WindowManagerService

             WindowManagerService(WMS)是Android中图形用户接口的引擎，它管理着所有窗口.这里说的管理是指“创建，添加，删除”，以及将某个窗口设置为焦点窗口(正在与用户交互的窗口)。在WMS中，窗口由两部分内容构成的，一部分是描述该窗口的类WindowState,另一部分是该窗口在屏幕上对应的界面Surface.

     一  WMS的启动过程

SystemServer.java 
  
  private void run() {
  ...
   try {
            startBootstrapServices();
            startCoreServices();
            startOtherServices();
        } catch (Throwable ex) {
            Slog.e("System", "******************************************");
            Slog.e("System", "************ Failure starting system services", ex);
            throw ex;
        }
  ...
  }
  
  
   /**
     * Starts a miscellaneous grab bag of stuff that has yet to be refactored
     * and organized.
     */
    private void startOtherServices() {
	
	  WindowManagerService wm = null;
	   Slog.i(TAG, "Window Manager");
            wm = WindowManagerService.main(context, inputManager,
                    mFactoryTestMode != FactoryTest.FACTORY_TEST_LOW_LEVEL,
                    !mFirstBoot, mOnlyCore);
            ServiceManager.addService(Context.WINDOW_SERVICE, wm);
            ServiceManager.addService(Context.INPUT_SERVICE, inputManager);
			
			...
			   wm.displayReady();
			     wm.systemReady();
	
	}

WindowManagerService.java

public static WindowManagerService main(final Context context,
            final InputManagerService im,
            final boolean haveInputMethods, final boolean showBootMsgs,
            final boolean onlyCore) {
        final WindowManagerService[] holder = new WindowManagerService[1];
        DisplayThread.getHandler().runWithScissors(new Runnable() {
            @Override
            public void run() {
                holder[0] = new WindowManagerService(context, im,
                        haveInputMethods, showBootMsgs, onlyCore);
            }
        }, 0);
        return holder[0];
    }

DisplayThread.java
 public static Handler getHandler() {
        synchronized (DisplayThread.class) {
            ensureThreadLocked();
            return sHandler;
        }
    }

 WindowManagerService.java
 private WindowManagerService(Context context, InputManagerService inputManager,
            boolean haveInputMethods, boolean showBootMsgs, boolean onlyCore) {
        mContext = context;
        mHaveInputMethods = haveInputMethods;
        mAllowBootMessages = showBootMsgs;
        mOnlyCore = onlyCore;
        mLimitedAlphaCompositing = context.getResources().getBoolean(
                com.android.internal.R.bool.config_sf_limitedAlpha);
        mHasPermanentDpad = context.getResources().getBoolean(
                com.android.internal.R.bool.config_hasPermanentDpad);
        mInTouchMode = context.getResources().getBoolean(
                com.android.internal.R.bool.config_defaultInTouchMode);
        mInputManager = inputManager; // Must be before createDisplayContentLocked.
        mDisplayManagerInternal = LocalServices.getService(DisplayManagerInternal.class);
        mDisplaySettings = new DisplaySettings();
        mDisplaySettings.readSettingsLocked();

        LocalServices.addService(WindowManagerPolicy.class, mPolicy);

        mPointerEventDispatcher = new PointerEventDispatcher(mInputManager.monitorInput(TAG));

        mFxSession = new SurfaceSession();
        mDisplayManager = (DisplayManager)context.getSystemService(Context.DISPLAY_SERVICE);
        Display[] displays = mDisplayManager.getDisplays();
        for (Display display : displays) {
            createDisplayContentLocked(display);
        }

        mKeyguardDisableHandler = new KeyguardDisableHandler(mContext, mPolicy);    
        ...

        // Get persisted window scale setting
        mWindowAnimationScaleSetting = Settings.Global.getFloat(context.getContentResolver(),
                Settings.Global.WINDOW_ANIMATION_SCALE, mWindowAnimationScaleSetting);
        mTransitionAnimationScaleSetting = Settings.Global.getFloat(context.getContentResolver(),
                Settings.Global.TRANSITION_ANIMATION_SCALE, mTransitionAnimationScaleSetting);
        setAnimatorDurationScale(Settings.Global.getFloat(context.getContentResolver(),
                Settings.Global.ANIMATOR_DURATION_SCALE, mAnimatorDurationScaleSetting));

