Android Fragment, going back without recreating/reloading Fragment

Question

I've seen quite a few questions on SO about Fragments and I still can't seem to figure out if what I want to do is possible, and more so if my design pattern is just flawed and I need to re-work the entire process. Basically, like most questions that have been asked, I have an ActionBar with NavigationTabs (using ActionBarSherlock), then within each Tab there is a FragementActivity and then the FragmentActivities push new Fragments when a row is selected (I'm trying to re-create an iOS Project in Android and it's just a basic Navigation based app with some tabs that can drill down into specific information). When I click the back button on the phone the previous Fragment is loaded but the Fragment re-creates itself (so the WebServices are called again for each view) and this isn't needed since the information won't change in a previous view when going backwards. So basically what I want to figure out is how do I setup my Fragments so that when I push the back button on the phone, the previous Fragment is just pulled up with the previous items already created. Below is my current code :

    //This is from my FragmentActivity Class that contains the ActionBar and Tab Selection Control
    @Override
public void onTabSelected(ActionBar.Tab tab, FragmentTransaction ft) {
    // TODO Auto-generated method stub
    int selectedTab = tab.getPosition();

    if (selectedTab == 0) {
        SalesMainScreen salesScreen = new SalesMainScreen();
        ft.replace(R.id.content, salesScreen);
    }
    else if (selectedTab == 1) {
        ClientMainScreen clientScreen = new ClientMainScreen();
        ft.replace(R.id.content, clientScreen);
    }.....

   //This is within the ClientMainScreen Fragment Class, which handles moving to the Detail Fragment
   row.setOnClickListener(new View.OnClickListener() {
                        @Override
                        public void onClick(View view) {
                            //Do something if Row is clicked
                            try{
                                String selectedClientName = clientObject.getString("ClientName");
                                String selectedClientID = clientObject.getString("ClientID");
                                String selectedValue = clientObject.getString("ClientValue");
                                transaction = getFragmentManager().beginTransaction();
                                ClientDetailScreen detailScreen = new ClientDetailScreen();
                                detailScreen.clientID = selectedClientID;
                                detailScreen.clientName = selectedClientName;
                                detailScreen.clientValue = selectedValue;
                                int currentID = ((ViewGroup)getView().getParent()).getId();
                                transaction.replace(currentID,detailScreen);
                                transaction.addToBackStack(null);
                                transaction.commit();

                            }
                            catch (Exception e) {
                                e.printStackTrace();
                            }
                        }
                    });....

     //And then this is the Client Detail Fragment, with the method being called to Call the Web Service and create thew (since what is displayed on this screen is dependent on what is found in the Web Service
          @Override
public View onCreateView(LayoutInflater inflater, ViewGroup group, Bundle saved) {
    return inflater.inflate(R.layout.clientdetailscreen, group, false);
}

@Override
public void onActivityCreated (Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);

    //Setup Preferences File Link
    this.preferences = PreferenceManager.getDefaultSharedPreferences(getActivity());

    //initialize the table object
    mainTable = (TableLayout)getActivity().findViewById(R.id.mainTable);

    //setup the detail table
    setupRelatedClientSection();

}

The Client Detail Screen can then drill down one more time, using the same method as the Client Main Screen but when I go back from that new screen to the Detail Screen the seuptRelatedClientSection() method is called again and so the entire Fragment is rebuilt when really I just want to pull up a saved version of that screen. Is this possible with my current setup, or did I approach this the wrong way?

Answer 1

Try using fragementTransaction.add instead of replace

Answer 2

I believe that you are looking for show() and hide().

I think you can still add them to the backstack.

 transaction.hide(currentFragment);
 transaction.show(detailScreen);
 transaction.addToBackStack(null);
 transaction.commit();

I didnt have my code to look at but i believe this is how it would go... Try it out unless someone else has a better way. I have not tried the backstack with show() hide() but i believe that it takes the changes that are made before the transactions commit and will undo them if the back button is pressed. Please get back to me on this cause i am interested to know.

You also have to make sure that the detail fragment is created before you call this. Since it is based on the click of someitem then you should probably create the details fragment every time you click to make sure the correct details fragment is created.

Answer 3

I'm posting this answer for people who may refer this question in future.

Following code will demonstrate how to open FragmentB from FragmentA and going back to FragmentA from FragmentB (without refreshing FragmentA) by pressing back button.

public class FragmentA extends Fragment{

   ...

   void openFragmentB(){

       FragmentManager fragmentManager = 
           getActivity().getSupportFragmentManager();
       FragmentB fragmentB = FragmentB.newInstance();

       if (fragmentB.isAdded()) {

           return;
       } else {

           fragmentManager.
               beginTransaction().
               add(R.id.mainContainer,fragmentB).
               addToBackStack(FragmentB.TAG).
               commit();
      }
   }
}

public class FragmentB extends Fragment{

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

    ...

    public static FragmentB newInstance(){

        FragmentB fragmentB = new FragmentB();
        return fragmentB;
    }

    @Override
    public void onResume() {

        super.onResume();
        // add this piece of code in onResume method
        this.getView().setFocusableInTouchMode(true);
        this.getView().requestFocus();
    }
}

In your MainActivity override onBackPressed()

class MainActivity extends Activity{
    ...

    @Override
    public void onBackPressed() {

        if (getFragmentManager().getBackStackEntryCount() > 0) {

            getFragmentManager().popBackStack();
        } else {

            super.onBackPressed();
        }
    } 
}