Android之Window与WIndowManager - HelloWorld开发者社区

基本概念

Window、PhoneWindow

顶层窗口样式和行为的抽象类, 概括了Android窗口的基本属性和基本功能。该类实例的getDecorView()方法返回的DecorView被用来作为顶层视图添加到WM中。

创建时机: ActivityThread.handleLaunchActivity ---> ActivityThread.performLaunchActivity --->Activity.attach

WindowManager、WindowManagerImpl、WindowManagerGlobal

WindowManager与一个特定的Display相关联

WindowManagerService

对系统中的所有窗口进行管理。WindowManager是运行在Application process中的, WindowManagerService是在system_server进程中运行, 两者的通信是通过中间的会话层IWindowSession来进行的。

添加一个根View到WindowManager中

{
    final WindowManager wm = (WindowManager)getSystemService(Context.WINDOW_SERVICE);
    WindowManager.LayoutParams lp = new WindowManager.LayoutParams(
                wm.getDefaultDisplay().getWidth(),wm.getDefaultDisplay().getHeight());
    lp.type = WindowManager.LayoutParams.TYPE_APPLICATION;
    lp.flags = WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE;
    lp.format = PixelFormat.TRANSLUCENT;
    wm.addView(maskView, lp);
}

相关类简化结构

public class PhoneWindow extends Window{
    private DecorView mDecor;
}

public interface ViewManager{
    public void addView(View view, ViewGroup.LayoutParams params);
    public void updateViewLayout(View view, ViewGroup.LayoutParams params);
    public void removeView(View view);
}

public interface WindowManager extends ViewManager {
    public static class LayoutParams extends ViewGroup.LayoutParams{
        //X position for this window
        public int x;
        public int y;
        public int type;
        public int flags;
    }
}

public final class WindowManagerImpl implements WindowManager {
    private final WindowManagerGlobal mGlobal = WindowManagerGlobal.getInstance();
    private final Display mDisplay;
    
    public void addView(@NonNull View view, @NonNull ViewGroup.LayoutParams params) {
        mGlobal.addView(view, params, mDisplay, mParentWindow);
    }
}


public final class WindowManagerGlobal {
    //表示View树的根节点
    private final ArrayList<View> mViews = new ArrayList<View>();
    //表示ViewRootImpl,一个根view对应一个ViewRootImpl
    private final ArrayList<ViewRootImpl> mRoots = new ArrayList<ViewRootImpl>();
    //表示根view的WindowManager.LayoutParams
    private final ArrayList<WindowManager.LayoutParams> mParams = new ArrayList<WindowManager.LayoutParams>();
            
    public void addView(View view, ViewGroup.LayoutParams params,Display display, Window parentWindow) {

         final WindowManager.LayoutParams wparams = (WindowManager.LayoutParams) params;
         ...
         ViewRootImpl root = new ViewRootImpl(view.getContext(), display);
         view.setLayoutParams(wparams);
        mViews.add(view);
        mRoots.add(root);
        mParams.add(wparams);
        ...
        //通过ViewRootImpl来更新界面并完成Window的添加过程
        root.setView(view, wparams, panelParentView);
    }
}


public final class ViewRootImpl implements ViewParent{
    
   public void setView(View view, WindowManager.LayoutParams attrs, View panelParentView) {
           //1、完成异步刷新请求，重绘界面
           requestLayout();
           ...
           //2、通过WindowSession最终完成window的添加过程, WindowSession内部通过WindowManagerService来实现Window的添加
           int res = mWindowSession.addToDisplay(mWindow, mSeq, mWindowAttributes,
                            getHostVisibility(), mDisplay.getDisplayId(),
                            mAttachInfo.mContentInsets, mAttachInfo.mStableInsets,
                            mAttachInfo.mOutsets, mInputChannel);
   }
}

Window的创建过程

Activity对应的PhoneWindow创建过程及添加时机

首先看下ActivityThead中的两个重要的方法：
       performLaunchActivity( );
       handleResumeActivity( );
创建时机：

在performLaunchActivity中，会调用activity.attach方法建立一个window。

Activity的View附属到Window上：setContentView()

添加时机：

在handleResumeActivity方法中启动activity的时候，首先会调用Activity的onResume方法，>接着调用Activity的makeVisible方法,在该方法中将主窗口加入到WindowManager中

代码如下：

void makeVisible() {
    if (!mWindowAdded) {
        ViewManager wm = getWindowManager();
        wm.addView(mDecor, getWindow().getAttributes());//实际上是把主窗口的顶级view加入到WindowMangaer
        mWindowAdded = true;
    }
    mDecor.setVisibility(View.VISIBLE);
}

Dialog的Window创建过程

创建窗口：构造函数中
初始化DecorView并将Dialog的View添加到DecorView中：setContentView（）
将DecorView添加到Window中并显示：show（）

public class Dialog implements DialogInterface, ... {
    
    Dialog(Context context,int themeResId, boolean createContextThemeWrapper) {
        if (createContextThemeWrapper) {
            mContext = new ContextThemeWrapper(context, themeResId);
        } else {
            mContext = context;
        }
    
        mWindowManager = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
    
        final Window w = new PhoneWindow(mContext);
        mWindow = w;
        w.setCallback(this);
        w.setOnWindowDismissedCallback(this);
        w.setWindowManager(mWindowManager, null, null);
        w.setGravity(Gravity.CENTER);
    
        mListenersHandler = new ListenersHandler(this);
    }
    
    public void setContentView(@LayoutRes int layoutResID) {
        mWindow.setContentView(layoutResID);
    }
    public void show() {
        mDecor = mWindow.getDecorView();
        mWindowManager.addView(mDecor, l);
    }
}

Window添加过程

实际上是根视图的添加过程，在WindowManager层已经没有Window的概念，Window的概念存在于UI层，是对于Activity、Dialog、Toast等而言的。

WindowManager.addView()：调用2
WindowManagerGlobal.addView():
1. 创建ViewRootImpl
2. 调用3
ViewRootImpl.setView()：
1. requestLayout()
2. mWindowSession.addToDisplay

总结

通过WindowManager.addView(View view, ViewGroup.LayoutParams params)可以看到：Window是一个抽象的概念，它以View的形式存在（不同于PhoneWindow，该Window是顶层View样式和行为的抽象类）,但同时Activity、Dialog、Toast等又必须通过Window与View建立关联。根View一一对应ViewRootImpl，WindowManager内部通过ViewRootImpl进行Window（即根View）的添加、删除、更新，而ViewRootImpl内部通过WindowSession和WindowManagerService通信，最终WindowManagerService完成根View的添加、删除、更新。

Android中的Activity、Dialog、Toast、PopupWindow、菜单、状态栏都是通过Window来实现对应的View的，视图都对应一个Window。

从WmS的角度看，一个窗口并不是Window类，而是一个View类

参考：
http://blog.csdn.net/geloin/article/details/42779025