如何从viewPager调用Fragment的类？

Question

我没有外观问题但是当它开始时，它什么也没有显示。 我认为只会夸大布局，但我想把我所有的所有内容称为片段类

类PlaceholderFragment：

public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View rootView = null;
        switch (getArguments().getInt(ARG_SECTION_NUMBER)) {
            case 1:
                rootView = (View) inflater.inflate(R.layout.fragment_first, container, false);
                break;
            case 2:
                rootView = (View) inflater.inflate(R.layout.fragment_second, container, false);
                break;
            case 3:
                rootView = (View) inflater.inflate(R.layout.fragment_third, container, false);
                break;
        }
        return rootView;
    }

我的班级FirstFragment：

public class PrimerFragment extends AppCompatActivity {

Location location;
LocationManager locationManager;
LocationListener locationListener;
AlertDialog alert = null;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.fragment_primer);

    resultado = (TextView) findViewById(R.id.resultado);
    resultado.setText("Hello");

    locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);
}  

我知道我的班级不完整但只想尝试为什么什么都不显示。并且甚至不显示Toast。 感谢