1.概述
在14.0系统产品rom定制化开发中,对于处理屏幕旋转方向，首先有kernel底层处理，从底层驱动gsensor 中获取数据，从而判断屏幕方向的，
然后事件上报后 最后由WMS就是WindowManagerService 来处理旋转的相关事件,接下来看下强制app横屏显示功能如何实现
2.系统强制app横屏显示功能实现的核心类
framework/base/services/java/com/android/server/wm/DisplayRotation.java
3.系统强制app横屏显示功能实现的核心功能分析和处理
在系统中wms主要是处理屏幕相关的核心类，WMS中在处理屏幕自动旋转，主要是调用
DisplayRotation的freezeRotation方法锁定用户指定的屏幕方向，调用thawRotation方法，解锁用户固定屏幕，
恢复屏幕自动旋转。最后调用updateRotationUnchecked，发送新的Configuration变化，
以及如果布局发生变化，也会重新计算布局。
通过上述源码分析，在系统中关于处理屏幕方法的系统中就是DisplayRotation.java 里负责处理的，这里根据系统当前的旋转方向
具体需要看源码然后分析具体的旋转功能
int rotationForOrientation(@ScreenOrientation int orientation,
@Surface.Rotation int lastRotation) {
if (isFixedToUserRotation()) {
return mUserRotation;
}
int sensorRotation = mOrientationListener != null
? mOrientationListener.getProposedRotation() // may be -1
: -1;
if (sensorRotation < 0) {
sensorRotation = lastRotation;
}
final int lidState = mDisplayPolicy.getLidState();
final int dockMode = mDisplayPolicy.getDockMode();
final boolean hdmiPlugged = mDisplayPolicy.isHdmiPlugged();
final boolean carDockEnablesAccelerometer =
mDisplayPolicy.isCarDockEnablesAccelerometer();
final boolean deskDockEnablesAccelerometer =
mDisplayPolicy.isDeskDockEnablesAccelerometer();
final int preferredRotation;
if (!isDefaultDisplay) {
preferredRotation = mUserRotation;
} else if (lidState == LID_OPEN && mLidOpenRotation >= 0) {
preferredRotation = mLidOpenRotation;
} else if (dockMode == Intent.EXTRA_DOCK_STATE_CAR
&& (carDockEnablesAccelerometer || mCarDockRotation >= 0)) {
preferredRotation = carDockEnablesAccelerometer ? sensorRotation : mCarDockRotation;
} else if ((dockMode == Intent.EXTRA_DOCK_STATE_DESK
|| dockMode == Intent.EXTRA_DOCK_STATE_LE_DESK
|| dockMode == Intent.EXTRA_DOCK_STATE_HE_DESK)
&& (deskDockEnablesAccelerometer || mDeskDockRotation >= 0)) {
preferredRotation = deskDockEnablesAccelerometer ? sensorRotation : mDeskDockRotation;
} else if (hdmiPlugged && mDemoHdmiRotationLock) {
preferredRotation = mDemoHdmiRotation;
} else if (hdmiPlugged && dockMode == Intent.EXTRA_DOCK_STATE_UNDOCKED
&& mUndockedHdmiRotation >= 0) {
preferredRotation = mUndockedHdmiRotation;
} else if (mDemoRotationLock) {
preferredRotation = mDemoRotation;
} else if (mDisplayPolicy.isPersistentVrModeEnabled()) {
preferredRotation = mPortraitRotation;
} else if (orientation == ActivityInfo.SCREEN_ORIENTATION_LOCKED) {
preferredRotation = lastRotation;
} else if (!mSupportAutoRotation) {
preferredRotation = -1;
} else if ((mUserRotationMode == WindowManagerPolicy.USER_ROTATION_FREE
&& (orientation == ActivityInfo.SCREEN_ORIENTATION_USER
|| orientation == ActivityInfo.SCREEN_ORIENTATION_UNSPECIFIED
|| orientation == ActivityInfo.SCREEN_ORIENTATION_USER_LANDSCAPE
|| orientation == ActivityInfo.SCREEN_ORIENTATION_USER_PORTRAIT
|| orientation == ActivityInfo.SCREEN_ORIENTATION_FULL_USER))
|| orientation == ActivityInfo.SCREEN_ORIENTATION_SENSOR
|| orientation == ActivityInfo.SCREEN_ORIENTATION_FULL_SENSOR
|| orientation == ActivityInfo.SCREEN_ORIENTATION_SENSOR_LANDSCAPE
|| orientation == ActivityInfo.SCREEN_ORIENTATION_SENSOR_PORTRAIT) {
if (mAllowAllRotations == ALLOW_ALL_ROTATIONS_UNDEFINED) {
mAllowAllRotations = mContext.getResources().getBoolean(
R.bool.config_allowAllRotations)
? ALLOW_ALL_ROTATIONS_ENABLED
: ALLOW_ALL_ROTATIONS_DISABLED;
}
if (sensorRotation != Surface.ROTATION_180
|| mAllowAllRotations == ALLOW_ALL_ROTATIONS_ENABLED
|| orientation == ActivityInfo.SCREEN_ORIENTATION_FULL_SENSOR
|| orientation == ActivityInfo.SCREEN_ORIENTATION_FULL_USER) {
preferredRotation = sensorRotation;
} else {
preferredRotation = lastRotation;
}
} else if (mUserRotationMode == WindowManagerPolicy.USER_ROTATION_LOCKED
&& orientation != ActivityInfo.SCREEN_ORIENTATION_NOSENSOR
&& orientation != ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE
&& orientation != ActivityInfo.SCREEN_ORIENTATION_PORTRAIT
&& orientation != ActivityInfo.SCREEN_ORIENTATION_REVERSE_LANDSCAPE
&& orientation != ActivityInfo.SCREEN_ORIENTATION_REVERSE_PORTRAIT) {
preferredRotation = mUserRotation;
} else {
// No overriding preference.
