GLSurfaceView的简单分析及巧妙借用
Posted 湖广午王
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学习在android中使用OpenGLES，就不得不提到一个控件：GLSurfaceView。本篇博客将介绍GLSurfaceView的基本使用、GLSurfaceView的源码的简单分析，以及使用GLSurfaceView渲染图像到SurfaceView/TextureView或者PBuffer上等。
关于GLSurfaceView
GLSurfaceView继承了SurfaceView，实现了SurfaceHolder.Callback2接口。
SurfaceView在View的基础上是创建了独立的Surface，拥有SurfaceHolder来管理它的Surface，渲染的工作可以不再在主线程中做了。可以通过SurfaceHolder得到Canvas，在单独的线程中，利用Canvas绘制需要显示的内容，然后更新到Surface上。
而GLSurfaceView，它主要是在SurfaceView的基础上实现了一个GLThread（EGLContext创建GL环境所在线程即为GL线程），绘制的工作直接通过OpenGL来进行，绘制的内容默认情况下依旧是绘制到SurfaceView所提供的Surface上。
参照GLSurfaceView的实现，我们可以自行创建GL环境，来进行GL渲染。实现自行制定指定载体、后台渲染等功能。
GLSurfaceView的使用
GLSurfaceView作为一个View，实例化上基本和其他View相当。可以选择在xml布局文件中增加，然后在Java代码中取得它的控制权。也可以在Java代码中直接new，然后呈现出来。GLSurfaceView必须加入到一个布局中，才能正确的使用，否则有可能会造成崩溃
，这和GLSurfaceView的attachToWindow和detachFromWindow中相关操作。
GLSurfaceView具有onResume和onPause两个同Activity及Fragment中的生命周期同名的方法。一般来说，在Activity或者Fragment中的onResume和onPause方法中，需要主动调用GLSurfaceView的实例的这两个方法。
GLSurfaceView的基本使用代码如下：
mGLView= (GLSurfaceView) findViewById(R.id.mGLView);
//GLContext设置为OpenGLES2.0
mGLView.setEGLContextClientVersion(2);
//在setRenderer之前，可以调用以下方法来进行EGL设置
//mGLView.setEGLConfigChooser(); //颜色、深度、模板等等设置
//mGLView.setEGLWindowSurfaceFactory(); //窗口设置
//mGLView.setEGLContextFactory(); //EGLContext设置
//设置渲染器，渲染主要就是由渲染器来决定
mGLView.setRenderer(new GLSurfaceView.Renderer()
@Override
public void onSurfaceCreated(GL10 gl, EGLConfig config)
//todo surface被创建后需要做的处理
@Override
public void onSurfaceChanged(GL10 gl, int width, int height)
//todo 渲染窗口大小发生改变的处理
@Override
public void onDrawFrame(GL10 gl)
//todo 执行渲染工作
);
/*渲染方式，RENDERMODE_WHEN_DIRTY表示被动渲染，只有在调用requestRender或者onResume等方法时才会进行渲染。RENDERMODE_CONTINUOUSLY表示持续渲染*/
mGLView.setRenderMode(GLSurfaceView.RENDERMODE_WHEN_DIRTY);GLSurfaceView源码分析
GLSurfaceView中，对于GL环境的操作，出queueEvent是将事件放入队列中，到GL线程中执行外，其他方法基本都是在主线程（也可以是其他线程，非当前GLSurfaceView实例的GL线程）中修改某个状态值，然后取消GL线程的等待，在GL线程中根据状态值作相应的操作，并在操作后反馈给调用方法的那个线程，当然有的方法也不需要反馈。
GLSurfaceView主要方法及中文注释如下：
public class GLSurfaceView extends SurfaceView implements SurfaceHolder.Callback2
public final static int RENDERMODE_WHEN_DIRTY = 0;
public final static int RENDERMODE_CONTINUOUSLY = 1;
public GLSurfaceView(Context context)
super(context);
init();
public GLSurfaceView(Context context, AttributeSet attrs)
super(context, attrs);
init();
//调试用的
public void setDebugFlags(int debugFlags);
public int getDebugFlags();
//设置暂停的时候是否保持EglContext
public void setPreserveEGLContextOnPause(boolean preserveOnPause);
public boolean getPreserveEGLContextOnPause();
//设置渲染器，这个非常重要，渲染工作就依靠渲染器了
//调用此方法会开启一个新的线程，即GL线程
public void setRenderer(Renderer renderer)
checkRenderThreadState();
if (mEGLConfigChooser == null)
mEGLConfigChooser = new SimpleEGLConfigChooser(true);
if (mEGLContextFactory == null)
mEGLContextFactory = new DefaultContextFactory();
