How to get a context in a recycler view adapter

Question

I'm trying to use picasso library to be able to load url to imageView, but I'm not able to get the context to use the picasso library correctly.

public class FeedAdapter extends RecyclerView.Adapter<FeedAdapter.ViewHolder> {
    private List<Post> mDataset;



    // Provide a reference to the views for each data item
    // Complex data items may need more than one view per item, and
    // you provide access to all the views for a data item in a view holder
    public class ViewHolder extends RecyclerView.ViewHolder {
        // each data item is just a string in this case
        public TextView txtHeader;
        public ImageView pub_image;
        public ViewHolder(View v) {
            super(v);
            txtHeader = (TextView) v.findViewById(R.id.firstline);
            pub_image = (ImageView) v.findViewById(R.id.imageView);


        }
    }




    // Provide a suitable constructor (depends on the kind of dataset)
    public FeedAdapter(List<Post> myDataset) {
        mDataset = myDataset;
    }

    // Create new views (invoked by the layout manager)
    @Override
    public FeedAdapter.ViewHolder onCreateViewHolder(ViewGroup parent,
                                                   int viewType) {
        // create a new view
        View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.feedholder, parent, false);
        // set the view's size, margins, paddings and layout parameters
        ViewHolder vh = new ViewHolder(v);
        return vh;
    }

    // Replace the contents of a view (invoked by the layout manager)
    @Override
    public void onBindViewHolder(ViewHolder holder, int position) {
        // - get element from your dataset at this position
        // - replace the contents of the view with that element

        holder.txtHeader.setText(mDataset.get(position).getPost_text());

        Picasso.with(this.context).load("http://i.imgur.com/DvpvklR.png").into(holder.pub_image);


    }

    // Return the size of your dataset (invoked by the layout manager)
    @Override
    public int getItemCount() {
        return mDataset.size();
    }

}

score 404 · Accepted Answer · edited Aug 18 '16 at 12:09

404

You have a few options here:

Pass Context as an argument to FeedAdapter and keep it as class field
Use dependency injection to inject Context when you need it. I strongly suggest reading about it. There is a great tool for that -- Dagger by Square
Get it from any View object. In your case this might work for you:

holder.pub_image.getContext()

As pub_image is a ImageView.

edited Aug 18 '16 at 12:09

Ben Grant

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answered Aug 21 '15 at 09:35

pelotasplus

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102

I prefer the third option, getting the context from the view. It is the simplest and most straightforward solution. – Dick Lucas Jun 13 '16 at 16:08
or, far better, pass in the Picasso instance, rather than holding a Picasso instance on the class instance and lazy-loading it. – Eric Cochran Jul 13 '16 at 20:04
10

Each ViewHolder contains an instance of itemView that you pass in the constructor. Use that one like this: itemView.getContext() – Oct 20 '16 at 10:03
3

You can't do #2, can you? I tried that, but this will end up being your `ApplicationContext` and not tied to the activity, leading to a runtime crash from within Glide. – boltup_im_coding Mar 05 '18 at 01:34
2

how to pass the component object to the adapter in case I want to use #2? – Ezio Mar 27 '18 at 11:00
In the third option, you can get context from itemView. Like this: `holder.itemView.getContext()` – Huy Nguyen May 19 '19 at 16:04
3rd one is super simple. Just get the package name in the onBindViewHolder or wherever you like, using. "Context context = viewHolder.mAppIcon.getContext();" then pass it – user7418129 Mar 28 '20 at 14:54
Could 3rd result in a leak? – Minh Nghĩa Dec 15 '20 at 02:48

Farhad Navayazdan · Answer 2 · 2021-12-09T09:05:13.330

47

Edit As solidak said in the comments section, the original answer could lead to memory leak issues, and it's a bad practice to use this method, so it's better to use another method to access the context.

Original answer:

You can add a global variable:

private Context context;

then assign the context from here:

@Override
public FeedAdapter.ViewHolder onCreateViewHolder(ViewGroup parent,int viewType) {
    // create a new view
    View v=LayoutInflater.from(parent.getContext()).inflate(R.layout.feedholder, parent, false);
    // set the view's size, margins, paddings and layout parameters
    ViewHolder vh = new ViewHolder(v);
    // set the Context here 
    context = parent.getContext();
    return vh;
}

Happy Codding :)

edited Dec 09 '21 at 09:05

answered Jan 19 '16 at 09:44

Farhad Navayazdan

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I strongly suggest AGAINST having global references to Context. This could lead to horrible memory leak issues!! – solidak Feb 21 '17 at 19:09
1

if you subclass viewholder, it can be private. – r3dm4n Jun 14 '17 at 16:16
If the adapter is attached to a RecyclerView then that context is guaranteed to be needed anyway. If you might unattach the adapter, then it's still fine unless for some reason you hold a strong reference to this adapter after it's been detached, in which case you should clear out the cached context, there is a method like `onDetachedFromRecyclerView` or something. – androidguy Dec 21 '17 at 22:18

score 39 · Answer 3 · answered Feb 07 '18 at 10:00

39

Short answer:

Context context;

@Override
public void onAttachedToRecyclerView(RecyclerView recyclerView) {
    super.onAttachedToRecyclerView(recyclerView);
    context = recyclerView.getContext();
}

Explanation why other answers are not great:

Passing Context to the adapter is completely unnecessary, since RecyclerView you can access it from inside the class
Obtaining Context at ViewHolder level means that you do it every time you bind or create a ViewHolder. You duplicate operations.
I don't think you need to worry about any memory leak. If your adapter lingers outside your Activity lifespan (which would be weird) then you already have a leak.

answered Feb 07 '18 at 10:00

Maciej Beimcik

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In this case, shall we implement `onDetachedFromRecyclerView()` and release context? – John Pang Nov 28 '18 at 07:46
@JohnPang not really unless you want to be extremely defensive. If you keep the adapter reference within the Activity, you are safe. – Maciej Beimcik Dec 17 '18 at 09:46
And if you **don't** keep a reference to the adapter within the activity? :P – l33t Jan 30 '22 at 21:44
you're on your own :) today I think I would implement this method as @JohnPang suggested just in case – Maciej Beimcik Feb 01 '22 at 07:30

score 20 · Answer 4 · answered Apr 16 '16 at 14:41

You can use pub_image context (holder.pub_image.getContext()) :

@Override
public void onBindViewHolder(ViewHolder ViewHolder, int position) {

    holder.txtHeader.setText(mDataset.get(position).getPost_text());

    Picasso.with(holder.pub_image.getContext()).load("http://i.imgur.com/DvpvklR.png").into(holder.pub_image);


}

score 10 · Answer 5 · edited May 04 '17 at 18:42

10

you can use this:

itemView.getContext()

edited May 04 '17 at 18:42

Jonathan.Brink

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answered May 04 '17 at 16:43

张家宝

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score 8 · Answer 6 · answered Jul 13 '16 at 11:03

You can use like this view.getContext()

Example

holder.tv_room_name.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            Toast.makeText(v.getContext(), "", Toast.LENGTH_SHORT).show();


        }
    });

score 6 · Answer 7 · edited Dec 20 '18 at 21:50

6

You can define:

Context ctx;

And on onCreate initialise ctx to:

ctx=parent.getContext();

Note: Parent is a ViewGroup.

edited Dec 20 '18 at 21:50

answered Dec 20 '18 at 21:15

Marcos vitouley

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score 5 · Answer 8 · answered Aug 21 '15 at 09:31

5

Create a constructor of FeedAdapter :

Context context; //global
public FeedAdapter(Context context)
{
   this.context = context;  
}

and in Activity

FeedAdapter obj = new FeedAdapter(this);

answered Aug 21 '15 at 09:31

Karan

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Blue_Alien · Answer 9 · 2015-08-21T09:38:35.373

5

First globally declare

Context mContext;

pass context with the constructor, by modifying it.

public FeedAdapter(List<Post> myDataset, Context context) {
    mDataset = myDataset;
    this.mContext = context;
}

then use the mContext whereever you need it

edited Aug 21 '15 at 09:38

answered Aug 21 '15 at 09:33

Blue_Alien

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score 4 · Answer 10 · edited Mar 29 '20 at 16:27

4

View mView;
mView.getContext();

edited Mar 29 '20 at 16:27

double-beep

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answered Mar 29 '20 at 14:14

Rohit Daftari

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While this code may solve the question, [including an explanation](//meta.stackexchange.com/q/114762) of how and why this solves the problem would really help to improve the quality of your post, and probably result in more up-votes. Remember that you are answering the question for readers in the future, not just the person asking now. Please [edit] your answer to add explanations and give an indication of what limitations and assumptions apply. [From Review](/review/low-quality-posts/25721105) – double-beep Mar 29 '20 at 16:27

score 3 · Answer 11 · answered Feb 04 '22 at 12:38

3

SOLUTION:

When using viewbinding use

holder.binding.productImg.context

Otherwise use

holder.productImg.context

Chill Pill :)

answered Feb 04 '22 at 12:38

Ali Akram

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score 2 · Answer 12 · answered Aug 21 '15 at 09:40

First add a global variable

Context mContext;

Then change your constructor to this

public FeedAdapter(Context context, List<Post> myDataset) {
    mContext = context;
    mDataset = myDataset;
}

The pass your context when creating the adapter.

FeedAdapter myAdapter = new FeedAdapter(this,myDataset);

score 1 · Answer 13 · edited Nov 07 '20 at 00:01

If you are using Databinding on layout you can get the context from holder. An exemple below.

@Override
public void onBindViewHolder(@NonNull GenericViewHolder holder, int position) {
    View currentView = holder.binding.getRoot().findViewById(R.id.cycle_count_manage_location_line_layout);// id of your root layout
    currentView.setBackgroundColor(ContextCompat.getColor(holder.binding.getRoot().getContext(), R.color.light_green));
}

How to get a context in a recycler view adapter

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