ListView里Android自带adapter使用

ListView listView;Button button;Button button01;ArrayAdapter add;@Overrideprotected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.activity_main);    setView();}private void setView() {    listView = (ListView) findViewById(R.id.listView);    button = (Button) findViewById(R.id.button);    button01 = (Button) findViewById(R.id.button2);    final List<Integer> a=new ArrayList<Integer>();    a.add(1);    a.add(1);    a.add(1);    a.add(1);    a.add(1);     add=new ArrayAdapter(this,android.R.layout.simple_list_item_1,a);    listView.setAdapter(add);    button.setOnClickListener(new View.OnClickListener() {        @Override        public void onClick(View v) {            a.add(2);            add.notifyDataSetChanged();        }    });}