前言

一直想要分析一下surface 的创建到SurfaceFlinger之间的关系，由于它们之间牵扯的东西比较多，终于感觉理的差不多了，记录一下。
一个应用想要完成一个View的显示大致需要以下三部
1、应用需要先和SurfaceFlinger建立通道，及连接SurfaceFlinger 拿到SurfaceFlinger 的远端代理。
2、向SurfaceFlinger申请去创建Surface。
3、注册Vsync，等待向Surface里面绘制内容, 然后SurfaceFlinger 通过软件合成或者硬件合成，最后显示在屏幕上。
所以后面大概会围绕这三部进行分析

一、Activity 连接 SurfaceFlinger

应用的启动流程，我们这里不做具体的分析。
大致了解luancher 点击图标去启动应用后,
1、luancher会调用ActivityManagerService的startActivity() 接口，请求去启动一个activity。
2、ActivityManagerService会通过Socket去连接到Zegote，Zegote会为将要启动的应用fork一个进程。
3、然后启动这个进程的时候会调用到ActivityThread的
zygote会fork一个子进程作为APP对应的进程handleLaunchActivity() 接口。

开始时候给一些用的到的类下个定义，方便后面梳理代码
View：作为所有图形的基类。
ViewGroup:对View继承扩展为视图容器类。
Window:它概括了Android窗口的基本属性和基本功能。(抽象类)
PhoneWindow:Window的子类。
DecorView：界面的根View，PhoneWindow的内部类。
ViewRootImpl:ViewRoot是GUI管理系统与GUI呈现系统之间的桥梁。

我们后面的详细分析就从这个地方开始
frameworks/base/core/java/android/app/ActivityThread.java

/**
     * Extended implementation of activity launch. Used when server requests a launch or relaunch.
     */
    @Override
    public Activity handleLaunchActivity(ActivityClientRecord r,
            PendingTransactionActions pendingActions, Intent customIntent) {
        // If we are getting ready to gc after going to the background, well
        // we are back active so skip it.
        unscheduleGcIdler();
        mSomeActivitiesChanged = true;

        if (r.profilerInfo != null) {
            mProfiler.setProfiler(r.profilerInfo);
            mProfiler.startProfiling();
        }

        // Make sure we are running with the most recent config.
        handleConfigurationChanged(null, null);

        if (localLOGV) Slog.v(
            TAG, "Handling launch of " + r);

        // Initialize before creating the activity
        if (!ThreadedRenderer.sRendererDisabled) {
            GraphicsEnvironment.earlyInitEGL();
        }
        WindowManagerGlobal.initialize();

        final Activity a = performLaunchActivity(r, customIntent);
        ... ...

我们看到从handleLaunchActivity（）方法进入到了 performLaunchActivity（）里面，而 performLaunchActivity（）注释是 activity启动的实现核心。

/**  Core implementation of activity launch. */
    private Activity performLaunchActivity(ActivityClientRecord r, Intent customIntent) {
    	// 获的packageInfo，是为了后面从 packageInfo对象拿到Application
        ActivityInfo aInfo = r.activityInfo;
        if (r.packageInfo == null) {
            r.packageInfo = getPackageInfo(aInfo.applicationInfo, r.compatInfo,
                    Context.CONTEXT_INCLUDE_CODE);
        }

		// 获得ComponentName，是为了后面New Activity是做参数的
        ComponentName component = r.intent.getComponent();
        if (component == null) {
            component = r.intent.resolveActivity(
                mInitialApplication.getPackageManager());
            r.intent.setComponent(component);
        }

        if (r.activityInfo.targetActivity != null) {
            component = new ComponentName(r.activityInfo.packageName,
                    r.activityInfo.targetActivity);
        }

        ContextImpl appContext = createBaseContextForActivity(r);
        Activity activity = null;
        try {
            java.lang.ClassLoader cl = appContext.getClassLoader();
            // 得到activity 对象 为了后面调用activity的 attach方法
            activity = mInstrumentation.newActivity(
                    cl, component.getClassName(), r.intent);
            StrictMode.incrementExpectedActivityCount(activity.getClass());
            r.intent.setExtrasClassLoader(cl);
            r.intent.prepareToEnterProcess();
            if (r.state != null) {
                r.state.setClassLoader(cl);
            }
        } catch (Exception e) {
            if (!mInstrumentation.onException(activity, e)) {
                throw new RuntimeException(
                    "Unable to instantiate activity " + component
                    + ": " + e.toString(), e);
            }
        }

        try {
            // app 后面attch方法的参数
            Application app = r.packageInfo.makeApplication(false, mInstrumentation);