// We will do exactly what the application asked us to do.
preferredRotation = -1;
}
switch (orientation) {
case ActivityInfo.SCREEN_ORIENTATION_PORTRAIT:
// Return portrait unless overridden.
if (isAnyPortrait(preferredRotation)) {
return preferredRotation;
}
return mPortraitRotation;
case ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE:
// Return landscape unless overridden.
if (isLandscapeOrSeascape(preferredRotation)) {
return preferredRotation;
}
return mLandscapeRotation;
case ActivityInfo.SCREEN_ORIENTATION_REVERSE_PORTRAIT:
// Return reverse portrait unless overridden.
if (isAnyPortrait(preferredRotation)) {
return preferredRotation;
}
return mUpsideDownRotation;
case ActivityInfo.SCREEN_ORIENTATION_REVERSE_LANDSCAPE:
// Return seascape unless overridden.
if (isLandscapeOrSeascape(preferredRotation)) {
return preferredRotation;
}
return mSeascapeRotation;
case ActivityInfo.SCREEN_ORIENTATION_SENSOR_LANDSCAPE:
case ActivityInfo.SCREEN_ORIENTATION_USER_LANDSCAPE:
// Return either landscape rotation.
if (isLandscapeOrSeascape(preferredRotation)) {
return preferredRotation;
}
if (isLandscapeOrSeascape(lastRotation)) {
return lastRotation;
}
return mLandscapeRotation;
case ActivityInfo.SCREEN_ORIENTATION_SENSOR_PORTRAIT:
case ActivityInfo.SCREEN_ORIENTATION_USER_PORTRAIT:
// Return either portrait rotation.
if (isAnyPortrait(preferredRotation)) {
return preferredRotation;
}
if (isAnyPortrait(lastRotation)) {
return lastRotation;
}
return mPortraitRotation;
default:
if (preferredRotation >= 0) {
return preferredRotation;
}
return Surface.ROTATION_0;
}
}
在上述的DisplayRotation.java的相关源码中分析得知，系统在开机过程中，首选在wms中先调用rotationForOrientation函数来获取rotation，来获取当前屏幕的旋转方向，获取当前的屏幕方向后，在根据当前屏幕方向来进行具体的系统方向旋转，最终会调用到
rotationForOrientation(int orientation, int lastRotation) 来获取屏幕的方向值，在具体负责处理app具体的方向旋转当app进入
到activity后由rotationForOrientation()来判断屏幕需要显示的方向，最后处理屏幕的具体旋转方向
具体是在
switch (orientation) {
case ActivityInfo.SCREEN_ORIENTATION_PORTRAIT:
// Return portrait unless overridden.
if (isAnyPortrait(preferredRotation)) {
return preferredRotation;
}
- return mPortraitRotation;
+ return Surface.ROTATION_90;
case ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE:
// Return landscape unless overridden.
if (isLandscapeOrSeascape(preferredRotation)) {
return preferredRotation;
}
return mLandscapeRotation;
case ActivityInfo.SCREEN_ORIENTATION_REVERSE_PORTRAIT:
// Return reverse portrait unless overridden.
if (isAnyPortrait(preferredRotation)) {
return preferredRotation;
}
return mUpsideDownRotation;
case ActivityInfo.SCREEN_ORIENTATION_REVERSE_LANDSCAPE:
// Return seascape unless overridden.
if (isLandscapeOrSeascape(preferredRotation)) {
return preferredRotation;
}
return mSeascapeRotation;
在上述的DisplayRotation.java的相关源码中分析得知，系统判定屏幕旋转方向具体是在rotationForOrientation(int orientation, int lastRotation) 中
当处理屏幕旋转方向时，根据当前屏幕旋转的方向，需要处理是根据
case ActivityInfo.SCREEN_ORIENTATION_PORTRAIT的时候，判断当前需要旋转到什么方向，
这时候系统在进入app的时候当设置屏幕方向的时候，如果需要横屏显示这时候就需要设置方向旋转90度，所以在上面判断如果当前是竖屏，在这里设置旋转90的屏幕方向就可以了从而实现功能