深入理解WMS(四):从WMS的角度分析Activity之间的关系

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system_server_AMS类图.png

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Activity_Window_相关类图.png

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system_server_AMS类图.png

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总体类图.png

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流程图.png

一、相关概念
1、ActivityThread:为应用程序的主线程类,所有的APK程序都有且仅有一个ActivityThread,程序的入口为该类static main()函数
Activity:Activity包含一个Window,该Window在Activity的attach方法中通过调用new PhoneWindow()创建一个window;
2、PhoneWindow:继承Window类,是把一个FrameLayout进行一定的包装,并提供了一组通用的窗口操作接口,内部包含一个DecorView
3、View:最基本的UI组件,表示屏幕上的一个矩形区域;
4、DecorView:该类是一个 FrameLayout 的子类,并且是 PhoneWindow 中的一个内部类。Decor的英文是 Decoration,即“修饰”的意思,DecorView 就是对普通的 FrameLayout 进行了一定的修饰,比如添加一个通用的 Title bar,并响应特定的按键消息等。;
5、Window:表示顶层窗口,管理界面的显示和事件的响应;每个Activity 均会创建一个PhoneWindow对象,是Activity和整个View系统交互的接口,该类提供了一组通用的窗口(Window)操作 API,这里的窗口仅仅是程序层面上的,WMS 所管理的窗口并不是 Window 类,而是一个 View 或者 ViewGroup 类,一般就是指DecorView 类,即一个 DecorView 就是 WmS 所管理的一个窗口。Window 是一个 abstract 类型。
6、WindowManager:一个interface,继承自ViewManager。所在应用进程的窗口管理器;有一个implementation WindowManagerImpl;
主要用来管理窗口的一些状态、属性、view增加、删除、更新、窗口顺序、消息收集和处理等。
7、ViewRootImpl:通过IWindowSession接口与全局窗口管理器进行交互:界面控制和消息响应;WMS 管理客户端窗口时,需要通知客户端进行某种操作,这些都是通过异步消息完成的
二、步骤
Step1:
当启动Activity时,system_server进程通过AMS(ActivityManagerService)的远程代理ApplicationThreadProxy(即应用进程的Binder,IApplicationThread)的scheduleLaunchActivit(),标示SCHEDULE_LAUNCH_ACTIVITY_TRANSACTION,底层binder驱动启动应用进程XXXActivity,到应用进程的ActivityThread的内部类ApplicationThread的父类ApplicationNative的onTransact,再到scheduleLaunchActivity().
Step2:
ApplicationThread的scheduleLaunchActivity:通过sendMessage(H.LAUNCH_ACTIVITY, r),发到UI线程的ActivityThread 的H处理即handleLaunchActivity:
ActivityThread.java

    public final class ActivityThread {
      private void handleLaunchActivity(ActivityClientRecord r, Intent customIntent, String reason) {
        // Initialize before creating the activity
        WindowManagerGlobal.initialize();
        Activity a = performLaunchActivity(r, customIntent);
        if (a != null) {
            r.createdConfig = new Configuration(mConfiguration);
            reportSizeConfigurations(r);
            Bundle oldState = r.state;
            handleResumeActivity(r.token, false, r.isForward,
                    !r.activity.mFinished && !r.startsNotResumed, r.lastProcessedSeq, reason);
        ...
        } 
    }
}

其中WindowManagerGlobal.initialize;是先取到WMS(WindowManagerService)的远程代理IWindowManager

WindowManagerGlobal.java

public final class WindowManagerGlobal {
    public static void initialize() {
        getWindowManagerService();
    }
    public static IWindowManager getWindowManagerService() {
        synchronized (WindowManagerGlobal.class) {
            if (sWindowManagerService == null) {
                sWindowManagerService = IWindowManager.Stub.asInterface(
                        ServiceManager.getService("window"));
                try {
                    sWindowManagerService = getWindowManagerService();
                    ValueAnimator.setDurationScale(sWindowManagerService.getCurrentAnimatorScale());
                } catch (RemoteException e) {
                    throw e.rethrowFromSystemServer();
                }
            }
            return sWindowManagerService;
        }
    }
}

