Android8.0 图形引擎与窗体管理服务

版权声明：未经本人同意，不得转载 https://blog.csdn.net/u013928208/article/details/83027650

以上四篇从图形引擎的硬件抽象层，数据驱动，渲染，输出等方面来看Android的图形引擎，从引擎的输入这一角度来看，引擎数据输入端主要有UI, Camera, Media 等，今天我们从UI的角度来看，以Activity的setContentView为切入点，贯穿PhoneWindow, ViewRootImpl, WindowManager, WindowManagerService,直到引擎入口SufaceComposerClient和Surface。

1. RootView的创建

frameworks\base\core\java\android\app\Activity.java
在Activity的onCreate()生命周期函数中调用setContentView方法

   public void setContentView(@LayoutRes int layoutResID) {
        getWindow().setContentView(layoutResID); //设置布局
        initWindowDecorActionBar();
    }

frameworks\base\core\java\com\android\internal\policy\PhoneWindow.java
PhoneWindow继承自Window类，重载了父类的setContentView方法

 @Override
    public void setContentView(int layoutResID) {
        ......
        if (mContentParent == null) {
            installDecor(); // DecorView 关联到 Window
        } 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); // 解析布局
        }
        mContentParent.requestApplyInsets();
        final Callback cb = getCallback();
        if (cb != null && !isDestroyed()) {
            cb.onContentChanged();
        }
        mContentParentExplicitlySet = true;
    }

frameworks\base\core\java\com\android\internal\policy\PhoneWindow.java
创建DecorView，添加到PhoneWindow, 并解析布局，添加到DecorView中

 private void installDecor() {
        mForceDecorInstall = false;
        if (mDecor == null) {
            mDecor = generateDecor(-1); // 生成DecorView
            mDecor.setDescendantFocusability(ViewGroup.FOCUS_AFTER_DESCENDANTS);
            mDecor.setIsRootNamespace(true);
            if (!mInvalidatePanelMenuPosted && mInvalidatePanelMenuFeatures != 0) {
                mDecor.postOnAnimation(mInvalidatePanelMenuRunnable);
            }
        } else {
            mDecor.setWindow(this); //关联 PhoneWindow 和 DecorView
        }
        if (mContentParent == null) {
            mContentParent = generateLayout(mDecor); //生成内容区

            // Set up decor part of UI to ignore fitsSystemWindows if appropriate.
            mDecor.makeOptionalFitsSystemWindows();

            final DecorContentParent decorContentParent = (DecorContentParent) mDecor.findViewById(
                    R.id.decor_content_parent);
        }
    }

frameworks\base\core\java\android\app\ActivityThread.java
Activity的onResume函数唤醒时才将解析好的View加到PhoneWindow

 final void handleResumeActivity(IBinder token,
            boolean clearHide, boolean isForward, boolean reallyResume, int seq, String reason) {
        ActivityClientRecord r = mActivities.get(token);
            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;
                    // Normally the ViewRoot sets up callbacks with the Activity
                    // in addView->ViewRootImpl#setView. If we are instead reusing
                    // the decor view we have to notify the view root that the
                    // callbacks may have changed.
                    ViewRootImpl impl = decor.getViewRootImpl();
                    if (impl != null) {
                        impl.notifyChildRebuilt();
                    }
                }
                if (a.mVisibleFromClient) {
                    if (!a.mWindowAdded) {
                        a.mWindowAdded = true;
                        wm.addView(decor, l); //调用ViewManager 的addView方法
                    } else {
                        // The activity will get a callback for this {@link LayoutParams} change
                        // earlier. However, at that time the decor will not be set (this is set
                        // in this method), so no action will be taken. This call ensures the
                        // callback occurs with the decor set.
                        a.onWindowAttributesChanged(l);
                    }
                }
            }
        }
    }

frameworks\base\core\java\android\view\WindowManagerImpl.java
WindowManagerImpl继承自WindowManager，间接继承自ViewManager