if (mEGLWindowSurfaceFactory == null)
mEGLWindowSurfaceFactory = new DefaultWindowSurfaceFactory();
mRenderer = renderer;
mGLThread = new GLThread(mThisWeakRef);
mGLThread.start();
//设置EGLContext工厂，不设置就用默认的
public void setEGLContextFactory(EGLContextFactory factory);
//设置EGLSurface工厂，不设置就用默认的
public void setEGLWindowSurfaceFactory(EGLWindowSurfaceFactory factory);
//设置EglConfig，一般颜色深度等等，利用此方法设置。不设置就用默认的
public void setEGLConfigChooser(EGLConfigChooser configChooser);
//内部调用setEGLConfigChooser
public void setEGLConfigChooser(boolean needDepth);
//内部调用setEGLConfigChooser
public void setEGLConfigChooser(int redSize, int greenSize, int blueSize,
int alphaSize, int depthSize, int stencilSize);
//设置EGLContextVersion，比如2，即OpenGLES2.0
public void setEGLContextClientVersion(int version);
//设置渲染方式，有RENDERMODE_CONTINUOUSLY表示不断渲染
//以及RENDERMODE_WHEN_DIRTY表示在需要的时候才会渲染
//渲染的时候要求调用requestRender，必须在setRenderer后调用
public void setRenderMode(int renderMode);
public int getRenderMode();
//主动请求渲染
public void requestRender();
public void surfaceCreated(SurfaceHolder holder);
public void surfaceDestroyed(SurfaceHolder holder);
public void surfaceChanged(SurfaceHolder holder, int format, int w, int h);
@Override
public void surfaceRedrawNeeded(SurfaceHolder holder)
if (mGLThread != null)
mGLThread.requestRenderAndWait();
//生命周期，一般在Activity、Fragment的onPause中调用
public void onPause();
//生命周期，一般在Activity、Fragment的onResume中调用
public void onResume();
//向GL线程发送一个任务
public void queueEvent(Runnable r);
//附加到Window上时被调用，外部不可调用
protected void onAttachedToWindow();
//从Window上被移除时调用，外部不可调用
protected void onDetachedFromWindow();
//渲染器接口
public interface Renderer
//Surface被创建时被调用，通常在此进行渲染的初始化
void onSurfaceCreated(GL10 gl, EGLConfig config);
//Surface大小被改变时被调用
void onSurfaceChanged(GL10 gl, int width, int height);
//执行渲染时被调用，以完成用户渲染工作
void onDrawFrame(GL10 gl);
//非常重要的一个EGL帮助类，GL环境的建立依靠此类
private static class EglHelper
public EglHelper(WeakReference<GLSurfaceView> glSurfaceViewWeakRef)
mGLSurfaceViewWeakRef = glSurfaceViewWeakRef;
//EGL的初始化，可以参考此方法
public void start()
if (LOG_EGL)
Log.w("EglHelper", "start() tid=" + Thread.currentThread().getId());
/*
* Get an EGL instance
*/
mEgl = (EGL10) EGLContext.getEGL();
/*
* Get to the default display.
*/
mEglDisplay = mEgl.eglGetDisplay(EGL10.EGL_DEFAULT_DISPLAY);
if (mEglDisplay == EGL10.EGL_NO_DISPLAY)
throw new RuntimeException("eglGetDisplay failed");
/*
* We can now initialize EGL for that display
*/
int[] version = new int[2];
if(!mEgl.eglInitialize(mEglDisplay, version))
throw new RuntimeException("eglInitialize failed");
GLSurfaceView view = mGLSurfaceViewWeakRef.get();
if (view == null)
mEglConfig = null;
mEglContext = null;
else
mEglConfig = view.mEGLConfigChooser.chooseConfig(mEgl, mEglDisplay);
/*
* Create an EGL context. We want to do this as rarely as we can, because an
* EGL context is a somewhat heavy object.