            if (localLOGV) Slog.v(TAG, "Performing launch of " + r);
            if (localLOGV) Slog.v(
                    TAG, r + ": app=" + app
                    + ", appName=" + app.getPackageName()
                    + ", pkg=" + r.packageInfo.getPackageName()
                    + ", comp=" + r.intent.getComponent().toShortString()
                    + ", dir=" + r.packageInfo.getAppDir());

            if (activity != null) {
                CharSequence title = r.activityInfo.loadLabel(appContext.getPackageManager());
                Configuration config = new Configuration(mCompatConfiguration);
                if (r.overrideConfig != null) {
                    config.updateFrom(r.overrideConfig);
                }
                if (DEBUG_CONFIGURATION) Slog.v(TAG, "Launching activity "
                        + r.activityInfo.name + " with config " + config);
                Window window = null;
                if (r.mPendingRemoveWindow != null && r.mPreserveWindow) {
                    window = r.mPendingRemoveWindow;
                    r.mPendingRemoveWindow = null;
                    r.mPendingRemoveWindowManager = null;
                }
                appContext.setOuterContext(activity);
                // 与phonewindow建立关系。并做一些初始准备
                activity.attach(appContext, this, getInstrumentation(), r.token,
                        r.ident, app, r.intent, r.activityInfo, title, r.parent,
                        r.embeddedID, r.lastNonConfigurationInstances, config,
                        r.referrer, r.voiceInteractor, window, r.configCallback);

                if (customIntent != null) {
                    activity.mIntent = customIntent;
                }
                r.lastNonConfigurationInstances = null;
                checkAndBlockForNetworkAccess();
                activity.mStartedActivity = false;
                int theme = r.activityInfo.getThemeResource();
                if (theme != 0) {
                    activity.setTheme(theme);
                }

                activity.mCalled = false;
                if (r.isPersistable()) {
                    mInstrumentation.callActivityOnCreate(activity, r.state, r.persistentState);
                } else {

//回调activity的OnCreate的方法                   
mInstrumentation.callActivityOnCreate(activity, r.state);
                }
                if (!activity.mCalled) {
                    throw new SuperNotCalledException(
                        "Activity " + r.intent.getComponent().toShortString() +
                        " did not call through to super.onCreate()");
                }
                r.activity = activity;
            }
            r.setState(ON_CREATE);

            mActivities.put(r.token, r);

        } catch (SuperNotCalledException e) {
            throw e;

        } catch (Exception e) {
            if (!mInstrumentation.onException(activity, e)) {
                throw new RuntimeException(
                    "Unable to start activity " + component
                    + ": " + e.toString(), e);
            }
        }

        return activity;
    }

frameworks/base/core/java/android/app/Activity.java
attch方法主要创建了PhoneWindow对象、调用setCallback设置回调、调用了setWindowManager设置窗口管理者

    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, ActivityConfigCallback activityConfigCallback) {
        attachBaseContext(context);

        mFragments.attachHost(null /*parent*/);
		// new 出来 PhoneWindow
        mWindow = new PhoneWindow(this, window, activityConfigCallback);
        mWindow.setWindowControllerCallback(this);
        mWindow.setCallback(this);
        mWindow.setOnWindowDismissedCallback(this);
        mWindow.getLayoutInflater().setPrivateFactory(this);
        if (info.softInputMode != WindowManager.LayoutParams.SOFT_INPUT_STATE_UNSPECIFIED) {
            mWindow.setSoftInputMode(info.softInputMode);
        }
        if (info.uiOptions != 0) {
            mWindow.setUiOptions(info.uiOptions);
        }
        mUiThread = Thread.currentThread();

        mMainThread = aThread;
        mInstrumentation = instr;
        mToken = token;
        mIdent = ident;
        mApplication = application;
        mIntent = intent;
        mReferrer = referrer;
        mComponent = intent.getComponent();
        mActivityInfo = info;
        mTitle = title;
        mParent = parent;
        mEmbeddedID = id;
        mLastNonConfigurationInstances = lastNonConfigurationInstances;
        if (voiceInteractor != null) {
            if (lastNonConfigurationInstances != null) {
                mVoiceInteractor = lastNonConfigurationInstances.voiceInteractor;
            } else {
                mVoiceInteractor = new VoiceInteractor(voiceInteractor, this, this,
                        Looper.myLooper());
            }
        }
      //创建了一个WindowManagerImpl对象，因此Activity的mWindowManager成员变量就是WindowManagerImpl对象，后面调用addView方法就用的这个mWindowManager对象
        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;

        mWindow.setColorMode(info.colorMode);

        setAutofillCompatibilityEnabled(application.isAutofillCompatibilityEnabled());
        enableAutofillCompatibilityIfNeeded();
    }```

attch() 方法调用后，就会调用 mInstrumentation.callActivityOnCreate()  方法去回调activity的 onCreate() 方法。