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

frameworks\base\core\java\android\view\WindowManagerGlobal.java
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); //新建

            view.setLayoutParams(wparams);

            mViews.add(view); //管理所有的View
            mRoots.add(root); //管理所有根ViewRootImpl
            mParams.add(wparams); //管理布局参数

            // do this last because it fires off messages to start doing things
            try {
                root.setView(view, wparams, panelParentView); // 设置当前根布局参数
            } catch (RuntimeException e) {
                // BadTokenException or InvalidDisplayException, clean up.
                if (index >= 0) {
                    removeViewLocked(index, true);
                }
                throw e;
            }
        }
    }

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

 public ViewRootImpl(Context context, Display display) {
        mContext = context;
        mWindowSession = WindowManagerGlobal.getWindowSession(); //获取WMS的Session
        mDisplay = display;
        mBasePackageName = context.getBasePackageName();
        mThread = Thread.currentThread();
        mLocation = new WindowLeaked(null);
        mLocation.fillInStackTrace();
        mWindow = new W(this); //绘制IWindow, 接收来自WMS的命令
        ......
}

2. 连接到WindowManagerService

frameworks\base\core\java\android\view\WindowManagerGlobal.java
连接WMS, 获取连接sWindowSession

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

frameworks\base\services\core\java\com\android\server\wm\WindowManagerService.java
返回一个Session令牌给ViewRootImpl类

 @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;
    }

3. View的绘制

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

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    public void setView(View view, WindowManager.LayoutParams attrs, View panelParentView) {
        synchronized (this) {
            if (mView == null) {
                mView = view;
                ......
				requestLayout(); //请求布局
                ......
                try {
                    mOrigWindowType = mWindowAttributes.type;
                    mAttachInfo.mRecomputeGlobalAttributes = true;
                    collectViewAttributes();
                    // mWindow 是 IWinbdow的子类 W 实例
                    res = mWindowSession.addToDisplay(mWindow, mSeq, mWindowAttributes,
                            getHostVisibility(), mDisplay.getDisplayId(),
                            mAttachInfo.mContentInsets, mAttachInfo.mStableInsets,
                            mAttachInfo.mOutsets, mInputChannel);
                } catch (RemoteException e) {
                   ......
                } finally {
                    if (restore) {
                        attrs.restore();
                    }
                }
            }
        }
    }

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

  @Override
    public void requestLayout() {
        if (!mHandlingLayoutInLayoutRequest) {
            checkThread();
            mLayoutRequested = true;
            scheduleTraversals(); //调度绘制
        }
    }

  void scheduleTraversals() {
        if (!mTraversalScheduled) {
            mTraversalScheduled = true; //打开绘制开关
            mTraversalBarrier = mHandler.getLooper().getQueue().postSyncBarrier();
            mChoreographer.postCallback(
                    Choreographer.CALLBACK_TRAVERSAL, mTraversalRunnable, null);
            if (!mUnbufferedInputDispatch) {
                scheduleConsumeBatchedInput();
            }
            notifyRendererOfFramePending();
            pokeDrawLockIfNeeded();
        }
    }
  final TraversalRunnable mTraversalRunnable = new TraversalRunnable();
  final class TraversalRunnable implements Runnable {
        @Override
        public void run() {
            doTraversal(); //执行
        }
    }

 void doTraversal() {
        if (mTraversalScheduled) {
            mTraversalScheduled = false;
            mHandler.getLooper().getQueue().removeSyncBarrier(mTraversalBarrier);

            if (mProfile) {
                Debug.startMethodTracing("ViewAncestor");
            }

            performTraversals(); // 著名的 performTraversals

            if (mProfile) {
                Debug.stopMethodTracing();
                mProfile = false;
            }
        }
    }

frameworks\base\core\java\android\view\ViewRootImpl.java — performTraversals()
performTraversals 方法太长，我们选段分析

if (!cancelDraw && !newSurface) {
            if (mPendingTransitions != null && mPendingTransitions.size() > 0) {
                for (int i = 0; i < mPendingTransitions.size(); ++i) {
                    mPendingTransitions.get(i).startChangingAnimations();
                }
                mPendingTransitions.clear();
            }

            performDraw(); //绘制
        } else {
            if (isViewVisible) {
                // Try again
                scheduleTraversals(); //重试
            } else if (mPendingTransitions != null && mPendingTransitions.size() > 0) {
                for (int i = 0; i < mPendingTransitions.size(); ++i) {
                    mPendingTransitions.get(i).endChangingAnimations();
                }
                mPendingTransitions.clear();
            }
        }

        mIsInTraversal = false;