*/
mEglContext = view.mEGLContextFactory.createContext(mEgl, mEglDisplay, mEglConfig);
if (mEglContext == null || mEglContext == EGL10.EGL_NO_CONTEXT)
mEglContext = null;
throwEglException("createContext");
if (LOG_EGL)
Log.w("EglHelper", "createContext " + mEglContext + " tid=" + Thread.currentThread().getId());
mEglSurface = null;
//创建EGLSurface，使GL的渲染，能够渲染到用户指定的Surface
//默认的Surface就是SurfaceHolder的Surface
public boolean createSurface()
if (LOG_EGL)
Log.w("EglHelper", "createSurface() tid=" + Thread.currentThread().getId());
/*
* Check preconditions.
*/
if (mEgl == null)
throw new RuntimeException("egl not initialized");
if (mEglDisplay == null)
throw new RuntimeException("eglDisplay not initialized");
if (mEglConfig == null)
throw new RuntimeException("mEglConfig not initialized");
/*
* The window size has changed, so we need to create a new
* surface.
*/
destroySurfaceImp();
/*
* Create an EGL surface we can render into.
*/
GLSurfaceView view = mGLSurfaceViewWeakRef.get();
if (view != null)
mEglSurface = view.mEGLWindowSurfaceFactory.createWindowSurface(mEgl,
mEglDisplay, mEglConfig, view.getHolder());
else
mEglSurface = null;
if (mEglSurface == null || mEglSurface == EGL10.EGL_NO_SURFACE)
int error = mEgl.eglGetError();
if (error == EGL10.EGL_BAD_NATIVE_WINDOW)
Log.e("EglHelper", "createWindowSurface returned EGL_BAD_NATIVE_WINDOW.");
return false;
/*
* Before we can issue GL commands, we need to make sure
* the context is current and bound to a surface.
*/
if (!mEgl.eglMakeCurrent(mEglDisplay, mEglSurface, mEglSurface, mEglContext))
/*
* Could not make the context current, probably because the underlying
* SurfaceView surface has been destroyed.
*/
logEglErrorAsWarning("EGLHelper", "eglMakeCurrent", mEgl.eglGetError());
return false;
return true;
//通过EGL得到GL，然后用户设置了Wrapper的话会给得到的GL做个包装
//同时也会解析一下用户的Debug意图，看看要不要debug
GL createGL();
//绘制完成之后，调用此方法，将绘制的内容输出到前台，让用户可以看到
public int swap();
//销毁Surface的方法，具体实现在destroySurfaceImp方法中
public void destroySurface();
//销毁GL环境
public void finish();
//GL线程，此类中存在的方法，GLSurfaceView中有同名的，
//基本都是提供给GLSurfaceView作为真正的实现调用
static class GLThread extends Thread
//销毁EglSurface
private void stopEglSurfaceLocked();
//销毁EglContext
private void stopEglContextLocked();
//GL线程的主要逻辑都在这个方法里面，这个方法比较复杂
//GLSurfaceView的核心就在这个里面了，最后在单独分析这个里面的逻辑
private void guardedRun() throws InterruptedException;
public boolean ableToDraw()
return mHaveEglContext && mHaveEglSurface && readyToDraw();
private boolean readyToDraw()
return (!mPaused) && mHasSurface && (!mSurfaceIsBad)
&& (mWidth > 0) && (mHeight > 0)
&& (mRequestRender || (mRenderMode == RENDERMODE_CONTINUOUSLY));
//设置渲染方法，见GLSurfaceView的setRenderMode
public void setRenderMode(int renderMode);
