前言
在Android系统中，很多应用都需要根据具体情况来控制状态栏和导航栏的显示和隐藏，又或者将状态栏透明，实现诸如沉浸式、全面屏灯效果，而要实现这些效果，都离不开SystemUIVisibility属性。由于SystemUIVisibilityy属性主要用来控制系统状态栏和导航栏的行为，而状态栏和导航栏都属于SystemUI模块的StatusBar，所以SystemUIVisibility属性的消费者肯定包含StatusBar。另外当状态栏和导航栏发生变化的时候，窗口的布局一般也会跟着发生变化，这就意味着窗口管理者PhoneWindowManager肯定也要消费SystemUIVisibility属性。本篇文章我们就来具体分析一下和这个属性有关的代码。
一、SystemUIVisibility属性常见常见取值
1、为窗口设置SystemUIVisibility属性的方式有两种，一种是直接在窗口的WindowManager.LayoutParams对象的systemUiVisibility属性上进行设置，并通过WindowManager.updateViewLayout()方法使其生效。
frameworks/base/core/java/android/view/WindowManager.java
public interface WindowManager extends ViewManager {public static class LayoutParams extends ViewGroup.LayoutParams implements Parcelable {//隐藏窗口的所有装饰，比如状态栏和导航栏public static final int FLAG_FULLSCREEN = 0x00000400;//控制窗口状态栏、导航栏的显示和隐藏public int systemUiVisibility;}
}
2、另一种是在一个已经显示在窗口上的控件中调用setSystemUiVisibility方法，传入如下属性。
frameworks/base/core/java/android/view/View.java
public class View implements Drawable.Callback, KeyEvent.Callback,AccessibilityEventSource {
//隐藏导航栏
public static final int SYSTEM_UI_FLAG_HIDE_NAVIGATION = 0x00000002;
//隐藏状态栏
public static final int SYSTEM_UI_FLAG_FULLSCREEN = 0x00000004;
}
这种方式最终影响的其实是窗口的WindowManager.LayoutParams对象的subtreeSystemUiVisibility属性。
public interface WindowManager extends ViewManager {public static class LayoutParams extends ViewGroup.LayoutParams implements Parcelable {//控制窗口状态栏、导航栏的显示和隐藏public int subtreeSystemUiVisibility;}
}
窗口的状态栏导航栏显示与否，最终其实是受以上两个属性共同影响的。接下来我们具体来分析一下View的setSystemUiVisibility方法是如何生效的。
二、View的setSystemUiVisibility方法调用流程
1、View的setSystemUiVisibility方法如下所示。
public class View implements Drawable.Callback, KeyEvent.Callback,AccessibilityEventSource {int mSystemUiVisibility;protected ViewParent mParent;public void setSystemUiVisibility(int visibility) {if (visibility != mSystemUiVisibility) {mSystemUiVisibility = visibility;//保存SystemUIVisibility属性if (mParent != null && mAttachInfo != null && !mAttachInfo.mRecomputeGlobalAttributes) {mParent.recomputeViewAttributes(this);//通知父控件子控件属性发生了变化}}}
}
setSystemUiVisibility方法首先将属性赋值给mSystemUiVisibility，然后会调用父控件的recomputeViewAttributes方法，通知父控件子控件属性发生了变化。ViewParent是一个接口，在Android中有两个类实现了这个接口，它们分别是ViewGroup和ViewRootImpl。
2、ViewGroup和ViewRootImpl和recomputeViewAttributes方法相关的代码如下所示。
frameworks/base/core/java/android/view/View.java
public abstract class ViewGroup extends View implements ViewParent, ViewManager {@Overridepublic void recomputeViewAttributes(View child) {if (mAttachInfo != null && !mAttachInfo.mRecomputeGlobalAttributes) {ViewParent parent = mParent;if (parent != null) parent.recomputeViewAttributes(this);}}
}
frameworks/base/core/java/android/view/ViewRootImpl.java
public final class ViewRootImpl implements ViewParent,View.AttachInfo.Callbacks, ThreadedRenderer.DrawCallbacks,AttachedSurfaceControl {final View.AttachInfo mAttachInfo;@Overridepublic void recomputeViewAttributes(View child) {checkThread();//检测线程是不是UI线程if (mView == child) {mAttachInfo.mRecomputeGlobalAttributes = true;//标记需要重新计算本地属性if (!mWillDrawSoon) {scheduleTraversals();//进一步调用scheduleTraversals方法。}}}
}
结合Android 9.0系统源码_窗口管理（二）WindowManager对窗口的管理过程，我们知道包括Activity的跟布局DecorView在内的任何View，WindowManager在将它添加到窗口上的过程中，最终都会创建一个ViewRootImpl，并将View设置给ViewRootImpl，这样根View的父类就变成了ViewRootImpl。这就意味着不管任何子View调用recomputeViewAttributes方法，最终所触发的都是ViewRootImpl的recomputeViewAttributes，而ViewRootImpl会进一步调用scheduleTraversals方法。
3、ViewRootImpl和scheduleTraversals方法相关的代码如下所示。
public final class ViewRootImpl implements ViewParent,View.AttachInfo.Callbacks, ThreadedRenderer.DrawCallbacks,AttachedSurfaceControl {final Choreographer mChoreographer;//编舞者final TraversalRunnable mTraversalRunnable = new TraversalRunnable();//回调对象void scheduleTraversals() {if (!mTraversalScheduled) {mTraversalScheduled = true;mTraversalBarrier = mHandler.getLooper().getQueue().postSyncBarrier();//等待系统垂直刷新同步信号，回调TraversalRunnable对象的run方法mChoreographer.postCallback(Choreographer.CALLBACK_TRAVERSAL, mTraversalRunnable, null);notifyRendererOfFramePending();pokeDrawLockIfNeeded();}}final class TraversalRunnable implements Runnable {@Overridepublic void run() {doTraversal();//继续执行doTraversal}}void doTraversal() {if (mTraversalScheduled) {mTraversalScheduled = false;mHandler.getLooper().getQueue().removeSyncBarrier(mTraversalBarrier);if (mProfile) {Debug.startMethodTracing("ViewAncestor");}//执行performTraversalsperformTraversals();if (mProfile) {Debug.stopMethodTracing();mProfile = false;}}}
}
scheduleTraversals方法会为编舞者对象设置回调，最终会等待系统垂直刷新同步信号，回调TraversalRunnable对象的run方法，该方法会调用doTraversal方法，然后进一步调用performTraversals方法。
4、ViewRootImpl的performTraversals方法代码逻辑非常多，这里只列出了我们需要关注的代码。
