Problemas com setListAdapter

package com.example.lab08;

import java.util.ArrayList;
import java.util.List;

import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.TextView;
import android.widget.ListView;
import android.os.Build;

public class MainActivity extends ActionBarActivity {
	
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		
		List<String> continentes = new ArrayList<String>();
		continentes.add("África");
		continentes.add("América");
		continentes.add("Antártida");
		continentes.add("Ásia");
		continentes.add("Europa");
		continentes.add("Oceania");
		
		this.setListAdapter(new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1,continentes));
		

		if (savedInstanceState == null) {
			getSupportFragmentManager().beginTransaction()
					.add(R.id.container, new PlaceholderFragment()).commit();
		}
	}

	@Override
	public boolean onCreateOptionsMenu(Menu menu) {

		getMenuInflater().inflate(R.menu.main, menu);
		return true;
	}

	@Override
	public boolean onOptionsItemSelected(MenuItem item) {
		int id = item.getItemId();
		if (id == R.id.action_settings) {
			return true;
		}
		return super.onOptionsItemSelected(item);
	}

	public static class PlaceholderFragment extends Fragment {

		public PlaceholderFragment() {
		}

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

}