        // Track changes to DevicePolicyManager state so we can enable/disable keyguard.
        IntentFilter filter = new IntentFilter();
        filter.addAction(DevicePolicyManager.ACTION_DEVICE_POLICY_MANAGER_STATE_CHANGED);
        mContext.registerReceiver(mBroadcastReceiver, filter);

        mSettingsObserver = new SettingsObserver();
        updateShowImeWithHardKeyboard();

        mHoldingScreenWakeLock = mPowerManager.newWakeLock(
                PowerManager.SCREEN_BRIGHT_WAKE_LOCK | PowerManager.ON_AFTER_RELEASE, TAG);
        mHoldingScreenWakeLock.setReferenceCounted(false);
        mAnimator = new WindowAnimator(this);
        mAllowTheaterModeWakeFromLayout = context.getResources().getBoolean(
                com.android.internal.R.bool.config_allowTheaterModeWakeFromWindowLayout);

        LocalServices.addService(WindowManagerInternal.class, new LocalService());
		//初始化策略
	   initPolicy();

        // Add ourself to the Watchdog monitors.
        Watchdog.getInstance().addMonitor(this);
        SurfaceControl.openTransaction();
        try {
            createWatermarkInTransaction();
            mFocusedStackFrame = new FocusedStackFrame(
                    getDefaultDisplayContentLocked().getDisplay(), mFxSession);
        } finally {
            SurfaceControl.closeTransaction();
        }
        updateCircularDisplayMaskIfNeeded();
        showEmulatorDisplayOverlayIfNeeded();
    }

 WindowManagerService.java
 
 private void initPolicy() {
        UiThread.getHandler().runWithScissors(new Runnable() {
            @Override
            public void run() {
                WindowManagerPolicyThread.set(Thread.currentThread(), Looper.myLooper());

                mPolicy.init(mContext, WindowManagerService.this, WindowManagerService.this);
                mAnimator.mAboveUniverseLayer = mPolicy.getAboveUniverseLayer()
                        * TYPE_LAYER_MULTIPLIER
                        + TYPE_LAYER_OFFSET;
            }
        }, 0);
    }

         分析：在“android.display”线程(DisplayThread.java)中执行WindowManagerService对象的初始化过程，其中final H mH = new H();此处H继承于Handler，无参初始化的过程，便会采用当前所在线程 的Looper。也就是说WindowManagerService.H.handleMessage()方法运行在“android.display”这个线程。

WMS.java
public void createDisplayContentLocked(final Display display) {
        if (display == null) {
            throw new IllegalArgumentException("getDisplayContent: display must not be null");
        }
        getDisplayContentLocked(display.getDisplayId());
    }
	
	 public DisplayContent getDisplayContentLocked(final int displayId) {
        DisplayContent displayContent = mDisplayContents.get(displayId);
        if (displayContent == null) {
            final Display display = mDisplayManager.getDisplay(displayId);
            if (display != null) {
                displayContent = newDisplayContentLocked(display);
            }
        }
        return displayContent;
    }

分析：创建DisplayContent,用于支持多屏幕的功能.比如目前除了本身真实的屏幕之外,还有Wifi display虚拟屏幕。

Handler.java

 public final boolean runWithScissors(final Runnable r, long timeout) {
        if (r == null) {
            throw new IllegalArgumentException("runnable must not be null");
        }
        if (timeout < 0) {
            throw new IllegalArgumentException("timeout must be non-negative");
        }
      //当前线程跟当前Handler都指向同一个Looper,则直接运行
        if (Looper.myLooper() == mLooper) {
            r.run();
            return true;
        }

        BlockingRunnable br = new BlockingRunnable(r);
        return br.postAndWait(this, timeout);
    }

 private static final class BlockingRunnable implements Runnable {
        private final Runnable mTask;
        private boolean mDone;

        public BlockingRunnable(Runnable task) {
            mTask = task;
        }

        @Override
        public void run() {
            try {
                mTask.run();
            } finally {
                synchronized (this) {
                    mDone = true;
                    notifyAll();
                }
            }
        }

        public boolean postAndWait(Handler handler, long timeout) {
            if (!handler.post(this)) {
                return false;
            }

            synchronized (this) {
                if (timeout > 0) {
                    final long expirationTime = SystemClock.uptimeMillis() + timeout;
                    while (!mDone) {
                        long delay = expirationTime - SystemClock.uptimeMillis();
                        if (delay <= 0) {
                            return false; // timeout
                        }
                        try {
                            wait(delay);
                        } catch (InterruptedException ex) {
                        }
                    }
                } else {
                    while (!mDone) {
                        try {
                            wait();
                        } catch (InterruptedException ex) {
                        }
                    }
                }
            }
            return true;
        }
    }

        分析:BlockingRunnable.postAndWait()方法是阻塞操作,就是先将消息放入Handler所指向的线程, 此处是指”android.ui”线程, 由于该方法本身运行在”android.display”线程. 也就意味着”android.display”线程会进入等待状态, 直到handler线程执行完成后再唤醒”android.display”线程. 那么PWM.init()便是运行在”android.ui”线程,属于同步阻塞操作.

