三角形为OpenGL ES支持的面，同样创建一个DrawTriangle Activity，定义6个顶点使用三种不同模式来绘制三角形：
float vertexArray[] = { -0.8f, -0.4f * 1.732f, 0.0f, 0.0f, -0.4f * 1.732f, 0.0f, -0.4f, 0.4f * 1.732f, 0.0f, 0.0f, -0.0f * 1.732f, 0.0f, 0.8f, -0.0f * 1.732f, 0.0f, 0.4f, 0.4f * 1.732f, 0.0f,};
本例绘制
public void DrawScene(GL10 gl) { super.DrawScene(gl); ByteBuffer vbb = ByteBuffer.allocateDirect(vertexArray.length*4); vbb.order(ByteOrder.nativeOrder()); FloatBuffer vertex = vbb.asFloatBuffer(); vertex.put(vertexArray); vertex.position(0); gl.glLoadIdentity(); gl.glTranslatef(0, 0, -4); gl.glEnableClientState(GL10.GL_VERTEX_ARRAY); gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertex); index++; index%=10; switch(index){ case 0: case 1: case 2: gl.glColor4f(1.0f, 0.0f, 0.0f, 1.0f); gl.glDrawArrays(GL10.GL_TRIANGLES, 0, 6); break; case 3: case 4: case 5: gl.glColor4f(0.0f, 1.0f, 0.0f, 1.0f); gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 0, 6); break; case 6: case 7: case 8: case 9: gl.glColor4f(0.0f, 0.0f, 1.0f, 1.0f); gl.glDrawArrays(GL10.GL_TRIANGLE_FAN, 0, 6); break; } gl.glDisableClientState(GL10.GL_VERTEX_ARRAY); }
这里index 的目的是为了延迟一下显示（更好的做法是使用固定时间间隔）。前面说过GLSurfaceView 的渲染模式有两种，一种是连续不断的更新屏幕，另一种为on-demand ，只有在调用requestRender() 在更新屏幕。 缺省为RENDERMODE_CONTINUOUSLY 持续刷新屏幕。
OpenGLDemos 使用的是缺省的RENDERMODE_CONTINUOUSLY持续刷新屏幕 ，因此Activity的drawScene 会不断的执行。本例中屏幕上顺序以红，绿，蓝色显示TRIANGLES, TRIANGLE_STRIP,TRIANGLE_FAN。
完整代码：
MainActivity.java
package com.example.gltest;import java.nio.ByteBuffer;import java.nio.ByteOrder;import java.nio.FloatBuffer;import javax.microedition.khronos.opengles.GL10;import android.opengl.GLSurfaceView;import android.os.Bundle;import android.app.Activity;import android.view.Menu;import android.view.Window;import android.view.WindowManager;public class MainActivity extends Activity implements IOpenGLDemo{ float vertexArray[] = { -0.8f, -0.4f * 1.732f, 0.0f, -0.4f, 0.4f * 1.732f, 0.0f, 0.0f, -0.4f * 1.732f, 0.0f, 0.4f, 0.4f * 1.732f, 0.0f, }; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); this.requestWindowFeature(Window.FEATURE_NO_TITLE); getWindow() .setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN); mGLSurfaceView = new GLSurfaceView(this); mGLSurfaceView.setRenderer(new OpenGLRenderer(this)); setContentView(mGLSurfaceView); } // public void DrawScene(GL10 gl) {// gl.glClearColor(1.0f, 0.0f, 0.0f, 0.0f);// // Clears the screen and depth buffer.// gl.glClear(GL10.GL_COLOR_BUFFER_BIT// | GL10.GL_DEPTH_BUFFER_BIT);// // } public void DrawScene(GL10 gl) { //super.DrawScene(gl); ByteBuffer vbb = ByteBuffer.allocateDirect(vertexArray.length*4); vbb.order(ByteOrder.nativeOrder()); FloatBuffer vertex = vbb.asFloatBuffer(); vertex.put(vertexArray); vertex.position(0); gl.glLoadIdentity(); gl.glTranslatef(0, 0, -4); gl.glEnableClientState(GL10.GL_VERTEX_ARRAY); gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertex); int index = 0; index ++; index%=10; switch(index){ case 0: case 1: case 2: gl.glColor4f(1.0f, 0.0f, 0.0f, 1.0f); gl.glDrawArrays(GL10.GL_TRIANGLES, 0, 6); break; case 3: case 4: case 5: gl.glColor4f(0.0f, 1.0f, 0.0f, 1.0f); gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 0, 6); break; case 6: case 7: case 8: case 9: gl.glColor4f(0.0f, 0.0f, 1.0f, 1.0f); gl.glDrawArrays(GL10.GL_TRIANGLE_FAN, 0, 6); break; } gl.glDisableClientState(GL10.GL_VERTEX_ARRAY); } @Override protected void onResume() { // Ideally a game should implement // onResume() and onPause() // to take appropriate action when the //activity looses focus super.onResume(); mGLSurfaceView.onResume(); } @Override protected void onPause() { // Ideally a game should implement onResume() //and onPause() // to take appropriate action when the //activity looses focus super.onPause(); mGLSurfaceView.onPause(); } private GLSurfaceView mGLSurfaceView; } 后面的 OpenGLRenderer.java和 IOpenGLDemo.java一样。