public int getRenderMode();
//请求一次渲染
public void requestRender();
//请求一次渲染，并等待渲染完成
public void requestRenderAndWait();
//创建Surface
public void surfaceCreated();
//销毁Surface
public void surfaceDestroyed();
public void onPause();
public void onResume();
//Surface的大小被改变时调用
public void onWindowResize(int w, int h);
//请求退出渲染线程，并等待退出
public void requestExitAndWait();
//请求是否EglContext
public void requestReleaseEglContextLocked();
//向GL线程发送一个任务
public void queueEvent(Runnable r);
//debug使用的
static class LogWriter extends Writer
//很多方法都会调用此方法，会检查mGLThread不为null
//即保证调用此方法的方法，必须在setRenderer之前调用
private void checkRenderThreadState();
//主要就是用来做同步用的，利用Object的wait和notifyAll
private static class GLThreadManager
渲染的主要逻辑在GLThread的guardedRun()方法中，对guardedRun()方法梳理下。
private void guardedRun() throws InterruptedException
mEglHelper = new EglHelper(mGLSurfaceViewWeakRef);
mHaveEglContext = false;
mHaveEglSurface = false;
mWantRenderNotification = false;
try
GL10 gl = null;
boolean createEglContext = false;
boolean createEglSurface = false;
boolean createGlInterface = false;
boolean lostEglContext = false;
boolean sizeChanged = false;
boolean wantRenderNotification = false;
boolean doRenderNotification = false;
boolean askedToReleaseEglContext = false;
int w = 0;
int h = 0;
Runnable event = null;
while (true)
synchronized (sGLThreadManager)
while (true)
//外部请求退出GL线程
if (mShouldExit)
return;
/*外部请求在GL线程中处理的事件没有处理完时，就优先处理这些事件*/
if (! mEventQueue.isEmpty())
event = mEventQueue.remove(0);
break;
//暂停和恢复状态变化时，onResume和onPause状态变化
boolean pausing = false;
if (mPaused != mRequestPaused)
pausing = mRequestPaused;
mPaused = mRequestPaused;
/*GLSurfaceView的onPause和onResume都会用wait方法等待GL线程的响应，这时候主线程阻塞。此处调用notifyAll通知onPause和onResume，放弃主线程的阻塞。GLSurfaceView中其他很多方法也存在wait方法，基本与此类似
*/
sGLThreadManager.notifyAll();
if (LOG_PAUSE_RESUME)
Log.i("GLThread", "mPaused is now " + mPaused + " tid=" + getId());
// 需要释放EglContext时候执行的工作
if (mShouldReleaseEglContext)
if (LOG_SURFACE)
Log.i("GLThread", "releasing EGL context because asked to tid=" + getId());
stopEglSurfaceLocked();
stopEglContextLocked();
mShouldReleaseEglContext = false;
askedToReleaseEglContext = true;
// EglContext丢失时，销毁EglSurface和EglContext
if (lostEglContext)
stopEglSurfaceLocked();
stopEglContextLocked();
lostEglContext = false;
//接收了暂停信号，而且当前EglSurface存在时，销毁EglSurface
if (pausing && mHaveEglSurface)
if (LOG_SURFACE)
Log.i("GLThread", "releasing EGL surface because paused tid=" + getId());
stopEglSurfaceLocked();
/*接收了暂停信号，而且当前EglContext存在时，根据用户设置，来决定是否销毁EglContext*/
if (pausing && mHaveEglContext)
GLSurfaceView view = mGLSurfaceViewWeakRef.get();
boolean preserveEglContextOnPause = view == null ?
