Android屏幕旋转流程（2）

（1）疑问

（1）settings put system user_rotation 1是什么意思？

答：设置用户期望的屏幕转向，0代表：Surface.ROTATION_0竖屏；1代表：Surface.ROTATION_90横屏；

（2）设置user_rotation和GSensor哪个优先级更高，比如user_rotation = 0期待竖屏，但是打开屏幕旋转且处于横屏时，应该是横屏还是竖屏？

答：此时GSensor优先级更高，横屏显示，具体原因看第三个问题。

（3）SystemUI中的“自动旋转”按钮影响的是哪个数据和系统的值？

答：会影响Settings.System.ACCELEROMETER_ROTATION和DisplayRotation.userRotationMode的值。

// When not otherwise specified by the activity's screenOrientation, rotation should be determined by the system (that is, using sensors).
public final int USER_ROTATION_FREE = 0;//When not otherwise specified by the activity's screenOrientation, rotation is set by the user.
public final int USER_ROTATION_LOCKED = 1;USER_ROTATION_FREE ：如果应用不指定屏幕方向，sensor传感器决定
USER_ROTATION_LOCKED：如果应用不指定屏幕方向，user决定方向，即user_rotation数据库值

打开自动旋转时候设置的是Settings.System.ACCELEROMETER_ROTATION的值，并且为1，否则设置成0，这个值会直接影响DisplayRotation.userRotationMode的值。

final int userRotationMode = Settings.System.getIntForUser(resolver,Settings.System.ACCELEROMETER_ROTATION, 0, UserHandle.USER_CURRENT) !=0? WindowManagerPolicy.USER_ROTATION_FREE: WindowManagerPolicy.USER_ROTATION_LOCKED;

也就说如果打开了自动旋转，userRotationMode = USER_ROTATION_FREE，代表通过sensor决定；
否则设置成USER_ROTATION_LOCKED，由user_rotation决定。

（2）屏幕旋转流程

在Framework中，屏幕旋转功能主要是由WMS模块中的DisplayRotation对象来完成，在启动WindowManagerService过程中，创建DisplayContent对象时，会创建一个对应的DisplayRotation负责屏幕旋转逻辑，一个DisiplayContent对象对应一个DisplayRotation对象，或者说DisplayContent对象中持有一个DisplayRotation对象。

在DisplayRotation中，将获取Sensor数据并转换成具体方向旋转角度值的逻辑交给了OrientationListener对象来负责。

总结如下：DisplayContent负责控制，DisplayRotation负责执行，OrientationListener负责获取数据。

（A）DisplayRotation的初始化

//frameworks/base/services/core/java/com/android/server/wm/DisplayRotation.javaDisplayRotation(WindowManagerService service, DisplayContent displayContent,DisplayPolicy displayPolicy, DisplayWindowSettings displayWindowSettings,Context context, Object lock) {// 是否支持自动旋转mSupportAutoRotation =mContext.getResources().getBoolean(R.bool.config_supportAutoRotation);// lid open 时指定的旋转角度mLidOpenRotation = readRotation(R.integer.config_lidOpenRotation);// 放在car dock时指定的旋转角度mCarDockRotation = readRotation(R.integer.config_carDockRotation);// 放在desk dock时指定的旋转角度mDeskDockRotation = readRotation(R.integer.config_deskDockRotation);// Hdmi连接时指定的旋转角度mUndockedHdmiRotation = readRotation(R.integer.config_undockedHdmiRotation);if (isDefaultDisplay) {final Handler uiHandler = UiThread.getHandler();// 创建OrientationListener对象mOrientationListener = new OrientationListener(mContext, uiHandler);// 初始化mOrientationListener.setCurrentRotation(mRotation);// 监听SettingsProvider中的变化mSettingsObserver = new SettingsObserver(uiHandler);mSettingsObserver.observe();}}

屏幕旋转离不开Sensor的监听，具体是由OrientationListener来负责，它会获取Sensor对象、监听Sensor数据、将Sensor的数据转换成旋转角度，并通知WindowManagerService更新方向。

