Android NavigationView change title onBackPressed

Question

I have a NavigationView that changes certain Fragment by clicking on its item and setting toolbar's title with item's name:

fragmentTransaction = getFragmentManager().beginTransaction();
    int id = item.getItemId();
    switch (id){
        case R.id.studying:
            fragmentTransaction.replace(R.id.container, studyFragment).addToBackStack(null);
            break;
        case R.id.events:
            fragmentTransaction.replace(R.id.container, eventsFragment).addToBackStack(null);
            break;
        case R.id.discount:
            fragmentTransaction.replace(R.id.container, discountsFragment).addToBackStack(null);
            break;
        case R.id.bookmarks:
            fragmentTransaction.replace(R.id.container, bookmarksFragment).addToBackStack(null);
            break;
        case R.id.settings:
            fragmentTransaction.replace(R.id.container, settingsFragment).addToBackStack(null);
            break;
        case R.id.prolong_sign:
            fragmentTransaction.replace(R.id.container, prolongFragment).addToBackStack(null);
            break;
        case R.id.contacts:
            fragmentTransaction.replace(R.id.container, contactsFragment).addToBackStack(null);
            break;
    }
    toolbarTitle.setText(item.getTitle().toString());
    fragmentTransaction.commit();

Proving better usability I override onBackPressed method:

 @Override
public void onBackPressed() {
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    if (drawer.isDrawerOpen(GravityCompat.START)) {
        drawer.closeDrawer(GravityCompat.START);
    } else {
        FragmentManager fm = getFragmentManager();
        if (fm.getBackStackEntryCount() > 0 && fm.getBackStackEntryCount() != 1) {
            fm.popBackStackImmediate();
        } else if (fm.getBackStackEntryCount() == 1) {
            toolbarTitle.setText("TEST");
            fm.popBackStackImmediate();
        } else {
            super.onBackPressed();
        }
    }
}

If I back to the first Fragment, my toolbarTitle sets okay according to:

 else if (fm.getBackStackEntryCount() == 1) {
            toolbarTitle.setText("TEST");
            fm.popBackStackImmediate();
        }

But I don't know how to make toolbarTitle to change title correctly on each onBackPressed and make previous item in NavigationView checked. Can you help me with it?

EDIT

I created an interface

public interface OnToolbarTitle {
void setTitle(String title);

}

implemented it MainActivity and overrided

 @Override
public void setTitle(String title) {
    toolbarTitle.setText(title);
}

And tried to use it in Fragments by attaching it in Fragments:

@Override
public void onAttach(Context context) {
    super.onAttach(context);
    titleSetter = (OnToolbarTitle) context;
}

@Override
public void onResume() {
    super.onResume();
    titleSetter.setTitle("Test-frag3");
}

But I got NullPointerException in line with setTitle() method.

EDIT

Ok I solved my problem by accessing Toolbar in fragment.

    View view = getActivity().findViewById(R.id.toolbar);
    TextView title = (TextView) view.findViewById(R.id.toolbar_title);
    title.setText("study lol");

Still, I'd be glad to see, how can I achive it with interface.

Marcin Orlowski · Accepted Answer · 2016-05-24T12:25:49.513

4

You should consider making your fragments setting the title. I.e. define interface like:

interface HostContract {
    setTitle(String title);
}

and make your activity implement it. Then in each fragment you should call ((HostContract)getActivity).setTitle() in fragment's onResume(). This way you set the title when your fragment goes into game (be it because it is newly added, or because you took previous one from backstack, which should solve your problem. And that's basically all you need to do.

edited May 24 '16 at 12:25

answered May 23 '16 at 15:23

Marcin Orlowski

72,056
11
123
141

I believe that you direct me to right way, but I'm not sure, that I know enough about interfaces. I changed my post. – Peter Parker May 24 '16 at 07:31
You may want to read this [How to send data from DialogFragment to a Fragment?](http://stackoverflow.com/a/18579638/1235698) for more detailed instruction. – Marcin Orlowski May 24 '16 at 09:54
Thank you, Marcin! – Peter Parker May 24 '16 at 12:10

score 0 · Answer 2 · answered May 23 '16 at 15:23

0

your if...else should be like

if (fm.getBackStackEntryCount() > 0 && fm.getBackStackEntryCount() != 1) {
        fm.popBackStackImmediate();
        toolbarTitle.setText("TEST");
 } else if (fm.getBackStackEntryCount() == 1) {
        toolbarTitle.setText("TEST");
        fm.popBackStackImmediate();
 } else {
        super.onBackPressed();
 }

answered May 23 '16 at 15:23

Ravi Theja

3,371
1
22
34

How do I know what `Fragment` is active? :))))) – Peter Parker May 24 '16 at 06:52

Android NavigationView change title onBackPressed

2 Answers2