PhoneWindowManager.java 
 /** {@inheritDoc} */
    @Override
    public void init(Context context, IWindowManager windowManager,
            WindowManagerFuncs windowManagerFuncs) {
        mContext = context;
        mWindowManager = windowManager;
        mWindowManagerFuncs = windowManagerFuncs;
        mWindowManagerInternal = LocalServices.getService(WindowManagerInternal.class);
        mDreamManagerInternal = LocalServices.getService(DreamManagerInternal.class);

        mHandler = new PolicyHandler();
        mWakeGestureListener = new MyWakeGestureListener(mContext, mHandler);
        mOrientationListener = new MyOrientationListener(mContext, mHandler);
        try {
            mOrientationListener.setCurrentRotation(windowManager.getRotation());
        } catch (RemoteException ex) { }
        mSettingsObserver = new SettingsObserver(mHandler);
        mSettingsObserver.observe();
        mShortcutManager = new ShortcutManager(context, mHandler);
        mShortcutManager.observe();
        mUiMode = context.getResources().getInteger(
                com.android.internal.R.integer.config_defaultUiModeType);
        mHomeIntent =  new Intent(Intent.ACTION_MAIN, null);
        mHomeIntent.addCategory(Intent.CATEGORY_HOME);
        mHomeIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK
                | Intent.FLAG_ACTIVITY_RESET_TASK_IF_NEEDED);
       

       ...
        context.registerReceiver(mMultiuserReceiver, filter);

        // monitor for system gestures
        mSystemGestures = new SystemGesturesPointerEventListener(context,
                new SystemGesturesPointerEventListener.Callbacks() {
                    @Override
                    public void onSwipeFromTop() {
                        if (mStatusBar != null) {
                            requestTransientBars(mStatusBar);
                        }
                    }
                    @Override
                    public void onSwipeFromBottom() {
                        if (mNavigationBar != null && mNavigationBarOnBottom) {
                            requestTransientBars(mNavigationBar);
                        }
                    }
                    @Override
                    public void onSwipeFromRight() {
                        if (mNavigationBar != null && !mNavigationBarOnBottom) {
                            requestTransientBars(mNavigationBar);
                        }
                    }
                    @Override
                    public void onDebug() {
                        // no-op
                    }
                });
        mImmersiveModeConfirmation = new ImmersiveModeConfirmation(mContext);
        mWindowManagerFuncs.registerPointerEventListener(mSystemGestures);


        // Controls rotation and the like.
        initializeHdmiState();

        // Match current screen state.
        if (!mPowerManager.isInteractive()) {
            goingToSleep(WindowManagerPolicy.OFF_BECAUSE_OF_USER);
        }
    }

WMS.displayReady
 public void displayReady() {
        displayReady(Display.DEFAULT_DISPLAY);
        synchronized(mWindowMap) {
            final DisplayContent displayContent = getDefaultDisplayContentLocked();
            readForcedDisplaySizeAndDensityLocked(displayContent);
            mDisplayReady = true;
        }
        try {
            mActivityManager.updateConfiguration(null);
        } catch (RemoteException e) {
        }
        synchronized(mWindowMap) {
            mIsTouchDevice = mContext.getPackageManager().hasSystemFeature(
                    PackageManager.FEATURE_TOUCHSCREEN);
            configureDisplayPolicyLocked(getDefaultDisplayContentLocked());
        }
        try {
            mActivityManager.updateConfiguration(null);
        } catch (RemoteException e) {
        }
    }

WMS.systemReady
public void systemReady() {
    mPolicy.systemReady();
}

 PhoneWindowManager.java
 
 public void systemReady() {
        mKeyguardDelegate = new KeyguardServiceDelegate(mContext);
        mKeyguardDelegate.onSystemReady();

        readCameraLensCoverState();
        updateUiMode();
        synchronized (mLock) {
            updateOrientationListenerLp();
            mSystemReady = true;
            mHandler.post(new Runnable() {
                @Override
                public void run() {
                    updateSettings();
                }
            });
        }
    }

分析：整个启动过程涉及3个线程: SystemServer主线程, “android.display”, “android.ui”, 整个过程是采用阻塞方式(利用Handler.runWithScissors)执行的. 其中WindowManagerService.mH的Looper运行在 “android.display”进程，也就意味着WMS.H.handleMessage()在该线程执行。