how to solve this?

import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;

public class PhotoFragment extends Fragment {

    public Button mDeleteButton;

    @Override
    public void onCreate(Bundle savedInstanceState) {
       mDeleteButton= (Button) findViewById(R.id.deleteButton);
        super.onCreate(savedInstanceState);

    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_photo, container, false);

        return rootView;
    }
}

import android.app.ActionBar;
import android.app.Activity;
import android.app.FragmentTransaction;
import android.os.Bundle;
import android.util.Log;

public class MainActivity extends Activity implements ActionBar.TabListener {

    public static final String TAG = MainActivity.class.getSimpleName();

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);


    }

    @Override
    public void onTabSelected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {


    }

    @Override
    public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {

    }

    @Override
    public void onTabReselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {

    }
}