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

 private void performDraw() {
        .....
        final boolean fullRedrawNeeded = mFullRedrawNeeded;
        mFullRedrawNeeded = false;

        mIsDrawing = true;
        Trace.traceBegin(Trace.TRACE_TAG_VIEW, "draw");
        try {
            draw(fullRedrawNeeded);
        } finally {
            mIsDrawing = false;
            Trace.traceEnd(Trace.TRACE_TAG_VIEW);
        }
        .....
    }

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

  /**
     * @return true if drawing was successful, false if an error occurred
     */
    private boolean drawSoftware(Surface surface, AttachInfo attachInfo, int xoff, int yoff,
            boolean scalingRequired, Rect dirty) {

        // Draw with software renderer.
        final Canvas canvas;
        try {
            final int left = dirty.left;
            final int top = dirty.top;
            final int right = dirty.right;
            final int bottom = dirty.bottom;

            canvas = mSurface.lockCanvas(dirty); //锁定画布
            ......
        } catch (Surface.OutOfResourcesException e) {
            handleOutOfResourcesException(e);
            return false;
        } catch (IllegalArgumentException e) {
            Log.e(mTag, "Could not lock surface", e);
            // Don't assume this is due to out of memory, it could be
            // something else, and if it is something else then we could
            // kill stuff (or ourself) for no reason.
            mLayoutRequested = true;    // ask wm for a new surface next time.
            return false;
        }

        try {
           ......
        } finally {
            try {
                surface.unlockCanvasAndPost(canvas); //解锁和提交数据
            } catch (IllegalArgumentException e) {
                Log.e(mTag, "Could not unlock surface", e);
                mLayoutRequested = true;    // ask wm for a new surface next time.
                //noinspection ReturnInsideFinallyBlock
                return false;
            }

            if (LOCAL_LOGV) {
                Log.v(mTag, "Surface " + surface + " unlockCanvasAndPost");
            }
        }
        return true;
    }

frameworks\base\core\java\android\view\Surface.java

private void unlockSwCanvasAndPost(Canvas canvas) {
        if (canvas != mCanvas) {
            throw new IllegalArgumentException("canvas object must be the same instance that "
                    + "was previously returned by lockCanvas");
        }
        if (mNativeObject != mLockedObject) {
            Log.w(TAG, "WARNING: Surface's mNativeObject (0x" +
                    Long.toHexString(mNativeObject) + ") != mLockedObject (0x" +
                    Long.toHexString(mLockedObject) +")");
        }
        if (mLockedObject == 0) {
            throw new IllegalStateException("Surface was not locked");
        }
        try {
            nativeUnlockCanvasAndPost(mLockedObject, canvas);
        } finally {
            nativeRelease(mLockedObject);
            mLockedObject = 0;
        }
    }

frameworks\base\core\jni\android_view_Surface.cpp

static void nativeUnlockCanvasAndPost(JNIEnv* env, jclass clazz,
        jlong nativeObject, jobject canvasObj) {
    sp<Surface> surface(reinterpret_cast<Surface *>(nativeObject));
    if (!isSurfaceValid(surface)) {
        return;
    }

    // detach the canvas from the surface
    Canvas* nativeCanvas = GraphicsJNI::getNativeCanvas(env, canvasObj);
    nativeCanvas->setBitmap(SkBitmap());