我们MainActivity一般会重写 onCreate方法调用setContentView去加载layout，

```cpp
 @Override
	protected void onCreate(Bundle arg0) {
		super.onCreate(arg0);
		//加载布局信息
		setContentView(R.layout.my_activity);
	}

frameworks/base/core/java/android/app/Activity.java

    public void setContentView(@LayoutRes int layoutResID) {
    	// 这里的window就是我们上面在attch方法里面new 出来的 PhoneWindow
        getWindow().setContentView(layoutResID);
        initWindowDecorActionBar();
    }

frameworks/base/core/java/com/android/internal/policy/PhoneWindow.java

    @Override
    public void setContentView(int layoutResID) {
        // Note: FEATURE_CONTENT_TRANSITIONS may be set in the process of installing the window
        // decor, when theme attributes and the like are crystalized. Do not check the feature
        // before this happens.
        if (mContentParent == null) {
        //创建DecorView
            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 {
        // 加载UI布局
            mLayoutInflater.inflate(layoutResID, mContentParent);
        }
        mContentParent.requestApplyInsets();
        final Callback cb = getCallback();
        if (cb != null && !isDestroyed()) {
            cb.onContentChanged();
        }
        mContentParentExplicitlySet = true;
    }

等上面decoView 获得、UI布局资源加载之后，就会又回到
handleResumeActivity（）方法里面，调用activity的 makeVisible()方法。

    public void handleResumeActivity(IBinder token, boolean finalStateRequest, boolean isForward,
            String reason) {
   ... ...
               if (r.activity.mVisibleFromClient) {
                r.activity.makeVisible();
            }
   ... ...
 }

frameworks/base/core/java/android/app/Activity.java

    void makeVisible() {
        if (!mWindowAdded) {
        // 调用 windowManagerImpl里面的 addView
        // windowManagerImpl 继承自 WindowManager, WindowManager 继承自 ViewManager
            ViewManager wm = getWindowManager();
            wm.addView(mDecor, getWindow().getAttributes());
            mWindowAdded = true;
        }
        mDecor.setVisibility(View.VISIBLE);
    }

从这个开始才正式来到我们的Window 相关的。
上面 wm.addView 会调到 windowManagerImpl的 addView
frameworks/base/core/java/android/view/WindowManagerImpl.java

    @Override
    public void addView(@NonNull View view, @NonNull ViewGroup.LayoutParams params) {
        applyDefaultToken(params);
        // mGlobal 是 WindowManagerGlobal对象
        mGlobal.addView(view, params, mContext.getDisplay(), mParentWindow);
    }f

frameworks/base/core/java/android/view/WindowManagerGlobal.java

   // 参数1、view 就是上面传下来的doctView , 
   // 参数2、这个也是前面带下来的
   // 参数3、这个display是mContext里面的，但是mContext具体从哪里赋值的没有摸清楚，不是重点先不管了。
   // 参数4、parentWindow 在我们创建activity.java 中调用 phoneWindow的父类的setWindowManager的时候调用到了 WindowManagerImpl的createLocalWindowManager，这里的 parentWindow就是phoneWindow 
    public void addView(View view, ViewGroup.LayoutParams params,
            Display display, Window parentWindow) {

        if (view == null) {
            throw new IllegalArgumentException("view must not be null");
        }
        if (display == null) {
            throw new IllegalArgumentException("display must not be null");
        }
        if (!(params instanceof WindowManager.LayoutParams)) {
            throw new IllegalArgumentException("Params must be WindowManager.LayoutParams");
        }



        final WindowManager.LayoutParams wparams = (WindowManager.LayoutParams) params;
        if (parentWindow != null) {
            Slog.e("WindowManager", " parentWindow != null" );
            parentWindow.adjustLayoutParamsForSubWindow(wparams);
        } else {
            // If there's no parent, then hardware acceleration for this view is
            // set from the application's hardware acceleration setting.
            final Context context = view.getContext();
            if (context != null
                    && (context.getApplicationInfo().flags
                            & ApplicationInfo.FLAG_HARDWARE_ACCELERATED) != 0) {
                wparams.flags |= WindowManager.LayoutParams.FLAG_HARDWARE_ACCELERATED;
            }
        }

       // 虽然DecorView已经被创建出来了，但是目前DecorView跟PhoneWindow是没有任何关系的。
       // 大家思考一个问题，DecorView是怎么添加到PhoneWindow上面的？ 其实就是这个ViewRootImpl 串起来的
        ViewRootImpl root;
        View panelParentView = null;

        synchronized (mLock) {
            // Start watching for system property changes.
            if (mSystemPropertyUpdater == null) {
                mSystemPropertyUpdater = new Runnable() {
                    @Override public void run() {
                        synchronized (mLock) {
