Активити или фрагмент (android)?

// In first fragment
public View onCreateView(LayoutInflater inflater, ViewGroup container,
			Bundle savedInstanceState) {
		View view = inflater.inflate(R.layout.frag_1, null);
		Button button1 = (Button) view.findViewById(R.id.button1);
		button1.setOnClickListener(new OnClickListener() {
			@Override
			public void onClick(View v) {
				try {
	            	MainActivity.fragmentTransaction = MainActivity.fragmentManager.beginTransaction();
	    			Fragment2 fragment2 = new Fragment2();
	    			MainActivity.fragmentTransaction.replace(R.id.fragment_container, fragment2);
	    			MainActivity.fragmentTransaction.addToBackStack(fragment2.toString());
	    			MainActivity.fragmentTransaction.commit();
				} catch (Exception e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
		});
		
		return view;
	}