Android Fragments不调用Backstack

Question

I have a class "bancoActivity" that extends Fragment implements ActionBar.TabListener that calls another class "pagamentos" extends Fragment implements ActionBar.TabListener. When I'm in class "pagamentos" and click on the physical button "back" nothing happens, and when i click again the application finish. I leave there my code so that your can analyze. Obrigado.

part of the bancoActivity:

@Override
public void onItemClick(AdapterView<?> customviewadapter, View view, int position, long id) {   
    listViewItem item = items.get(position);
    String Titulo = item.Title;

    if(Titulo.equals("Pagamentos")) {
        FragmentManager fragmentManager2 = getFragmentManager();
        FragmentTransaction fragmentTransaction2 = fragmentManager2.beginTransaction();
        pagamentos fragment2 = new pagamentos();
        fragmentTransaction2.hide(bancoActivity.this);
        fragmentTransaction2.add(android.R.id.content, fragment2);
        fragmentTransaction2.addToBackStack("banco");
        fragmentTransaction2.commit();
    }
}

part of the pagamentos:

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
     getActivity().setContentView(R.layout.pagamentos);
     FragmentManager fm = getFragmentManager();

the two activities extends and implements:

public class pagamentos extends Fragment implements ActionBar.TabListener{
public class bancoActivity  extends Fragment implements ActionBar.TabListener

Answer 1

I'm a newbie too, but I'll take a stab at it...

I think you need to instantiate both fragments from the activity that holds them, and use 1 fragment manager to do the switching. Its hard for me to tell without your whole code, but I have a similar setup working, here is how:

public class MainActivity extends Activity implements ActionBar.TabListener {

    public static final int SEARCH_FRAG = 1;
public static final int MAP_FRAG = 2;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    fragMan = (FragmentManager) getFragmentManager();
    mapFrag = ExtendedMapFragment.newInstance();
    searchFrag = SearchFragment.newInstance();
    if (mapShown == false) {
        swapFrags(SEARCH_FRAG);
    } else {
        swapFrags(MAP_FRAG);
    }
     ActionBar actionBar = getActionBar();
     actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
     actionBar.setDisplayShowTitleEnabled(true);
     searchTab = actionBar.newTab()
                .setText(R.string.search_tab_label)
                .setTabListener(this);
        actionBar.addTab(searchTab);
     mapTab = actionBar.newTab()
             .setText(R.string.map_tab_label)
             .setTabListener(this);
        actionBar.addTab(mapTab);
     if (savedInstanceState != null) {
         actionBar.setSelectedNavigationItem(savedInstanceState.getInt("currentTab"));
     }
     actionBar = null;

}

    public void swapFrags(int whatFrag) {
    if (whatFrag == SEARCH_FRAG) {
        //switch to frag 1, ie searchFrag
        FragmentTransaction trans = fragMan.beginTransaction();
        trans.replace(R.id.map, searchFrag);
        mapShown = false;
        trans.addToBackStack(null);
        trans.commit();
    }
    if (whatFrag == MAP_FRAG) {
        //switch to frag 2, ie mapFrag
        if (lbServ != null) {
            update.autoCenter(lbServ.getCurrentLatLng());
        }
        FragmentTransaction trans = fragMan.beginTransaction();
        trans.replace(R.id.map, mapFrag);
        mapShown = true;
        trans.addToBackStack(null);
        trans.commit();
    }
}

}

The swapFrags() method is also called from my onTabSelected callback. I think, since I only have one fragment manager, and the same manager is calling all the addToBackStack() methods, it is more organized. When I open the app, select a new tab, then hit physical back key, it goes back to the previous tab, which is what you are after, no?

One thing I found difficult to learn with fragments is that all calls, keys, etc. go to the activity first. Push a button on the fragment, the activity that holds it gets the callback first (whether it uses it or not), then if there is a listener in the fragment it will get the call also, but fragments can't do really anything outside themselves, and fragment transactions involve objects outside the fragment.

I suppose you could set up an interface between fragment and activity, with a method like swapFrags() in the activity, where the fragment can ask to be swapped, that should do it too I think.