                            for (int i = mRoots.size() - 1; i >= 0; --i) {
                                mRoots.get(i).loadSystemProperties();
                            }
                        }
                    }
                };
                SystemProperties.addChangeCallback(mSystemPropertyUpdater);
            }

            int index = findViewLocked(view, false);
            if (index >= 0) {
                if (mDyingViews.contains(view)) {
                    // Don't wait for MSG_DIE to make it's way through root's queue.
                    mRoots.get(index).doDie();
                } else {
                    throw new IllegalStateException("View " + view
                            + " has already been added to the window manager.");
                }
                // The previous removeView() had not completed executing. Now it has.
            }

            // If this is a panel window, then find the window it is being
            // attached to for future reference.
            if (wparams.type >= WindowManager.LayoutParams.FIRST_SUB_WINDOW &&
                    wparams.type <= WindowManager.LayoutParams.LAST_SUB_WINDOW) {
                final int count = mViews.size();
                for (int i = 0; i < count; i++) {
                    if (mRoots.get(i).mWindow.asBinder() == wparams.token) {
                        panelParentView = mViews.get(i);
                    }
                }
            }

            // 看看new ViewRootImpl做了什么 	
            root = new ViewRootImpl(view.getContext(), display);
            view.setLayoutParams(wparams);

           //Window所对应的view
            mViews.add(view);
            //Window所对应的ViewRootImpl
            mRoots.add(root);
            //Window所对应的布局参数
            mParams.add(wparams);

            // do this last because it fires off messages to start doing things
            try {
                // 在这里会调用 ViewROotImpl的setView
                root.setView(view, wparams, panelParentView);
                Slog.e("WindowManager"," root.setView end" );
            } catch (RuntimeException e) {
                // BadTokenException or InvalidDisplayException, clean up.
                if (index >= 0) {
                    removeViewLocked(index, true);
                }
                throw e;
            }
        }
    }

frameworks/base/core/java/android/view/ViewRootImpl.java

... ...
在创建ViewRootImpl的时候还会创建一个Surface,注意这个Surface还是没有任何数据的，后面会进行赋值
public final Surface mSurface = new Surface();
... ...
public ViewRootImpl(Context context, Display display) {
        mContext = context;
        // 注意整个windowSession, 它是从windowManagerService中的openSession() 得来的
        mWindowSession = WindowManagerGlobal.getWindowSession();
        mDisplay = display;
        mBasePackageName = context.getBasePackageName();
        mThread = Thread.currentThread();
        mLocation = new WindowLeaked(null);
        mLocation.fillInStackTrace();
        mWidth = -1;
        mHeight = -1;
        mDirty = new Rect();
        mTempRect = new Rect();
        mVisRect = new Rect();
        mWinFrame = new Rect();
        mWindow = new W(this);
        mTargetSdkVersion = context.getApplicationInfo().targetSdkVersion;
        mViewVisibility = View.GONE;
        mTransparentRegion = new Region();
        mPreviousTransparentRegion = new Region();
        mFirst = true; // true for the first time the view is added
        mAdded = false;
        mAttachInfo = new View.AttachInfo(mWindowSession, mWindow, display, this, mHandler, this,
                context);
        mAccessibilityManager = AccessibilityManager.getInstance(context);
        mAccessibilityManager.addAccessibilityStateChangeListener(
                mAccessibilityInteractionConnectionManager, mHandler);
        mHighContrastTextManager = new HighContrastTextManager();
        mAccessibilityManager.addHighTextContrastStateChangeListener(
                mHighContrastTextManager, mHandler);
        mViewConfiguration = ViewConfiguration.get(context);
        mDensity = context.getResources().getDisplayMetrics().densityDpi;
        mNoncompatDensity = context.getResources().getDisplayMetrics().noncompatDensityDpi;
        mFallbackEventHandler = new PhoneFallbackEventHandler(context);
        mChoreographer = Choreographer.getInstance();
        mDisplayManager = (DisplayManager)context.getSystemService(Context.DISPLAY_SERVICE);

        if (!sCompatibilityDone) {
            sAlwaysAssignFocus = mTargetSdkVersion < Build.VERSION_CODES.P;