public final class ViewRootImpl implements ViewParent,View.AttachInfo.Callbacks, ThreadedRenderer.DrawCallbacks,AttachedSurfaceControl {final IWindowSession mWindowSession;//和WMS通信的Binder对象，具体为Session对象public final WindowManager.LayoutParams mWindowAttributes = new WindowManager.LayoutParams();//窗口属性final View.AttachInfo mAttachInfo;//控件信息private void performTraversals() {final View host = mView;if (host == null || !mAdded) {return;}if (mWaitForBlastSyncComplete) {mRequestedTraverseWhilePaused = true;return;}mIsInTraversal = true;mWillDrawSoon = true;boolean windowSizeMayChange = false;WindowManager.LayoutParams lp = mWindowAttributes;//将当前窗口的最新属性赋值给lpint desiredWindowWidth;int desiredWindowHeight;final int viewVisibility = getHostVisibility();final boolean viewVisibilityChanged = !mFirst&& (mViewVisibility != viewVisibility || mNewSurfaceNeeded|| mAppVisibilityChanged);mAppVisibilityChanged = false;final boolean viewUserVisibilityChanged = !mFirst &&((mViewVisibility == View.VISIBLE) != (viewVisibility == View.VISIBLE));WindowManager.LayoutParams params = null;...代码省略...//收集mView的属性，判断是否需要更新paramsif (collectViewAttributes()) {params = lp;}...代码省略...//此方法最终会触发WindowManagerService的relayoutWindow方法relayoutWindow(params, viewVisibility, insetsPending);...代码省略... //测量performMeasure(childWidthMeasureSpec, childHeightMeasureSpec);...代码省略... //布局performLayout(lp, mWidth, mHeight);...代码省略... //绘制performDraw();...代码省略... }private int relayoutWindow(WindowManager.LayoutParams params, int viewVisibility,boolean insetsPending) throws RemoteException {...代码省略... //调用IWindowSession的relayout方法，该方法最终会触发WindowManagerService的relayoutWindow方法int relayoutResult = mWindowSession.relayout(mWindow, mSeq, params,(int) (mView.getMeasuredWidth() * appScale + 0.5f),(int) (mView.getMeasuredHeight() * appScale + 0.5f), viewVisibility,insetsPending ? WindowManagerGlobal.RELAYOUT_INSETS_PENDING : 0, frameNumber,mWinFrame, mPendingOverscanInsets, mPendingContentInsets, mPendingVisibleInsets,mPendingStableInsets, mPendingOutsets, mPendingBackDropFrame, mPendingDisplayCutout,mPendingMergedConfiguration, mSurface);}}
performTraversals首先调用collectViewAttributes方法收集所有子View的属性，然后调用relayoutWindow方法，该方法最终会触发WindowManagerService的relayoutWindow方法，然后回继续调用触发View测量的performMeasure方法，触发View布局的performLayout方法和触发View绘制的performDraw方法。
三、获取最新的SystemUIVisibility属性
1、ViewRootImpl的collectViewAttributes方法是一个很关键的方法，此方法会重新计算最新的SystemUIVisibility属性。
public final class ViewRootImpl implements ViewParent,View.AttachInfo.Callbacks, ThreadedRenderer.DrawCallbacks,AttachedSurfaceControl {public final WindowManager.LayoutParams mWindowAttributes = new WindowManager.LayoutParams();//窗口属性final View.AttachInfo mAttachInfo;//控件信息private boolean collectViewAttributes() {//判断是否需要重新计算本地属性if (mAttachInfo.mRecomputeGlobalAttributes) {//Log.i(mTag, "Computing view hierarchy attributes!");mAttachInfo.mRecomputeGlobalAttributes = false;boolean oldScreenOn = mAttachInfo.mKeepScreenOn;mAttachInfo.mKeepScreenOn = false;//清空已经存在的SystemUiVisibility属性mAttachInfo.mSystemUiVisibility = 0;mAttachInfo.mHasSystemUiListeners = false;//重新获取窗口视图mView最新的的SystemUI属性，赋值给mAttachInfomView.dispatchCollectViewAttributes(mAttachInfo, 0);...代码暂时省略...}return false;}}
collectViewAttributes首先会清空当前窗口视图mView已经存在的SystemUiVisibility属性，然后调用View的dispatchCollectViewAttributes方法重新获取最新的的SystemUiVisibility属性。
2、View的dispatchCollectViewAttributes方法如下所示。
public class View implements Drawable.Callback, KeyEvent.Callback,AccessibilityEventSource {int mSystemUiVisibility;void dispatchCollectViewAttributes(AttachInfo attachInfo, int visibility) {performCollectViewAttributes(attachInfo, visibility);}void performCollectViewAttributes(AttachInfo attachInfo, int visibility) {if ((visibility & VISIBILITY_MASK) == VISIBLE) {if ((mViewFlags & KEEP_SCREEN_ON) == KEEP_SCREEN_ON) {attachInfo.mKeepScreenOn = true;}//将最新的systemuivisiblity赋予AttachInfo的mSystemUiVisibility 属性attachInfo.mSystemUiVisibility |= mSystemUiVisibility;//设置最新的SystemUiVisibility监听对象，如果不为空，则将AttachInfo的mHasSystemUiListeners属性设置为true。ListenerInfo li = mListenerInfo;if (li != null && li.mOnSystemUiVisibilityChangeListener != null) {attachInfo.mHasSystemUiListeners = true;}}}}
3、接着看ViewRootImpl的collectViewAttributes方法。