（B）OrientationListener监听Gsensor数据

//frameworks/base/services/core/java/com/android/server/wm/DisplayRotation.java
private class OrientationListener extends WindowOrientationListener implements Runnable {transient boolean mEnabled;OrientationListener(Context context, Handler handler,@Surface.Rotation int defaultRotation) {super(context, handler, defaultRotation);}@Overridepublic void onProposedRotationChanged(@Surface.Rotation int rotation) {ProtoLog.v(WM_DEBUG_ORIENTATION, "onProposedRotationChanged, rotation=%d", rotation);// Send interaction power boost to improve redraw performance.mService.mPowerManagerInternal.setPowerBoost(Boost.INTERACTION, 0);dispatchProposedRotation(rotation);if (isRotationChoiceAllowed(rotation)) {mRotationChoiceShownToUserForConfirmation = rotation;final boolean isValid = isValidRotationChoice(rotation);sendProposedRotationChangeToStatusBarInternal(rotation, isValid);} else {mRotationChoiceShownToUserForConfirmation = ROTATION_UNDEFINED;mService.updateRotation(false /* alwaysSendConfiguration */,false /* forceRelayout */);}}@Overridepublic void enable() {mEnabled = true;getHandler().post(this);ProtoLog.v(WM_DEBUG_ORIENTATION, "Enabling listeners");}@Overridepublic void disable() {mEnabled = false;getHandler().post(this);ProtoLog.v(WM_DEBUG_ORIENTATION, "Disabling listeners");}@Overridepublic void run() {if (mEnabled) {super.enable();} else {super.disable();}}}

我们看一下它的父类WindowOrientationListener相关。

//frameworks/base/services/core/java/com/android/server/wm/WindowOrientationListener.java
public abstract class WindowOrientationListener {public WindowOrientationListener(Context context, Handler handler,@Surface.Rotation int defaultRotation) {this(context, handler, defaultRotation, SensorManager.SENSOR_DELAY_UI);}private WindowOrientationListener(Context context, Handler handler,@Surface.Rotation int defaultRotation, int rate) {mContext = context;mHandler = handler;mDefaultRotation = defaultRotation;mSensorManager = (SensorManager) context.getSystemService(Context.SENSOR_SERVICE);mRate = rate;List<Sensor> l = mSensorManager.getSensorList(Sensor.TYPE_DEVICE_ORIENTATION);Sensor wakeUpDeviceOrientationSensor = null;Sensor nonWakeUpDeviceOrientationSensor = null;for (Sensor s : l) {if (s.isWakeUpSensor()) {wakeUpDeviceOrientationSensor = s;} else {nonWakeUpDeviceOrientationSensor = s;}}if (wakeUpDeviceOrientationSensor != null) {mSensor = wakeUpDeviceOrientationSensor;} else {mSensor = nonWakeUpDeviceOrientationSensor;}if (mSensor != null) {//优先使用此种Sensor监听mOrientationJudge = new OrientationSensorJudge();}if (mOrientationJudge == null) {mSensor = mSensorManager.getDefaultSensor(USE_GRAVITY_SENSOR? Sensor.TYPE_GRAVITY : Sensor.TYPE_ACCELEROMETER);if (mSensor != null) {// Create listener only if sensors do exist//还有另外一种选择mOrientationJudge = new AccelSensorJudge(context);}}}abstract boolean isRotationResolverEnabled();public abstract void onProposedRotationChanged(int rotation);
}

OrientationSensorJudge和AccelSensorJudge都是继承自OrientationJudge，而OrientationJudge类作为SensorEventListener的实现类来接收Sensor事件，根据不同的Sensor会有不同的OrientationJudge对象与之匹配，之所以这样做是因为不同的Sensor上报的原始数据不同，因此需要做不同的转换才能获得最终的旋转角度值。

//frameworks/base/services/core/java/com/android/server/wm/WindowOrientationListener.java
abstract class OrientationJudge implements SensorEventListener {//...@Overridepublic abstract void onAccuracyChanged(Sensor sensor, int accuracy);@Overridepublic abstract void onSensorChanged(SensorEvent event);}

final class OrientationSensorJudge extends OrientationJudge {public void onSensorChanged(SensorEvent event) {int reportedRotation = (int) event.values[0];if (reportedRotation < 0 || reportedRotation > 3) {return;}//...finalizeRotation(reportedRotation);}@Overridepublic void onAccuracyChanged(Sensor sensor, int accuracy) { }
}private void finalizeRotation(int reportedRotation) {int newRotation;synchronized (mLock) {mDesiredRotation = reportedRotation;newRotation = evaluateRotationChangeLocked();}if (newRotation >= 0) {mLastRotationResolution = newRotation;mLastRotationResolutionTimeStamp = SystemClock.uptimeMillis();//最终回调子类实现的onProposedRotationChanged函数onProposedRotationChanged(newRotation);}}

