深入WindowManager

Dialog(Context context, int theme, boolean createContextThemeWrapper) {
   // 从ContextImpl的集合获取WM系统服务
   mWindowManager = (WindowManager)context.getSystemService(Context.WINDOW_SERVICE);
   // 构建Window对象
   Window w = PolicyManager.makeNewWindow(mContext);
   mWindow = w;
   // 实现Window.Callback接口, 为了后续的事件的传递
   w.setCallback(this);
   // Window 和 WM 进行关联
   w.setWindowManager(mWindowManager, null, null);

}

// Window类
public void setWindowManager(WindowManager wm, IBinder appToken, String appName, boolean hardwareAccelerated) {
   mWindowManager = ((WindowManagerImpl)wm).createLocalWindowManager(this);
}

// 继续跟踪
// WindowManagerImpl类
public WindowManagerImpl createLocalWindowManager(Window parentWindow) {
   return new WindowManagerImpl(mDisplay, parentWindow);
}

// 手机窗口显示View的入口, View被添加到WM中
public void addView(View view, ViewGroup.LayoutParams params, Display display, Window parentWindow) {
    // 省略非关键代码
        ViewRootImpl root;
        View panelParentView = null;
        synchronized (mLock) {
            // 1.构建了ViewRootImpl
            root = new ViewRootImpl(view.getContext(), display);
            // 2.设置View的布局参数
            view.setLayoutParams(wparams);
            // 3.分别对View, ViewRootImpl,param进行存储
            mViews.add(view);
            mRoots.add(root);
            mParams.add(wparams);
        }
        try{
            // 4.通过ViewRootImpl#setView()将View显示到手机窗口
            root.setView(view, wparams, panelParentView);            
        }
}

public ViewRootImpl(Context context, Display display) {
    // 省略非重要代码
    // 获取Window Session, 也就是与WindowManagerService建立连接
    mWindowSession = WindowManagerGlobal.getWindowSession();
    // 保存创建本对象时的线程, 用于在更新UI的时候只能是mThread线程的条件判断
    // 这也就为什么需要在UI线程才可以更新, 因为`ViewRootImpl`是在UI线程创建的
    mThread = Thread.currentThread();
}

// WindowManagerGlobal
public static IWindowSession getWindowSession() {
   synchronized (WindowManagerGlobal.class) {
       if (sWindowSession == null) {
           try {
               InputMethodManager imm = InputMethodManager.getInstance();
               // 1. 获取了WindowManagerService
               IWindowManager windowManager = getWindowManagerService();
               // 2. 与WindowManagerService建立了一个Session, 并返回
               sWindowSession = windowManager.openSession(...);
               } catch (RemoteException e) {
               Log.e(TAG, "Failed to open window session", e);
           }
       }
       return sWindowSession;
   }
}

// 看一下获取WMS的实现
public static IWindowManager getWindowManagerService() {
   synchronized (WindowManagerGlobal.class) {
       if (sWindowManagerService == null) {
           // 典型的Binder通信
           sWindowManagerService = IWindowManager.Stub.asInterface(
                   ServiceManager.getService("window"));
       }
       return sWindowManagerService;
   }
}

@Override   // ViewRootImpl类
public void requestLayout() {
   if (!mHandlingLayoutInLayoutRequest) {
       // 检测当前线程是否是创建ViewRootImpl对象的线程
       // 通常子线程更新的崩溃是在这里抛出的异常
       checkThread();
       mLayoutRequested = true;
       // 向 handler 发送 DO_TRAVERSAL 消息
       scheduleTraversals();
   }
}