android学习13——android egl hello world

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from:http://www.cnblogs.com/zhouyang209117/p/5415486.html

通常情况下我们使用GLSurfaceview来实现opengl渲染.GLSurfaceview实现上是对SurfaceView和EGL的封装.为了从本质上理解渲染流程,使用EGL和SurfaceView来写一个Demo.
首先要封装一个EGLHelper用来操作EGL.下面代码的详细解释请参考参考资料3. EGLHelper.java代码如下:

public class EglHelper {    EGL10 mEgl;    EGLDisplay mEglDisplay;    EGLSurface mEglSurface;    EGLConfig mEglConfig;    EGLContext mEglContext;    public EglHelper(){}    public void start(int[] configSpec)    {        mEgl = (EGL10) EGLContext.getEGL();        mEglDisplay = mEgl.eglGetDisplay(EGL10.EGL_DEFAULT_DISPLAY);        int[] version = new int[2];        mEgl.eglInitialize(mEglDisplay, version);        EGLConfig[] configs = new EGLConfig[1];        int[] num_config = new int[1];        mEgl.eglChooseConfig(mEglDisplay, configSpec, configs, 1,                num_config);        mEglConfig = configs[0];        mEglContext = mEgl.eglCreateContext(mEglDisplay, mEglConfig,                EGL10.EGL_NO_CONTEXT, null);        mEglSurface = null;    }    public GL createSurface(SurfaceHolder holder) {        if (mEglSurface != null) {            mEgl.eglMakeCurrent(mEglDisplay, EGL10.EGL_NO_SURFACE,                    EGL10.EGL_NO_SURFACE, EGL10.EGL_NO_CONTEXT);            mEgl.eglDestroySurface(mEglDisplay, mEglSurface);        }        mEglSurface = mEgl.eglCreateWindowSurface(mEglDisplay,                mEglConfig, holder, null);        mEgl.eglMakeCurrent(mEglDisplay, mEglSurface, mEglSurface,                mEglContext);        GL gl = mEglContext.getGL();        return gl;    }    public boolean swap() {        mEgl.eglSwapBuffers(mEglDisplay, mEglSurface);        return mEgl.eglGetError() != EGL11.EGL_CONTEXT_LOST;    }    public void finish() {        if (mEglSurface != null) {            mEgl.eglMakeCurrent(mEglDisplay, EGL10.EGL_NO_SURFACE,                    EGL10.EGL_NO_SURFACE,                    EGL10.EGL_NO_CONTEXT);            mEgl.eglDestroySurface(mEglDisplay, mEglSurface);            mEglSurface = null;        }        if (mEglContext != null) {            mEgl.eglDestroyContext(mEglDisplay, mEglContext);            mEglContext = null;        }        if (mEglDisplay != null) {            mEgl.eglTerminate(mEglDisplay);            mEglDisplay = null;        }    }}

需要写一个类继承SurfaceView.要在SurfaceView的surfaceCreated和surfaceChanged执行之后再进行opengl的相关操作.代码如下:

public class MySurfaceView extends SurfaceView implements SurfaceHolder.Callback {    public SurfaceHolder mHolder;    private int w, h;    private Context context;    public MySurfaceView(Context context) {        super(context);        this.context = context;        init();    }    public MySurfaceView(Context context, AttributeSet attrs) {        super(context, attrs);        init();    }    private void init() {        mHolder = getHolder();        mHolder.addCallback(this);    }    @Override    public void onWindowFocusChanged(boolean hasFocus) {        super.onWindowFocusChanged(hasFocus);        EglHelper eglHelper = new EglHelper();        int[] configSpec = {                EGL10.EGL_DEPTH_SIZE, 0,                EGL10.EGL_NONE        };        eglHelper.start(configSpec);        GL10 gl = (GL10) eglHelper.createSurface(mHolder);        gl.glClearColor(1f, 0f, 0f, 0f);        gl.glViewport(0, 0, w, h);        gl.glClear(GL10.GL_COLOR_BUFFER_BIT);        eglHelper.swap();    }    public void surfaceCreated(SurfaceHolder holder) {    }    public void surfaceDestroyed(SurfaceHolder holder) {    }    public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {        this.w = w;        this.h = h;    }}

整个程序源代码: https://github.com/zhouyang209117/AndroidTutorial/tree/master/OpenGL/EGLHelloWorld
参考资料

Sayed Y, Hashimi, Satya Komatineni. Pro Android. Apress. pp325-362. 2009.
(美)Kevin Brothaler著, 刘力平,苏统华译. OpenGL ES应用开发实践指南 android卷. 机械工业出版社. pp1-26. 2014.
Aaftab Munshi, Dan Ginsburg, Dave Shreiner. OpenGL ES 2.0 Programming Guide. addison wesley. pp35-56

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