I have two fragments and a main activity. The first fragment, FriendsFragment (extends ListFragment) is displayed on the screen and when the user clicks an item, the main Activity replaces the FriendsFragment with FeedFragment, then calls a method from FeedFragment to update the textView.
I'm getting an error that the textView object in the FeedFragment class is null even though I instantiate using the findViewById
method.
I have looked at related questions and have tried the solutions but nothing is working. I've tried doing getView().findViewById(R.id.feed_view)
, getActivity().findViewById(R.id.feed_view)
, and I've tried putting these in onActivityCreated()
and onCreateView()
The only thing that worked is writing this code in onActivityCreated():
text = getView().findViewById(R.id.feed_view);
text.setText("some string");
but this is not what I want
FeedFragments.java
public class FeedFragment extends Fragment {
private static String TAG = "Feed Fragment";
private TextView text;
@Override
public void onActivityCreated(Bundle savedInstanceState) {
Log.i(TAG, "Entered FeedFragment.java onActivityCreated()");
super.onActivityCreated(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
Log.i(TAG, "Entered FeedFragment.java onCreateView()");
View v = inflater.inflate(R.layout.fragment_feed, container,false);;
text = v.findViewById(R.id.feed_view);
return v;
}
public void updateDisplay(int position)
{
Log.i(TAG, "FeedFragment.java: updateDisplay()");
text.setText(position);
}
MainActivity.java
// previously declared feedFragment: feedFragment = new FeedFragment();
public void onItemSelected(int position)
{
Log.i(TAG, "Entered onItemSelected(" + position + ")");
fragManager = getFragmentManager();
FragmentTransaction fragTransaction = fragManager.beginTransaction();
fragTransaction.replace(R.id.fragment_container, feedFragment, "feed_fragment");
fragTransaction.addToBackStack(null);
fragTransaction.commit();
feedFragment.updateDisplay(position);
}
fragment_feed.xml
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<TextView
android:id="@+id/feed_view"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@string/greeting" />
</ScrollView>
activity_main.xml
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/fragment_container"
android:layout_width="match_parent"
android:layout_height="match_parent" />
onViewcreated() is being called after updateDisplay() because the system doesn't run it right away.
you need to pass a value to the feedFragment on it's creation and store it in a bundle and retrieve it after the fragment internal code is run by the system.
the way you solve it is like this:
when you instantiate feedFragment you do it like this:
feedFragment = FeedFragment.newInstance(position)
and inside FeedFragment class you should have a static code:
private static final String ARG_PARAM1 = "param1";
public static FeedFragment newInstance(int param1) {
FeedFragment fragment = new FeedFragment();
Bundle args = new Bundle();
args.putInt(ARG_PARAM1, param1);
fragment.setArguments(args);
return fragment;
}
and non static code:
private int mParam1;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
mParam1 = getArguments().getInt(ARG_PARAM1);
}
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
Log.i(TAG, "Entered FeedFragment.java onCreateView()");
View v = inflater.inflate(R.layout.fragment_feed, container,false);;
text = v.findViewById(R.id.feed_view);
text.setText(String.valueOf(mParam1));
return v;
}
I wrapped mParam1 in String.valueOf() because when you pass integer to setText it thinks you try to use a Strings.xml resource instead of the number you chose.
also I used very generic variable names. please change them to something meaningful so that your code makes sense.
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