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，，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
1 package org.yanzi.camera.preview; 2 3 import javax.microedition.khronos.egl.EGLConfig; 4 import javax.microedition.khronos.opengles.GL10; 5 6 import org.yanzi.camera.CameraInterface; 7 8 import android.content.Context; 9 import android.graphics.SurfaceTexture;10 import android.opengl.GLES11Ext;11 import android.opengl.GLES20;12 import android.opengl.GLSurfaceView;13 import android.opengl.GLSurfaceView.Renderer;14 import android.util.AttributeSet;15 import android.util.Log;16 17 public class CameraGLSurfaceView extends GLSurfaceView implements Renderer, SurfaceTexture.OnFrameAvailableListener {18 private static final String TAG = "yanzi";19 Context mContext;20 SurfaceTexture mSurface;21 int mTextureID = -1;22 DirectDrawer mDirectDrawer;23 public CameraGLSurfaceView(Context context, AttributeSet attrs) {24 super(context, attrs);25 // TODO Auto-generated constructor stub26 mContext = context;27 setEGLContextClientVersion(2);28 setRenderer(this);29 setRenderMode(RENDERMODE_WHEN_DIRTY);30 }31 @Override32 public void onSurfaceCreated(GL10 gl, EGLConfig config) {33 // TODO Auto-generated method stub34 Log.i(TAG, "onSurfaceCreated...");35 mTextureID = createTextureID();36 mSurface = new SurfaceTexture(mTextureID);37 mSurface.setOnFrameAvailableListener(this);38 mDirectDrawer = new DirectDrawer(mTextureID);39 CameraInterface.getInstance().doOpenCamera(null);40 41 }42 @Override43 public void onSurfaceChanged(GL10 gl, int width, int height) {44 // TODO Auto-generated method stub45 Log.i(TAG, "onSurfaceChanged...");46 GLES20.glViewport(0, 0, width, height);47 if(!CameraInterface.getInstance().isPreviewing()){48 CameraInterface.getInstance().doStartPreview(mSurface, 1.33f);49 }50 51 52 }53 @Override54 public void onDrawFrame(GL10 gl) {55 // TODO Auto-generated method stub56 Log.i(TAG, "onDrawFrame...");57 GLES20.glClearColor(1.0f, 1.0f, 1.0f, 1.0f);58 GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT | GLES20.GL_DEPTH_BUFFER_BIT);59 mSurface.updateTexImage();60 float[] mtx = new float[16];61 mSurface.getTransformMatrix(mtx);62 mDirectDrawer.draw(mtx);63 }64 65 @Override66 public void onPause() {67 // TODO Auto-generated method stub68 super.onPause();69 CameraInterface.getInstance().doStopCamera();70 }71 private int createTextureID()72 {73 int[] texture = new int[1];74 75 GLES20.glGenTextures(1, texture, 0);76 GLES20.glBindTexture(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, texture[0]);77 GLES20.glTexParameterf(GLES11Ext.GL_TEXTURE_EXTERNAL_OES,78 GL10.GL_TEXTURE_MIN_FILTER,GL10.GL_LINEAR); 79 GLES20.glTexParameterf(GLES11Ext.GL_TEXTURE_EXTERNAL_OES,80 GL10.GL_TEXTURE_MAG_FILTER, GL10.GL_LINEAR);81 GLES20.glTexParameteri(GLES11Ext.GL_TEXTURE_EXTERNAL_OES,82 GL10.GL_TEXTURE_WRAP_S, GL10.GL_CLAMP_TO_EDGE);83 GLES20.glTexParameteri(GLES11Ext.GL_TEXTURE_EXTERNAL_OES,84 GL10.GL_TEXTURE_WRAP_T, GL10.GL_CLAMP_TO_EDGE);85 86 return texture[0];87 }88 public SurfaceTexture _getSurfaceTexture(){89 return mSurface;90 }91 @Override92 public void onFrameAvailable(SurfaceTexture surfaceTexture) {93 // TODO Auto-generated method stub94 Log.i(TAG, "onFrameAvailable...");95 this.requestRender();96 }97 98 }
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.
