Enable an ActionBar Button each time navigation within tabs occurs.

Question

I have a main activity in which I designate tabs using three fragments. I have a button on the ActionBar which navigates to a different fragment say "Info about the app" Once user navigates to this particular fragment (Info) I disable it so that it is not called again and again. Then on the back key in the main activity I re-enable it. So far so good. But I am not able to re-enable it for one scenario: Say if user navigates to the info fragment and does not press back, but however if he navigates to a different tab, the info button is still disabled because back-press has not been called. I tried a lot of things in onStart() and onResume() of fragments but I am not able to reference the menuItem in any of those as I get a null pointer.

Code Reference: (MainActivity while calling the info fragment from onOptionsSelected):

public boolean onOptionsItemSelected(MenuItem item) {

        mMenuItem = item; 
        switch (item.getItemId()) {
        case R.id.info:
            Tab d = getActionBar().getSelectedTab();

            System.out.println(""+d.getText().toString()); 
            FragmentManager fragmentManager = getFragmentManager();  
            FragmentTransaction fragmentTransaction = fragmentManager  
                    .beginTransaction();  

            String a = d.getText().toString(); 
            if(a.equalsIgnoreCase("Reminders")){ 
                FragmentContact fragmentcontact = new FragmentContact(); 
                fragmentTransaction.replace(R.id.realtabcontent, fragmentcontact);  
                mMenuItem.setEnabled(false); 
                //mMenuItem.setIcon(R.drawable.btn_age_01); 
            }
            else if(a.equalsIgnoreCase("Notifications")){
                FragmentContact fragmentcontact = new FragmentContact();
                fragmentTransaction.replace(R.id.realtabcontent2, fragmentcontact);  
                mMenuItem.setEnabled(false); 

            }
            else if(a.equalsIgnoreCase("Contacts")){
                FragmentContact fragmentcontact = new FragmentContact(); 
                fragmentTransaction.replace(R.id.realtabcontent3, fragmentcontact); 
                mMenuItem.setEnabled(false); 

            }
            fragmentTransaction.addToBackStack(null);
            fragmentTransaction.commit();  



            break;

on Back key(Main Activity):

@Override
    public void onBackPressed() {
        mMenuItem.setEnabled(true);
        super.onBackPressed();
    }

Are reminders, notification and contacts fragments lie under Info action bar button? i.e. these are part of Info button. — Mr Roshan Pawar
Info is an alltogether different fragment, it is navigable from any of the three, this navigation does not open a different intent however it just navigates from any of the three fragment tabs into the same view. That is it gets displayed without hanging the tab. — Skynet
If yes, why not try to set default : mMenuItem.setEnabled(true); inside switchc-case. — Mr Roshan Pawar
Nope wont work, just tried it, there will not be a default case ever I think.. — Skynet
I need to reference the mMenuItem in the onStart and onResume of every fragment somehow.. I think that is the only work around. — Skynet

Skynet Skynet · Accepted Answer · 2013-12-05T07:30:21

The solution was very simple, to set an options menu for individual "Fragments" use:

setHasOptionsMenu(true);

Cheers!!

Enable an ActionBar Button each time navigation within tabs occurs.

1 Answers