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Editorial Team
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Asked: 2026-05-27T12:19:12+00:00

I’ve been on Android for a while, after using Android libraries based on OpenGL

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I’ve been on Android for a while, after using Android libraries based on OpenGL ES, I’ve decided to take the plunge and learn it myself. It seems to be a pretty steep learning curve but I’m committed and always willing to learn. However, after reading whatever beginner tutorials I could find, I’m struggling to string together my first application. I’m simply trying to display a triangle on the screen, but so far all I end up with is a black screen.

If anyone is able to point out where I’m going wrong (and if possible explain why), I’d be really appreciative! Thanks! (Below is the Renderer, I saw no point in including the Activity as well).

public class OpenGLRenderer implements Renderer {

private OpenGLActivity mContext;

public OpenGLRenderer(OpenGLActivity pContext) {
    mContext = pContext;
}

@Override
public void onSurfaceCreated(GL10 gl, EGLConfig config) {
    gl.glHint(GL10.GL_PERSPECTIVE_CORRECTION_HINT, GL10.GL_FASTEST);

    gl.glClearColor(0.0f, 0.0f, 0.0f, 1f);
    gl.glShadeModel(GL10.GL_FLAT);

    gl.glDisable(GL10.GL_DEPTH_TEST);
    gl.glDisable(GL10.GL_DITHER);
    gl.glDisable(GL10.GL_LIGHTING);
    gl.glDisable(GL10.GL_MULTISAMPLE);

    gl.glEnable(GL10.GL_TEXTURE_2D);
    gl.glEnable(GL10.GL_BLEND);
    gl.glEnable(GL10.GL_TEXTURE_COORD_ARRAY);
    gl.glEnable(GL10.GL_VERTEX_ARRAY);
    gl.glEnable(GL10.GL_CULL_FACE);

    gl.glFrontFace(GL10.GL_CCW);
    gl.glCullFace(GL10.GL_BACK);     

    gl.glBlendFunc(GL10.GL_SRC_ALPHA, GL10.GL_ONE_MINUS_SRC_ALPHA);

    gl.glViewport(0, 0, 480,  800);
    gl.glMatrixMode(GL10.GL_PROJECTION);
    gl.glLoadIdentity();
    gl.glOrthof(0.0f, 1.0f, 0.0f, 1.0f, -1.0f, 1.0f);
}

@Override
public void onDrawFrame(GL10 gl) {
    gl.glClear(GL10.GL_COLOR_BUFFER_BIT);
    gl.glLoadIdentity();

    gl.glDisable(GL10.GL_TEXTURE_2D);
    gl.glColor4f(0f, 1f, 0f, 1f);

    float[] vertices = new float[ ]{1,0, 0,1, -1,0};
    FloatBuffer buffer = ByteBuffer.allocateDirect(24).order(ByteOrder.nativeOrder()).asFloatBuffer();

    buffer.put(vertices);

    gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);

    gl.glVertexPointer(2, GL10.GL_FLOAT, 0, buffer);

    gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 0, 3);

    gl.glDisableClientState(GL10.GL_VERTEX_ARRAY);
}

@Override
public void onSurfaceChanged(GL10 gl, int width, int height) {
    gl.glViewport(0, 0, 480,  800);
    gl.glLoadIdentity();
}
}
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1 Answer

  1. Editorial Team

    This is a lot of code for just displaying a triangle, probably copied from somewhere. You should try to remove line after line in the onSurfaceCreated method and look if somethings changing. You should also post your activity here.

    Here are to examples of rendering a triangle

    http://blog.jayway.com/2009/12/03/opengl-es-tutorial-for-android-part-i/

    http://code.google.com/p/android-gamedev/source/browse/trunk/src/com/badlogic/gamedev/samples/TriangleSample.java

    And since you’re learning OpenGL you should have a look at the Jayway tutorials. They helped me a lot

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