GLSurfaceView使用之第二篇画三角形

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

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

import android.app.Activity;
import android.opengl.GLSurfaceView;
import android.opengl.GLU;
import android.os.Bundle;
import android.util.Log;

public class MainActivity extends Activity {

	private final String TAG = "MainActivity";

	private GLSurfaceView glSurefaceView;

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		glSurefaceView = new GLSurfaceView(this);
		glSurefaceView.setRenderer(new GLSurfaceViewRender());
		this.setContentView(glSurefaceView);
	}

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

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

	class GLSurfaceViewRender implements GLSurfaceView.Renderer {

		@Override
		public void onSurfaceCreated(GL10 gl, EGLConfig config) {
			Log.i(TAG, "onSurfaceCreated");

			// 设置背景颜色
			gl.glClearColor(0.0f, 0f, 0f, 0.5f);
			// 启用顶点数组（否则glDrawArrays不起作用）
			gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
		}

		@Override
		public void onSurfaceChanged(GL10 gl, int width, int height) {
			Log.i(TAG, "onSurfaceChanged");
			// 设置输出屏幕大小
			gl.glViewport(0, 0, width, height);
		}

		private float[] mTriangleArray = {
				// X, Y, Z 这是一个等边三角形
				-0.5f, -0.25f, 0, 0.5f, -0.25f, 0, 0.0f, 0.559016994f, 0 };

		@Override
		public void onDrawFrame(GL10 gl) {
			Log.i(TAG, "onDrawFrame");
			// 清除屏幕和深度缓存(如果不调用该代码, 将不显示glClearColor设置的颜色)
			// 同样如果将该代码放到 onSurfaceCreated 中屏幕会一直闪动
			gl.glClear(GL10.GL_COLOR_BUFFER_BIT);

			gl.glColor4f(1.0f, 0.0f, 0.0f, 1.0f);

			FloatBuffer mTriangleBuffer = BufferUtil
					.floatToBuffer(mTriangleArray);
			gl.glVertexPointer(3, GL10.GL_FLOAT, 0, mTriangleBuffer);
			gl.glDrawArrays(GL10.GL_TRIANGLES, 0, 3);
			//
			gl.glLoadIdentity();
			// 平移 (矩阵相乘)
			gl.glTranslatef(-0.2f, 0.3f, 0f);

		}
	}

	static class BufferUtil {
		public static FloatBuffer mBuffer;

		public static FloatBuffer floatToBuffer(float[] a) {
			// 先初始化buffer，数组的长度*4，因为一个float占4个字节
			ByteBuffer mbb = ByteBuffer.allocateDirect(a.length * 4);
			// 数组排序用nativeOrder
			mbb.order(ByteOrder.nativeOrder());
			mBuffer = mbb.asFloatBuffer();
			mBuffer.put(a);
			mBuffer.position(0);
			return mBuffer;
		}
	}
}