hello world

this is my first application of android.

here is the source of the hello world ?

ok .that is begin :

   @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_activity01);                TextView mytest=(TextView) findViewById(R.id.buttion_01);        mytest.setText("nihao");           }

evey time why you want get a TextView or other View object,you need setContentView first