大意是RENDERMODE_CONTINUOUSLY模式就会一直Render，如果设置成RENDERMODE_WHEN_DIRTY，就是当有数据时才rendered或者主动调用了GLSurfaceView的requestRender.默认是连续模式，很显然Camera适合脏模式，一秒30帧，当有数据来时再渲染。
2、正因是RENDERMODE_WHEN_DIRTY所以就要告诉GLSurfaceView什么时候Render，也就是啥时候进到onDrawFrame()这个函数里。SurfaceTexture.OnFrameAvailableListener这个接口就干了这么一件事，当有数据上来后会进到
public void onFrameAvailable(SurfaceTexture surfaceTexture) {// TODO Auto-generated method stubLog.i(TAG, "onFrameAvailable...");this.requestRender();}
这里，然后执行requestRender()。
3、网上有一些OpenGL ES的示例是在Activity里实现了SurfaceTexture.OnFrameAvailableListener此接口，其实这个无所谓。无论是被谁实现，关键看在回调里干了什么事。
4、与TextureView里对比可知，TextureView预览时因为实现了SurfaceTextureListener会自动创建SurfaceTexture。但在GLSurfaceView里则要手动创建同时绑定一个纹理ID。
5、本文在onSurfaceCreated()里打开Camera，在onSurfaceChanged()里开启预览，默认1.33的比例。原因是相比前两种预览，此处SurfaceTexture创建需要一定时间。如果想要开预览时由Activity发起，则要GLSurfaceView利用Handler将创建的SurfaceTexture传递给Activity。
二、DirectDrawer.java 此类非常关键，负责将SurfaceTexture内容绘制到屏幕上
1 package org.yanzi.camera.preview; 2 3 import java.nio.ByteBuffer; 4 import java.nio.ByteOrder; 5 import java.nio.FloatBuffer; 6 import java.nio.ShortBuffer; 7 8 import android.opengl.GLES11Ext; 9 import android.opengl.GLES20; 10 import android.opengl.Matrix; 11 12 public class DirectDrawer { 13 private final String vertexShaderCode = 14 "attribute vec4 vPosition;" + 15 "attribute vec2 inputTextureCoordinate;" + 16 "varying vec2 textureCoordinate;" + 17 "void main()" + 18 "{"+ 19 "gl_Position = vPosition;"+ 20 "textureCoordinate = inputTextureCoordinate;" + 21 "}"; 22 23 private final String fragmentShaderCode = 24 "#extension GL_OES_EGL_image_external : require\n"+ 25 "precision mediump float;" + 26 "varying vec2 textureCoordinate;\n" + 27 "uniform samplerExternalOES s_texture;\n" + 28 "void main() {" + 29 " gl_FragColor = texture2D( s_texture, textureCoordinate );\n" + 30 "}"; 31 32 private FloatBuffer vertexBuffer, textureVerticesBuffer; 33 private ShortBuffer drawListBuffer; 34 private final int mProgram; 35 private int mPositionHandle; 36 private int mTextureCoordHandle; 37 38 private short drawOrder[] = { 0, 1, 2, 0, 2, 3 }; // order to draw vertices 39 40 // number of coordinates per vertex in this array 41 private static final int COORDS_PER_VERTEX = 2; 42 43 private final int vertexStride = COORDS_PER_VERTEX * 4; // 4 bytes per vertex 44 45 static float squareCoords[] = { 46 -1.0f, 1.0f, 47 -1.0f, -1.0f, 48 1.0f, -1.0f, 49 1.0f, 1.0f, 50 }; 51 52 static float textureVertices[] = { 53 0.0f, 1.0f, 54 1.0f, 1.0f, 55 1.0f, 0.0f, 56 0.0f, 0.0f, 57 }; 58 59 private int texture; 60 61 public DirectDrawer(int texture) 62 { 63 this.texture = texture; 64 // initialize vertex byte buffer for shape coordinates 65 ByteBuffer bb = ByteBuffer.allocateDirect(squareCoords.length * 4); 66 bb.order(ByteOrder.nativeOrder()); 67 vertexBuffer = bb.asFloatBuffer(); 68 vertexBuffer.put(squareCoords); 69 vertexBuffer.position(0); 70 71 // initialize byte buffer for the draw list 72 ByteBuffer dlb = ByteBuffer.allocateDirect(drawOrder.length * 2); 73 dlb.order(ByteOrder.nativeOrder()); 74 drawListBuffer = dlb.asShortBuffer(); 75 drawListBuffer.put(drawOrder); 76 drawListBuffer.position(0); 77 78 ByteBuffer bb2 = ByteBuffer.allocateDirect(textureVertices.length * 4); 79 bb2.order(ByteOrder.nativeOrder()); 80 textureVerticesBuffer = bb2.asFloatBuffer(); 81 textureVerticesBuffer.put(textureVertices); 82 textureVerticesBuffer.position(0); 83 84 int vertexShader = loadShader(GLES20.GL_VERTEX_SHADER, vertexShaderCode); 85 int fragmentShader = loadShader(GLES20.GL_FRAGMENT_SHADER, fragmentShaderCode); 86 87 mProgram = GLES20.glCreateProgram(); // create empty OpenGL ES Program 88 GLES20.glAttachShader(mProgram, vertexShader); // add the vertex shader to program 89 GLES20.glAttachShader(mProgram, fragmentShader); // add the fragment shader to program 90 GLES20.glLinkProgram(mProgram); // creates OpenGL ES program executables 91 } 92 93 public void draw(float[] mtx) 94 { 95 GLES20.glUseProgram(mProgram); 96 97 GLES20.glActiveTexture(GLES20.GL_TEXTURE0); 