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WMS—啟動過程

本文轉載自   查看原文   2018-01-30 15:16   934    Android 系統底層

基於Android 6.0源碼， 分析WMS的啟動過程。

一. 概述

  • Surface:代表畫布
  • WMS: 添加window的過程主要功能是添加Surface,管理所有的Surface布局,以及Z軸排序問題;
  • SurfaceFinger: 將Surface按次序混合並顯示到物理屏幕上;

1.1 WMS全貌

wms_relation

 

  • WMS繼承於IWindowManager.Stub, 作為Binder服務端;
  • WMS的成員變量mSessions保存着所有的Session對象,Session繼承於IWindowSession.Stub, 作為Binder服務端;
  • 成員變量mPolicy: 實例對象為PhoneWindowManager,用於實現各種窗口相關的策略;
  • 成員變量mChoreographer: 用於控制窗口動畫,屏幕旋轉等操作;
  • 成員變量mDisplayContents: 記錄一組DisplayContent對象,這個跟多屏輸出相關;
  • 成員變量mTokenMap: 保存所有的WindowToken對象; 以IBinder為key,可以是IAppWindowToken或者其他Binder的Bp端;
    • 另一端情況:ActivityRecord.Token extends IApplicationToken.Stub
  • 成員變量mWindowMap: 保存所有的WindowState對象;以IBinder為key, 是IWindow的Bp端;
    • 另一端情況: ViewRootImpl.W extends IWindow.Stub
  • 一般地,每一個窗口都對應一個WindowState對象, 該對象的成員變量mClient用於跟應用端交互,成員變量mToken用於跟AMS交互.

二. 啟動過程

private void startOtherServices() {
    ...
    // [見小節2.1]
    WindowManagerService wm = WindowManagerService.main(context, inputManager,
    mFactoryTestMode != FactoryTest.FACTORY_TEST_LOW_LEVEL,
    !mFirstBoot, mOnlyCore);
    
    wm.displayReady(); // [見小節2.5]
    ...
    wm.systemReady(); // [見小節2.6]
}

2.1 WMS.main

[-> 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() {

        public void run() {
            //運行在"android.display"線程[見小節2.2]
            holder[0] = new WindowManagerService(context, im,
                    haveInputMethods, showBootMsgs, onlyCore);
        }
    }, 0);
    return holder[0];
}

2.2 WindowManagerService

 1 private WindowManagerService(Context context, InputManagerService inputManager, boolean haveInputMethods, boolean showBootMsgs, boolean onlyCore) {
 2     mContext = context;
 3     mHaveInputMethods = haveInputMethods;
 4     mAllowBootMessages = showBootMsgs;
 5     mOnlyCore = onlyCore;
 6     ...
 7     mInputManager = inputManager; 
 8     mDisplayManagerInternal = LocalServices.getService(DisplayManagerInternal.class);
 9     mDisplaySettings = new DisplaySettings();
10     mDisplaySettings.readSettingsLocked();
11 
12     LocalServices.addService(WindowManagerPolicy.class, mPolicy);
13     mPointerEventDispatcher = new PointerEventDispatcher(mInputManager.monitorInput(TAG));
14 
15     mFxSession = new SurfaceSession();
16     mDisplayManager = (DisplayManager)context.getSystemService(Context.DISPLAY_SERVICE);
17     mDisplays = mDisplayManager.getDisplays();
18 
19     for (Display display : mDisplays) {
20         //創建DisplayContent[見小節2.2.1]
21         createDisplayContentLocked(display);
22     }
23 
24     mKeyguardDisableHandler = new KeyguardDisableHandler(mContext, mPolicy);
25     ...
26 
27     mAppTransition = new AppTransition(context, mH);
28     mAppTransition.registerListenerLocked(mActivityManagerAppTransitionNotifier);
29     mActivityManager = ActivityManagerNative.getDefault();
30     ...
31     mAnimator = new WindowAnimator(this);
32     
33 
34     LocalServices.addService(WindowManagerInternal.class, new LocalService());
35     //初始化策略[見小節2.3]
36     initPolicy();
37 
38     Watchdog.getInstance().addMonitor(this);
39 
40     SurfaceControl.openTransaction();
41     try {
42         createWatermarkInTransaction();
43         mFocusedStackFrame = new FocusedStackFrame(
44                 getDefaultDisplayContentLocked().getDisplay(), mFxSession);
45     } finally {
46         SurfaceControl.closeTransaction();
47     }
48 
49     updateCircularDisplayMaskIfNeeded();
50     showEmulatorDisplayOverlayIfNeeded();
51 }

