Android : Set ImageView on ImageView if something

I want set gridview for questions and if the question is answered add a bubble top or bottom of the question image (Like in the image).

I've done everything (the gridview and if answered....) except for this bubble, I don't know how to do it.

I have added the codes of my application

Like in this image:

The base adapter activitiy

public class ImgAdapter extends BaseAdapter {
    private Context mContext;
    private ColorMatrixColorFilter cf;
    String Questions = Question.Questions;
    int level = Levels.level;

    public ImgAdapter(Context c) {
        mContext = c;
        ColorMatrix matrix = new ColorMatrix();
        matrix.setSaturation(0); //0 means grayscale
        cf = new ColorMatrixColorFilter(matrix);
    }

    public int getCount() {
        return mThumbIds.length;

    }

    public Object getItem(int position) {
        return null;
    }

    public long getItemId(int position) {
        return 0;
    }

    public View getView(int position, View convertView, ViewGroup parent) {
        ImageView imageView;
        SharedPreferences pref = mContext.getSharedPreferences(Questions, Context.MODE_PRIVATE);

        imageView = (ImageView) convertView;
        imageView = new ImageView(mContext);
        int size = mContext.getResources().getDimensionPixelSize(R.dimen.width);
        imageView.setLayoutParams(new GridView.LayoutParams(size, size));
        imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
        imageView.setAdjustViewBounds(true);
        imageView.setImageResource(mThumbIds[position]);


        if(pref.getBoolean("answered"+position, false)){
            imageView.setImageResource(mThumbIds[position]);
        }

        return imageView;
    }


    public static Integer[] mThumbIds =
    {
        R.drawable.1,
        R.drawable.2,
        R.drawable.3,
        R.drawable.4,
        R.drawable.5,
        R.drawable.6,
        R.drawable.7,
        R.drawable.8,
        R.drawable.9,
        R.drawable.10,
        R.drawable.11,
        R.drawable.12,
        R.drawable.13,
        R.drawable.14,
        R.drawable.15,
        R.drawable.16,
        R.drawable.17,
        R.drawable.18,
        R.drawable.19,
        R.drawable.20
    };


}

And questions activity:

public class Questions extends Activity {

    public static ArrayList<QuestionId> items;
    public static int numCorrect;
    public static final String Questions = "LogoSettings"; // Shared Preferences
    public static int Correct;

    public static int Coins;
    int level = Levels.level;

    TextView completed;
    /*TextView correct;*/

    ImgAdapter imgAdapter;




    @Override
    protected void onCreate(Bundle savedInstanceState) {
        SharedPreferences pref = getSharedPreferences(Questions, MODE_PRIVATE);
        Editor editor = pref.edit();
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_logo_quiz);
        LinearLayout v = (LinearLayout) findViewById(R.id.layout);
        v.setBackgroundColor(0xffECECEC);


        Correct = pref.getInt(level+"Correctt", 0);


        completed = (TextView) findViewById(R.id.Correct);
        completed.setText("Completed: " + Correct + "/18");

        imgAdapter = new ImgAdapter(this);

        items = new ArrayList<QuestionId>();
        for(int i = 0; i < ImgAdapter.mThumbIds.length; i++) // set ids
        items.add(new QuestionId(i, Questions.this)); // add the questions


        GridView gridview = (GridView) findViewById(R.id.Questions);
        gridview.setAdapter(imgAdapter);
        gridview.setVerticalScrollBarEnabled(false);
        gridview.setOnItemClickListener(new OnItemClickListener() {
            public void onItemClick(AdapterView<?> parent, View v, int position, long id) {
                Intent intent = new Intent(Questions.this, Answer.class);
                intent.putExtra("id", position);
                onActivityResult(position, position, intent); // to pass id
                startActivityForResult(intent, position);

            }
        });
    }



    protected void onActivityResult(int requestCode, int resultCode, Intent i) {
        SharedPreferences pref = getSharedPreferences(Questions, MODE_PRIVATE);
        int id = i.getExtras().getInt("id"); // get id
        if(pref.getBoolean(level+"answered"+id, true)){ // if item answered
            completed = (TextView) findViewById(R.id.Correct);
            Correct = pref.getInt(level+"Correctt", 0); 
            imgAdapter.notifyDataSetChanged();
            completed.setText("Completed: " + Correct + "/18");

        }

}

}