    // unlock surface
    status_t err = surface->unlockAndPost(); // finally, 如果还记得上一篇我们分析过的那个函数的话
    if (err < 0) {
        doThrowIAE(env);
    }
}

4. 连接到图形引擎SurfaceFlinger

frameworks\base\core\java\android\view\ViewRootImpl.java
向WMS添加Window

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

public int addWindow(Session session, IWindow client, int seq,
            WindowManager.LayoutParams attrs, int viewVisibility, int displayId,
            Rect outContentInsets, Rect outStableInsets, Rect outOutsets,
            InputChannel outInputChannel) {

        boolean reportNewConfig = false;
        WindowState parentWindow = null;
        long origId;
        final int callingUid = Binder.getCallingUid();
        final int type = attrs.type;

        synchronized(mWindowMap) {
            if (!mDisplayReady) {
                throw new IllegalStateException("Display has not been initialialized");
            }

           //处理窗口层级
           .......

            win.attach(); //关联图形引擎, win 是 WindowState 类型
            
            mWindowMap.put(client.asBinder(), win);
            win.mToken.addWindow(win);
            ........
            }

           ......

        return res;
    }

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); //窗口添加
    }

frameworks\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");
            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++;
    }

frameworks\base\core\java\android\view\SurfaceSession.java

  /** Create a new connection with the surface flinger. */
    public SurfaceSession() {
        mNativeClient = nativeCreate();
    }

frameworks\base\core\jni\android_view_SurfaceSession.cpp
创建SurfaceComposerClient

static jlong nativeCreate(JNIEnv* env, jclass clazz) {
    SurfaceComposerClient* client = new SurfaceComposerClient(); //finally, 如果你还记得这个类的话，它是连接图形引擎的中介
    client->incStrong((void*)nativeCreate);
    return reinterpret_cast<jlong>(client);
}

frameworks\native\libs\gui\SurfaceComposerClient.cpp
SurfaceComposerClient 被创建的时候会自动连接到SurfaceFlinger

void SurfaceComposerClient::onFirstRef() {
    sp<ISurfaceComposer> sm(ComposerService::getComposerService());
    if (sm != 0) {
        auto rootProducer = mParent.promote();
        sp<ISurfaceComposerClient> conn;
        conn = (rootProducer != nullptr) ? sm->createScopedConnection(rootProducer) :
                sm->createConnection();
        if (conn != 0) {
            mClient = conn;
            mStatus = NO_ERROR;
        }
    }
}

5. Surface的创建

frameworks\base\core\java\android\view\ViewRootImpl.java — performTraversals()

 try {
        ......
        //亲求布局窗口
        relayoutResult = relayoutWindow(params, viewVisibility, insetsPending);
       ......
    }            

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

private int relayoutWindow(WindowManager.LayoutParams params, int viewVisibility,
            boolean insetsPending) throws RemoteException {

        float appScale = mAttachInfo.mApplicationScale;
        boolean restore = false;
        if (params != null && mTranslator != null) {
            restore = true;
            params.backup();
            mTranslator.translateWindowLayout(params);
        }
        ......
        //Session 的 layout
        int relayoutResult = mWindowSession.relayout(
                mWindow, mSeq, params,
                (int) (mView.getMeasuredWidth() * appScale + 0.5f),
                (int) (mView.getMeasuredHeight() * appScale + 0.5f),
                viewVisibility, insetsPending ? WindowManagerGlobal.RELAYOUT_INSETS_PENDING : 0,
                mWinFrame, mPendingOverscanInsets, mPendingContentInsets, mPendingVisibleInsets,
                mPendingStableInsets, mPendingOutsets, mPendingBackDropFrame,
                mPendingMergedConfiguration, mSurface);
         .....
        return relayoutResult;
    }

