GLSurfaceView是OpenGL中的一个类，也是可以预览Camera的，而且在预览Camera上有其独到之处。独到之处在哪？当使用Surfaceview无能为力、痛不欲生时就只有使用GLSurfaceView了，它能够真正做到让Camera的数据和显示分离，所以搞明白了这个，，像Camera只开预览不显示这都是小菜，妥妥的。Android4.0的自带Camera源码是用SurfaceView预览的，但到了4.2就换成了GLSurfaceView来预览。如今到了4.4又用了自家的TextureView，所以从中可以窥探出新增TextureView的用意。
虽说Android4.2的Camera源码是用GLSurfaceView预览的，但是进行了大量的封装又封装的，由于是OpenGL小白，真是看的不知所云。俺滴要求不高，只想弄个可拍照的摸清GLSurfaceView在预览Camera上的使用流程。经过一番百度一无所获，后来翻出去Google一大圈也没发现可用的。倒是很多人都在用GLSurfaceView和Surfaceview同时预览Camera，Surfaceview用来预览数据，在上面又铺了一层GLSurfaceView绘制一些信息。无奈自己摸索，整出来的是能拍照也能得到数据，但是界面上不是一块白板就是一块黑板啥都不显示。后来在stackoverflow终于找到了一个可用的链接，哈哈，苍天啊，终于柳暗花明了！参考此链接，自己又改改摸索了一天才彻底搞定。之所以费这么多时间是不明白OpenGL ES2.0的绘制基本流程，跟简单的OpenGL的绘制还是稍有区别。下面上源码:
一、CameraGLSurfaceView.java 此类继承GLSurfaceView，并实现了两个接口
package org.yanzi.camera.preview;import javax.microedition.khronos.egl.EGLConfig;import javax.microedition.khronos.opengles.GL10;import org.yanzi.camera.CameraInterface;import android.content.Context;import android.graphics.SurfaceTexture;import android.opengl.GLES11Ext;import android.opengl.GLES20;import android.opengl.GLSurfaceView;import android.opengl.GLSurfaceView.Renderer;import android.util.AttributeSet;import android.util.Log;public class CameraGLSurfaceView extends GLSurfaceView implements Renderer, SurfaceTexture.OnFrameAvailableListener {private static final String TAG = "yanzi";Context mContext;SurfaceTexture mSurface;int mTextureID = -1;DirectDrawer mDirectDrawer;public CameraGLSurfaceView(Context context, AttributeSet attrs) {super(context, attrs);// TODO Auto-generated constructor stubmContext = context;setEGLContextClientVersion(2);setRenderer(this);setRenderMode(RENDERMODE_WHEN_DIRTY);}@Overridepublic void onSurfaceCreated(GL10 gl, EGLConfig config) {// TODO Auto-generated method stubLog.i(TAG, "onSurfaceCreated…");mTextureID = createTextureID();mSurface = new SurfaceTexture(mTextureID);mSurface.setOnFrameAvailableListener(this);mDirectDrawer = new DirectDrawer(mTextureID);CameraInterface.getInstance().doOpenCamera(null);}@Overridepublic void onSurfaceChanged(GL10 gl, int width, int height) {// TODO Auto-generated method stubLog.i(TAG, "onSurfaceChanged…");GLES20.glViewport(0, 0, width, height);if(!CameraInterface.getInstance().isPreviewing()){CameraInterface.getInstance().doStartPreview(mSurface, 1.33f);}}@Overridepublic void onDrawFrame(GL10 gl) {// TODO Auto-generated method stubLog.i(TAG, "onDrawFrame…");GLES20.glClearColor(1.0f, 1.0f, 1.0f, 1.0f);GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT | GLES20.GL_DEPTH_BUFFER_BIT);mSurface.updateTexImage();float[] mtx = new float[16];mSurface.getTransformMatrix(mtx);mDirectDrawer.draw(mtx);}@Overridepublic void onPause() {// TODO Auto-generated method stubsuper.onPause();CameraInterface.getInstance().doStopCamera();}private int createTextureID(){int[] texture = new int[1];GLES20.glGenTextures(1, texture, 0);GLES20.glBindTexture(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, texture[0]);GLES20.glTexParameterf(GLES11Ext.GL_TEXTURE_EXTERNAL_OES,GL10.GL_TEXTURE_MIN_FILTER,GL10.GL_LINEAR);GLES20.glTexParameterf(GLES11Ext.GL_TEXTURE_EXTERNAL_OES,GL10.GL_TEXTURE_MAG_FILTER, GL10.GL_LINEAR);GLES20.glTexParameteri(GLES11Ext.GL_TEXTURE_EXTERNAL_OES,GL10.GL_TEXTURE_WRAP_S, GL10.GL_CLAMP_TO_EDGE);GLES20.glTexParameteri(GLES11Ext.GL_TEXTURE_EXTERNAL_OES,GL10.GL_TEXTURE_WRAP_T, GL10.GL_CLAMP_TO_EDGE);return texture[0];}public SurfaceTexture _getSurfaceTexture(){return mSurface;}@Overridepublic void onFrameAvailable(SurfaceTexture surfaceTexture) {// TODO Auto-generated method stubLog.i(TAG, "onFrameAvailable…");this.requestRender();}}关于这个类进行简单说明:
1、Renderer这个接口里有三个回调:onSurfaceCreated()onSurfaceChanged()onDrawFrame(),在onSurfaceCreated里设置了GLSurfaceView的版本:setEGLContextClientVersion(2); 如果没这个设置是啥都画不出来了，因为Android支持OpenGL ES1.1和2.0及最新的3.0，而且版本间差别很大。不告诉他版本他不知道用哪个版本的api渲染。在设置setRenderer(this);后，再设置它的模式为RENDERMODE_WHEN_DIRTY。这个也很关键，看api：
When renderMode is RENDERMODE_CONTINUOUSLY, the renderer is called repeatedly to re-render the scene. When renderMode is RENDERMODE_WHEN_DIRTY, the renderer only rendered when the surface is created, or when requestRender is called. Defaults to RENDERMODE_CONTINUOUSLY.
Using RENDERMODE_WHEN_DIRTY can improve battery life and overall system performance by allowing the GPU and CPU to idle when the view does not need to be updated.
己欲立先立人，已欲达先达人。
