Question

I am reading tutorials online on how to load textures in an android application and passing them in shaders. I have found this method

    public static int loadTexture(final Context context, final int resourceId)
{
    final int[] textureHandle = new int[1];

    GLES20.glGenTextures(1, textureHandle, 0);

    if (textureHandle[0] != 0)
    {
        final BitmapFactory.Options options = new BitmapFactory.Options();
        options.inScaled = false;   // No pre-scaling

        // Read in the resource
        final Bitmap bitmap = BitmapFactory.decodeResource(context.getResources(), resourceId, options);

        // Bind to the texture in OpenGL
        GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, textureHandle[0]);

        // Set filtering
        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);

        // Load the bitmap into the bound texture.
        GLUtils.texImage2D(GLES20.GL_TEXTURE_2D, 0, bitmap, 0);

        // Recycle the bitmap, since its data has been loaded into OpenGL.
        bitmap.recycle();
    }

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

    return textureHandle[0];
}

but how do I use it? what do I put as parameters when calling this method??? what is that integer that it returns? I suppose from my knowledge of opengl that the int it returns is is just the “number” of the texture in case I am loading many textures. The texture handle if you may. But what about the rest???

Answer 1

ANDROID AND CONTEXT If you look through the various Android APIs, you’ll notice that many of them take an android.content.Context object as a parameter. You’ll also see that an Activity or a Service is usually used as a Context. This works because both of these classes extend from Context.

What’s Context exactly? Per the Android reference documentation, it’s an entity that represents various environment data. It provides access to local files, databases, class loaders associated to the environment, services including system-level services, and more. Throughout this book, and in your day-to- day coding with Android, you’ll see the Context passed around frequently. From: “Android in Practice” book.

So the above method should be called inside the mainactivity class with 1st parameter being one of getApplicationContext(), getContext(), getBaseContext() or this

resourceID represents an the resource file that you wish to work with. In my case I had a BMP image inside res/drawable folder and this could be got by writing

R.res.myimagename.bmp

and this simple code returns a simple integer that is the location of the resource file so in fact resourceID. In other terms it somewhat like a relative path to the resource file