how to render a map in android opengl

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I'm trying to show a bitmap in android opengl-es3.1. The bitmap is created with Bitmap.createBitmap(width, height, Bitmap.Config.ALPHA_8); and I filled the bitmap with pixels.

Here is the bitmap I created:

But the emulator show a strange thing:

Here is the main render code:

// generate map
private void initMap(OccupancyGrid occupancyGrid) {
    int height = occupancyGrid.info.height;
    int width = occupancyGrid.info.width;

    Bitmap newMap = Bitmap.createBitmap(width, height, Bitmap.Config.ALPHA_8);

    int[] pixels;
    int bytePixel;

    int curr = 0;
    for (int y = 0; y < height; y++) {
        pixels = new int[width];

        for (int x = 0; x < width; x++) {
            // Pixels are ARGB packed ints.
            bytePixel = occupancyGrid.data[curr++];

            if (bytePixel == -1) {
                // black color
                pixels[x] = gradient[101];
            } else {
                // gray color
                pixels[x] = gradient[bytePixel];
            }
        }

        newMap.setPixels(pixels, 0, width, 0, y, width, 1);
    }
    bitmap = newMap;
}

@Override
public void onSurfaceChanged(GL10 gl, int width, int height) {
    gl.glViewport(0, 0, width, height);
}

@Override
public void onDrawFrame(GL10 gl) {
    // enable
    GLES31.glEnable(GLES31.GL_TEXTURE_2D);
    final int[] textureIds = new int[1];
    //create
    GLES31.glGenTextures(1, textureIds, 0);

    // bind
    GLES31.glBindTexture(GLES31.GL_TEXTURE_2D, textureIds[0]);

    //set default param
    GLES31.glTexParameterf(GLES31.GL_TEXTURE_2D, GLES31.GL_TEXTURE_MIN_FILTER, GLES31.GL_NEAREST);
    GLES31.glTexParameterf(GLES31.GL_TEXTURE_2D, GLES31.GL_TEXTURE_MAG_FILTER, GLES31.GL_NEAREST);
    GLES31.glTexParameteri(GLES31.GL_TEXTURE_2D, GLES31.GL_TEXTURE_BASE_LEVEL, 0);
    GLES31.glTexParameteri(GLES31.GL_TEXTURE_2D, GLES31.GL_TEXTURE_MAX_LEVEL, 0);
    // load bitmap
    GLUtils.texImage2D(GLES31.GL_TEXTURE_2D, 0, bitmap, 0);

    // vertex
    gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
    gl.glEnableClientState(GL10.GL_TEXTURE_COORD_ARRAY);
    gl.glVertexPointer(3, GL10.GL_FLOAT, 0, surfaceVertices);
    gl.glTexCoordPointer(2, GL10.GL_FLOAT, 0, textureVertices);


    GLES31.glDrawArrays(GLES31.GL_TRIANGLE_STRIP, 0, 4);
}

View the full code in repository in repository link

And by the way, I'm a beginner of both ROS and opengl, I read the code of VisualizationView and OccupyGridLayer in ros-anroid project, I can't understand the Tile class clearly.

Does it(a tile) represent a point in map data? A Tile corresponds A TexureBitmap, and the size of TextureBitmap is 1024, I'm confused.

Any way, my purpose is to show a ros map in android app. I can handle the ros websocket bridge, but I really need some help of opengl.