How to set background colour on Open GL ES Android

I am currently playing about with lesson 08 here

http://insanitydesign.com/wp/projects/nehe-android-ports/

I would like to change the background colour from black to white. In order to do this at the start of onDrawFrame() I have called

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

This does indeed set a white background screen, but also results in nothing else showing up on the screen! Clearly this is therefore an incorrect method, but why, and how do I fix it?!

Many thanks in advance.

Edit (5 days later): 开发者_运维百科Does nobody know at all?!!

The white screen is because you have set the alpha value to 0.0f.

The parameter signature is:- gl.glClearColor(float red, float green, float blue, float alpha) where floats are any value between 0.0 to 1.0.

More the float value of alpha more opaque the screen is.

After you call gl.glClearColor(), redraw everything else. gl.glClearColor() does not change background color, it simply fills the screen with white color (which in effect erases everything you've previously drawn).