在android中使用OpenGL

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：

packagecom.example.androidgldemo;importandroid.opengl.GLSurfaceView;importandroid.os.Bundle;importandroid.app.Activity;importandroid.view.Menu;publicclassAndroidGLDemoextendsActivity{@OverrideprotectedvoidonCreate(BundlesavedInstanceState){super.onCreate(savedInstanceState);GLSurfaceViewglView=newGLSurfaceView(this);AndroidGLDemoRendererrenderer=newAndroidGLDemoRenderer();glView.setRenderer(renderer);setContentView(glView);}@OverridepublicbooleanonCreateOptionsMenu(Menumenu){//Inflatethemenu;thisaddsitemstotheactionbarifitispresent.getMenuInflater().inflate(R.menu.activity_main,menu);returntrue;}}

然后是Renderer的实现：

packagecom.example.androidgldemo;importjava.nio.ByteBuffer;importjava.nio.ByteOrder;importjava.nio.FloatBuffer;importjava.nio.IntBuffer;importjavax.microedition.khronos.egl.EGLConfig;importjavax.microedition.khronos.opengles.GL10;importandroid.opengl.GLSurfaceView.Renderer;publicclassAndroidGLDemoRendererimplementsRenderer{float[]mTriangleData=newfloat[]{0.1f,0.6f,0.0f,-0.3f,0.0f,0.0f,0.3f,0.1f,0.0f};int[]mTriangleColor=newint[]{65535,0,0,0,0,65535,0,0,0,0,65535,0,};float[]mRectData=newfloat[]{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=newint[]{0,65535,0,0,0,0,65535,0,65535,0,0,0,65535,65535,0,0,};FloatBuffermTriangleDataBuffer;IntBuffermTriangleColorBuffer;FloatBuffermRectDataBuffer;IntBuffermRectColorBuffer;publicAndroidGLDemoRenderer(){mTriangleDataBuffer=bufferUtil(mTriangleData);mTriangleColorBuffer=bufferUtil(mTriangleColor);mRectDataBuffer=bufferUtil(mRectData);mRectColorBuffer=bufferUtil(mRectColor);}@OverridepublicvoidonDrawFrame(GL10gl){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);}@OverridepublicvoidonSurfaceChanged(GL10gl,intwidth,intheight){gl.glViewport(0,0,width,height);gl.glMatrixMode(GL10.GL_PROJECTION);gl.glLoadIdentity();floatratio=(float)width/height;gl.glFrustumf(-ratio,ratio,-1,1,1,10);}@OverridepublicvoidonSurfaceCreated(GL10gl,EGLConfigconfig){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);}publicIntBufferbufferUtil(int[]arr){IntBufferbuffer;ByteBufferqbb=ByteBuffer.allocateDirect(arr.length*4);qbb.order(ByteOrder.nativeOrder());buffer=qbb.asIntBuffer();buffer.put(arr);buffer.position(0);returnbuffer;}publicFloatBufferbufferUtil(float[]arr){FloatBufferbuffer;ByteBufferqbb=ByteBuffer.allocateDirect(arr.length*4);qbb.order(ByteOrder.nativeOrder());buffer=qbb.asFloatBuffer();buffer.put(arr);buffer.position(0);returnbuffer;}}

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:

02-2623:12:08.945:E/OpenGLES(2750):Applicationcom.example.androidgldemo(SDKtarget17)calledaGL11PointermethodwithanindirectBuffer.02-2623:12:08.968:W/dalvikvm(2750):threadid=11:threadexitingwithuncaughtexception(group=0x40d57930)02-2623:12:08.984:E/AndroidRuntime(2750):FATALEXCEPTION:GLThread1693802-2623:12:08.984:E/AndroidRuntime(2750):java.lang.IllegalArgumentException:MustuseanativeorderdirectBuffer02-2623:12:08.984:E/AndroidRuntime(2750):atcom.google.android.gles_jni.GLImpl.glVertexPointerBounds(NativeMethod)02-2623:12:08.984:E/AndroidRuntime(2750):atcom.google.android.gles_jni.GLImpl.glVertexPointer(GLImpl.java:1122)02-2623:12:08.984:E/AndroidRuntime(2750):atcom.example.androidgldemo.AndroidGLDemoRenderer.onDrawFrame(AndroidGLDemoRenderer.java:63)02-2623:12:08.984:E/AndroidRuntime(2750):atandroid.opengl.GLSurfaceView$GLThread.guardedRun(GLSurfaceView.java:1516)02-2623:12:08.984:E/AndroidRuntime(2750):atandroid.opengl.GLSurfaceView$GLThread.run(GLSurfaceView.java:1240)

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