Update existing Preference-item in a PreferenceActivity upon returning from a (sub)PreferenceScreen

Question

I have a PreferenceActivity with a bunch of (Sub)PreferenceScreens. Each such (Sub)PreferenceScreen represents an account and has the account-username as its title.

PreferenceScreen root = mgr.createPreferenceScreen(this);
for (MyAccountClass account : myAccounts) {
    final PreferenceScreen accScreen = mgr.createPreferenceScreen(this);

    accScreen.setTitle(account.getUsername());

    // add Preferences to the accScreen
    // (for instance a "change username"-preference)
    ...

    root.add(accScreen);
}

As the user enters sub-PreferenceScreen, and edits the account user-name, I want the outer PreferenceScreen to update it's PreferenceScreen-title for the account in question.

I've tried to add...

usernamePref.setOnPreferenceChangeListener(new OnPreferenceChangeListener() {
    public boolean onPreferenceChange(Preference preference, Object newValue) {
        accScreen.setTitle(newValue.toString());
        return true;
    }
});

...but the accScreen.setTitle does not seem to take effect on the outer PreferenceScreen. I've note that calling onContentChanged(); actually makes it work, but I realize that this is probably not the preferred way of doing it.

I suspect I should call postInvalidate() on some view somewhere, but I really can't figure out on what view and when to do it.

PreferenceScreen android:summary update ! may be experiening the same problem as me.

Any help appreciated.

Answer 1

I found a solution to this. I have a hierarchy like this, each of these is a PreferenceScreen:

main settings
  -> users list
    -> user1 settings
    -> user2 settings
    ...

In the users list, title of the sub-screen is dependent on the user settings. Now when I create the user list, I store the list adapter to a variable in my PreferenceActivity.

 PreferenceScreen usersListScreen = ...
 userScreenListAdapter = (BaseAdapter)usersListScreen.getRootAdapter();

Now when userX-settings are edited, I set the titles in the usersListScreen and after that call:

userScreenListAdapter.notifyDataSetChanged();

which updates the list UI and the changes are visible.

Answer 2

notifyDataSetChanged() is right solution. But I want to add recursive iterator for all PreferenceScreens, as far as I got a problem to find real parent of a Preference. For complicated structure of Preferences I recommend this killer-code:

private void updateAll_PrefereneScreens(PreferenceGroup group) {
    if (group instanceof PreferenceScreen) {
        BaseAdapter adapter = (BaseAdapter) ((PreferenceScreen) group).getRootAdapter();
        adapter.notifyDataSetChanged();
    }
    for (int i=0; i<group.getPreferenceCount(); i++) {
        Preference pref = group.getPreference(i);
        if (pref instanceof PreferenceGroup) {
            updateAll_PrefereneScreens((PreferenceGroup) pref);
        }
    }
}

I call it after every setSummary() to ensure it works properly:

findPreference("KEY").setSummary(str);
updateAll_PrefereneScreens(getPreferenceScreen());