一、提要
偶然在Android developers看到这篇教程，遍一步步做了下来，下面是一点记录。
二、在Android中绘制OpenGL es的方法
为了在Android应用中使用OpenGL绘制图形，我们必须创建一个View容器。一个最直接的方法就是implement GLSurfaceView 和a GLSurfaceView.Renderer。前者就是容器，后者控制View中渲染的内容。
还有两种方法是SurfaceView和TextureView，但有点小复杂。
最终效果：
三、必要的声明
在manifest文件中添加下面的代码：
四、主Activity类
package com.example.opengles; import android.opengl.GLSurfaceView; import android.os.Bundle; import android.app.Activity; import android.content.Context; import android.view.Menu; public class OpenGLActivity extends Activity { private GLSurfaceView mGLView; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); mGLView = new MyGLSurfaceView(this); setContentView(mGLView); } @Override public boolean onCreateOptionsMenu(Menu menu) { getMenuInflater().inflate(R.menu.activity_open_gl, menu); return true; } @Override protected void onPause() { super.onPause(); // The following call pauses the rendering thread. // If your OpenGL application is memory intensive, // you should consider de-allocating objects that // consume significant memory here. mGLView.onPause(); } @Override protected void onResume() { super.onResume(); // The following call resumes a paused rendering thread. // If you de-allocated graphic objects for onPause() // this is a good place to re-allocate them. mGLView.onResume(); } } class MyGLSurfaceView extends GLSurfaceView { public MyGLSurfaceView(Context context){ super(context); // Create an OpenGL ES 2.0 context. setEGLContextClientVersion(2); // Set the Renderer for drawing on the GLSurfaceView setRenderer(new MyRender()); // Render the view only when there is a change in the drawing data setRenderMode(GLSurfaceView.RENDERMODE_WHEN_DIRTY); } }
四、渲染器类
package com.example.opengles; import java.nio.ByteBuffer; import java.nio.ByteOrder; import java.nio.FloatBuffer; import javax.microedition.khronos.egl.EGLConfig; import javax.microedition.khronos.opengles.GL10; import android.opengl.GLES20; import android.opengl.GLSurfaceView; public class MyRender implements GLSurfaceView.Renderer { private Triangle mTriangle; @Override public void onDrawFrame(GL10 gl) { // TODO Auto-generated method stub // Draw background color GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT); // Draw triangle mTriangle.draw(); } @Override public void onSurfaceChanged(GL10 gl, int width, int height) { // TODO Auto-generated method stub // Adjust the viewport based on geometry changes, // such as screen rotation GLES20.glViewport(0, 0, width, height); } public static int loadShader(int type, String shaderCode){ // create a vertex shader type (GLES20.GL_VERTEX_SHADER) // or a fragment shader type (GLES20.GL_FRAGMENT_SHADER) int shader = GLES20.glCreateShader(type); // add the source code to the shader and compile it GLES20.glShaderSource(shader, shaderCode); GLES20.glCompileShader(shader); return shader; } @Override public void onSurfaceCreated(GL10 gl, EGLConfig config) { // TODO Auto-generated method stub // Set the background frame color GLES20.glClearColor(0.0f, 0.0f, 0.0f, 1.0f); mTriangle = new Triangle(); } } class Triangle { private final String vertexShaderCode = "attribute vec4 vPosition;" + "void main() {" + " gl_Position = vPosition;" + "}"; private final String fragmentShaderCode = "precision mediump float;" + "uniform vec4 vColor;" + "void main() {" + " gl_FragColor = vColor;" + "}"; private final FloatBuffer vertexBuffer; private final int mProgram; private int mPositionHandle; private int mColorHandle; // number of coordinates per vertex in this array static final int COORDS_PER_VERTEX = 3; static float triangleCoords[] = { // in counterclockwise order: 0.0f, 0.622008459f, 0.0f, // top -0.5f, -0.311004243f, 0.0f, // bottom left 0.5f, -0.311004243f, 0.0f // bottom right }; private final int vertexCount = triangleCoords.length / COORDS_PER_VERTEX; private final int vertexStride = COORDS_PER_VERTEX * 4; // bytes per vertex // Set color with red, green, blue and alpha (opacity) values float color[] = { 0.63671875f, 0.76953125f, 0.22265625f, 1.0f }; public Triangle() { // initialize vertex byte buffer for shape coordinates ByteBuffer bb = ByteBuffer.allocateDirect( // (number of coordinate values * 4 bytes per float) triangleCoords.length * 4); // use the device hardware's native byte order bb.order(ByteOrder.nativeOrder()); // create a floating point buffer from the ByteBuffer vertexBuffer = bb.asFloatBuffer(); // add the coordinates to the FloatBuffer vertexBuffer.put(triangleCoords); // set the buffer to read the first coordinate vertexBuffer.position(0); // prepare shaders and OpenGL program int vertexShader = MyRender.loadShader(GLES20.GL_VERTEX_SHADER, vertexShaderCode); int fragmentShader = MyRender.loadShader(GLES20.GL_FRAGMENT_SHADER, fragmentShaderCode); mProgram = GLES20.glCreateProgram(); // create empty OpenGL Program GLES20.glAttachShader(mProgram, vertexShader); // add the vertex shader to program GLES20.glAttachShader(mProgram, fragmentShader); // add the fragment shader to program GLES20.glLinkProgram(mProgram); // create OpenGL program executables } public void draw() { // Add program to OpenGL environment GLES20.glUseProgram(mProgram); // get handle to vertex shader's vPosition member mPositionHandle = GLES20.glGetAttribLocation(mProgram, "vPosition"); // Enable a handle to the triangle vertices GLES20.glEnableVertexAttribArray(mPositionHandle); // Prepare the triangle coordinate data GLES20.glVertexAttribPointer(mPositionHandle, COORDS_PER_VERTEX, GLES20.GL_FLOAT, false, vertexStride, vertexBuffer); // get handle to fragment shader's vColor member mColorHandle = GLES20.glGetUniformLocation(mProgram, "vColor"); // Set color for drawing the triangle GLES20.glUniform4fv(mColorHandle, 1, color, 0); // Draw the triangle GLES20.glDrawArrays(GLES20.GL_TRIANGLES, 0, vertexCount); // Disable vertex array GLES20.glDisableVertexAttribArray(mPositionHandle); } }
这个类中最重要的三个函数是
onSurfaceCreated() - 初始化OpenGL环境onDrawFrame() - 绘制ViewonSurfaceChanged() - 当View发生改变的时候掉用是不是很熟悉，就是Qt的OpenGL中的paintGL() ，resizeGL() ，initializeGL() 。最后运行的时候会在屏幕上绘制一个三角形，用的是ShaderLanguage，这个就直接copy了，当然也可以用那种比较原始的一个个定义点定义颜色来绘图。
注意：OpenGL的程序在模拟器中没办法跑起来，需要真机调试。
五、参考资料
android develop：http://developer.android.com/training/graphics/opengl/environment.html