            sCompatibilityDone = true;
        }

        loadSystemProperties();
    }

frameworks/base/core/java/android/view/WindowManagerGlobal.java

    public static IWindowSession getWindowSession() {
        synchronized (WindowManagerGlobal.class) {
            if (sWindowSession == null) {
                try {
                    InputMethodManager imm = InputMethodManager.getInstance();
                    IWindowManager windowManager = getWindowManagerService();
                    // windowManager  就是 windowManagerService 
                    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;
        }
    }f

frameworks/base/services/core/java/com/android/server/wm/WindowManagerService.java

    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");
        // 后面在ViewRootImpl的setView() 调用 Session的addDisplay
        Session session = new Session(this, callback, client, inputContext);
        return session;
    }

frameworks/base/core/java/android/view/ViewRootImpl.java

public void setView(View view, WindowManager.LayoutParams attrs, View panelParentView) {
... ...
                    res = mWindowSession.addToDisplay(mWindow, mSeq, mWindowAttributes,
                            getHostVisibility(), mDisplay.getDisplayId(), mWinFrame,
                            mAttachInfo.mContentInsets, mAttachInfo.mStableInsets,
                            mAttachInfo.mOutsets, mAttachInfo.mDisplayCutout, mInputChannel);
... ...
}

frameworks/base/services/core/java/com/android/server/wm/Session.java


    @Override
    public int addToDisplay(IWindow window, int seq, WindowManager.LayoutParams attrs,
            int viewVisibility, int displayId, Rect outFrame, Rect outContentInsets,
            Rect outStableInsets, Rect outOutsets,
            DisplayCutout.ParcelableWrapper outDisplayCutout, InputChannel outInputChannel) {
        return mService.addWindow(this, window, seq, attrs, viewVisibility, displayId, outFrame,
                outContentInsets, outStableInsets, outOutsets, outDisplayCutout, outInputChannel);
    }

frameworks/base/services/core/java/com/android/server/wm/WindowManagerService.java

    public int addWindow(Session session, IWindow client, int seq,
            LayoutParams attrs, int viewVisibility, int displayId, Rect outFrame,
            Rect outContentInsets, Rect outStableInsets, Rect outOutsets,
            DisplayCutout.ParcelableWrapper outDisplayCutout, InputChannel outInputChannel) {
            
    ... ... 
            final WindowState win = new WindowState(this, session, client, token, parentWindow,
                    appOp[0], seq, attrs, viewVisibility, session.mUid,
                    session.mCanAddInternalSystemWindow);
     ... ...
     // 这里会调用 mSession.windowAddedLocked()最终会new SurfaceSession
            win.attach();
     ... ... 
    }

frameworks/base/services/core/java/com/android/server/wm/WindowState.java

    void attach() {
        if (localLOGV) Slog.v(TAG, "Attaching " + this + " token=" + mToken);
        mSession.windowAddedLocked(mAttrs.packageName);
    }

fameworks/base/services/core/java/com/android/server/wm/Session.java

    void windowAddedLocked(String packageName) {
        mPackageName = packageName;
        mRelayoutTag = "relayoutWindow: " + mPackageName;
        if (mSurfaceSession == null) {
            if (WindowManagerService.localLOGV) Slog.v(
                TAG_WM, "First window added to " + this + ", creating SurfaceSession");
                // 终于看到了new SurfaceSession
            mSurfaceSession = new SurfaceSession();
            if (SHOW_TRANSACTIONS) Slog.i(
                    TAG_WM, "  NEW SURFACE SESSION " + mSurfaceSession);
            mService.mSessions.add(this);
            if (mLastReportedAnimatorScale != mService.getCurrentAnimatorScale()) {
                mService.dispatchNewAnimatorScaleLocked(this);
            }
        }
        mNumWindow++;
    }

    /** Create a new connection with the surface flinger. */
    // 注释就告诉我们了，去创建和 SurfaceFlinger连接
    public SurfaceSession() {
        mNativeClient = nativeCreate();
    }

frameworks/base/core/jni/android_view_SurfaceSession.cpp

static jlong nativeCreate(JNIEnv* env, jclass clazz) {
// 每一个应用被创建的时候都会去和surfaceFlinger进行连接
// 交代一个事情，一个应用可以持有多个surfaceFlinger的远端代理及多次连接，应用持有surfaceFlinger的远端代理的数量及连接次数和window有关，应用add几个window就连接多少次。
    SurfaceComposerClient* client = new SurfaceComposerClient();
    client->incStrong((void*)nativeCreate);
    return reinterpret_cast<jlong>(client);
}