最终调用到OrientationListener的onProposedRotationChanged函数。

//frameworks/base/services/core/java/com/android/server/wm/WindowOrientationListener.java
final class AccelSensorJudge extends OrientationJudge {public void onSensorChanged(SensorEvent event) {float x = event.values[ACCELEROMETER_DATA_X];float y = event.values[ACCELEROMETER_DATA_Y];float z = event.values[ACCELEROMETER_DATA_Z];	  final long now = event.timestamp;final long then = mLastFilteredTimestampNanos;final float timeDeltaMS = (now - then) * 0.000001f;//各种计算函数// Determine new proposed rotation.oldProposedRotation = mProposedRotation;if (mPredictedRotation < 0 || isPredictedRotationAcceptableLocked(now)) {mProposedRotation = mPredictedRotation;}proposedRotation = mProposedRotation;// Tell the listener.if (proposedRotation != oldProposedRotation && proposedRotation >= 0) {//最终回调子类实现的onProposedRotationChanged函数onProposedRotationChanged(proposedRotation);}}@Overridepublic void onAccuracyChanged(Sensor sensor, int accuracy) {}//判断当前的方向改变是否需要更新到系统private boolean isPredictedRotationAcceptableLocked(long now) {// The predicted rotation must have settled long enough.//当前角度需要保持40ms以上if (now < mPredictedRotationTimestampNanos + PROPOSAL_SETTLE_TIME_NANOS) {return false;}// The last flat state (time since picked up) must have been sufficiently long ago.//从手机平放着拿起需要500ms才会转屏if (now < mFlatTimestampNanos + PROPOSAL_MIN_TIME_SINCE_FLAT_ENDED_NANOS) {return false;}// The last swing state (time since last movement to put down) must have been sufficiently long ago.//晃动后300ms内都不能转屏if (now < mSwingTimestampNanos + PROPOSAL_MIN_TIME_SINCE_SWING_ENDED_NANOS) {return false;}// The last acceleration state must have been sufficiently long ago.//加速转动的时候500ms都不能转屏if (now < mAccelerationTimestampNanos+ PROPOSAL_MIN_TIME_SINCE_ACCELERATION_ENDED_NANOS) {return false;}// The last touch must have ended sufficiently long ago.//手没有触摸屏幕500ms才能转屏if (mTouched || now < mTouchEndedTimestampNanos+ PROPOSAL_MIN_TIME_SINCE_TOUCH_END_NANOS) {return false;}// Looks good!return true;}
}

可以看出以上二种实现，最终都会调用子类的onProposedRotationChanged函数来更新屏幕方向。

（C）监听SettingsProvider字段

另外在涉及到方向旋转功能上，DisplayRotation中还监听了以下四个SettingsProvider中的字段：

//frameworks/base/services/core/java/com/android/server/wm/DisplayRotation.javaprivate class SettingsObserver extends ContentObserver {SettingsObserver(Handler handler) {super(handler);}void observe() {final ContentResolver resolver = mContext.getContentResolver();resolver.registerContentObserver(Settings.Secure.getUriFor(Settings.Secure.SHOW_ROTATION_SUGGESTIONS), false, this,UserHandle.USER_ALL);resolver.registerContentObserver(Settings.System.getUriFor(Settings.System.ACCELEROMETER_ROTATION), false, this,UserHandle.USER_ALL);resolver.registerContentObserver(Settings.System.getUriFor(Settings.System.USER_ROTATION), false, this,UserHandle.USER_ALL);resolver.registerContentObserver(Settings.Secure.getUriFor(Settings.Secure.CAMERA_AUTOROTATE), false, this,UserHandle.USER_ALL);updateSettings();}@Overridepublic void onChange(boolean selfChange) {if (updateSettings()) {mService.updateRotation(true /* alwaysSendConfiguration */,false /* forceRelayout */);}}}

• Settings.System.ACCELEROMETER_ROTATION：该字段表示屏幕旋转模式，是否使用加速度传感器控制屏幕的方向旋转，开启时表示自由模式，关闭表示锁定模式；
• Settings.System.USER_ROTATION：用户设置的屏幕旋转方向值，当没有使用加速度传感器，且顶层Activity没有指定旋转方向时作为默认值使用；

