Turning on Depth Buffer makes everything disappear !

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I finally got to use textures on Android using OpenGL ES, and I found that its turn I started using the Depth buffer for some proper rendering. The moment I uncommented

gl.glEnable(GL10.GL_DEPTH_BUFFER);

The object disappeared and became invisible. Not even a pixel of the object was visible. Then a colleague of mine gave me a hint about clearing buffers !

Uffff ! I corrected the line
"gl.glClear(GL10.GL_COLOR_BUFFER_BIT);"
--to--
"gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);"

and everything was fine again !