false : view.mPreserveEGLContextOnPause;
if (!preserveEglContextOnPause)
stopEglContextLocked();
if (LOG_SURFACE)
Log.i("GLThread", "releasing EGL context because paused tid=" + getId());
/*Surface不存在（不是EglSurface），而且当前并没有在等待Surface*/
if ((! mHasSurface) && (! mWaitingForSurface))
if (LOG_SURFACE)
Log.i("GLThread", "noticed surfaceView surface lost tid=" + getId());
if (mHaveEglSurface)
stopEglSurfaceLocked();
mWaitingForSurface = true;
mSurfaceIsBad = false;
sGLThreadManager.notifyAll();
// Surface存在，而且在等待Surface
if (mHasSurface && mWaitingForSurface)
if (LOG_SURFACE)
Log.i("GLThread", "noticed surfaceView surface acquired tid=" + getId());
mWaitingForSurface = false;
sGLThreadManager.notifyAll();
if (doRenderNotification)
if (LOG_SURFACE)
Log.i("GLThread", "sending render notification tid=" + getId());
mWantRenderNotification = false;
doRenderNotification = false;
mRenderComplete = true;
sGLThreadManager.notifyAll();
// 当前环境准备好了渲染执行，否则进入下一轮等待及判断
if (readyToDraw())
// 没有EglContext就需要借助EglHelper来创建EglContext
if (! mHaveEglContext)
if (askedToReleaseEglContext)
askedToReleaseEglContext = false;
else
try
mEglHelper.start();
catch (RuntimeException t)
sGLThreadManager.releaseEglContextLocked(this);
throw t;
mHaveEglContext = true;
createEglContext = true;
sGLThreadManager.notifyAll();
/*有了EglContext,但是没有EglSurface，就需要设置一些状态，以便后续操作*/
if (mHaveEglContext && !mHaveEglSurface)
mHaveEglSurface = true;
createEglSurface = true;
createGlInterface = true;
sizeChanged = true;
/*有eglSurface时，需要判断是否需要执行surface sizechange*/
if (mHaveEglSurface)
if (mSizeChanged)
sizeChanged = true;
w = mWidth;
h = mHeight;
mWantRenderNotification = true;
if (LOG_SURFACE)
Log.i("GLThread",
"noticing that we want render notification tid="
+ getId());
// Destroy and recreate the EGL surface.
createEglSurface = true;
mSizeChanged = false;
mRequestRender = false;
sGLThreadManager.notifyAll();
if (mWantRenderNotification)
wantRenderNotification = true;
//注意此处break，跳出等待的循环
break;
// By design, this is the only place in a GLThread thread where we wait().
if (LOG_THREADS)
Log.i("GLThread", "waiting tid=" + getId()
+ " mHaveEglContext: " + mHaveEglContext
+ " mHaveEglSurface: " + mHaveEglSurface
+ " mFinishedCreatingEglSurface: " + mFinishedCreatingEglSurface
+ " mPaused: " + mPaused
+ " mHasSurface: " + mHasSurface
+ " mSurfaceIsBad: " + mSurfaceIsBad
+ " mWaitingForSurface: " + mWaitingForSurface
+ " mWidth: " + mWidth
+ " mHeight: " + mHeight
+ " mRequestRender: " + mRequestRender
+ " mRenderMode: " + mRenderMode);
sGLThreadManager.wait();
/*外部请求在GL线程中处理的事件没有处理完时，就优先处理这些事件*/
if (event != null)
event.run();
event = null;
continue;
//后续就是根据上面的判断设置，来执行相应的操作
if (createEglSurface)
if (LOG_SURFACE)
Log.w("GLThread", "egl createSurface");
//创建EglSurface
if (mEglHelper.createSurface())
synchronized(sGLThreadManager)
mFinishedCreatingEglSurface = true;
sGLThreadManager.notifyAll();
else
synchronized(sGLThreadManager)
mFinishedCreatingEglSurface = true;
mSurfaceIsBad = true;
sGLThreadManager.notifyAll();
continue;
createEglSurface = false;
if (createGlInterface)
gl = (GL10) mEglHelper.createGL();
createGlInterface = false;
if (createEglContext)
if (LOG_RENDERER)
Log.w("GLThread", "onSurfaceCreated");
GLSurfaceView view = mGLSurfaceViewWeakRef.get();
if (view != null)
try
Trace.traceBegin(Trace.TRACE_TAG_VIEW, "onSurfaceCreated");
