我使用 GLSurfaceView 遇到了不同的行为。AFAIK 程序有责任清除每帧的缓冲区（颜色和深度）。这意味着如果我不清除缓冲区，我将获得最后一帧的内容（或之前的一帧以进行双缓冲）。
无论在某些设备上做什么，似乎缓冲区都被清除了。我在一些测试设备上运行了 Addison Wesley OpenglES2.0 Programming Guide 中的“Hello Triangle”程序的以下修改，结果不同：
- Acer Iconia A500 (4.0.3)：未清除（预期行为）
- 索尼 XPERIA Go (4.0.4)：清除
- Galaxy S3 (4.1.1)：清除
- LG Optimus 4x HD (4.0.3)：未清除
- 三星 Galaxy Tab 20.1 (4.0.4)：未清除
- 摩托罗拉 Xoom（3.2）：未清除
- Galaxy S2（4.1.2 - 植根）：清除
有没有办法强制每次绘制回调都获得不变的缓冲区？
清除屏幕的设备的结果如下所示：
测试活动如下所示：
package com.example.glcleartest;
import java.nio.Buffer;
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.opengl.GLES20;
import android.opengl.GLSurfaceView;
import android.opengl.GLSurfaceView.Renderer;
import android.os.Bundle;
import android.app.Activity;
import android.util.Log;
public class MainActivity extends Activity {
protected static final int NUM_VERTICES = 3;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
GLSurfaceView glview = (GLSurfaceView) findViewById(R.id.glview);
glview.setEGLConfigChooser(false);
glview.setEGLContextClientVersion(2);
glview.setRenderer(new Renderer() {
private int programObject;
private FloatBuffer vertexBuffer;
@Override
public void onSurfaceCreated(GL10 gl, EGLConfig config) {
}
@Override
public void onSurfaceChanged(GL10 gl, int width, int height) {
GLES20.glViewport(0, 0, width, height);
init();
}
@Override
public void onDrawFrame(GL10 gl) {
float x = 0.1f*(float) Math.sin(System.currentTimeMillis()/1000.0);
float[] vVertices = new float[]{x, 0.5f, 0.0f,
x-0.5f, -0.5f, 0.0f,
x+0.5f, -0.5f, 0.0f};
vertexBuffer.rewind();
vertexBuffer.put(vVertices);
vertexBuffer.rewind();
// Use the program object
GLES20.glUseProgram(programObject);
int handle = GLES20.glGetUniformLocation(programObject, "uColor");
float r = (float) (0.5f+Math.sin(System.currentTimeMillis()/1000.0));
float g = (float) (0.5f+Math.sin(System.currentTimeMillis()/300.0));
GLES20.glUniform4f(handle, r, g,0,1);
// Load the vertex data
GLES20.glVertexAttribPointer(0, 3, GLES20.GL_FLOAT, false, 0, vertexBuffer);
GLES20.glEnableVertexAttribArray(0);
GLES20.glDrawArrays(GLES20.GL_TRIANGLES, 0, 3);
}
private void error(String s) {
Log.e("GLTEST", s);
}
private int loadShader(int shaderType, String source) {
if (shaderType != GLES20.GL_FRAGMENT_SHADER && shaderType != GLES20.GL_VERTEX_SHADER) {
throw new RuntimeException("Illegal shader type");
}
int shader = GLES20.glCreateShader(shaderType);
if (shader != 0) {
GLES20.glShaderSource(shader, source);
GLES20.glCompileShader(shader);
int[] compiled = new int[1];
GLES20.glGetShaderiv(shader, GLES20.GL_COMPILE_STATUS, compiled, 0);
if (compiled[0] == 0) {
error("Could not compile shader :");
error(GLES20.glGetShaderInfoLog(shader));
GLES20.glDeleteShader(shader);
shader = 0;
throw new RuntimeException("Shader Syntax / compilation error");
}
}
return shader;
}
private void init() {
String vShaderStr = "attribute vec4 vPosition; \n" +
"void main() \n" + "{ \n" +
" gl_Position = vPosition; \n" +
"} \n";
String fShaderStr = "precision mediump float; \n" +
"uniform vec4 uColor;" +
"void main() \n" +
"{ \n" +
" gl_FragColor = uColor; \n" +
"} \n";
ByteBuffer vbb = ByteBuffer.allocateDirect(NUM_VERTICES*3*4);
vbb.order(ByteOrder.nativeOrder());
vertexBuffer = vbb.asFloatBuffer();
int vertexShader;
int fragmentShader;
// Load the vertex/fragment shaders
vertexShader = loadShader(GLES20.GL_VERTEX_SHADER, vShaderStr);
fragmentShader = loadShader(GLES20.GL_FRAGMENT_SHADER, fShaderStr);
// Create the program object
programObject = GLES20.glCreateProgram();
if (programObject == 0)
return;
GLES20.glAttachShader(programObject, vertexShader);
GLES20.glAttachShader(programObject, fragmentShader);
// Bind vPosition to attribute 0
GLES20.glBindAttribLocation(programObject, 0, "vPosition");
// Link the program
GLES20.glLinkProgram(programObject);
int[] linkStatus = new int[1];
GLES20.glGetProgramiv(programObject, GLES20.GL_LINK_STATUS, linkStatus, 0);
if (linkStatus[0] != GLES20.GL_TRUE) {
error("Could not link program: ");
error(GLES20.glGetProgramInfoLog(programObject));
GLES20.glDeleteProgram(programObject);
programObject = 0;
}
}
});
}
}