安卓锁屏亮屏流程

注意点：对于锁屏来说，灭屏时，锁屏就会进行加载，并且加载完成，之后在亮屏时进行显示。
亮屏时，KeyguardService先后会调用以下方法：onStartedWakeUp(),onScreenTurningOn(),onScreenTurnedOn(),锁屏亮屏显示布局的主要操作就在onScreenTurningOn()。
1、首先onScreenTurningOn在PWM中被调起，开始进行亮屏流程。

// 在 DisplayManager 的 DisplayPowerController 线程上调用。
    @Override
    public void screenTurningOn(final ScreenonListener screenOnListener) {
        if (DEBUG_WAKEUP) Slog.i(TAG, "Screen turning on...");

        Trace.asyncTraceBegin(Trace.TRACE_TAG_WINDOW_MANAGER, "screenTurningOn", 0 );
        updateScreenOffSleepToken(false);
        mDefaultDisplayPolicy.screenTurnedOn(screenOnListener);

        synchronized (mLock) {
            if (mKeyguardDelegate != null && mKeyguardDelegate.hasKeyguard()) {//一般走此处
                mHandler.removeMessages(MSG_KEYGUARD_DRAWN_TIMEOUT);
    //移除掉消息队列中的绘制超时消息            mHandler.sendEmptyMessageDelayed(MSG_KEYGUARD_DRAWN_TIMEOUT,
                        getKeyguardDrawnTimeout());
     //获取绘制时长后，发送绘制超时消息，完成绘制           mKeyguardDelegate.onScreenTurningOn(mKeyguardDrawnCallback);
            } else {
                if (DEBUG_WAKEUP) Slog.d(TAG,
                        "null mKeyguardDelegate: setting mKeyguardDrawComplete.");
                mHandler.sendEmptyMessage(MSG_KEYGUARD_DRAWN_COMPLETE);
            }
        }
    }

2、调用KeyguardServiceDelegate.onScreenTurningOn()方法

public void onScreenTurningOn(final DrawnListener drawnListener) {
        if (mKeyguardService != null) {
            if (DEBUG) Log.v(TAG, "onScreenTurnedOn(showListener = " + drawnListener + ")");
            mKeyguardService.onScreenTurningOn(new KeyguardShowDelegate(drawnListener));
        } else {
            // try again when we establish a connection
            Slog.w(TAG, "onScreenTurningOn(): no keyguard service!");
            // This shouldn't happen, but if it does, show the scrim immediately and
            // invoke the listener's callback after the service actually connects.
            mDrawnListenerWhenConnect = drawnListener;
        }
        mKeyguardState.screenState = SCREEN_STATE_TURNING_ON;
    }

3、此处调用了KeyguardService中的onScreenTurningOn方法

public void onScreenTurningOn(IKeyguardDrawnCallback callback) {
            Trace.beginSection("KeyguardService.mBinder#onScreenTurningOn");
            checkPermission();
            mKeyguardViewMediator.onScreenTurningOn(callback);
            mKeyguardLifecyclesDispatcher.dispatch(KeyguardLifecyclesDispatcher.SCREEN_TURNING_ON);
            Trace.endSection();
        }

4、调用KeyguardViewMediator中的onScreenTurningOn

public void onScreenTurningOn(IKeyguardDrawnCallback callback) {
        Trace.beginSection("KeyguardViewMediator#onScreenTurningOn");
        notifyScreenOn(callback);
        Trace.endSection();
    }
private void notifyScreenOn(IKeyguardDrawnCallback callback) {
        if (DEBUG) Log.d(TAG, "notifyScreenOn");
        Message msg = mHandler.obtainMessage(NOTIFY_SCREEN_TURNING_ON, callback);
        mHandler.sendMessage(msg);
    }

5、此处，向消息队列中发送了NOTIFY_SCREEN_TURNING_ON消息。接收到消息后的执行逻辑如下

case NOTIFY_SCREEN_TURNING_ON:
                    Trace.beginSection(
                            "KeyguardViewMediator#handleMessage NOTIFY_SCREEN_TURNING_ON");
                    handleNotifyScreenTurningOn((IKeyguardDrawnCallback) msg.obj);
                    Trace.endSection();
                    break;
private void handleNotifyScreenTurningOn(IKeyguardDrawnCallback callback) {
        Trace.beginSection("KeyguardViewMediator#handleNotifyScreenTurningOn");
        synchronized (KeyguardViewMediator.this) {
            if (DEBUG) Log.d(TAG, "handleNotifyScreenTurningOn");
            mKeyguardViewControllerLazy.get().onScreenTurningOn();
            if (callback != null) {
                if (mWakeAndUnlocking) {
                    mDrawnCallback = callback;
                } else {
                    notifyDrawn(callback);
                }
            }
        }
        Trace.endSection();
    }

6、此处执行了notifyDrawn(callback);

private void notifyDrawn(final IKeyguardDrawnCallback callback) {
        Trace.beginSection("KeyguardViewMediator#notifyDrawn");
        try {
            callback.onDrawn();
        } catch (RemoteException e) {
            Slog.w(TAG, "Exception calling onDrawn():", e);
        }
        Trace.endSection();
    }

7、这个callback.onDrow()回调到KeyguardServiceDelegate中

 private final class KeyguardShowDelegate extends IKeyguardDrawnCallback.Stub {
        private DrawnListener mDrawnListener;

        KeyguardShowDelegate(DrawnListener drawnListener) {
            mDrawnListener = drawnListener;
        }

        @Override
        public void onDrawn() throws RemoteException {
            if (DEBUG) Log.v(TAG, "**** SHOWN CALLED ****");
            if (mDrawnListener != null) {
                mDrawnListener.onDrawn();
            }
        }
    };

8、此处执行mDrawnListener.onDrawn();这里实际上是调用到PWM中

final DrawnListener mKeyguardDrawnCallback = new DrawnListener() {
        @Override
        public void onDrawn() {
            if (DEBUG_WAKEUP) Slog.d(TAG, "mKeyguardDelegate.ShowListener.onDrawn.");
            mHandler.sendEmptyMessage(MSG_KEYGUARD_DRAWN_COMPLETE);
        }
    };

从而发送锁屏绘制完成的消息。