Fragment interaction listeners in FragmentPagers

Question

I am creating a tabbed application using a FragmentPagerAdapter and android.support.v4.view.ViewPager. In order to follow best practices and separation of concerns I have separated my app into several different fragments. Each of the fragments has an interaction listener that requires an Activity to subscribe to. Since I only have one activity in the entire app do I have to make the parent (tabbed navigation) activity implement all the listeners in the entire app? This seems like it would be bad practice and create one large monolithic Activity class that controls the flow of everything.

I have three fragments inside of another fragment that I use as a home page tab. The home page fragment implements the interfaces of the three sub fragments. The problem is that the home page fragment is not an Activity so the sub fragments throw an exception on onAttach.

What am I missing? How can I implement fragment listeners in a tabbed application without making one large and messy Activity class

For next time, I would suggest organizing the questions, list them out. I don't know the main problem or goal in this post. — The Original Android, May 19 '15 at 18:23

score 2 · Accepted Answer · edited May 23 '17 at 12:08

After researching further with different keywords I found a good answer here: https://stackoverflow.com/a/23144683/2435006

They key was to make an onAttachFragment(Fragment f) method rather than using the onAttach(Activity a) and calling it in the onCreate method.

Here is the example from the answer above:

public void onAttachFragment(Fragment fragment)
{
    try
    {
        mListener = (OnInteractionListener) fragment;

    } catch (ClassCastException e)
    {
          throw new ClassCastException(fragment.toString() + " must implement OnInteractionListener");
    }
 }


 @Override
 public void onCreate(Bundle savedInstanceState)
 {
    Log.i(TAG, "onCreate");
    super.onCreate(savedInstanceState);

    this.mContext = getActivity().getApplicationContext();
    onAttachFragment(getParentFragment());
    ....
 }

score 0 · Answer 2 · answered May 18 '15 at 23:37

0

I think you need a good sample related to Fragments. Here is a sample with detailed explanations @ ViewPager with FragmentPagerAdapter. The listeners are at onCreateView method at the Fragment. You don't want to set a bunch of listeners in the Activity.

answered May 18 '15 at 23:37

The Original Android

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I have the listeners for button clicks related to the fragments in site the `onCreateView` in each fragment but in order to have them speak to each other they need to implement an interaction listener. The onClick handlers for the fragments call the methods in the interaction listeners so the Activity that implements the Fragments can do logic across fragments. I want the fragment that implements the two sub fragments to handle the cross-fragment logic (if that makes sense?). – LukeP May 19 '15 at 17:54
@LukeP, Having child fragments inside one fragment may make sense, some have done so. You have another option of not having any child fragment but show/hide layouts/buttons/listview or any GUI object. Would you consider that? – The Original Android May 19 '15 at 18:22

Fragment interaction listeners in FragmentPagers

2 Answers2