在“android.display”線程中執行WindowManagerService對象的初始化過程，其中final H mH = new H();此處H繼承於Handler，無參初始化的過程，便會采用當前所在線程 的Looper。那就是說WindowManagerService.H.handleMessage()方法運行在“android.display”線程。

2.2.1 WMS.createDisplayContentLocked

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;
}

創建DisplayContent,用於支持多屏幕的功能.比如目前除了本身真實的屏幕之外,還有Wifi display虛擬屏幕.

2.3 WMS.initPolicy

rivate void initPolicy() {
    //運行在"android.ui"線程
    UiThread.getHandler().runWithScissors(new Runnable() {
        public void run() {
            WindowManagerPolicyThread.set(Thread.currentThread(), Looper.myLooper());
            //此處mPolicy為PhoneWindowManager.[見小節2.4]
            mPolicy.init(mContext, WindowManagerService.this, WindowManagerService.this);
        }
    }, 0);
}

2.3.1 Handler.runWithScissors

[-> Handler.java]

public final boolean runWithScissors(final Runnable r, long timeout) {
    //當前線程跟當前Handler都指向同一個Looper,則直接運行
    if (Looper.myLooper() == mLooper) {
        r.run();
        return true;
    }

    BlockingRunnable br = new BlockingRunnable(r);
    //[見小節2.3.2]
    return br.postAndWait(this, timeout);
}

2.3.2 postAndWait

[-> Handler.java ::BlockingRunnable]

 1 private static final class BlockingRunnable implements Runnable {
 2     private final Runnable mTask;
 3     private boolean mDone;
 4 
 5     public BlockingRunnable(Runnable task) {
 6         mTask = task;
 7     }
 8 
 9     public void run() {
10         try {
11             mTask.run();
12         } finally {
13             synchronized (this) {
14                 mDone = true;
15                 notifyAll();
16             }
17         }
18     }
19 
20     public boolean postAndWait(Handler handler, long timeout) {
21         if (!handler.post(this)) {
22             return false;
23         }
24 
25         synchronized (this) {
26             if (timeout > 0) {
27                 final long expirationTime = SystemClock.uptimeMillis() + timeout;
28                 while (!mDone) {
29                     long delay = expirationTime - SystemClock.uptimeMillis();
30                     if (delay <= 0) {
31                         return false; // timeout
32                     }
33                     try {
34                         wait(delay);
35                     } catch (InterruptedException ex) {
36                     }
37                 }
38             } else {
39                 while (!mDone) {
40                     try {
41                         wait();
42                     } catch (InterruptedException ex) {
43                     }
44                 }
45             }
46         }
47         return true;
48     }
49 }

由此可見, BlockingRunnable.postAndWait()方法是阻塞操作,就是先將消息放入Handler所指向的線程, 此處是指”android.ui”線程, 由於該方法本身運行在”android.display”線程. 也就意味着”android.display”線程會進入等待狀態, 直到handler線程執行完成后再喚醒”android.display”線程. 那么PWM.init()便是運行在”android.ui”線程,屬於同步阻塞操作.

