Jak ustawić text w textview?

public class MainActivity extends ActionBarActivity {
    Button p1;
    TextView t1;
    public void obsluga_przycisku(View v)
    {
    	t1.setText("dziala");
    	//Toast.makeText(getApplicationContext(), "dziala", 10).show();
    }
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        p1=(Button) findViewById(R.id.przycisk1);
        t1=(TextView) findViewById(R.id.poletekstowe);
        if (savedInstanceState == null) {
            getSupportFragmentManager().beginTransaction()
                    .add(R.id.container, new PlaceholderFragment())
                    .commit();
        }
    }

t1=(TextView) findViewById(R.id.poletekstowe);