android中使用OpenGL ES

在android中使用OpenGL ES需要三个步骤：1. 创建GLSurfaceView组件，使用Activity来显示GLSurfaceView组建。2. 为GLSurfaceView组建创建GLSurfaceView.Renderer实例，实现GLSurfaceView.Renderer类时需要实现该接口里的三个方法：abstract void onDrawFrame(GL10 gl)：Called to draw the current frame.abstract void onSurfaceChanged(GL10 gl, int width, int height)：Called when the surface changed size.abstract void onSurfaceCreated(GL10 gl, EGLConfig config)：Called when the surface is created or recreated.3. 调用GLSurfaceView组建的setRenderer (GLSurfaceView.Renderer renderer) 方法指定Renderer对象，该对象将会完成GLSurfaceView里3D图形的绘制。然后来看一个Demo，首先是主Activity：

package com.example.androidgldemo;

import android.opengl.GLSurfaceView;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;

public class AndroidGLDemo extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
GLSurfaceView glView = new GLSurfaceView(this);
AndroidGLDemoRenderer renderer = new AndroidGLDemoRenderer();
glView.setRenderer(renderer);
setContentView(glView);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.activity_main, menu);
return true;
}
}

然后是Renderer的实现：

package com.example.androidgldemo;

import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.FloatBuffer;
import java.nio.IntBuffer;

import javax.microedition.khronos.egl.EGLConfig;
import javax.microedition.khronos.opengles.GL10;

import android.opengl.GLSurfaceView.Renderer;

public class AndroidGLDemoRenderer implements Renderer {
float[] mTriangleData = new float[] {
0.1f, 0.6f, 0.0f,
-0.3f, 0.0f, 0.0f,
0.3f, 0.1f, 0.0f
};
int[] mTriangleColor = new int[] {
65535, 0, 0, 0,
0, 65535, 0, 0,
0, 0, 65535, 0,
};

float[] mRectData = new float[] {
0.4f, 0.4f, 0.0f,
0.4f, -0.4f, 0.0f,
-0.4f, 0.4f, 0.0f,
-0.4f, -0.4f, 0.0f
};

int[] mRectColor = new int[] {
0, 65535, 0, 0,
0, 0, 65535, 0,
65535, 0, 0, 0,
65535, 65535, 0, 0,
};

FloatBuffer mTriangleDataBuffer;
IntBuffer mTriangleColorBuffer;

FloatBuffer mRectDataBuffer;
IntBuffer mRectColorBuffer;

public AndroidGLDemoRenderer() {
mTriangleDataBuffer= bufferUtil(mTriangleData);
mTriangleColorBuffer = bufferUtil(mTriangleColor);

mRectDataBuffer = bufferUtil(mRectData);
mRectColorBuffer = bufferUtil(mRectColor);
}

@Override
public void onDrawFrame(GL10 gl) {
gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);
gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
gl.glEnableClientState(GL10.GL_COLOR_ARRAY);
gl.glMatrixMode(GL10.GL_MODELVIEW);

gl.glLoadIdentity();
gl.glTranslatef(-0.6f, 0.0f, -1.5f);
gl.glVertexPointer(3, GL10.GL_FLOAT, 0, mTriangleDataBuffer);
gl.glColorPointer(4, GL10.GL_FIXED, 0, mTriangleColorBuffer);
gl.glDrawArrays(GL10.GL_TRIANGLES, 0, 3);

gl.glLoadIdentity();
gl.glTranslatef(0.6f, 0.8f, -1.5f);
gl.glVertexPointer(3, GL10.GL_FLOAT, 0, mRectDataBuffer);
gl.glColorPointer(4, GL10.GL_FIXED, 0, mRectColorBuffer);
gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 0, 4);

gl.glFinish();
gl.glDisableClientState(GL10.GL_VERTEX_ARRAY);
}

@Override
public void onSurfaceChanged(GL10 gl, int width, int height) {
gl.glViewport(0, 0, width, height);
gl.glMatrixMode(GL10.GL_PROJECTION);
gl.glLoadIdentity();
float ratio = (float) width / height;
gl.glFrustumf(-ratio, ratio, -1, 1, 1, 10);
}

@Override
public void onSurfaceCreated(GL10 gl, EGLConfig config) {
gl.glDisable(GL10.GL_DITHER);
gl.glHint(GL10.GL_PERSPECTIVE_CORRECTION_HINT, GL10.GL_FASTEST);
gl.glClearColor(0, 0, 0, 0);
gl.glShadeModel(GL10.GL_SMOOTH);
gl.glEnable(GL10.GL_DEPTH_TEST);
gl.glDepthFunc(GL10.GL_LEQUAL);
}

public IntBuffer bufferUtil(int []arr){
IntBuffer buffer;

ByteBuffer qbb = ByteBuffer.allocateDirect(arr.length * 4);
qbb.order(ByteOrder.nativeOrder());

buffer = qbb.asIntBuffer();
buffer.put(arr);
buffer.position(0);

return buffer;
}

public FloatBuffer bufferUtil(float []arr){
FloatBuffer buffer;

ByteBuffer qbb = ByteBuffer.allocateDirect(arr.length * 4);
qbb.order(ByteOrder.nativeOrder());

buffer = qbb.asFloatBuffer();
buffer.put(arr);
buffer.position(0);

return buffer;
}
}

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注意构造函数中那些Buffer的创建方式。在这个地方，不能直接使用FloatBuffer/IntBuffer 的wrap() method。直接用这个method创建出来的buffer会导致JE:

02-26 23:12:08.945: E/OpenGLES(2750): Application com.example.androidgldemo (SDK target 17) called a GL11 Pointer method with an indirect Buffer.02-26 23:12:08.968: W/dalvikvm(2750): threadid=11: thread exiting with uncaught exception (group=0x40d57930)02-26 23:12:08.984: E/AndroidRuntime(2750): FATAL EXCEPTION: GLThread 1693802-26 23:12:08.984: E/AndroidRuntime(2750): java.lang.IllegalArgumentException: Must use a native order direct Buffer02-26 23:12:08.984: E/AndroidRuntime(2750): 	at com.google.android.gles_jni.GLImpl.glVertexPointerBounds(Native Method)02-26 23:12:08.984: E/AndroidRuntime(2750): 	at com.google.android.gles_jni.GLImpl.glVertexPointer(GLImpl.java:1122)02-26 23:12:08.984: E/AndroidRuntime(2750): 	at com.example.androidgldemo.AndroidGLDemoRenderer.onDrawFrame(AndroidGLDemoRenderer.java:63)02-26 23:12:08.984: E/AndroidRuntime(2750): 	at android.opengl.GLSurfaceView$GLThread.guardedRun(GLSurfaceView.java:1516)02-26 23:12:08.984: E/AndroidRuntime(2750): 	at android.opengl.GLSurfaceView$GLThread.run(GLSurfaceView.java:1240)