//frameworks/base/services/core/java/com/android/server/wm/DisplayRotation.java
private boolean updateSettings() {final ContentResolver resolver = mContext.getContentResolver();// 是否更新旋转方向值boolean shouldUpdateRotation = false;synchronized (mLock) {// 是否更新旋转方向监听boolean shouldUpdateOrientationListener = false;// Configure rotation suggestions.final int showRotationSuggestions =ActivityManager.isLowRamDeviceStatic()? Settings.Secure.SHOW_ROTATION_SUGGESTIONS_DISABLED: Settings.Secure.getIntForUser(resolver,Settings.Secure.SHOW_ROTATION_SUGGESTIONS,Settings.Secure.SHOW_ROTATION_SUGGESTIONS_DEFAULT,UserHandle.USER_CURRENT);if (mShowRotationSuggestions != showRotationSuggestions) {mShowRotationSuggestions = showRotationSuggestions;shouldUpdateOrientationListener = true;}// Configure rotation lock.final int userRotation = Settings.System.getIntForUser(resolver,Settings.System.USER_ROTATION, Surface.ROTATION_0,UserHandle.USER_CURRENT);if (mUserRotation != userRotation) {mUserRotation = userRotation;shouldUpdateRotation = true;}final int userRotationMode = Settings.System.getIntForUser(resolver,Settings.System.ACCELEROMETER_ROTATION, 0, UserHandle.USER_CURRENT) != 0? WindowManagerPolicy.USER_ROTATION_FREE: WindowManagerPolicy.USER_ROTATION_LOCKED;if (mUserRotationMode != userRotationMode) {mUserRotationMode = userRotationMode;shouldUpdateOrientationListener = true;shouldUpdateRotation = true;}// 更新方向旋转监听状态if (shouldUpdateOrientationListener) {updateOrientationListenerLw(); // Enable or disable the orientation listener.}final int cameraRotationMode = Settings.Secure.getIntForUser(resolver,Settings.Secure.CAMERA_AUTOROTATE, 0,UserHandle.USER_CURRENT);if (mCameraRotationMode != cameraRotationMode) {mCameraRotationMode = cameraRotationMode;shouldUpdateRotation = true;}}return shouldUpdateRotation;}

• shouldUpdateRotation = true表示需要更新旋转角度；
• shouldUpdateOrientationListener = true表示要更新旋转方向的监听状态；
• mUserRotationMode表示当前的方向旋转模式；

（D）方向旋转Sensor监听的注册与解除

旋转角度监听状态的更新在DisplayRotation.updateOrientationListenerLw()方法中，这里会进行旋转角度相关Sensor的注册和解除流程。

查看代码发现，在亮灭屏流程中，当keyguard绘制状态、window状态发生变化后，也都会通过DisplayRotation.updateOrientationListener()方法更新方向旋转Sensor的监听状态。

public void updateOrientationListener() {synchronized (mLock) {updateOrientationListenerLw();}}

下面就来看一下，系统在什么场景下需要监听相关Sensor来进行方向旋转，什么情况下不需要监听。

private void updateOrientationListenerLw() {if (mOrientationListener == null || !mOrientationListener.canDetectOrientation()) {// If sensor is turned off or nonexistent for some reason.return;}// 是否正在进行点亮屏幕的操作final boolean screenOnEarly = mDisplayPolicy.isScreenOnEarly();// 是否唤醒系统final boolean awake = mDisplayPolicy.isAwake();// keyguard绘制是否完成final boolean keyguardDrawComplete = mDisplayPolicy.isKeyguardDrawComplete();// 窗口绘制是否完成final boolean windowManagerDrawComplete = mDisplayPolicy.isWindowManagerDrawComplete();boolean disable = true;// 只有在屏幕唤醒状态，且keyguard和窗口全部绘制完成的情况下，才会有资格注册sensor监听if (screenOnEarly&& (awake || mOrientationListener.shouldStayEnabledWhileDreaming())&& ((keyguardDrawComplete && windowManagerDrawComplete))) {if (needSensorRunning()) {disable = false;// Enable listener if not already enabled.if (!mOrientationListener.mEnabled) {mOrientationListener.enable();}}}// Check if sensors need to be disabled.if (disable) {mOrientationListener.disable();}}

对于旋转角度Sensor的注册/解除，会有多个因素决定，如是否亮屏、Keyguard绘制是否完成等。其规则是，在屏幕唤醒状态，且keyguard和窗口全部绘制完成的情况下，如果needSensorRunning()方法返回true，就会注册Sensor去监听方向旋转。