android opengl 原理及开发（2）绘制基本图形

工程名称为vertex,标识点的意思，点是3d图形空间最基本元素，三角形的绘制通过指定三个点，线由两个点连接构成，对边型至少由三个vertex构成，

Activity 名为VertexActivity

package com.android.vertex;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.WindowManager;

import java.io.File;


public class VertexActivity extends Activity {

    VertexView mView;

    @Override protected void onCreate(Bundle icicle) {
        super.onCreate(icicle);
        mView = new VertexView(getApplication());
		setContentView(mView);
    }

    @Override protected void onPause() {
        super.onPause();
        mView.onPause();
    }

    @Override protected void onResume() {
        super.onResume();
        mView.onResume();
    }
}

VertexActivity 创建时会加载
VertexView ，这里要注意activity状态改变时一定要让view状态同步，因为这会影响opengl绘制线程的状态，比如activity pause状态时，GLSurfaceView的绘制线程也回同步

到pause状态。

VertexView 继承GLSurfaceView ，MyRenderer实现GLSurface.renderer接口，负责具体绘制

VertexView.java 代码：

package com.android.vertex;


import android.content.Context;
import android.opengl.GLSurfaceView;
import android.util.AttributeSet;
import android.util.Log;
import android.view.KeyEvent;
import android.view.MotionEvent;


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


import javax.microedition.khronos.egl.EGL10;
import javax.microedition.khronos.egl.EGLConfig;
import javax.microedition.khronos.egl.EGLContext;
import javax.microedition.khronos.egl.EGLDisplay;
import javax.microedition.khronos.opengles.GL10;


import android.opengl.GLES10;


/**
* An implementation of SurfaceView that uses the dedicated surface for
* displaying an OpenGL animation. This allows the animation to run in a
* separate thread, without requiring that it be driven by the update mechanism
* of the view hierarchy.
*
* The application-specific rendering code is delegated to a GLView.Renderer
* instance.
*/
class VertexView extends GLSurfaceView {
  private static String TAG = "vertex";
	private MyRenderer mRenderer;
	


  public VertexView(Context context) {
    super(context);
	//set this if you use opengl es version 2.0
    //setEGLContextClientVersion(2);
    mRenderer = new MyRenderer();
    setRenderer(mRenderer);
  }


  private static class MyRenderer implements GLSurfaceView.Renderer {

		private float red = 0.9f;
		private float green = 0.2f;
		private float blue = 0.2f;
		
    public MyRenderer() {
     
    }


    public void onDrawFrame(GL10 gl) {
    	gl.glClearColor(red, green, blue, 1.0f);
    }


    public void onSurfaceChanged(GL10 gl, int width, int height) {
     gl.glViewport(0,0,width,height);
		  gl.glClear(GL10.GL_COLOR_BUFFER_BIT);
    }


    public void onSurfaceCreated(GL10 gl, EGLConfig config) {
     
    }

  }

}

实际绘制动作 在MyRederer实现的三个接口函数里，

如果我们想通过按键事件与绘制线程交互可以用上一篇文章提到的queueEvent方法操作绘制线程对象mRederer，

在VertexView类中添加按键事件处理

//comunicate with render thread 
	public boolean onTouchEvent(final MotionEvent event) {
		queueEvent(new Runnable() {
			public void run() {
				mRenderer.setColor(event.getX() / getWidth(), event.getY() / getHeight(), 1.0f);
			}
		} );


		return true;
	}

MyRenderer类中添加setColor，改变颜色。

public void setColor(float r, float g, float b) {
			red = r;
			green = g;
			blue = b;
		}