public final class ViewRootImpl implements ViewParent,View.AttachInfo.Callbacks, ThreadedRenderer.DrawCallbacks,AttachedSurfaceControl {public final WindowManager.LayoutParams mWindowAttributes = new WindowManager.LayoutParams();//窗口属性final View.AttachInfo mAttachInfo;//控件信息private boolean collectViewAttributes() {//判断是否需要重新计算本地属性if (mAttachInfo.mRecomputeGlobalAttributes) {...代码省略...//移除被禁用的SystemUiVisibility属性mAttachInfo.mSystemUiVisibility &= ~mAttachInfo.mDisabledSystemUiVisibility;//让params引用指向mWindowAttributes对象WindowManager.LayoutParams params = mWindowAttributes;mAttachInfo.mSystemUiVisibility |= getImpliedSystemUiVisibility(params);if (mAttachInfo.mKeepScreenOn != oldScreenOn|| mAttachInfo.mSystemUiVisibility != params.subtreeSystemUiVisibility|| mAttachInfo.mHasSystemUiListeners != params.hasSystemUiListeners) {applyKeepScreenOnFlag(params);//将重新获取的窗口视图mView的SystemUiVisibility保存到窗口的LayoutParams属性中params.subtreeSystemUiVisibility = mAttachInfo.mSystemUiVisibility;params.hasSystemUiListeners = mAttachInfo.mHasSystemUiListeners;//调用View的dispatchWindowSystemUiVisiblityChanged方法mView.dispatchWindowSystemUiVisiblityChanged(mAttachInfo.mSystemUiVisibility);return true;}}return false;}}
在重新获得mView的SystemUiVisibility属性之后，首先会从该属性中移除被禁用的SystemUiVisibility属性，然后让params引用指向mWindowAttributes对象，并将重新获取的保存在mAttachInfo对象中的SystemUiVisibility属性保存到当前窗口的LayoutParams属性中，最后会调用当前View的dispatchWindowSystemUiVisiblityChanged方法。
4、View的dispatchWindowSystemUiVisiblityChanged方法如下所示。
public class View implements Drawable.Callback, KeyEvent.Callback,AccessibilityEventSource {@Deprecatedpublic void dispatchWindowSystemUiVisiblityChanged(int visible) {onWindowSystemUiVisibilityChanged(visible);//调用onWindowSystemUiVisibilityChanged方法}public void onWindowSystemUiVisibilityChanged(int visible) {//默认为空实现}
}
该方法会进一步调用onWindowSystemUiVisibilityChanged方法，onWindowSystemUiVisibilityChanged方法默认为空实现，但是如果当前mView为DecorView时则不同，DecorView实现了此方法。
四、DecorView更新状态栏和导航栏背景颜色
1、DecorView的onWindowSystemUiVisibilityChanged方法如下所示。
frameworks/base/core/java/com/android/internal/policy/DecorView.java
public class DecorView extends FrameLayout implements RootViewSurfaceTaker, WindowCallbacks {@Overridepublic void onWindowSystemUiVisibilityChanged(int visible) {//调用updateColorViews方法updateColorViews(null /* insets */, true /* animate */);}}
onWindowSystemUiVisibilityChanged方法会调用一个updateColorViews这个关键方法。
2、updateColorViews会调用updateColorViewInt方法更新导航栏和状态栏的背景颜色。
public class DecorView extends FrameLayout implements RootViewSurfaceTaker, WindowCallbacks {WindowInsets updateColorViews(WindowInsets insets, boolean animate) {//获取窗口的SystemUIVisibility属性int sysUiVisibility = attrs.systemUiVisibility | getWindowSystemUiVisibility();//判断窗口类型是否是输入法final boolean isImeWindow = mWindow.getAttributes().type == WindowManager.LayoutParams.TYPE_INPUT_METHOD;//判断窗口类型不是浮动窗口和输入法，则让SystemUIVisibility属性生效if (!mWindow.mIsFloating || isImeWindow) {//获取是否禁止窗口动画的标记boolean disallowAnimate = !isLaidOut();disallowAnimate |= ((mLastWindowFlags ^ attrs.flags)& FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS) != 0;mLastWindowFlags = attrs.flags;if (insets != null) {mLastTopInset = getColorViewTopInset(insets.getStableInsetTop(),insets.getSystemWindowInsetTop());mLastBottomInset = getColorViewBottomInset(insets.getStableInsetBottom(),insets.getSystemWindowInsetBottom());mLastRightInset = getColorViewRightInset(insets.getStableInsetRight(),insets.getSystemWindowInsetRight());mLastLeftInset = getColorViewRightInset(insets.getStableInsetLeft(),insets.getSystemWindowInsetLeft());// Don't animate if the presence of stable insets has changed, because that// indicates that the window was either just added and received them for the// first time, or the window size or position has changed.boolean hasTopStableInset = insets.getStableInsetTop() != 0;disallowAnimate |= (hasTopStableInset != mLastHasTopStableInset);mLastHasTopStableInset = hasTopStableInset;boolean hasBottomStableInset = insets.getStableInsetBottom() != 0;disallowAnimate |= (hasBottomStableInset != mLastHasBottomStableInset);mLastHasBottomStableInset = hasBottomStableInset;boolean hasRightStableInset = insets.getStableInsetRight() != 0;disallowAnimate |= (hasRightStableInset != mLastHasRightStableInset);mLastHasRightStableInset = hasRightStableInset;boolean hasLeftStableInset = insets.getStableInsetLeft() != 0;disallowAnimate |= (hasLeftStableInset != mLastHasLeftStableInset);mLastHasLeftStableInset = hasLeftStableInset;mLastShouldAlwaysConsumeNavBar = insets.shouldAlwaysConsumeNavBar();}boolean navBarToRightEdge = isNavBarToRightEdge(mLastBottomInset, mLastRightInset);boolean navBarToLeftEdge = isNavBarToLeftEdge(mLastBottomInset, mLastLeftInset);int navBarSize = getNavBarSize(mLastBottomInset, mLastRightInset, mLastLeftInset);//更新导航栏颜色，mNavigationColorViewState为导航栏的相关筛选条件updateColorViewInt(mNavigationColorViewState, sysUiVisibility,mWindow.mNavigationBarColor, mWindow.mNavigationBarDividerColor, navBarSize/*导航栏高度*/,navBarToRightEdge || navBarToLeftEdge, navBarToLeftEdge,0 /* sideInset */, animate && !disallowAnimate, false /* force */);boolean statusBarNeedsRightInset = navBarToRightEdge&& mNavigationColorViewState.present;boolean statusBarNeedsLeftInset = navBarToLeftEdge&& mNavigationColorViewState.present;int statusBarSideInset = statusBarNeedsRightInset ? mLastRightInset: statusBarNeedsLeftInset ? mLastLeftInset : 0;//更新状态栏颜色，mStatusColorViewState为状态栏的相关筛选条件updateColorViewInt(mStatusColorViewState, sysUiVisibility,calculateStatusBarColor(), 0, mLastTopInset/*状态栏高度*/,false /* matchVertical */, statusBarNeedsLeftInset, statusBarSideInset,animate && !disallowAnimate,mForceWindowDrawsStatusBarBackground);}...代码省略...}}
关于DecorView更新状态栏、导航栏背景颜色的具体过程，请参考Android 9.0系统源码_SystemUI（八）PhoneWindow更新状态栏和导航栏背景颜色的流程解析。
五、WindowManagerService的relayoutWindow方法
1、重新回到第二节第4步ViewRootImpl的performTraversals方法中。
public final class ViewRootImpl implements ViewParent,View.AttachInfo.Callbacks, ThreadedRenderer.DrawCallbacks,AttachedSurfaceControl {final IWindowSession mWindowSession;//和WMS通信的Binder对象，具体为Session对象public final WindowManager.LayoutParams mWindowAttributes = new WindowManager.LayoutParams();//窗口属性final View.AttachInfo mAttachInfo;//控件信息private void performTraversals() {...代码省略...//收集mView的属性，判断是否需要更新paramsif (collectViewAttributes()) {params = lp;}...代码省略...//此方法最终会触发WindowManagerService的relayoutWindow方法relayoutWindow(params, viewVisibility, insetsPending);...代码省略... //测量performMeasure(childWidthMeasureSpec, childHeightMeasureSpec);...代码省略... //布局performLayout(lp, mWidth, mHeight);...代码省略... //绘制performDraw();...代码省略... }private int relayoutWindow(WindowManager.LayoutParams params, int viewVisibility,boolean insetsPending) throws RemoteException {...代码省略... //调用IWindowSession的relayout方法，该方法最终会触发WindowManagerService的relayoutWindow方法int relayoutResult = mWindowSession.relayout(mWindow, mSeq, params,(int) (mView.getMeasuredWidth() * appScale + 0.5f),(int) (mView.getMeasuredHeight() * appScale + 0.5f), viewVisibility,insetsPending ? WindowManagerGlobal.RELAYOUT_INSETS_PENDING : 0, frameNumber,mWinFrame, mPendingOverscanInsets, mPendingContentInsets, mPendingVisibleInsets,mPendingStableInsets, mPendingOutsets, mPendingBackDropFrame, mPendingDisplayCutout,mPendingMergedConfiguration, mSurface);}}
在调用collectViewAttributes获取最新的systemUIVisibiliy属性之后，会调用relayoutWindow方法，该方法进一步调用IWindowSession的relayout方法，IWindowSession的具体实现类为Session。
2、Session的relayout方法如下所示。
frameworks/base/services/core/java/com/android/server/wm/Session.java
class Session extends IWindowSession.Stub implements IBinder.DeathRecipient {final WindowManagerService mService;@Overridepublic int relayout(IWindow window, WindowManager.LayoutParams attrs,int requestedWidth, int requestedHeight, int viewFlags, int flags, long frameNumber,ClientWindowFrames outFrames, MergedConfiguration mergedConfiguration,SurfaceControl outSurfaceControl, InsetsState outInsetsState,InsetsSourceControl[] outActiveControls, Point outSurfaceSize) {int res = mService.relayoutWindow(this, window, attrs,requestedWidth, requestedHeight, viewFlags, flags, frameNumber,outFrames, mergedConfiguration, outSurfaceControl, outInsetsState,outActiveControls, outSurfaceSize);return res;}
}
relayout方法会进一步调用WindowManagerService的relayoutWindow方法。
3、WindowManagerService的relayoutWindow方法如下所示。
frameworks/base/services/core/java/com/android/server/wm/WindowManagerService.java
public class WindowManagerService extends IWindowManager.Stubimplements Watchdog.Monitor, WindowManagerPolicy.WindowManagerFuncs {public int relayoutWindow(Session session, IWindow client, int seq, LayoutParams attrs/**窗口属性**/,int requestedWidth, int requestedHeight, int viewVisibility/**根View控件是否可见**/, int flags,long frameNumber, Rect outFrame, Rect outOverscanInsets, Rect outContentInsets,Rect outVisibleInsets, Rect outStableInsets, Rect outOutsets, Rect outBackdropFrame,DisplayCutout.ParcelableWrapper outCutout, MergedConfiguration mergedConfiguration,Surface outSurface) {int result = 0;boolean configChanged;//是否有状态栏的使用权限final boolean hasStatusBarPermission =mContext.checkCallingOrSelfPermission(permission.STATUS_BAR)== PackageManager.PERMISSION_GRANTED;//是否有状态栏服务的使用权限final boolean hasStatusBarServicePermission =mContext.checkCallingOrSelfPermission(permission.STATUS_BAR_SERVICE)== PackageManager.PERMISSION_GRANTED;long origId = Binder.clearCallingIdentity();final int displayId;synchronized(mWindowMap) {//获取当前要操作的窗口对象WindowState win = windowForClientLocked(session, client, false);if (win == null) {return 0;}//获取窗口所属的屏幕设备iddisplayId = win.getDisplayId();//窗口动画WindowStateAnimator winAnimator = win.mWinAnimator;if (viewVisibility != View.GONE) {win.setRequestedSize(requestedWidth, requestedHeight);}win.setFrameNumber(frameNumber);int attrChanges = 0;int flagChanges = 0;if (attrs != null) {//如果窗口属性不为空，这里会对窗口的相关属性进行一次预处理mPolicy.adjustWindowParamsLw(win, attrs, hasStatusBarServicePermission);// if they don't have the permission, mask out the status bar bitsif (seq == win.mSeq) {int systemUiVisibility = attrs.systemUiVisibility| attrs.subtreeSystemUiVisibility;if ((systemUiVisibility & DISABLE_MASK) != 0) {if (!hasStatusBarPermission) {systemUiVisibility &= ~DISABLE_MASK;}}win.mSystemUiVisibility = systemUiVisibility;}if (win.mAttrs.type != attrs.type) {throw new IllegalArgumentException("Window type can not be changed after the window is added.");}// Odd choice but less odd than embedding in copyFrom()if ((attrs.privateFlags & WindowManager.LayoutParams.PRIVATE_FLAG_PRESERVE_GEOMETRY)!= 0) {attrs.x = win.mAttrs.x;attrs.y = win.mAttrs.y;attrs.width = win.mAttrs.width;attrs.height = win.mAttrs.height;}//检测窗口标记和样式是否发生了变化flagChanges = win.mAttrs.flags ^= attrs.flags;attrChanges = win.mAttrs.copyFrom(attrs);if ((attrChanges & (WindowManager.LayoutParams.LAYOUT_CHANGED| WindowManager.LayoutParams.SYSTEM_UI_VISIBILITY_CHANGED)) != 0) {win.mLayoutNeeded = true;}if (win.mAppToken != null && ((flagChanges & FLAG_SHOW_WHEN_LOCKED) != 0|| (flagChanges & FLAG_DISMISS_KEYGUARD) != 0)) {win.mAppToken.checkKeyguardFlagsChanged();}if (((attrChanges & LayoutParams.ACCESSIBILITY_TITLE_CHANGED) != 0)&& (mAccessibilityController != null)&& (win.getDisplayId() == DEFAULT_DISPLAY)) {// No move or resize, but the controller checks for title changes as wellmAccessibilityController.onSomeWindowResizedOrMovedLocked();}if ((flagChanges & PRIVATE_FLAG_HIDE_NON_SYSTEM_OVERLAY_WINDOWS) != 0) {updateNonSystemOverlayWindowsVisibilityIfNeeded(win, win.mWinAnimator.getShown());}}...代码省略... if (focusMayChange) {//System.out.println("Focus may change: " + win.mAttrs.getTitle());if (updateFocusedWindowLocked(UPDATE_FOCUS_WILL_PLACE_SURFACES,false /*updateInputWindows*/)) {imMayMove = false;}//System.out.println("Relayout " + win + ": focus=" + mCurrentFocus);}...代码省略... }
}
relayoutWindow方法会调用一个关键方法updateFocusedWindowLocked。
4、WindowManagerService的updateFocusedWindowLocked方法如下所示。
public class WindowManagerService extends IWindowManager.Stubimplements Watchdog.Monitor, WindowManagerPolicy.WindowManagerFuncs {//窗口管理策略的接口类WindowManagerPolicy（WMP），它用来定义一个窗口策略所要遵循的通用规范。final WindowManagerPolicy mPolicy;//根窗口RootWindowContainer mRoot;boolean updateFocusedWindowLocked(int mode, boolean updateInputWindows) {//获取当前最新的焦点窗口WindowState newFocus = mRoot.computeFocusedWindow();if (mCurrentFocus != newFocus) {//如果窗口焦点发生了变化Trace.traceBegin(TRACE_TAG_WINDOW_MANAGER, "wmUpdateFocus");// This check makes sure that we don't already have the focus// change message pending.mH.removeMessages(H.REPORT_FOCUS_CHANGE);mH.sendEmptyMessage(H.REPORT_FOCUS_CHANGE);// TODO(multidisplay): Focused windows on default display only.final DisplayContent displayContent = getDefaultDisplayContentLocked();boolean imWindowChanged = false;if (mInputMethodWindow != null) {//如果输入法窗口不为空final WindowState prevTarget = mInputMethodTarget;final WindowState newTarget =displayContent.computeImeTarget(true /* updateImeTarget*/);imWindowChanged = prevTarget != newTarget;if (mode != UPDATE_FOCUS_WILL_ASSIGN_LAYERS&& mode != UPDATE_FOCUS_WILL_PLACE_SURFACES) {final int prevImeAnimLayer = mInputMethodWindow.mWinAnimator.mAnimLayer;displayContent.assignWindowLayers(false /* setLayoutNeeded */);imWindowChanged |=prevImeAnimLayer != mInputMethodWindow.mWinAnimator.mAnimLayer;}}if (imWindowChanged) {//输入法窗口发生了变化mWindowsChanged = true;displayContent.setLayoutNeeded();newFocus = mRoot.computeFocusedWindow();}if (DEBUG_FOCUS_LIGHT || localLOGV) Slog.v(TAG_WM, "Changing focus from " +mCurrentFocus + " to " + newFocus + " Callers=" + Debug.getCallers(4));final WindowState oldFocus = mCurrentFocus;mCurrentFocus = newFocus;mLosingFocus.remove(newFocus);if (mCurrentFocus != null) {mWinAddedSinceNullFocus.clear();mWinRemovedSinceNullFocus.clear();}//调用WindowManagerPolicy的focusChangedLw方法int focusChanged = mPolicy.focusChangedLw(oldFocus, newFocus);if (imWindowChanged && oldFocus != mInputMethodWindow) {// Focus of the input method window changed. Perform layout if needed.if (mode == UPDATE_FOCUS_PLACING_SURFACES) {displayContent.performLayout(true /*initial*/, updateInputWindows);focusChanged &= ~FINISH_LAYOUT_REDO_LAYOUT;} else if (mode == UPDATE_FOCUS_WILL_PLACE_SURFACES) {// Client will do the layout, but we need to assign layers// for handleNewWindowLocked() below.displayContent.assignWindowLayers(false /* setLayoutNeeded */);}}if ((focusChanged & FINISH_LAYOUT_REDO_LAYOUT) != 0) {// The change in focus caused us to need to do a layout. Okay.displayContent.setLayoutNeeded();if (mode == UPDATE_FOCUS_PLACING_SURFACES) {displayContent.performLayout(true /*initial*/, updateInputWindows);}}if (mode != UPDATE_FOCUS_WILL_ASSIGN_LAYERS) {// If we defer assigning layers, then the caller is responsible for// doing this part.mInputMonitor.setInputFocusLw(mCurrentFocus, updateInputWindows);}displayContent.adjustForImeIfNeeded();// We may need to schedule some toast windows to be removed. The toasts for an app that// does not have input focus are removed within a timeout to prevent apps to redress// other apps' UI.displayContent.scheduleToastWindowsTimeoutIfNeededLocked(oldFocus, newFocus);Trace.traceEnd(TRACE_TAG_WINDOW_MANAGER);return true;}return false;}}
updateFocusedWindowLocked首先是获取最新的焦点窗口，之后还会判断当前窗口焦点是否发生了变化，如果发生了变化，则会调用WindowManagerPolicy的focusChangedLw方法。
五、PhoneWindowManager的updateSystemUiVisibilityLw方法
1、WindowManagerPolicy是一个抽象接口。
frameworks/base/services/core/java/com/android/server/policy/WindowManagerPolicy.java
public interface WindowManagerPolicy extends WindowManagerPolicyConstants {/*** 一个新的窗口持有了焦点*/public int focusChangedLw(WindowState lastFocus, WindowState newFocus);
}
结合Android 9.0系统源码_窗口管理（一）WindowManagerService的启动流程这篇文章我们可以知道，SystemServer在窗口WindowManagerService对象的时候，将PhoneWindowManager对象实例赋值给了mPolicy。
2、来看下PhoneWindowManager是如何实现focusChangedLw方法的。
frameworks/base/services/core/java/com/android/server/policy/PhoneWindowManager.java
public class PhoneWindowManager implements WindowManagerPolicy {@Overridepublic int focusChangedLw(WindowState lastFocus, WindowState newFocus) {mFocusedWindow = newFocus;if ((updateSystemUiVisibilityLw()&SYSTEM_UI_CHANGING_LAYOUT) != 0) {// If the navigation bar has been hidden or shown, we need to do another// layout pass to update that window.return FINISH_LAYOUT_REDO_LAYOUT;}return 0;}//更新窗口的SystemUiVisibility属性参数private int updateSystemUiVisibilityLw() {//获取当前的焦点窗口WindowState winCandidate = mFocusedWindow != null ? mFocusedWindow: mTopFullscreenOpaqueWindowState;//如果不存在焦点窗口则直接返回if (winCandidate == null) {return 0;}if (winCandidate.getAttrs().token == mImmersiveModeConfirmation.getWindowToken()) {winCandidate = isStatusBarKeyguard() ? mStatusBar : mTopFullscreenOpaqueWindowState;if (winCandidate == null) {return 0;}}final WindowState win = winCandidate;if ((win.getAttrs().privateFlags & PRIVATE_FLAG_KEYGUARD) != 0 && mKeyguardOccluded) {return 0;}int tmpVisibility = PolicyControl.getSystemUiVisibility(win, null)& ~mResettingSystemUiFlags& ~mForceClearedSystemUiFlags;if (mForcingShowNavBar && win.getSurfaceLayer() < mForcingShowNavBarLayer) {tmpVisibility &= ~PolicyControl.adjustClearableFlags(win, View.SYSTEM_UI_CLEARABLE_FLAGS);}//获取和SystemUIVisibility相关的各种窗口参数final int fullscreenVisibility = updateLightStatusBarLw(0 /* vis */,mTopFullscreenOpaqueWindowState, mTopFullscreenOpaqueOrDimmingWindowState);final int dockedVisibility = updateLightStatusBarLw(0 /* vis */,mTopDockedOpaqueWindowState, mTopDockedOpaqueOrDimmingWindowState);mWindowManagerFuncs.getStackBounds(WINDOWING_MODE_UNDEFINED, ACTIVITY_TYPE_HOME, mNonDockedStackBounds);mWindowManagerFuncs.getStackBounds(WINDOWING_MODE_SPLIT_SCREEN_PRIMARY, ACTIVITY_TYPE_STANDARD, mDockedStackBounds);final int visibility = updateSystemBarsLw(win, mLastSystemUiFlags, tmpVisibility);final int diff = visibility ^ mLastSystemUiFlags;final int fullscreenDiff = fullscreenVisibility ^ mLastFullscreenStackSysUiFlags;final int dockedDiff = dockedVisibility ^ mLastDockedStackSysUiFlags;final boolean needsMenu = win.getNeedsMenuLw(mTopFullscreenOpaqueWindowState);if (diff == 0 && fullscreenDiff == 0 && dockedDiff == 0 && mLastFocusNeedsMenu == needsMenu&& mFocusedApp == win.getAppToken()&& mLastNonDockedStackBounds.equals(mNonDockedStackBounds)&& mLastDockedStackBounds.equals(mDockedStackBounds)) {return 0;}mLastSystemUiFlags = visibility;mLastFullscreenStackSysUiFlags = fullscreenVisibility;mLastDockedStackSysUiFlags = dockedVisibility;mLastFocusNeedsMenu = needsMenu;mFocusedApp = win.getAppToken();final Rect fullscreenStackBounds = new Rect(mNonDockedStackBounds);final Rect dockedStackBounds = new Rect(mDockedStackBounds);mHandler.post(new Runnable() {@Overridepublic void run() {StatusBarManagerInternal statusbar = getStatusBarManagerInternal();if (statusbar != null) {//最终会触发状态栏管理服务StatusBarManagerService的setSystemUiVisibility方法，//通知状态栏和底部栏进行样式调整statusbar.setSystemUiVisibility(visibility, fullscreenVisibility,dockedVisibility, 0xffffffff, fullscreenStackBounds,dockedStackBounds, win.toString());statusbar.topAppWindowChanged(needsMenu);}}});return diff;}
