Android GLSurfaceView笔记

GLSurefaceView继承自SurfaceView，同时也拥有了OpenGL ES所提供的的强大的3D图形处理功能。目前主流的移动游戏引擎都使用该View。
GLSurefaceView的主要特性：
1、管理EGLDisplay，它表示一个显示屏
2、管理Surface（本质上就是一块内存区域）
3、GLSurefaceView会创建新的线程，以使整个渲染过程不至于阻塞UI主线程
4、用户可以自定义渲染方式，如通过setRender()设置一个Render。
使用基本步骤：
1、创建GLSurefaceView
2、初始化OpenGL ES环境
环境可以自己设置，ex:

     setEGLConfigChooser(boolean);setGLWrapper(GLWrapper);getHolder().setFormat(PixelFormat,TRANSLUCENT)setDebugFlag(int)

3、设置Renderer,setRender（）可以将用户自定义的一个Renderer加入实际的渲染流程中

 setRenderer(Renderer renderer);

4、设置Rendering Mode,默认情况下采用的是连续的渲染方式。

   setRenderMode(RENDERMODE_WHEN_DIRTY);

5、状态处理
注意处理程序的声明周期，例如Activity的暂停和恢复情况下的处理，在pause触发时，调用GLSurefaceView的onPause()，恢复时再调用onResume。

上述步骤发现，我们主要关注Renderer的实现，而EGL的创建过程，Surface的分配以及OpenGL ES的一些调用细节等都会被隐藏起来了。

实现原理：
其构造函数除了调用了其父类的方法就直接进入了init()方法

private void init() {SurfaceHolder holder = getHolder();holder.addCallback(this);}

该方法先通过父类获取当前的SurefaceHolder，然后添加自身为回调函数（自身实现了SurfaceHolder.Callback2，CallBack2继承自SurfaceHolder.Callback）,这样每当Surface有变化时，就能收到通知了。

     //当成功申请到一个Surface时调用，正常情况下只会发生一次public void surfaceCreated(SurfaceHolder holder);//当Surface改变时调用，如format,size的变动public void surfaceChanged(SurfaceHolder holder, int format, int width,int height);//当Surface销毁时调用public void surfaceDestroyed(SurfaceHolder holder);

SurfaceHolder如何被创建
SurfaceView.java

 private SurfaceHolder mSurfaceHolder = new SurfaceHolder() {....}

他是一个全局变量，在一开始就已经创建了实例。
Surface如何创建
SurfaceView继承于View,View树在ViewRoot创建时会申请到一个Surface。而SurfaceView的这个SurfaceView并非和ViewRoot的Surface是同一个。

@Overrideprotected void onAttachedToWindow() {super.onAttachedToWindow();mParent.requestTransparentRegion(this);//SurfaceView没有必要自己在创建一个ViewRoot，直接通过ViewRoot获取一个IWindowSessionmSession = getWindowSession();mLayout.token = getWindowToken();mLayout.setTitle("SurfaceView");mViewVisibility = getVisibility() == VISIBLE;if (!mGlobalListenersAdded) {ViewTreeObserver observer = getViewTreeObserver();observer.addOnScrollChangedListener(mScrollChangedListener);observer.addOnPreDrawListener(mDrawListener);mGlobalListenersAdded = true;}}

