How to add alert dialog(code) when add item to dynamic list view by code

the following code to add dynamic list view by button
public class MainActivity extends AppCompatActivity {
private ArrayListarrayList;
private ArrayAdapteradapter;
private EditText txtInput;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    ListView listView=(ListView)findViewById(R.id.listv);
    String[] items={"apple","banana","grape"};
    arrayList=new ArrayList<>(Arrays.asList(items));
    adapter=new ArrayAdapter<String>(this,R.layout.list_item,R.id.textView2,arrayList);
    listView.setAdapter(adapter);
    txtInput=(EditText)findViewById(R.id.txtinput);
    Button btadd=(Button)findViewById(R.id.btadd);
    btadd.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v)
        {
            String newitem=txtInput.getText().toString();
            arrayList.add(newitem);
            adapter.notifyDataSetChanged();

        }
    });

}

}
what i need to add alert dialog code with yes and NO when yes add item
when NO not added
Actually i need to modify code to accept alert dialog box with yes and NO
when press yes add item
when press NO not added