//调用GLSurfaceView设置的renderer的onSurfceCreated方法
view.mRenderer.onSurfaceCreated(gl, mEglHelper.mEglConfig);
finally
Trace.traceEnd(Trace.TRACE_TAG_VIEW);
createEglContext = false;
//surface大小被改变
if (sizeChanged)
if (LOG_RENDERER)
Log.w("GLThread", "onSurfaceChanged(" + w + ", " + h + ")");
GLSurfaceView view = mGLSurfaceViewWeakRef.get();
if (view != null)
try
Trace.traceBegin(Trace.TRACE_TAG_VIEW, "onSurfaceChanged");
view.mRenderer.onSurfaceChanged(gl, w, h);
finally
Trace.traceEnd(Trace.TRACE_TAG_VIEW);
sizeChanged = false;
if (LOG_RENDERER_DRAW_FRAME)
Log.w("GLThread", "onDrawFrame tid=" + getId());
//每帧绘制
GLSurfaceView view = mGLSurfaceViewWeakRef.get();
if (view != null)
try
Trace.traceBegin(Trace.TRACE_TAG_VIEW, "onDrawFrame");
view.mRenderer.onDrawFrame(gl);
finally
Trace.traceEnd(Trace.TRACE_TAG_VIEW);
int swapError = mEglHelper.swap();
switch (swapError)
case EGL10.EGL_SUCCESS:
break;
case EGL11.EGL_CONTEXT_LOST:
if (LOG_SURFACE)
Log.i("GLThread", "egl context lost tid=" + getId());
lostEglContext = true;
break;
default:
EglHelper.logEglErrorAsWarning("GLThread", "eglSwapBuffers", swapError);
synchronized(sGLThreadManager)
mSurfaceIsBad = true;
sGLThreadManager.notifyAll();
break;
if (wantRenderNotification)
doRenderNotification = true;
wantRenderNotification = false;
finally
/*
* clean-up everything...
*/
synchronized (sGLThreadManager)
stopEglSurfaceLocked();
stopEglContextLocked();
SurfaceView/TextureView或Pbuffer上的OpenGLES渲染
根据上面的分析，我们知道，GLSurfaceView有setEGLWindowSurfaceFactory借助此方法，我们可以将图像渲染到其他的地方，比如我们创建一个如下的自定义GLSurfaceView，就可以将图像渲染到外部指定surface上。但是遗憾的是，在某些手机上，这种方式会失效。
private class GLView extends GLSurfaceView
public GLView(Context context)
super(context);
init();
private void init()
getHolder().addCallback(null);
setEGLWindowSurfaceFactory(new GLSurfaceView.EGLWindowSurfaceFactory()
@Override
public EGLSurface createWindowSurface(EGL10 egl, EGLDisplay display, EGLConfig
config, Object window)
return egl.eglCreateWindowSurface(display,config,surface,null);
@Override
public void destroySurface(EGL10 egl, EGLDisplay display, EGLSurface surface)
egl.eglDestroySurface(display, surface);
);
setEGLContextClientVersion(2);
setRenderer(TextureController.this);
setRenderMode(RENDERMODE_WHEN_DIRTY);
setPreserveEGLContextOnPause(true);
public void attachedToWindow()
super.onAttachedToWindow();
public void detachedFromWindow()
super.onDetachedFromWindow();
那么如何办呢？我们可以新建一个类GLEnvironment，将GLSurfaceView内容全部复制出来，然后取消其继承和接口实现，将所有报错的代码删除掉，这样就相当于剔除了GLSurfaceView的SurfaceView而保留了它的GL环境，我们可以使用GLEnvironment来进行渲染，并自由的指定渲染载体，可以是SurfaceView/TextureView或Pbuffer，也可以是Pixmap。
同样是利用setEGLWindowSurfaceFactory方法来设置，当然可以改个名字更为贴切，比如setEGLSurfaceFactory，如下：
mEnv.setEGLSurfaceFactory(new GLEnvironment.EGLSurfaceFactory()
@Override
public EGLSurface createSurface(EGL10 egl, EGLDisplay display, EGLConfig config, Object nativeWindow)
/*使用SurfaceView或者TextureView,customWindow可以为SurfaceTexture\\SurfaceHolder或者Surface等*/
egl.eglCreateWindowSurface(display,config,customWindow,null);
//使用pbuffer
//reture egl.eglCreatePbufferSurface();
//使用pixmap
//return egl.eglCreatePixmapSurface();
@Override
public void destroySurface(EGL10 egl, EGLDisplay display, EGLSurface surface)
egl.eglDestroySurface(display,surface);
);具体代码请参考AndroidOpenGLDemo，在其中搜索GLEnvironment。
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