Android 调用glClear后，surfaceview如何保留颜色？

我刚刚开始学习openGL，正在android上工作，我被困在一些地方。请看下面的代码：-

    public void onDrawFrame(GL10 arg0) {

    glClear(GL_COLOR_BUFFER_BIT);
}

@Override
public void onSurfaceChanged(GL10 glUnused, int width, int height) {

    glViewport(0,0,width,height);
}

@Override
public void onSurfaceCreated(GL10 glUnused, EGLConfig config) {

    glClearColor(1.0f,0.0f,0.0f,0.0f);
}

---

在onSurfaceCreated中设置颜色，在onDrawFrame中清除颜色缓冲区。现在，一旦清除颜色缓冲区，为什么曲面的颜色仍然与onSurfaceCreated中设置的颜色相同？

glClearColor

指定将用于清除缓冲区的颜色。调用

glClear

时，此颜色将应用于缓冲区

如果需要暗表面，请将其更改为：

 glClearColor(0.0f,0.0f,0.0f,0.0f);