Android OpenGL学习札记(二)-三角形的绘制

Android OpenGL学习笔记(二)--三角形的绘制.

前面讲了一些Android OpenGl 的概念问题，这一节讲给大家讲一下如何画一个三角现出来.

一、新建一个Android工程命名为:OpenGL_Lesson2.

二、修改OpenGL_Lesson2.java代码如下:

 

package com.android.tutor; import android.app.Activity; import android.os.Bundle; public class OpenGL_Lesson2 extends Activity { private OpenGlView mOpenGlView; public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); mOpenGlView = new OpenGlView(this); setContentView(mOpenGlView); } }

三、新建一个类OpenGlView.java继承与GLSurfaceView,代码如下:

 

package com.android.tutor; import android.content.Context; import android.opengl.GLSurfaceView; public class OpenGlView extends GLSurfaceView { private OpenGlRender mOpenGlRender; public OpenGlView(Context context) { super(context); mOpenGlRender = new OpenGlRender(); setRenderer(mOpenGlRender); } }

四、新建一个OpenGlRender.java类继承与Renderer,代码如下:

 

package com.android.tutor; import java.nio.ByteBuffer; import java.nio.ByteOrder; import java.nio.FloatBuffer; import java.nio.ShortBuffer; import javax.microedition.khronos.egl.EGLConfig; import javax.microedition.khronos.opengles.GL10; import android.opengl.GLSurfaceView.Renderer; public class OpenGlRender implements Renderer { private float _red = 0f; private float _green = 25f; private float _blue = 200f; private ShortBuffer _indexBuffer; private FloatBuffer _vertexBuffer; private short[] _indicesArray = {0, 1, 2}; private int _nrOfVertices = 3; @Override public void onSurfaceCreated(GL10 gl, EGLConfig config) { gl.glEnableClientState(GL10.GL_VERTEX_ARRAY); initTriangle(); } @Override public void onSurfaceChanged(GL10 gl, int width, int height) { gl.glViewport(0, 0, width, height); } @Override public void onDrawFrame(GL10 gl) { gl.glClearColor(_red, _green, _blue, 1.0f); gl.glClear(GL10.GL_COLOR_BUFFER_BIT); gl.glColor4f(0.5f, 0f, 0f, 0.5f); gl.glVertexPointer(_nrOfVertices, GL10.GL_FLOAT, 0, _vertexBuffer); gl.glDrawElements(GL10.GL_TRIANGLES, _nrOfVertices, GL10.GL_UNSIGNED_SHORT, _indexBuffer); } private void initTriangle() { // float has 4 bytes ByteBuffer vbb = ByteBuffer.allocateDirect(_nrOfVertices * 3 * 4); vbb.order(ByteOrder.nativeOrder()); _vertexBuffer = vbb.asFloatBuffer(); // short has 4 bytes ByteBuffer ibb = ByteBuffer.allocateDirect(_nrOfVertices * 2); ibb.order(ByteOrder.nativeOrder()); _indexBuffer = ibb.asShortBuffer(); float[] coords = { -0.5f, -0.5f, 0f, // (x1, y1, z1) 0.5f, -0.5f, 0f, // (x2, y2, z2) 0f, 0.5f, 0f // (x3, y3, z3) }; _vertexBuffer.put(coords); _indexBuffer.put(_indicesArray); _vertexBuffer.position(0); _indexBuffer.position(0); } }

五、运行之，效果如下:

 

今天晚上就先不做详细解释了！改日在加上！谢谢~