98 GLES20.glBindTexture(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, texture); 99 100 // get handle to vertex shader's vPosition member101 mPositionHandle = GLES20.glGetAttribLocation(mProgram, "vPosition");102 103 // Enable a handle to the triangle vertices104 GLES20.glEnableVertexAttribArray(mPositionHandle);105 106 // Prepare the coordinate data107 GLES20.glVertexAttribPointer(mPositionHandle, COORDS_PER_VERTEX, GLES20.GL_FLOAT, false, vertexStride, vertexBuffer);108 109 mTextureCoordHandle = GLES20.glGetAttribLocation(mProgram, "inputTextureCoordinate");110 GLES20.glEnableVertexAttribArray(mTextureCoordHandle);111 112 // textureVerticesBuffer.clear();113 // textureVerticesBuffer.put( transformTextureCoordinates( textureVertices, mtx ));114 // textureVerticesBuffer.position(0);115 GLES20.glVertexAttribPointer(mTextureCoordHandle, COORDS_PER_VERTEX, GLES20.GL_FLOAT, false, vertexStride, textureVerticesBuffer);116 117 GLES20.glDrawElements(GLES20.GL_TRIANGLES, drawOrder.length, GLES20.GL_UNSIGNED_SHORT, drawListBuffer);118 119 // Disable vertex array120 GLES20.glDisableVertexAttribArray(mPositionHandle);121 GLES20.glDisableVertexAttribArray(mTextureCoordHandle);122 }123 124 private int loadShader(int type, String shaderCode){125 126 // create a vertex shader type (GLES20.GL_VERTEX_SHADER)127 // or a fragment shader type (GLES20.GL_FRAGMENT_SHADER)128 int shader = GLES20.glCreateShader(type);129 130 // add the source code to the shader and compile it131 GLES20.glShaderSource(shader, shaderCode);132 GLES20.glCompileShader(shader);133 134 return shader;135 }136 private float[] transformTextureCoordinates( float[] coords, float[] matrix)137 { 138 float[] result = new float[ coords.length ]; 139 float[] vt = new float[4]; 140 141 for ( int i = 0 ; i < coords.length ; i += 2 ) {142 float[] v = { coords[i], coords[i+1], 0 , 1 };143 Matrix.multiplyMV(vt, 0, matrix, 0, v, 0);144 result[i] = vt[0];145 result[i+1] = vt[1];146 }147 return result;148 }149 } 三、有了上面两个类就完成95%的工作，可以将GLSurfaceView看成是有生命周期的。在onPause里进行关闭Camera，在Activity里复写两个方法:
@Override protected void onResume() { // TODO Auto-generated method stub super.onResume(); glSurfaceView.bringToFront(); } @Override protected void onPause() { // TODO Auto-generated method stub super.onPause(); glSurfaceView.onPause(); }
这个glSurfaceView.bringToFront();其实不写也中。在布局里写入自定义的GLSurfaceView就ok了:
CameraActivity里只负责UI部分，CameraGLSurfaceView负责开Camera、预览，并调用DirectDrawer里的draw()进行绘制。其他代码就不上了。
注意事项:
1、在onDrawFrame()里，如果不调用mDirectDrawer.draw(mtx);是啥都显示不出来的！！！这是GLSurfaceView的特别之处。为啥呢？因为GLSurfaceView不是Android亲生的，而Surfaceview和TextureView是。所以得自己按照OpenGL ES的流程画。
2、究竟mDirectDrawer.draw(mtx)里在哪获取的Buffer目前杂家还么看太明白，貌似么有请求buffer，而是根据GLSurfaceView里创建的SurfaceTexture之前，生成的有个纹理ID。这个纹理ID一方面跟SurfaceTexture是绑定在一起的，另一方面跟DirectDrawer绑定，而SurfaceTexture作渲染载体。
3、参考链接里有,有人为了解决问题，给出了下面三段代码:
@Overridepublic void onDrawFrame(GL10 gl){ float[] mtx = new float[16]; mSurface.updateTexImage(); mSurface.getTransformMatrix(mtx); mDirectVideo.draw(mtx);} private float[] transformTextureCoordinates( float[] coords, float[] matrix) { float[] result = new float[ coords.length ]; float[] vt = new float[4]; for ( int i = 0 ; i < coords.length ; i += 2 ) { float[] v = { coords[i], coords[i+1], 0 , 1 }; Matrix.multiplyMV(vt, 0, matrix, 0, v, 0); result[i] = vt[0]; result[i+1] = vt[1]; } return result; }textureVerticesBuffer.clear();textureVerticesBuffer.put( transformTextureCoordinates( textureVertices, mtx ));textureVerticesBuffer.position(0);
我已经把代码都融入到了此demo，只不过在draw()方法里么有使用。原因是使用之后，得到的预览画面反而是变形的，而不用的话是ok的。上面的代码是得到SurfaceTexture的变换矩阵：mSurface.getTransformMatrix
然后将此矩阵传递给draw()，在draw的时候对textureVerticesBuffer作一个变化，然后再画。
下图是未加这个矩阵变换效果时:
下图为使用了变换矩阵，划片扭曲的还真说不上来咋扭曲的，但足以说明OpenGL ES在渲染效果上的强大，就是设置了个矩阵，不用一帧帧处理，就能得到不一样显示效果。
-----------------------------本文系原创，转载请注明作者yanzi1225627
版本号:PlayCamera_V3.0.0[2014-6-22].zip
CSDN下载链接:http://download.csdn.net/detail/yanzi1225627/7547263
百度云盘:
附个OpenGL ES简明教程：http://www.apkbus.com/android-20427-1-1.html