我使用GLSurfaceView遇到了不同的行为.

AFAIK是程序的责任,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,我会得到最后一帧的内容(或者之前用于双缓冲的内容).

似乎无论在某些设备上是什么,缓冲区都被清除了.我在Addison Wesley OpenglES2.0编程指南中对一些具有不同结果的测试设备进行了“Hello Triangle”程序的以下修改：

> Acer Iconia A500(4.0.3)：未清除(预期行为)

> Sony XPERIA Go(4.0.4)：已清除

> 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 – rooted)：清除

有没有办法强制在每个绘制回调中获得一个未更改的缓冲区？

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;

}

}

});

}

}