Context for RecyclerView.Adapter

Question

I want to add ProgressDialog in an adapter. AFAIK, .this for activity, and getActivity.getApplicationContext() for fragment. What about adapter? Is it possible?

I got error Unable to add window -- token null is not valid; is your activity running? when I use mContext.getApplicationContext().

EDIT:

In a fragment, I show cards by

allGroupsView = (RecyclerView) rootView.findViewById(R.id.allGroupsView);
adapterGroup = new AdapterGroup(getActivity().getApplicationContext(), results);
allGroupsView.setAdapter(adapterGroup);
allGroupsView.setLayoutManager(new LinearLayoutManager(getActivity().getApplicationContext()));

In class AdapterGroup

public class AdapterGroup extends RecyclerView.Adapter<RecyclerView.ViewHolder> {

private Context mContext;
private LayoutInflater inflater;
List<DataGroup> data= Collections.emptyList();
DataGroup current;

public AdapterGroup(Context context, List<DataGroup> results) {
    this.mContext = context;
    inflater = LayoutInflater.from(mContext);
    this.data = results;
}

// Inflate the layout when viewholder created
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View view = inflater.inflate(R.layout.card_view_row, parent, false);
    final MyHolder holder = new MyHolder(view);

    view.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Log.d("debug", String.valueOf(holder.getAdapterPosition()));
            getDetails(Config.GET_GROUP_DETAILS_URL, data.get(holder.getAdapterPosition()).groupName, data.get(holder.getAdapterPosition()).description);
        }
    });

    return holder;
}

private void getDetails(String url, String groupName, String description) {

    groupName = groupName.replace(" ", "%20");
    description = description.replace(" ", "%20");

    final String finalGroupName = groupName;
    final String finalDescription = description;

    class GetDetails extends AsyncTask<String, Void, String> {
        ProgressDialog loading;

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            loading = ProgressDialog.show(mContext.getApplicationContext(), null, "Please wait", true, true);
            loading.setCancelable(false);
        } // more code down from here

Solution 1

I've seen a lot of code where people keep reference to the Context in an Adapter. But in a RecyclerView.Adapter, the itemView (the view you already inflated from onCreateViewHolder) is accessible from your ViewHolder. For the most part, you should be dealing with the viewHolder anyways. So, use viewholder.itemView.getContext();. You can even expose a method in your viewholder getContext().

public Context getContext() {return itemView.getContext();}

Solution 2

Firstly, there are some differences between type of Contexts. Reference: https://possiblemobile.com/2013/06/context/

Example:

@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
     View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_layout, parent, false);
     return new ViewHolder(v);
} 

@Override
public void onBindViewHolder(ViewHolder viewHolder, final int position) {
    Context context = viewHolder.anyView.getContext();
}

Solution 3

Create a custom Adapter and add a Constructor so that the Context can be passed.

public class CustomAdapter extends ArrayAdapter<String> {

    private Context context;
    private List<String> stringList = null;

    public CustomAdapter(Context context, int resource, List<String> objects) {
        super(context, resource, objects);
        this.context = context;
        this.stringList = objects;
    }
}

Use this 'context' variable to show the ProgressDialog as per your requirement.

Solution 4

1.Pass activity context in constructor for adapter. if your calling from fragment pass it as getActivity().

2.You can also try itemView.getContext() in onBindViewHolder.

I am not sure about pros and cons of using #2 method because I always use #1.

Solution 5

In fragment add:

Context context;
#in onCreateView method:
context=getActivity();
allGroupsView = (RecyclerView) rootView.findViewById(R.id.allGroupsView);
adapterGroup = new AdapterGroup(context,results);
allGroupsView.setAdapter(adapterGroup);
allGroupsView.setLayoutManager(new LinearLayoutManager(getActivity()));

dont use getActivity.getApplicationContext() or context.getApplicationContext()

loading = ProgressDialog.show(mContext, null, "Please wait", true, true);

View more solutions

Comments

[OneCricketeer]

Question asked about RecyclerView.Adapter. Besides, storing the context member variable in a ArrayAdapter is redundant.

[vidulaJ]

You can use this for a RecyclerView Adapter as well.

[OneCricketeer]

Sure. I think the question already is doing this, though, as mContext appears to be the variable in the adapter and mContext.getApplicationContext is throwing an exception

[vidulaJ]

Did not have the code previously and the edit had been done after this answer. So using only mContext, a ProgressDialog could be started.

[August]

if I use mContext only without getApplicationContext it also throw the same exception

[OneCricketeer]

@August That may be because you also assigned mContext with a call to getApplicationContext when you initialized the adapter.

[vidulaJ]

You initialize Adapter variable inside a Fragment?

[August]

can you please take a look at my newly added codes?

[August]

Attempt to invoke virtual method 'java.lang.Object android.content.Context.getSystemService(java.lang.String)' on a null object reference

[WritingForAnroid]

By seeing updated code I feel its better to pass context in constructor.