Android Window

/**
 * Provides low-level communication with the system window manager for
 * operations that are bound to a particular context, display or parent window.
 * Instances of this object are sensitive to the compatibility info associated
 * with the running application.
 *
 * This object implements the {@link ViewManager} interface,
 * allowing you to add any View subclass as a top-level window on the screen.
 * Additional window manager specific layout parameters are defined for
 * control over how windows are displayed.  It also implements the {@link WindowManager}
 * interface, allowing you to control the displays attached to the device.
 * 
 * <p>Applications will not normally use WindowManager directly, instead relying
 * on the higher-level facilities in {@link android.app.Activity} and
 * {@link android.app.Dialog}.
 * 
 * <p>Even for low-level window manager access, it is almost never correct to use
 * this class.  For example, {@link android.app.Activity#getWindowManager}
 * provides a window manager for adding windows that are associated with that
 * activity -- the window manager will not normally allow you to add arbitrary
 * windows that are not associated with an activity.
 */
public final class WindowManagerImpl implements WindowManager {
    private final WindowManagerGlobal mGlobal = WindowManagerGlobal.getInstance();
    private final Display mDisplay;
    private final Window mParentWindow;
    private IBinder mDefaultToken;
    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);
    }
    /**
     * Sets the window token to assign when none is specified by the client or
     * available from the parent window.
     *
     * @param token The default token to assign.
     */
    public void setDefaultToken(IBinder token) {
        mDefaultToken = token;
    }
    @Override
    public void addView(@NonNull View view, @NonNull ViewGroup.LayoutParams params) {
        applyDefaultToken(params);
        mGlobal.addView(view, params, mDisplay, mParentWindow);
    }
    @Override
    public void updateViewLayout(@NonNull View view, @NonNull ViewGroup.LayoutParams params) {
        applyDefaultToken(params);
        mGlobal.updateViewLayout(view, params);
    }
    private void applyDefaultToken(@NonNull ViewGroup.LayoutParams params) {
        // Only use the default token if we don't have a parent window.
        if (mDefaultToken != null && mParentWindow == null) {
            if (!(params instanceof WindowManager.LayoutParams)) {
                throw new IllegalArgumentException("Params must be WindowManager.LayoutParams");
            }
            // Only use the default token if we don't already have a token.
            final WindowManager.LayoutParams wparams = (WindowManager.LayoutParams) params;
            if (wparams.token == null) {
                wparams.token = mDefaultToken;
            }
        }
    }
    @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;
    }
}

public static IWindowSession getWindowSession() {
        synchronized (WindowManagerGlobal.class) {
            if (sWindowSession == null) {
                try {
                    InputMethodManager imm = InputMethodManager.getInstance();
                    // a. 获取WMS
                    IWindowManager windowManager = getWindowManagerService();
                    // b.拉取session
                    sWindowSession = windowManager.openSession(
                            new IWindowSessionCallback.Stub() {
                                @Override
                                public void onAnimatorScaleChanged(float scale) {
                                    ValueAnimator.setDurationScale(scale);
                                }
                            },
                            imm.getClient(), imm.getInputContext());
                } catch (RemoteException e) {
                    Log.e(TAG, "Failed to open window session", e);
                }
            }
            // c.返回WMS中的session
            return sWindowSession;
        }
}
public static IWindowManager getWindowManagerService() {
        synchronized (WindowManagerGlobal.class) {
            if (sWindowManagerService == null) {
                // 进程间通信 binder使用
                sWindowManagerService = IWindowManager.Stub.asInterface(
                        ServiceManager.getService("window"));
                try {
                    sWindowManagerService = getWindowManagerService();
                    ValueAnimator.setDurationScale(sWindowManagerService.getCurrentAnimatorScale());
                } catch (RemoteException e) {
                    Log.e(TAG, "Failed to get WindowManagerService, cannot set animator scale", e);
                }
            }
            return sWindowManagerService;
        }
}
    
public void addView(View view, ViewGroup.LayoutParams params,
            Display display, Window parentWindow) {
        ...
        ViewRootImpl root;
        View panelParentView = null;
        synchronized (mLock) {
            // Start watching for system 
            // The previous removeView() had not completed executing. Now it has.
        
            // ...
            // If this is a panel window, then 
            // a.实例该View的ViewRootImpl
            root = new ViewRootImpl(view.getContext(), display);
            // b.设置布局位置参数
            view.setLayoutParams(wparams);
            // c.存储view,ViewRootImpl,params
            mViews.add(view);
            mRoots.add(root);
            mParams.add(wparams);
        }
        // do this last because it fires off messages to start doing things
        // d.将view添加到（显示View）
        root.setView(view, wparams, panelParentView);
      
    }