycleCallbackLocked(callback); } else { predecessor = callback; } callback = next; } } } }