SQLite App Crashing when I try to get data : When I click Show button, App will crash.  I am following a guide and just changing names here and there but for some reason, it keeps crashing.  please help me understand why this is happening.

This is my CustDbAdapter CODE:

public class CustDbAdapter {

    public static final String CUST_TABLE_NAME = "customers";
    public static final String _ID = "_id";
    public static final String CUSTLNAME = "custlname";
    public static final String CUSTFNAME = "custfname";
    public static final String CUSTPHONE = "custphone";
    private static final String DATABASE_NAME = "cool.db";
    static final int CUSTBASE_VERSION = 1;
    private static final String DATABASE_CREATE =
            "CREATE TABLE " + CUST_TABLE_NAME + " ("
                    + _ID + " INTEGER PRIMARY KEY AUTOINCREMENT,  "
                    + CUSTLNAME + " TEXT NOT NULL, "
                    + CUSTFNAME + " TEXT NOT NULL, "
                    + CUSTPHONE + " INTEGER NOT NULL, "

    private CustDbHelper dbhelper;
    private final Context context;
    private SQLiteDatabase db;

    public CustDbAdapter(Context c) {
        this.context = c;
        dbhelper = new CustDbHelper(context);
    }

    private  static  class CustDbHelper extends SQLiteOpenHelper {
        CustDbHelper(Context context){
            super(context, DATABASE_NAME, null, CUSTBASE_VERSION);
        }

        @Override
        public void onCreate(SQLiteDatabase db){
            try{
                db.execSQL(DATABASE_CREATE);
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

        @Override
        public  void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion){
            Log.w(TAG, "Upgrading database from version " + oldVersion + " to"
                    + newVersion + ", which will destroy all old data");
            db.execSQL("DROP TABLE IF EXIST " + CUST_TABLE_NAME);
            onCreate(db);
        }
    }


    public CustDbAdapter open() throws SQLException {

        dbhelper =  new CustDbHelper(context);
        db = dbhelper.getWritableDatabase();
        return this;
    }


    public void close(){
        dbhelper.close();
    }

    public long addCustomer(String lname, String fname, int phone) {
        ContentValues initialValues = new ContentValues();
        initialValues.put(CUSTLNAME, lname);
        initialValues.put(CUSTFNAME, fname);
        initialValues.put(CUSTPHONE, phone);
   
        return db.insert(CUST_TABLE_NAME, null, initialValues);

    }

    public Cursor getAllCustomer(){
        return db.query(CUST_TABLE_NAME, new String[]{_ID, CUSTLNAME,
                CUSTFNAME, CUSTPHONE}, null, null, null, null, null);
    }

}

And This is CustFragment that calls the Apapter.

public class CustFragment extends Fragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View v = inflater.inflate(R.layout.fragment_util_cust, container, false);
        return v;
    }

    @Override
    public void onViewCreated(View v, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(v, savedInstanceState);

        final Button btnShow = (Button)v.findViewById(R.id.b_utilcust_input);
        final TextView txtOutput = (TextView)v.findViewById(R.id.t_utilcust_output);

        final CustDbAdapter db = new CustDbAdapter(getActivity());

        btnShow.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                db.open();
                Cursor c = db.getAllCustomer();
                if (c.moveToFirst()){
                    txtOutput.setText("Name - Phone \n");
                    c.moveToNext();

                    do {
                        DisplayContact(c);
                    } while (c.moveToNext());
                }
                db.close();
            }

            private void DisplayContact(Cursor c){
 
                int idColumnIndex = c.getColumnIndex(CustDbAdapter._ID);
                int lnameColumnIndex = c.getColumnIndex(CustDbAdapter.CUSTLNAME);
                int fnameColumnIndex = c.getColumnIndex(CustDbAdapter.CUSTFNAME);
                int phoneColumnIndex = c.getColumnIndex(CustDbAdapter.CUSTPHONE);

                int currentID = c.getInt(idColumnIndex);
                String currentLName = c.getString(lnameColumnIndex);
                String currentFName = c.getString(fnameColumnIndex);
                int currentPhone = c.getInt(phoneColumnIndex);

                txtOutput.append("\n"
                        + currentID + " - " + currentLName +", "+currentFName +" Phone:" + currentPhone);

            }
        });
     }
}