2.4 PWM.init

[-> PhoneWindowManager.java]

 1 public void init(Context context, IWindowManager windowManager, WindowManagerFuncs windowManagerFuncs) {
 2     mContext = context;
 3     mWindowManager = windowManager;
 4     mWindowManagerFuncs = windowManagerFuncs;
 5     mWindowManagerInternal = LocalServices.getService(WindowManagerInternal.class);
 6     mActivityManagerInternal = LocalServices.getService(ActivityManagerInternal.class);
 7     mDreamManagerInternal = LocalServices.getService(DreamManagerInternal.class);
 8     mPowerManagerInternal = LocalServices.getService(PowerManagerInternal.class);
 9     mAppOpsManager = (AppOpsManager) mContext.getSystemService(Context.APP_OPS_SERVICE);
10     ...
11 
12     mHandler = new PolicyHandler(); //運行在"android.ui"線程
13     mWakeGestureListener = new MyWakeGestureListener(mContext, mHandler);
14     mOrientationListener = new MyOrientationListener(mContext, mHandler);
15     ...
16 
17     mPowerManager = (PowerManager)context.getSystemService(Context.POWER_SERVICE);
18     mBroadcastWakeLock = mPowerManager.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK,
19             "PhoneWindowManager.mBroadcastWakeLock");
20     mPowerKeyWakeLock = mPowerManager.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK,
21             "PhoneWindowManager.mPowerKeyWakeLock");
22     ...
23    
24     mGlobalKeyManager = new GlobalKeyManager(mContext);
25     ...
26     
27     if (!mPowerManager.isInteractive()) {
28         startedGoingToSleep(WindowManagerPolicy.OFF_BECAUSE_OF_USER);
29         finishedGoingToSleep(WindowManagerPolicy.OFF_BECAUSE_OF_USER);
30     }
31 
32     mWindowManagerInternal.registerAppTransitionListener(
33             mStatusBarController.getAppTransitionListener());
34 }

前面小節[2.1 ~ 2.4]介紹了WMS.main()方法, 接下來便是開始執行WMS.displayReady().

2.5 WMS.displayReady

 1 public void displayReady() {
 2     for (Display display : mDisplays) {
 3         displayReady(display.getDisplayId());
 4     }
 5 
 6     synchronized(mWindowMap) {
 7         final DisplayContent displayContent = getDefaultDisplayContentLocked();
 8         readForcedDisplayPropertiesLocked(displayContent);
 9         mDisplayReady = true;
10     }
11 
12     mActivityManager.updateConfiguration(null);
13 
14     synchronized(mWindowMap) {
15         mIsTouchDevice = mContext.getPackageManager().hasSystemFeature(
16                 PackageManager.FEATURE_TOUCHSCREEN);
17         configureDisplayPolicyLocked(getDefaultDisplayContentLocked());
18     }
19 
20     mActivityManager.updateConfiguration(null);
21 }

2.6 WMS.systemReady

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

2.6.1 PWM.systemReady

[-> PhoneWindowManager.java]

 1 public void systemReady() {
 2     mKeyguardDelegate = new KeyguardServiceDelegate(mContext);
 3     mKeyguardDelegate.onSystemReady();
 4 
 5     readCameraLensCoverState();
 6     updateUiMode();
 7     boolean bindKeyguardNow;
 8     synchronized (mLock) {
 9         updateOrientationListenerLp();
10         mSystemReady = true;
11         
12         mHandler.post(new Runnable() {
13             public void run() {
14                 updateSettings();
15             }
16         });
17 
18         bindKeyguardNow = mDeferBindKeyguard;
19         if (bindKeyguardNow) {
20             mDeferBindKeyguard = false;
21         }
22     }
23 
24     if (bindKeyguardNow) {
25         mKeyguardDelegate.bindService(mContext);
26         mKeyguardDelegate.onBootCompleted();
27     }
28     mSystemGestures.systemReady();
29 }

三. 總結

整個啟動過程涉及3個線程: system_server主線程, “android.display”, “android.ui”, 整個過程是采用阻塞方式(利用Handler.runWithScissors)執行的. 其中WindowManagerService.mH的Looper運行在 “android.display”進程，也就意味着WMS.H.handleMessage()在該線程執行。 流程如下:

wms_startup

 

 


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