Unable to fetch contents from Android database

I'm new to Android development. I'm facing a database problem in which I'm successfully able to create a database and insert data into it. But when it comes to fetching I'm unable to do that. I have a DBAdapter.java having -

public ArrayList<String> getAllCotacts() {
    ArrayList<String> array_list = new ArrayList<String>();

    Cursor res = db.rawQuery("select * from patients", null);
    res.moveToFirst();

    while (res.isAfterLast() == false) {
        array_list.add(res.getString(res.getColumnIndex(KEY_NAME)));
        res.moveToNext();
    }
    return array_list;
}

Now, I'm calling this array_list in an activity -

    DBAdapter db = new DBAdapter(this);
    final ArrayList array_list = db.getAllCotacts();
    final int itemCount = array_list.size();

    Button search = (Button) findViewById(R.id.searchbtn_searchpatient);
    search.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {

            for (int i = 0; i < itemCount; i++) {
                pd = new Button(myActivity.this);
                pd.setText(array_list.get(i).toString());
                pd.setTextSize(17);
                pd.setOnClickListener(pdClass);
                Layout.addView(pd, params);
            }
        }
    });

When I run my application then it says like - unfortunately, myapp has stopped.