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

 public int relayout(IWindow window, int seq, WindowManager.LayoutParams attrs,
            int requestedWidth, int requestedHeight, int viewFlags,
            int flags, Rect outFrame, Rect outOverscanInsets, Rect outContentInsets,
            Rect outVisibleInsets, Rect outStableInsets, Rect outsets, Rect outBackdropFrame,
            MergedConfiguration mergedConfiguration, Surface outSurface) {
        if (false) Slog.d(TAG_WM, ">>>>>> ENTERED relayout from "
                + Binder.getCallingPid());
        Trace.traceBegin(TRACE_TAG_WINDOW_MANAGER, mRelayoutTag);
        int res = mService.relayoutWindow(this, window, seq, attrs,
                requestedWidth, requestedHeight, viewFlags, flags,
                outFrame, outOverscanInsets, outContentInsets, outVisibleInsets,
                outStableInsets, outsets, outBackdropFrame, mergedConfiguration, outSurface);
        Trace.traceEnd(TRACE_TAG_WINDOW_MANAGER);
        if (false) Slog.d(TAG_WM, "<<<<<< EXITING relayout to "
                + Binder.getCallingPid());
        return res;
    }

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

    public int relayoutWindow(Session session, IWindow client, int seq,
            WindowManager.LayoutParams attrs, int requestedWidth,
            int requestedHeight, int viewVisibility, int flags,
            Rect outFrame, Rect outOverscanInsets, Rect outContentInsets,
            Rect outVisibleInsets, Rect outStableInsets, Rect outOutsets, Rect outBackdropFrame,
            MergedConfiguration mergedConfiguration, Surface outSurface) {
      
            if (viewVisibility == View.VISIBLE &&
                    (win.mAppToken == null || win.mAttrs.type == TYPE_APPLICATION_STARTING
                            || !win.mAppToken.isClientHidden())) {
                ......
                try {
                //创建Surface
                result = createSurfaceControl(outSurface, result, win, winAnimator);
                } catch (Exception e) {
                    mInputMonitor.updateInputWindowsLw(true /*force*/);

                    Slog.w(TAG_WM, "Exception thrown when creating surface for client "
                             + client + " (" + win.mAttrs.getTitle() + ")",
                             e);
                    Binder.restoreCallingIdentity(origId);
                    return 0;
                }
               ......
            }
          }
        Binder.restoreCallingIdentity(origId);
        return result;
    }

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

 private int createSurfaceControl(Surface outSurface, int result, WindowState win,
            WindowStateAnimator winAnimator) {
        if (!win.mHasSurface) {
            result |= RELAYOUT_RES_SURFACE_CHANGED;
        }

        WindowSurfaceController surfaceController;
        try {
            Trace.traceBegin(TRACE_TAG_WINDOW_MANAGER, "createSurfaceControl");
            surfaceController = winAnimator.createSurfaceLocked(win.mAttrs.type, win.mOwnerUid);
        } finally {
            Trace.traceEnd(TRACE_TAG_WINDOW_MANAGER);
        }
        if (surfaceController != null) {
            surfaceController.getSurface(outSurface);
            if (SHOW_TRANSACTIONS) Slog.i(TAG_WM, "  OUT SURFACE " + outSurface + ": copied");
        } else {
            // For some reason there isn't a surface.  Clear the
            // caller's object so they see the same state.
            Slog.w(TAG_WM, "Failed to create surface control for " + win);
            outSurface.release();
        }

        return result;
    }

frameworks\base\services\core\java\com\android\server\wm\WindowStateAnimator.java

WindowSurfaceController createSurfaceLocked(int windowType, int ownerUid) {
        final WindowState w = mWin;
        if (w.restoreSavedSurface()) {
            if (DEBUG_ANIM) Slog.i(TAG,
                    "createSurface: " + this + ": called when we had a saved surface");
            return mSurfaceController;
        }

        if (mSurfaceController != null) {
            return mSurfaceController;
        }

        w.setHasSurface(false);
        try {
           ......
           //创建 WindowSurfaceController
            mSurfaceController = new WindowSurfaceController(mSession.mSurfaceSession,
                    attrs.getTitle().toString(),
                    width, height, format, flags, this, windowType, ownerUid);
            mSurfaceFormat = format;

            w.setHasSurface(true);