Activity a = performLaunchActivity(r, customIntent);使用ClassLoader加载XXXActivity,这其中会创建ContextImpl、如果Application还没启动过,会先把Applicaition创建并onCreate,然后调用XXXActivity的attach();
在attach中:会创建改activity的对应的window即PhoneWindow,以及phoneWindow和WindowManagerImpl关联:
Activity:

final void attach(Context context, ActivityThread aThread,
            Instrumentation instr, IBinder token, int ident,
            Application application, Intent intent, ActivityInfo info,
            CharSequence title, Activity parent, String id,
            NonConfigurationInstances lastNonConfigurationInstances,
            Configuration config, String referrer, IVoiceInteractor voiceInteractor,
            Window window) {
        attachBaseContext(context);
        mFragments.attachHost(null /*parent*/);
        mWindow = new PhoneWindow(this, window);
        mWindow.setWindowControllerCallback(this);
        mWindow.setCallback(this);
        mWindow.setOnWindowDismissedCallback(this);
        mWindow.getLayoutInflater().setPrivateFactory(this);
        mMainThread = aThread;
        mInstrumentation = instr;
        mWindow.setWindowManager(
                (WindowManager)context.getSystemService(Context.WINDOW_SERVICE),
                mToken, mComponent.flattenToString(),
                (info.flags & ActivityInfo.FLAG_HARDWARE_ACCELERATED) != 0);
        if (mParent != null) {
            mWindow.setContainer(mParent.getWindow());
        }
        mWindowManager = mWindow.getWindowManager();
        mCurrentConfig = config;
}

其中:(WindowManager)context.getSystemService(Context.WINDOW_SERVICE)获取到是WindowManagerImpl:
这边会走到ContextImpl.getSystemService:

class ContextImpl extends Context {   
  @Override
    public Object getSystemService(String name) {
        return SystemServiceRegistry.getSystemService(this, name);
    }
}

SystemServiceRegistry:

final class SystemServiceRegistry {
  public static Object getSystemService(ContextImpl ctx, String name) {
        ServiceFetcher<?> fetcher = SYSTEM_SERVICE_FETCHERS.get(name);
        return fetcher != null ? fetcher.getService(ctx) : null;
    }
  private static final HashMap<Class<?>, String> SYSTEM_SERVICE_NAMES =
            new HashMap<Class<?>, String>();
    private static final HashMap<String, ServiceFetcher<?>> SYSTEM_SERVICE_FETCHERS =
            new HashMap<String, ServiceFetcher<?>>();
    private static int sServiceCacheSize;
    static {
        registerService(Context.ACCESSIBILITY_SERVICE, AccessibilityManager.class,
                new CachedServiceFetcher<AccessibilityManager>() {
            @Override
            public AccessibilityManager createService(ContextImpl ctx) {
                return AccessibilityManager.getInstance(ctx);
            }});
    registerService(Context.WINDOW_SERVICE, WindowManager.class,
                new CachedServiceFetcher<WindowManager>() {
            @Override
            public WindowManager createService(ContextImpl ctx) {
                return new WindowManagerImpl(ctx);
            }});
}

返回是new WindowManagerImpl(ctx);在performLaunchActivity函数中,走完attach后,继续调用mInstrumentation.callActivityOnCreate去实行XXXActivity的onCreate,这时候大家会写setContentView(R.layout.xxx)
Step3:
Activity.setContentView():
会调用getWindow().setContentView(layoutResID),即PhoneWindow类中的setContentView:主要是在PhoneWindow创建DecorView mDecor(This is the top-level view of the window, containing the window decor),然后从mDecor找出android.R.id.content: mContentParent(ViewGroup), 然后把activity设置的View添加到mContentParent.addView(view, params);

public void setContentView(@LayoutRes int layoutResID) {
        getWindow().setContentView(layoutResID);
        initWindowDecorActionBar();
}

PhoneWindow:

public class PhoneWindow extends Window implements MenuBuilder.Callback {
  public void setContentView(int layoutResID) {
        
        if (mContentParent == null) {
            installDecor();
        } else if (!hasFeature(FEATURE_CONTENT_TRANSITIONS)) {
            mContentParent.removeAllViews();
        }

        if (hasFeature(FEATURE_CONTENT_TRANSITIONS)) {
            final Scene newScene = Scene.getSceneForLayout(mContentParent, layoutResID,
                    getContext());
            transitionTo(newScene);
        } else {
            mLayoutInflater.inflate(layoutResID, mContentParent);
        }
        mContentParent.requestApplyInsets();
        final Callback cb = getCallback();
        if (cb != null && !isDestroyed()) {
            cb.onContentChanged();
        }
        mContentParentExplicitlySet = true;
    }
}

