I'm trying to work out the correct way to pass in an Object to a Fragment or DialogFragment without breaking the 'empty constructor' rule.
For example I have created a custom View and for each one I instantiate I want to associate a DiaglogFragment. This DialogFragment will be used to display controls with which the user can alter certain aspects of the custom View it is associated with. Because View is an Object I understand I cannot use setArguments().
I could implement a newInstance(View) method of my DialogFragment i.e. Factory pattern but then what happens if my Fragment is saved by the system and then restored at a later date? As far as I can tell there will be no reference to the View object?
Could someone tell me if I am using Fragments in the wrong way or is there way to achieve passing in an object to the Fragment which will also cope with the system reconstructing it at a later time.
In your DialogFragmnet
class, you create two methods:
newInstance
to make instance of your DialogFragment
setter to initialize your object
and add setRetainInstance(true);
in onCreate
public class YourDialogFragment extends DialogFragment {
ComplexVariable complexVar;
public static YourDialogFragment newInstance(int arg, ComplexVariable complexVar) {
YourDialogFragment frag = new MoveSongDialogFragment();
Bundle args = new Bundle();
args.putInt("count", arg);
frag.setArguments(args);
frag.setComplexVariable(complexVar);
return frag;
}
public void setComplexVariable(ComplexVariable complexVar) {
this.complexVar = complexVar;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setRetainInstance(true);
}
}
then, to show the dialog
FragmentManager manager = getSupportFragmentManager();
FragmentTransaction ft = manager.beginTransaction();
Fragment prev = manager.findFragmentByTag("yourTag");
if (prev != null) {
ft.remove(prev);
}
// Create and show the dialog.
DialogFragment newFragment = YourFragmentDialog.newInstance(argument, yourComplexObject);
newFragment.show(ft, "yourTag");