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POAutomatic buffer clear while using OpenGL on Android
 

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    <p>I'm writing a certain OpenGL application where I'd specifically like to draw frames incrementally. For this, I'd like to disable automatic clearing of buffer which I understand, is default behavior of GLSurfaceView.Renderer.onDrawFrame(). Can someone please help me on how to do this? I need to write the application in Java, not using native SDK.</p> <p>I understand that I could possibly do this by :-</p> <pre><code>(1) setting EGL_SWAP_BEHAVIOR_PRESERVED_BIT bit for EGL_SURFACE_TYPE attribute while doing [eglChooseConfig][1](), and (2) setting EGL_SWAP_BEHAVIOR attribute to EGL_BUFFER_PRESERVED by calling [eglSurfaceAttrib][2] on the EGLSurface object </code></pre> <p>However, I gather from the Khronos doc that:-</p> <pre><code>"EGL_SWAP_BEHAVIOR_PRESERVED_BIT are supported only if the EGL version is 1.4 or greater." "EGL_SWAP_BEHAVIOR is supported only if the EGL version is 1.2 or greater." </code></pre> <p>Now, I understand that I could access EGL in two ways in my Android application:-</p> <pre><code>(1) use the Khronos API class [EGL10][3] in javax.microedition.khronos.egl package (EGL11 doesn't seem to be implemented yet) (2) use the Android API class [EGL14][4] in android.opengl package (similar to using class android.opengl.GLES20) </code></pre> <p>The problem with (1) is that the version is &lt; 1.4 so it doesn't support the functionality I need. The problem with (2) is that <strong>my application simply crashes the moment I call any method in EGL14, and I'm not sure how I'm supposed to use it (I could not find a single example program / tutorial on how EGL14 is supposed to be used in an app)</strong>. In particular, I'd like to learn how to get a valid GL context from EGL14: in the case of EGL10, I could do that by calling javax.microedition.khronos.egl.EGLContext.getGL(). However, I see no equivalent method in class android.opengl.EGLContext. In fact, all EGL-related classes in android.opengl except EGL14 seem to be mostly empty.</p> <p>My best bet was to follow the same line of reasoning as in case of GLES20: to call the methods only inside the GLSurfaceView.Renderer methods: onDrawFrame(), onSurfaceCreated(), onSurfaceChanged(), because these supply valid GL (GL10) and EGL (EGLConfig) contexts as arguments. So I put following code inside onDrawFrame():-</p> <pre><code>public void onDrawFrame(GL10 gl) { ... android.opengl.EGLDisplay d = null; if ( (d = EGL14.eglGetDisplay(EGL14.EGL_DEFAULT_DISPLAY)) == EGL14.EGL_NO_DISPLAY) { Log.i("Triangle", "EGL14.eglGetDisplay() failed!"); } else { Log.i("Triangle", "EGL14.eglGetDisplay() succeeded!"); } ... } </code></pre> <p>I believe I won't have to instantiate EGL14 before calling the above since all methods are static. However, the call to EGL14.eglGetDisplay() crashes the app.</p> <p>Any help would be much appreciated, thanks:)</p>
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    1. COHello, I was facing the same problem, and I've just found out that my issue was a call to "glColorMask", after removing my call to this method everything got solved. Probably your issue's cause is different, but just in case it helps your I let you the hint.
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