Set Adapter In Fragment for ListView

Question

I'm new to Android. Trying to get a listview previously controlled in my Main Activity to a fragment.

My MainActivity extends FragmentActivity. I get a null pointer for the set adapter, and for the line containing the populateList() method.

Not sure if the solution is with getActivity() and/or the setListAdapter() option I've been reading about. I know that it is finding the items from the saves, but I'm not sure how to correct this issue. Any insight would be greatly appreciated.

Additional Info: I am using android.support.v4.app.FragmentActivity. FragmentS is within public class TabbedActivity extends Fragment {

public static class FragmentS extends Fragment {



        public FragmentS() {

        }
        List<LiftSave> LiftSaves = new ArrayList<LiftSave>();
        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.listview_s,
                    container, false);

            DatabaseHandler dbHandler;
            dbHandler = new DatabaseHandler (getActivity().getApplicationContext());
            if (dbHandler.getLiftSavesCount() != 0)
                LiftSaves.addAll(dbHandler.getAllLiftSaves());

            populateList();
            return rootView;
        }
        private void populateList() {
            ListView saveListView = (ListView)getActivity().findViewById(R.id.saveListView);
            ArrayAdapter<LiftSave> saveAdapter;
            saveAdapter = new SaveListAdapter();
            saveListView.setAdapter(saveAdapter);
        }

        public class SaveListAdapter extends ArrayAdapter<LiftSave> {
            public SaveListAdapter() {
                super(getActivity(), R.layout.listview_item, LiftSaves);
            }

            @Override
            public View getView(int position, View view, ViewGroup parent) {
                if (view == null)
                    view = getActivity().getLayoutInflater().inflate(R.layout.listview_item, parent, false);

                LiftSave currentLiftSave = LiftSaves.get(position);

                TextView liftName = (TextView) view.findViewById(R.id.liftName);
                liftName.setText(currentLiftSave.getLiftName());
                TextView maxValue = (TextView) view.findViewById(R.id.maxValue);
                maxValue.setText(currentLiftSave.getMaxValue());
                TextView weightAndReps = (TextView) view.findViewById(R.id.weightAndReps);
                weightAndReps.setText(currentLiftSave.getRepsAndWeight());
                TextView liftNotes = (TextView) view.findViewById(R.id.liftNotes);
                liftNotes.setText(currentLiftSave.getLiftNotes());
                TextView date = (TextView) view.findViewById(R.id.todayDate);
                date.setText(currentLiftSave.getTodayDate());

                return view;
            }

    }}

XML:

  <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".TabbedActivity$FragmentS"
    android:background="@android:color/holo_blue_dark">

<LinearLayout
android:id="@+id/tabSaveList"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical"
xmlns:android="http://schemas.android.com/apk/res/android">

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textAppearance="?android:attr/textAppearanceLarge"
    android:text="Saved Maxes"
    android:id="@+id/textView"
    android:layout_gravity="center"
    android:layout_marginTop="10dp"
    android:textColor="#fffaf4a1"
    android:textStyle="bold" />

<ListView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/saveListView" />


</LinearLayout>
</RelativeLayout>

Solution

I think the Problem is, that you search your Activity for the ListView but not the rootView you retrieved in onCreateView()

Maybe try this:

public static class FragmentS extends Fragment {

            private ListView saveListView;

            private List<LiftSave> LiftSaves = new ArrayList<LiftSave>();

            public FragmentS() {

            }

            @Override
            public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                     Bundle savedInstanceState) {
                View rootView = inflater.inflate(R.layout.listview_s,
                        container, false);
                saveListView = (ListView) rootView.findViewById(R.id.saveListView);

                DatabaseHandler dbHandler;
                dbHandler = new DatabaseHandler (getActivity().getApplicationContext());
                if (dbHandler.getLiftSavesCount() != 0)
                    LiftSaves.addAll(dbHandler.getAllLiftSaves());

                populateList();
                return rootView;
            }

            private void populateList() {
                ArrayAdapter<LiftSave> saveAdapter = new SaveListAdapter();

                saveListView.setAdapter(saveAdapter);
            }

...

Comments

[Rami]

1) Why you instanciate your adapter twice (in onCreateView()and then in populateList() ) ? ---- 2) Put List<LiftSave> LiftSaves = new ArrayList<LiftSave>(); before onCreateView() method

[Austin]

Haha, mostly out of confusion. I moved List<LiftSave> as you mentioned before onCreateView() . Thanks for your reply.

[Austin]

Unfortunately, I do. java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapte‌​r)' on a null object reference

[Rami]

Make sure you have a ListView object with saveListView as id, in listview_s.xml

[Austin]

There is, and the Id matches. FragmentS is contained in another class called public class TabbedActivity extends Fragment {. Not sure If that matters. Sorry for my formatting, not used to posting.

[Rami]

Can you post your listview_s.xml?

[Austin]

XML is up. Also mentioned that I'm using android.support.v4.app.FragmentActivity

[Austin]

Good thought. saveListView = rootView.findViewById(R.id.saveListView); is passing android.view.View, where android.widget.ListView is required. I cast it, and It worked. The ListView did populate. Many thanks for that. However, the entries are cut in half in the list like I've never seen.

[rubengees]

Great to hear! Maybe open another question with that specific problem and be sure to add a screenshot to show how exactly the entries are being cut.

[Austin]

I must have changed my XML after I posted it above. Haha. Its fixed and everything is working. Thanks @Rami and especially @RubyDerBoss!