[036]Choreographer Skipped真正含义

Choreographer: Skipped 60 frames!  The application may be doing too much work on its main thread.

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);
    }

    @Override
    protected void onResume() {
        Log.d("KobeWang", "MainActivity : onResume start");
        super.onResume();
        try {
            Thread.sleep(1000);
        } catch (Exception e) {

        }
        Log.d("KobeWang", "MainActivity : onResume end");
    }
}

03-11 19:01:25.679 15733 15733 D KobeWang: MainActivity : onResume start
03-11 19:01:26.682 15733 15733 D KobeWang: MainActivity : onResume end

    private Choreographer(Looper looper, int vsyncSource) {
        ...
        //每一帧的时间，如果60hz的屏幕，就是16ms，但是这里是微秒
        mFrameIntervalNanos = (long)(1000000000 / getRefreshRate())
        ...
    }

    private final class FrameDisplayEventReceiver extends DisplayEventReceiver
            implements Runnable {

        private long mTimestampNanos;
        private int mFrame;

        @Override
        public void onVsync(long timestampNanos, long physicalDisplayId, int frame) {
            ...
            //onVsync方法将会在Vsync信号接收之后被回调
            //mTimestampNanos就是这次Vsync信号接收的时间
            mTimestampNanos = timestampNanos;
            mFrame = frame;
            //往主线程的Looper中投放一个Asynchronous的Message，callback为this
            //这个Message被处理的时候就会调用下面run-doFrame的方法
            Message msg = Message.obtain(mHandler, this);
            msg.setAsynchronous(true);
            mHandler.sendMessageAtTime(msg, timestampNanos / TimeUtils.NANOS_PER_MS);
        }

        @Override
        public void run() {
            doFrame(mTimestampNanos, mFrame);
        }
    }

    void doFrame(long frameTimeNanos, int frame) {
        final long startNanos;
        synchronized (mLock) {
            ...
            //intendedFrameTimeNanos就是预计执行doFrame的时间点
            long intendedFrameTimeNanos = frameTimeNanos;
            //startNanos就是实际执行doFrame的时间点
            startNanos = System.nanoTime();
            //计算实际和预计的时间差
            final long jitterNanos = startNanos - frameTimeNanos;
            //如果时间差大于一帧的时间，也就是16ms
            if (jitterNanos >= mFrameIntervalNanos) {
                //计算丢掉的帧数=时间差/一帧的时长
                final long skippedFrames = jitterNanos / mFrameIntervalNanos;
                //SKIPPED_FRAME_WARNING_LIMIT默认是30
                if (skippedFrames >= SKIPPED_FRAME_WARNING_LIMIT) {
                    //如果丢掉的帧数大于30帧就打印LOG
                    Log.i(TAG, "Skipped " + skippedFrames + " frames!  "
                            + "The application may be doing too much work on its main thread.");
                }
             
            }
            ...
        }
    }

KobeWang: java.lang.Exception: KobeWang
KobeWang:   at android.view.ViewRootImpl.scheduleTraversals(ViewRootImpl.java:1694)
KobeWang:   at android.view.ViewRootImpl.requestLayout(ViewRootImpl.java:1425)
KobeWang:   at android.view.ViewRootImpl.setView(ViewRootImpl.java:856)
KobeWang:   at android.view.WindowManagerGlobal.addView(WindowManagerGlobal.java:387)
KobeWang:   at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:96)
KobeWang:   at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:4399)
KobeWang:   at android.app.servertransaction.ResumeActivityItem.execute(ResumeActivityItem.java:52)
KobeWang:   at android.app.servertransaction.TransactionExecutor.executeLifecycleState(TransactionExecutor.java:176)
KobeWang:   at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:97)
KobeWang:   at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2102)
KobeWang:   at android.os.Handler.dispatchMessage(Handler.java:107)
KobeWang:   at android.os.Looper.loop(Looper.java:214)
KobeWang:   at android.app.ActivityThread.main(ActivityThread.java:7501)
KobeWang:   at java.lang.reflect.Method.invoke(Native Method)
KobeWang:   at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
KobeWang:   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:935)

public class MainActivity extends AppCompatActivity {

    private Handler mHandler = new Handler();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);
    }

    @Override
    protected void onResume() {
        Log.d("KobeWang", "MainActivity : onResume start");
        super.onResume();
        mHandler.post(new Runnable() {
            @Override
            public void run() {
                try {
                    Thread.sleep(1000);
                } catch (Exception e) {

                }
            }
        });
        Log.d("KobeWang", "MainActivity : onResume end");
    }
}

2020-03-11 19:19:38.281 19118-19118/com.kobe.jankblock D/KobeWang: MainActivity : onResume start
2020-03-11 19:19:38.281 19118-19118/com.kobe.jankblock D/KobeWang: MainActivity : onResume end
2020-03-11 19:19:39.294 19118-19118/com.kobe.jankblock I/Choreographer: Skipped 60 frames!  The application may be doing too much work on its main thread.