       
        } catch (OutOfResourcesException e) {
            Slog.w(TAG, "OutOfResourcesException creating surface");
            mService.mRoot.reclaimSomeSurfaceMemory(this, "create", true);
            mDrawState = NO_SURFACE;
            return null;
        } 
       ......
        mLastHidden = true;

        if (WindowManagerService.localLOGV) Slog.v(TAG, "Created surface " + this);
        return mSurfaceController;
    }

frameworks\base\services\core\java\com\android\server\wm\WindowSurfaceController.java

 public WindowSurfaceController(SurfaceSession s, String name, int w, int h, int format,
            int flags, WindowStateAnimator animator, int windowType, int ownerUid) {
        ......

        if (DEBUG_SURFACE_TRACE) {
            mSurfaceControl = new SurfaceTrace(
                    s, name, w, h, format, flags, windowType, ownerUid);
        } else {
            //创建SurfaceControl
            mSurfaceControl = new SurfaceControl(
                    s, name, w, h, format, flags, windowType, ownerUid);
            Trace.traceEnd(TRACE_TAG_WINDOW_MANAGER);
        }
      ......
    }

frameworks\base\core\java\android\view\SurfaceControl.java
继续调用了JNI层的nativeCreate方法

 public SurfaceControl(SurfaceSession session, String name, int w, int h, int format, int flags,
            SurfaceControl parent, int windowType, int ownerUid)
                    throws OutOfResourcesException {
        ......
        mNativeObject = nativeCreate(session, name, w, h, format, flags,
            parent != null ? parent.mNativeObject : 0, windowType, ownerUid);
       ......
    }

frameworks\base\core\jni\android_view_SurfaceControl.cpp
JNI层创建了一个本地的SurfaceControl，SurfaceControl里面有创建Surface的函数，这个我们在上一篇已经提到

static jlong nativeCreate(JNIEnv* env, jclass clazz, jobject sessionObj,
        jstring nameStr, jint w, jint h, jint format, jint flags, jlong parentObject,
        jint windowType, jint ownerUid) {
    ScopedUtfChars name(env, nameStr);
    sp<SurfaceComposerClient> client(android_view_SurfaceSession_getClient(env, sessionObj));
    SurfaceControl *parent = reinterpret_cast<SurfaceControl*>(parentObject);
    //熟悉的味道
    sp<SurfaceControl> surface = client->createSurface(
            String8(name.c_str()), w, h, format, flags, parent, windowType, ownerUid);
    if (surface == NULL) {
        jniThrowException(env, OutOfResourcesException, NULL);
        return 0;
    }
    surface->incStrong((void *)nativeCreate);
    return reinterpret_cast<jlong>(surface.get());
}

6. 真假Surface

frameworks\base\services\core\java\com\android\server\wm\WindowManagerService.java
WindowManagerService的createSurfaceControl函数中，创建完SurfaceController后，继续调用了如下方法

  void getSurface(Surface outSurface) {
        outSurface.copyFrom(mSurfaceControl);
    }

frameworks\base\core\java\android\view\Surface.java
著名的 copyFrom 方法, 狸猫换太子的手法，高明

 public void copyFrom(SurfaceControl other) {
        ......
        long newNativeObject = nativeGetFromSurfaceControl(surfaceControlPtr);
        .....
    }

frameworks\base\core\jni\android_view_Surface.cpp
从SurfaceControl中取回Surface

static jlong nativeGetFromSurfaceControl(JNIEnv* env, jclass clazz,
        jlong surfaceControlNativeObj) {
    ......
    sp<SurfaceControl> ctrl(reinterpret_cast<SurfaceControl *>(surfaceControlNativeObj));
    sp<Surface> surface(ctrl->getSurface()); //此时会创建Surface返回给java层的Surface对象
    if (surface != NULL) {
        surface->incStrong(&sRefBaseOwner);
    }
    return reinterpret_cast<jlong>(surface.get());
}

OK, 今天就到这！