onAttachedToWindow为updateWindow提供触发源码链接

 /** @hide */protected void updateWindow(boolean force, boolean redrawNeeded) {if (!mHaveFrame) {return;}ViewRootImpl viewRoot = getViewRootImpl();if (viewRoot != null) {mTranslator = viewRoot.mTranslator;}if (mTranslator != null) {mSurface.setCompatibilityTranslator(mTranslator);}....................if (force || creating || formatChanged || sizeChanged || visibleChanged|| mLeft != mLocation[0] || mTop != mLocation[1]|| mUpdateWindowNeeded || mReportDrawNeeded || redrawNeeded || layoutSizeChanged) {try {final boolean visible = mVisible = mRequestedVisible;mLeft = mLocation[0];mTop = mLocation[1];mWidth = myWidth;mHeight = myHeight;mFormat = mRequestedFormat;mLayout.x = mLeft;mLayout.y = mTop;mLayout.width = getWidth();mLayout.height = getHeight();if (mTranslator != null) {mTranslator.translateLayoutParamsInAppWindowToScreen(mLayout);}mLayout.format = mRequestedFormat;mLayout.flags |=WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE| WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE| WindowManager.LayoutParams.FLAG_LAYOUT_NO_LIMITS| WindowManager.LayoutParams.FLAG_SCALED| WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE| WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE;if (!getContext().getResources().getCompatibilityInfo().supportsScreen()) {mLayout.privateFlags |=WindowManager.LayoutParams.PRIVATE_FLAG_COMPATIBLE_WINDOW;}mLayout.privateFlags |= WindowManager.LayoutParams.PRIVATE_FLAG_NO_MOVE_ANIMATION;if (mWindow == null) {Display display = getDisplay();mWindow = new MyWindow(this);mLayout.type = mWindowType;mLayout.gravity = Gravity.START|Gravity.TOP;mSession.addToDisplayWithoutInputChannel(mWindow, mWindow.mSeq, mLayout,mVisible ? VISIBLE : GONE, display.getDisplayId(), mContentInsets,mStableInsets);}boolean realSizeChanged;boolean reportDrawNeeded;int relayoutResult;mSurfaceLock.lock();try {mUpdateWindowNeeded = false;reportDrawNeeded = mReportDrawNeeded;mReportDrawNeeded = false;mDrawingStopped = !visible;if (DEBUG) Log.i(TAG, "Cur surface: " + mSurface);//重新申请一个SurfacerelayoutResult = mSession.relayout(mWindow, mWindow.mSeq, mLayout, mWidth, mHeight,visible ? VISIBLE : GONE,WindowManagerGlobal.RELAYOUT_DEFER_SURFACE_DESTROY,mWinFrame, mOverscanInsets, mContentInsets,mVisibleInsets, mStableInsets, mOutsets, mConfiguration,mNewSurface);if ((relayoutResult & WindowManagerGlobal.RELAYOUT_RES_FIRST_TIME) != 0) {reportDrawNeeded = true;}mSurfaceFrame.left = 0;mSurfaceFrame.top = 0;if (mTranslator == null) {mSurfaceFrame.right = mWinFrame.width();mSurfaceFrame.bottom = mWinFrame.height();} else {float appInvertedScale = mTranslator.applicationInvertedScale;mSurfaceFrame.right = (int) (mWinFrame.width() * appInvertedScale + 0.5f);mSurfaceFrame.bottom = (int) (mWinFrame.height() * appInvertedScale + 0.5f);}final int surfaceWidth = mSurfaceFrame.right;final int surfaceHeight = mSurfaceFrame.bottom;realSizeChanged = mLastSurfaceWidth != surfaceWidth|| mLastSurfaceHeight != surfaceHeight;mLastSurfaceWidth = surfaceWidth;mLastSurfaceHeight = surfaceHeight;} finally {mSurfaceLock.unlock();}try {redrawNeeded |= creating | reportDrawNeeded;SurfaceHolder.Callback callbacks[] = null;final boolean surfaceChanged = (relayoutResult& WindowManagerGlobal.RELAYOUT_RES_SURFACE_CHANGED) != 0;if (mSurfaceCreated && (surfaceChanged || (!visible && visibleChanged))) {mSurfaceCreated = false;if (mSurface.isValid()) {if (DEBUG) Log.i(TAG, "visibleChanged -- surfaceDestroyed");callbacks = getSurfaceCallbacks();for (SurfaceHolder.Callback c : callbacks) {c.surfaceDestroyed(mSurfaceHolder);}}}mSurface.transferFrom(mNewSurface);if (visible && mSurface.isValid()) {if (!mSurfaceCreated && (surfaceChanged || visibleChanged)) {mSurfaceCreated = true;mIsCreating = true;if (DEBUG) Log.i(TAG, "visibleChanged -- surfaceCreated");if (callbacks == null) {callbacks = getSurfaceCallbacks();}for (SurfaceHolder.Callback c : callbacks) {c.surfaceCreated(mSurfaceHolder);}}if (creating || formatChanged || sizeChanged|| visibleChanged || realSizeChanged) {if (DEBUG) Log.i(TAG, "surfaceChanged -- format=" + mFormat+ " w=" + myWidth + " h=" + myHeight);if (callbacks == null) {callbacks = getSurfaceCallbacks();}for (SurfaceHolder.Callback c : callbacks) {c.surfaceChanged(mSurfaceHolder, mFormat, myWidth, myHeight);}}if (redrawNeeded) {//申请了全新的Surface后，会通知到所有注册了callback函数的对象。if (DEBUG) Log.i(TAG, "surfaceRedrawNeeded");if (callbacks == null) {callbacks = getSurfaceCallbacks();}for (SurfaceHolder.Callback c : callbacks) {if (c instanceof SurfaceHolder.Callback2) {((SurfaceHolder.Callback2)c).surfaceRedrawNeeded(mSurfaceHolder);}}}}} finally {mIsCreating = false;if (redrawNeeded) {if (DEBUG) Log.i(TAG, "finishedDrawing");mSession.finishDrawing(mWindow);}mSession.performDeferredDestroy(mWindow);}} catch (RemoteException ex) {}}}

GLSurfaceView将会启动一个新线程来完后渲染，以防止程序阻塞UI线程（GLThread）,其在setRenderer时启动，然后不断等待和处理事件，同时还负责开展Render工作

  public void surfaceCreated() {synchronized(sGLThreadManager) {if (LOG_THREADS) {Log.i("GLThread", "surfaceCreated tid=" + getId());}mHasSurface = true;mFinishedCreatingEglSurface = false;sGLThreadManager.notifyAll();while (mWaitingForSurface&& !mFinishedCreatingEglSurface&& !mExited) {try {sGLThreadManager.wait();} catch (InterruptedException e) {Thread.currentThread().interrupt();}}}}

参考：
《深入理解Android内核设计思想》

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