}
PhoneWindowManager的focusChangedLw方法直接调用了updateSystemUiVisibilityLw方法，此方法会对窗口的SystemUiVisibility属性做一些处理，最终调用状态栏管理服务StatusBarManagerService的setSystemUiVisibility方法，通知状态栏和底部栏进行样式调整。
3、updateSystemUiVisibilityLw方法中有用到对SystemUIVisibility属性做处理的几个关键方法：updateLightStatusBarLw、chooseNavigationColorWindowLw、updateLightNavigationBarLw和updateSystemBarsLw，这里一并贴出，有兴趣的可以看下。
public class PhoneWindowManager implements WindowManagerPolicy {private int updateLightStatusBarLw(int vis, WindowState opaque, WindowState opaqueOrDimming) {final boolean onKeyguard = isStatusBarKeyguard() && !mKeyguardOccluded;final WindowState statusColorWin = onKeyguard ? mStatusBar : opaqueOrDimming;if (statusColorWin != null && (statusColorWin == opaque || onKeyguard)) {// If the top fullscreen-or-dimming window is also the top fullscreen, respect// its light flag.vis &= ~View.SYSTEM_UI_FLAG_LIGHT_STATUS_BAR;vis |= PolicyControl.getSystemUiVisibility(statusColorWin, null)& View.SYSTEM_UI_FLAG_LIGHT_STATUS_BAR;} else if (statusColorWin != null && statusColorWin.isDimming()) {// Otherwise if it's dimming, clear the light flag.vis &= ~View.SYSTEM_UI_FLAG_LIGHT_STATUS_BAR;}return vis;}@VisibleForTesting@Nullablestatic WindowState chooseNavigationColorWindowLw(WindowState opaque,WindowState opaqueOrDimming, WindowState imeWindow,@NavigationBarPosition int navBarPosition) {// If the IME window is visible and FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS is set, then IME// window can be navigation color window.final boolean imeWindowCanNavColorWindow = imeWindow != null&& imeWindow.isVisibleLw()&& navBarPosition == NAV_BAR_BOTTOM&& (PolicyControl.getWindowFlags(imeWindow, null)& WindowManager.LayoutParams.FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS) != 0;if (opaque != null && opaqueOrDimming == opaque) {// If the top fullscreen-or-dimming window is also the top fullscreen, respect it// unless IME window is also eligible, since currently the IME window is always show// above the opaque fullscreen app window, regardless of the IME target window.// TODO(b/31559891): Maybe we need to revisit this condition once b/31559891 is fixed.return imeWindowCanNavColorWindow ? imeWindow : opaque;}if (opaqueOrDimming == null || !opaqueOrDimming.isDimming()) {// No dimming window is involved. Determine the result only with the IME window.return imeWindowCanNavColorWindow ? imeWindow : null;}if (!imeWindowCanNavColorWindow) {// No IME window is involved. Determine the result only with opaqueOrDimming.return opaqueOrDimming;}// The IME window and the dimming window are competing. Check if the dimming window can be// IME target or not.if (LayoutParams.mayUseInputMethod(PolicyControl.getWindowFlags(opaqueOrDimming, null))) {// The IME window is above the dimming window.return imeWindow;} else {// The dimming window is above the IME window.return opaqueOrDimming;}}@VisibleForTestingstatic int updateLightNavigationBarLw(int vis, WindowState opaque, WindowState opaqueOrDimming,WindowState imeWindow, WindowState navColorWin) {if (navColorWin != null) {if (navColorWin == imeWindow || navColorWin == opaque) {// Respect the light flag.vis &= ~View.SYSTEM_UI_FLAG_LIGHT_NAVIGATION_BAR;vis |= PolicyControl.getSystemUiVisibility(navColorWin, null)& View.SYSTEM_UI_FLAG_LIGHT_NAVIGATION_BAR;} else if (navColorWin == opaqueOrDimming && navColorWin.isDimming()) {// Clear the light flag for dimming window.vis &= ~View.SYSTEM_UI_FLAG_LIGHT_NAVIGATION_BAR;}}return vis;}private int updateSystemBarsLw(WindowState win, int oldVis, int vis) {final boolean dockedStackVisible =mWindowManagerInternal.isStackVisible(WINDOWING_MODE_SPLIT_SCREEN_PRIMARY);final boolean freeformStackVisible =mWindowManagerInternal.isStackVisible(WINDOWING_MODE_FREEFORM);final boolean resizing = mWindowManagerInternal.isDockedDividerResizing();// We need to force system bars when the docked stack is visible, when the freeform stack// is visible but also when we are resizing for the transitions when docked stack// visibility changes.mForceShowSystemBars = dockedStackVisible || freeformStackVisible || resizing;final boolean forceOpaqueStatusBar = mForceShowSystemBars && !mForceStatusBarFromKeyguard;// apply translucent bar vis flagsWindowState fullscreenTransWin = isStatusBarKeyguard() && !mKeyguardOccluded? mStatusBar: mTopFullscreenOpaqueWindowState;vis = mStatusBarController.applyTranslucentFlagLw(fullscreenTransWin, vis, oldVis);vis = mNavigationBarController.applyTranslucentFlagLw(fullscreenTransWin, vis, oldVis);final int dockedVis = mStatusBarController.applyTranslucentFlagLw(mTopDockedOpaqueWindowState, 0, 0);final boolean fullscreenDrawsStatusBarBackground =drawsStatusBarBackground(vis, mTopFullscreenOpaqueWindowState);final boolean dockedDrawsStatusBarBackground =drawsStatusBarBackground(dockedVis, mTopDockedOpaqueWindowState);// prevent status bar interaction from clearing certain flagsint type = win.getAttrs().type;boolean statusBarHasFocus = type == TYPE_STATUS_BAR;if (statusBarHasFocus && !isStatusBarKeyguard()) {int flags = View.SYSTEM_UI_FLAG_FULLSCREEN| View.SYSTEM_UI_FLAG_HIDE_NAVIGATION| View.SYSTEM_UI_FLAG_IMMERSIVE| View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY| View.SYSTEM_UI_FLAG_LIGHT_STATUS_BAR;if (mKeyguardOccluded) {flags |= View.STATUS_BAR_TRANSLUCENT | View.NAVIGATION_BAR_TRANSLUCENT;}vis = (vis & ~flags) | (oldVis & flags);}if (fullscreenDrawsStatusBarBackground && dockedDrawsStatusBarBackground) {vis |= View.STATUS_BAR_TRANSPARENT;vis &= ~View.STATUS_BAR_TRANSLUCENT;} else if ((!areTranslucentBarsAllowed() && fullscreenTransWin != mStatusBar)|| forceOpaqueStatusBar) {vis &= ~(View.STATUS_BAR_TRANSLUCENT | View.STATUS_BAR_TRANSPARENT);}vis = configureNavBarOpacity(vis, dockedStackVisible, freeformStackVisible, resizing);// update status barboolean immersiveSticky =(vis & View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY) != 0;final boolean hideStatusBarWM =mTopFullscreenOpaqueWindowState != null&& (PolicyControl.getWindowFlags(mTopFullscreenOpaqueWindowState, null)& WindowManager.LayoutParams.FLAG_FULLSCREEN) != 0;final boolean hideStatusBarSysui =(vis & View.SYSTEM_UI_FLAG_FULLSCREEN) != 0;final boolean hideNavBarSysui =(vis & View.SYSTEM_UI_FLAG_HIDE_NAVIGATION) != 0;final boolean transientStatusBarAllowed = mStatusBar != null&& (statusBarHasFocus || (!mForceShowSystemBars&& (hideStatusBarWM || (hideStatusBarSysui && immersiveSticky))));final boolean transientNavBarAllowed = mNavigationBar != null&& !mForceShowSystemBars && hideNavBarSysui && immersiveSticky;final long now = SystemClock.uptimeMillis();final boolean pendingPanic = mPendingPanicGestureUptime != 0&& now - mPendingPanicGestureUptime <= PANIC_GESTURE_EXPIRATION;if (pendingPanic && hideNavBarSysui && !isStatusBarKeyguard() && mKeyguardDrawComplete) {// The user performed the panic gesture recently, we're about to hide the bars,// we're no longer on the Keyguard and the screen is ready. We can now request the bars.mPendingPanicGestureUptime = 0;mStatusBarController.showTransient();if (!isNavBarEmpty(vis)) {mNavigationBarController.showTransient();}}final boolean denyTransientStatus = mStatusBarController.isTransientShowRequested()&& !transientStatusBarAllowed && hideStatusBarSysui;final boolean denyTransientNav = mNavigationBarController.isTransientShowRequested()&& !transientNavBarAllowed;if (denyTransientStatus || denyTransientNav || mForceShowSystemBars) {// clear the clearable flags insteadclearClearableFlagsLw();vis &= ~View.SYSTEM_UI_CLEARABLE_FLAGS;}final boolean immersive = (vis & View.SYSTEM_UI_FLAG_IMMERSIVE) != 0;immersiveSticky = (vis & View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY) != 0;final boolean navAllowedHidden = immersive || immersiveSticky;if (hideNavBarSysui && !navAllowedHidden&& getWindowLayerLw(win) > getWindowLayerFromTypeLw(TYPE_INPUT_CONSUMER)) {// We can't hide the navbar from this window otherwise the input consumer would not get// the input events.vis = (vis & ~View.SYSTEM_UI_FLAG_HIDE_NAVIGATION);}vis = mStatusBarController.updateVisibilityLw(transientStatusBarAllowed, oldVis, vis);// update navigation barboolean oldImmersiveMode = isImmersiveMode(oldVis);boolean newImmersiveMode = isImmersiveMode(vis);if (win != null && oldImmersiveMode != newImmersiveMode) {final String pkg = win.getOwningPackage();mImmersiveModeConfirmation.immersiveModeChangedLw(pkg, newImmersiveMode,isUserSetupComplete(), isNavBarEmpty(win.getSystemUiVisibility()));}vis = mNavigationBarController.updateVisibilityLw(transientNavBarAllowed, oldVis, vis);final WindowState navColorWin = chooseNavigationColorWindowLw(mTopFullscreenOpaqueWindowState, mTopFullscreenOpaqueOrDimmingWindowState,mWindowManagerFuncs.getInputMethodWindowLw(), mNavigationBarPosition);vis = updateLightNavigationBarLw(vis, mTopFullscreenOpaqueWindowState,mTopFullscreenOpaqueOrDimmingWindowState,mWindowManagerFuncs.getInputMethodWindowLw(), navColorWin);return vis;}
}
