Question

I’m trying to render a XML layout to an OpenGL surface. That works correctly, and I can do 3D effects on the layout. But, when I try to update it and render it again, it does not work. With twiddling and trying different functions, the end result is either a black object, graphic corruption on widgets external to the surface, or the original object without any modification.

My code to transform a view to a bitmap is:

public static Bitmap toBitmap(final View view) {
    final Bitmap bitmap = Bitmap.createBitmap(400, 100,
            Bitmap.Config.ARGB_8888);
    final Canvas canvas = new Canvas(bitmap);
    final Paint paint = new Paint();

    view.setDrawingCacheEnabled(true);

    final int width = MeasureSpec.makeMeasureSpec(canvas.getWidth(),
            MeasureSpec.EXACTLY);
    final int height = MeasureSpec.makeMeasureSpec(canvas.getHeight(),
            MeasureSpec.EXACTLY);
    view.measure(width, height);
    view.layout(0, 0, view.getMeasuredWidth(), view.getMeasuredHeight());

    canvas.drawBitmap(view.getDrawingCache(), 0, 0, paint);

    return bitmap;
}

Then, in my object’s constructor, I call:

public static int loadTexture(final Bitmap bitmap) {
    GLES20.glGenTextures(1, textureHandle, 0);

    if (textureHandle[0] != 0) {
        GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, textureHandle[0]);
        GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D,
                GLES20.GL_TEXTURE_MIN_FILTER, GLES20.GL_NEAREST);
        GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D,
                GLES20.GL_TEXTURE_MAG_FILTER, GLES20.GL_NEAREST);
        GLUtils.texImage2D(GLES20.GL_TEXTURE_2D, 0, bitmap, 0);

        bitmap.recycle();
    }

    if (textureHandle[0] == 0) {
        throw new RuntimeException("Error loading texture.");
    }

    return textureHandle[0];
}

Calling the loadTexture() method again with an updated layout will render it black. I wrote another small method to try different ways:

public static int updateTexture(final Bitmap bitmap) {
    GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, textureHandle[0]);
    GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D,
            GLES20.GL_TEXTURE_MIN_FILTER, GLES20.GL_NEAREST);
    GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D,
            GLES20.GL_TEXTURE_MAG_FILTER, GLES20.GL_NEAREST);

    GLUtils.texSubImage2D(GLES20.GL_TEXTURE_2D, 0, 0, 0, bitmap);
    //GLUtils.texImage2D(GLES20.GL_TEXTURE_2D, 0, bitmap, 0);
    // GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, 0);

    return textureHandle[0];
}

This leaves the original texture unchanged, and produces an error:

<qgl2DrvAPI_glTexSubImage2D:502>: GL_INVALID_VALUE
glStartTilingQCOM: 0x501

Commenting the texSubImage2D() call and replacing it with texImage2D() does nothing, and produces no error message.

If anyone can shed light on anything I may have done wrong, that would be greatly appreciated.

Thanks!

Answer 1

Are you calling the update method from the OpenGL thread? You don’t need to specify again the texture parameters if you are using the texSubImage function.