Step4:
在ActivitThread.handleLaunchActivity函数走完performLaunchActivity后,接着走handleResumeActivity函数中,显示启动r = performResumeActivity(token, clearHide, reason);去走XXXActivity的onResume。
接着会对Activity的对应的window设置窗口类型:l.type = WindowManager.LayoutParams.TYPE_BASE_APPLICATION,WMS是对窗口进行操作,每个activity对应一个窗口,Framework会定义好几种窗口类型,比如系统Window、应用程序window、子Window等。这边的type类型很重要,没有这个,window显示不出来的。
接着会调用到ViewManager wm = a.getWindowManager();wm.addView(decor, l);走到WindowManagerImpl.addView:
ActivityThread:

final void handleResumeActivity(IBinder token,
            boolean clearHide, boolean isForward, boolean reallyResume, int seq, String reason) {
        ActivityClientRecord r = mActivities.get(token);
        ...
        r = performResumeActivity(token, clearHide, reason);
        ...
            if (r.window == null && !a.mFinished && willBeVisible) {
                r.window = r.activity.getWindow();
                View decor = r.window.getDecorView();
                decor.setVisibility(View.INVISIBLE);
                ViewManager wm = a.getWindowManager();
                WindowManager.LayoutParams l = r.window.getAttributes();
                a.mDecor = decor;
                l.type = WindowManager.LayoutParams.TYPE_BASE_APPLICATION;
                l.softInputMode |= forwardBit;
                if (r.mPreserveWindow) {
                    a.mWindowAdded = true;
                    r.mPreserveWindow = false;
                   
                    ViewRootImpl impl = decor.getViewRootImpl();
                    if (impl != null) {
                        impl.notifyChildRebuilt();
                    }
                }
                if (a.mVisibleFromClient && !a.mWindowAdded) {
                    a.mWindowAdded = true;
                    wm.addView(decor, l);
                }
             ...
    }

Step5:
WindowManagerImpl的addView又调用到WindowManagerGlobal.getInstance()的addView:
这个函数会创建root = new ViewRootImpl(view.getContext(), display);然后保存到mRoots.add(root)
接着调用到 root.setView(view, wparams, panelParentView);

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

public final class WindowManagerGlobal {
    public void addView(View view, ViewGroup.LayoutParams params,
            Display display, Window parentWindow) {
        ...
        ViewRootImpl root;
        View panelParentView = null;
        synchronized (mLock) {
            ...
            root = new ViewRootImpl(view.getContext(), display);
            view.setLayoutParams(wparams);
            mViews.add(view);
            mRoots.add(root);
            mParams.add(wparams);
        }
        // do this last because it fires off messages to start doing things
        try {
            root.setView(view, wparams, panelParentView);
        } catch (RuntimeException e) {
           
        }
    }
}

Step6:
ViewRootImpl.setView():
这个函数中,通过WindowManagerGloabl拿到IWindowSession mWindowSession及远程WMS的Seesion的对象,进行mWindowSession.addToDisplay,到system_server进程的Session中。

public final class ViewRootImpl implements ViewParent,
        View.AttachInfo.Callbacks, ThreadedRenderer.HardwareDrawCallbacks {
    public void setView(View view, WindowManager.LayoutParams attrs, View panelParentView) {
        synchronized (this) {
                ....
                try {
                    res = mWindowSession.addToDisplay(mWindow, mSeq, mWindowAttributes,
                            getHostVisibility(), mDisplay.getDisplayId(),
                            mAttachInfo.mContentInsets, mAttachInfo.mStableInsets,
                            mAttachInfo.mOutsets, mInputChannel);
                }            
            }
        ...
    }
}

这个mWindowSession是

public static IWindowSession getWindowSession() {
        synchronized (WindowManagerGlobal.class) {
            if (sWindowSession == null) {
                try {
                    InputMethodManager imm = InputMethodManager.getInstance();
                    IWindowManager windowManager = getWindowManagerService();
                    sWindowSession = windowManager.openSession(
                            new IWindowSessionCallback.Stub() {
                                @Override
                                public void onAnimatorScaleChanged(float scale) {
                                    ValueAnimator.setDurationScale(scale);
                                }
                            },
                            imm.getClient(), imm.getInputContext());
                } catch (RemoteException e) {
                    throw e.rethrowFromSystemServer();
                }
            }
            return sWindowSession;
        }
    }

调用到WindowManagerService的openSession方法:

public class WindowManagerService extends IWindowManager.Stub
        implements Watchdog.Monitor, WindowManagerPolicy.WindowManagerFuncs {
   @Override
    public IWindowSession openSession(IWindowSessionCallback callback, IInputMethodClient client,
            IInputContext inputContext) {
        if (client == null) throw new IllegalArgumentException("null client");
        if (inputContext == null) throw new IllegalArgumentException("null inputContext");
        Session session = new Session(this, callback, client, inputContext);
        return session;
    }
}

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