Fragment

public class MainActivity extends FragmentActivity implements OnClickListener{

    private FragmentManager me;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        me=getSupportFragmentManager();
        findViewById(R.id.qq).setOnClickListener(this);
        findViewById(R.id.ww).setOnClickListener(this);
        show(new Main2Activity());
    }

    private void show(Fragment fragment) {
        // TODO Auto-generated method stub
        me.beginTransaction().replace(R.id.ment,fragment).commit();
    }

    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub
        switch (v.getId()) {
        case id.qq:
            show(new Main2Activity());
            break;
        case id.ww:
            show(new Main3Activity());
            break;

        default:
            break;
        }
    }

    

}

public class Main2Activity extends Fragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        return inflater.inflate(R.layout.activity_main2,null);
    }

}