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I cant figure out how to fix this NullPointerException error for this project: (saw similar question but it wasn’t helpful)
MainActivity.java
public class MainActivity extends AppCompatActivity {
RecyclerView listWebsite;
RecyclerView.LayoutManager layoutManager;
NewsService mService;
ListSourceAdapter adapter;
SpotsDialog dialog;
SwipeRefreshLayout swipeLayout;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//Init cache
Paper.init(this);
//Init Service
mService = Common.getNewsService();
//Init View
swipeLayout = (SwipeRefreshLayout) findViewById(R.id.swipeRefresh);
swipeLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
@Override
public void onRefresh() {
loadWebsiteSource(true);
}
});
listWebsite = (RecyclerView) findViewById(R.id.list_source);
listWebsite.setHasFixedSize(true);
layoutManager = new LinearLayoutManager(this);
listWebsite .setLayoutManager(layoutManager);
dialog = new SpotsDialog(this);
loadWebsiteSource(false);
}
private void loadWebsiteSource(boolean isRefreshed) {
if(!isRefreshed)
{
String cache = Paper.book().read("cache");
if(cache != null && !cache.isEmpty())
{
WebSite webSite = new Gson().fromJson(cache,WebSite.class); //Convert cache from Json to Object
adapter = new ListSourceAdapter(getBaseContext(),webSite);
adapter.notifyDataSetChanged();
listWebsite.setAdapter(adapter);
}
else
{
dialog.show();
//Fetch new data
mService.getSources().enqueue(new Callback<WebSite>() {
@Override
public void onResponse(Call<WebSite> call, Response<WebSite> response) {
adapter = new ListSourceAdapter(getBaseContext(),response.body());
adapter.notifyDataSetChanged();
listWebsite.setAdapter(adapter);
//Save to cache
Paper.book().write("cache", new Gson().toJson(response.body()));
}
@Override
public void onFailure(Call<WebSite> call, Throwable t) {
}
});
}
}
else //If from Swipe to Refresh
{
dialog.show();
//Fetch new data
mService.getSources().enqueue(new Callback<WebSite>() {
@Override
public void onResponse(Call<WebSite> call, Response<WebSite> response) {
adapter = new ListSourceAdapter(getBaseContext(),response.body());
adapter.notifyDataSetChanged();
listWebsite.setAdapter(adapter);
//Save to cache
Paper.book().write("cache", new Gson().toJson(response.body()));
//Dismiss refresh progressing
swipeLayout.setRefreshing(false);
}
@Override
public void onFailure(Call<WebSite> call, Throwable t) {
}
});
}
}
}
ListSourceAdapter.java
class ListSourceViewHolder extends RecyclerView.ViewHolder
implements View.OnClickListener
{
ItemClickListener itemClickListener;
TextView source_title;
CircleImageView source_image;
public ListSourceViewHolder(View itemView) {
super(itemView);
source_image = (CircleImageView) itemView.findViewById(R.id.source_image);
source_title = (TextView) itemView.findViewById(R.id.source_name);
}
public void setItemClickListener(ItemClickListener itemClickListener) {
this.itemClickListener = itemClickListener;
}
@Override
public void onClick(View view) {
itemClickListener.onClick(view,getAdapterPosition(),false);
}
}
public class ListSourceAdapter extends RecyclerView.Adapter<ListSourceViewHolder> {
private Context context;
private WebSite webSite;
private FaviconGrabberService mService;
public ListSourceAdapter(Context context, WebSite webSite) {
this.context = context;
this.webSite = webSite;
mService = Common.getIconService();
}
@NonNull
@Override
public ListSourceViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
LayoutInflater inflater = LayoutInflater.from(parent.getContext());
View itemView = inflater.inflate(R.layout.source_layout, parent, false);
return new ListSourceViewHolder(itemView);
}
@Override
public void onBindViewHolder(final ListSourceViewHolder holder, int position) {
StringBuilder faviconAPI = new StringBuilder("https://favicongrabber.com/");
faviconAPI.append(webSite.getSources().get(position).getUrl());
mService.getIconUrl(faviconAPI.toString())
.enqueue(new Callback<FaviconGrabber>() {
@Override
public void onResponse(Call<FaviconGrabber> call, Response<FaviconGrabber> response) {
if(response.body().getIcons().size() > 0)
{
Picasso.with(context)
.load(response.body().getIcons().get(0).getUrl())
.into(holder.source_image);
}
}
@Override
public void onFailure(Call<FaviconGrabber> call, Throwable t) {
}
});
holder.source_title.setText(webSite.getSources().get(position).getName());
holder.setItemClickListener(new ItemClickListener() {
@Override
public void onClick(View view, int position, boolean isLongClick) {
//Implement part 2
}
});
}
@Override
public int getItemCount() {
return webSite.getSources().size(); //here I get a NullPointerException
}
}
I’m getting this error message by return webSite.getSources().size(); :
java.lang.NullPointerException: Attempt to invoke virtual method ‘java.util.List …Model.WebSite.getSources()’ on a null object reference at …Adapter.ListSourceAdapter.getItemCount(ListSourceAdapter.java:110)
I can give other part of project if you need, tnx!
Answer
The error is telling you that the object reference webSite is null. You need to check the process that is calling the ListSourceAdapter constructor to see what is causing it to send null to the constructor call.
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