Observe LiveData from ListView current Item - android-fragments

Question

Basically i want to retrieve a int(score) generated from the current ListViewItem and assign it back to concrete TextView in my ListView.I am using SharedViewModel with LiveData but when i observe nothing happens.I am using Nav Architecture Component with Single activity.I'll be glad if someone helps.Thank u , here's some code.
public class ListFrag extends Fragment {
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
model = ViewModelProviders.of(getActivity()).get(SharedViewModel.class);
model.getCurrentScore().observe(getViewLifecycleOwner(), new Observer<Integer>() {
#Override
public void onChanged(#Nullable Integer s) {
for (int i = 0; i < myListView.getAdapter().getCount(); i++) {
v = myListView.getAdapter().getView(i,null, myListView);
finalScore = v.findViewById(R.id.finalScoreView);
if (s != null) {
itemAdapter = new ItemAdapter(getActivity(),items,bushido,description,s,finalScore);
myListView.setAdapter(itemAdapter);
finalScore.setText(String.valueOf(s));
}
((BaseAdapter)myListView.getAdapter()).notifyDataSetChanged();
}
}
});
}
public class SharedViewModel extends ViewModel
{
private MutableLiveData<Integer> currentScore = new MutableLiveData<>();
public LiveData<Integer> getCurrentScore(){
return currentScore;
}
public void setCurrentScore(Integer finito) {
currentScore.setValue(finito);
}
}
public class ItemAdapter extends BaseAdapter {
LayoutInflater mInflater;
String[] items;
String[] bushido;
String[] description;
TextView finalscorre;
Integer scr;
public ItemAdapter(Context c,String[] i ,String [] p ,String[] d, Integer scc,TextView sc) {
items = i;
bushido = p;
description = d;
finalscorre = sc;
scr = scc;
mInflater = (LayoutInflater) c.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
#Override
public int getCount() {
return items.length;
}
#Override
public Object getItem(int i) {
return items[i];
}
#Override
public long getItemId(int i) {
return i;
}
#Override
public View getView(int i, View convertView, ViewGroup parent) {
View v = mInflater.inflate(R.layout.my_listview_detail, null);
TextView nameTextView = v.findViewById(R.id.NameTextView);
TextView bushidoTextView = v.findViewById(R.id.bushidoTextView);
TextView descriptionTextView = v.findViewById(R.id.descriptionTextView);
finalscorre = v.findViewById(R.id.finalScoreView);
String name = items[i];
String desc = description[i];
String bush = bushido[i];
finalscorre.setText("Waat");
nameTextView.setText(name);
descriptionTextView.setText(desc);
bushidoTextView.setText(bush);
ItemAdapter.this.notifyDataSetChanged();
return v;
}
}
When i try to assign the LiveData in TextView out of the ListView it works.But when i try this ,nothings happen (no errors and no result).

Answer 1

Adapters act as a bridge between the data (in your case, the string array you pass into the adapter), and the ListView (in your case, myListView). Any change to the ListView needs to be follow these steps:
make desired changes to the data itself
pass this new data to the adapter
adapter updates the list view
I have wrote some example code:
ItemAdapter
public class ItemAdapter extends BaseAdapter {
LayoutInflater mInflater;
String[] items;
String[] bushido;
String[] description;
// TextView finalscorre; // I commented out this TextView please see the comment below
Integer scr;
public ItemAdapter(Context c,String[] i ,String [] p ,String[] d, Integer scc,TextView sc) {
items = i;
bushido = p;
description = d;
// finalscorre = sc;
scr = scc;
mInflater = (LayoutInflater) c.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
public void updateItems(String[] i, String[] p, String[] d, Integer scc) {
items = i;
bushido = p;
description = d;
scr = scc;
// notify the adapter to refresh the list view.
notifyDataSetChanged()
}
#Override
public int getCount() {
return items.length;
}
#Override
public Object getItem(int i) {
return items[i];
}
#Override
public long getItemId(int i) {
return i;
}
#Override
public View getView(int i, View convertView, ViewGroup parent) {
View v = mInflater.inflate(R.layout.my_listview_detail, null);
TextView nameTextView = v.findViewById(R.id.NameTextView);
TextView bushidoTextView = v.findViewById(R.id.bushidoTextView);
TextView descriptionTextView = v.findViewById(R.id.descriptionTextView);
//finalscorre = v.findViewById(R.id.finalScoreView);
TextView finalscorre = v.findViewById(R.id.finalScoreView);
String name = items[i];
String desc = description[i];
String bush = bushido[i];
// finalscorre.setText("Waat");
finalscorre.setText(scr);
nameTextView.setText(name);
descriptionTextView.setText(desc);
bushidoTextView.setText(bush);
// ItemAdapter.this.notifyDataSetChanged(); Do NOT call this method inside getView
return v;
}
}
Fragment
public class ListFrag extends Fragment {
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
// Create and set adapter just once. Do not create or set new adapter in observer, for loop, etc.
itemAdapter = new ItemAdapter(getActivity(),items,bushido,description,s,finalScore);
myListView.setAdapter(itemAdapter);
model = ViewModelProviders.of(getActivity()).get(SharedViewModel.class);
model.getCurrentScore().observe(getViewLifecycleOwner(), new Observer<Integer>() {
#Override
public void onChanged(#Nullable Integer s) {
itemAdapter.updateItems(items,bushido,description,s);
}
});
}
}
I wasn't able to figure out what finalscorre supposed to be so I assumed that this is the text view that stores the final score that you mentioned, and all list view items should have the same value. If this is not the case please clarify in your question.
Also note that while this solution is enough to solve the specific problem you mentioned, their are some other improvements that can be made:
Use RecyclerView instead of ListView.
Instead of maintaining multiple String[], define a POJO that represent the item, and have a single array.
Also, checking this adapter implementation in google sample will help.

Answer 2

inside adapter you are doing nothing that will update your LiveData