Window是一个抽象的概念，每一个Window都对应着一个View和一个ViewRootImpl，Window和View通过ViewRootImpl来建立联系，View是Window存在的实体，应用无法直接访问Window，对Window的访问必须通过WindowManager

1.Window的添加过程

ViewManager.png

WindowManager继承自ViewManager

WindowManager.png

WindowManger的实现类是WindowMangerImpl

public final class WindowManagerImpl implements WindowManager {
    private final WindowManagerGlobal mGlobal = WindowManagerGlobal.getInstance();
    private final Display mDisplay;
    private final Window mParentWindow;

    public WindowManagerImpl(Display display) {
        this(display, null);
    }

    private WindowManagerImpl(Display display, Window parentWindow) {
        mDisplay = display;
        mParentWindow = parentWindow;
    }

    public WindowManagerImpl createLocalWindowManager(Window parentWindow) {
        return new WindowManagerImpl(mDisplay, parentWindow);
    }

    public WindowManagerImpl createPresentationWindowManager(Display display) {
        return new WindowManagerImpl(display, mParentWindow);
    }

    @Override
    public void addView(View view, ViewGroup.LayoutParams params) {
        mGlobal.addView(view, params, mDisplay, mParentWindow);
    }

    @Override
    public void updateViewLayout(View view, ViewGroup.LayoutParams params) {
        mGlobal.updateViewLayout(view, params);
    }

    @Override
    public void removeView(View view) {
        mGlobal.removeView(view, false);
    }

    @Override
    public void removeViewImmediate(View view) {
        mGlobal.removeView(view, true);
    }

    @Override
    public Display getDefaultDisplay() {
        return mDisplay;
    }
}

WindowMangerImpl的功能实际的操作转接给WindowManagerGlobal完成

   private static WindowManagerGlobal sDefaultWindowManager;
    private static IWindowManager sWindowManagerService;
    private static IWindowSession sWindowSession;

    private final Object mLock = new Object();

    private final ArrayList<View> mViews = new ArrayList<View>();
    private final ArrayList<ViewRootImpl> mRoots = new ArrayList<ViewRootImpl>();
    private final ArrayList<WindowManager.LayoutParams> mParams =
            new ArrayList<WindowManager.LayoutParams>();
    private final ArraySet<View> mDyingViews = new ArraySet<View>();
    private boolean mNeedsEglTerminate;

    private Runnable mSystemPropertyUpdater;

    private WindowManagerGlobal() {
    }

    public static WindowManagerGlobal getInstance() {
        synchronized (WindowManagerGlobal.class) {
            if (sDefaultWindowManager == null) {
                sDefaultWindowManager = new WindowManagerGlobal();
            }
            return sDefaultWindowManager;
        }
    }

    public static IWindowManager getWindowManagerService() {
        synchronized (WindowManagerGlobal.class) {
            if (sWindowManagerService == null) {
                sWindowManagerService = IWindowManager.Stub.asInterface(
                        ServiceManager.getService("window"));
            }
            return sWindowManagerService;
        }
    }

    public static IWindowSession getWindowSession() {
        synchronized (WindowManagerGlobal.class) {
            if (sWindowSession == null) {
                try {
                    InputMethodManager imm = InputMethodManager.getInstance();
                    IWindowManager windowManager = getWindowManagerService();
                    sWindowSession = windowManager.openSession(
                            imm.getClient(), imm.getInputContext());
                    float animatorScale = windowManager.getAnimationScale(2);
                    ValueAnimator.setDurationScale(animatorScale);
                } catch (RemoteException e) {
                    Log.e(TAG, "Failed to open window session", e);
                }
            }
            return sWindowSession;
        }
    }

    public static IWindowSession peekWindowSession() {
        synchronized (WindowManagerGlobal.class) {
            return sWindowSession;
        }
    }

WindowManagerGlobal通过getWindowManagerService获取了一个IWindowManager对象，通过getWindowSession调用windowManager.openSession获取一个IWindowSession对象

2.Window的删除过程

3.Window的更新过程