How to get a context in a recycler view adapter

java

context-injection

recycler-view

adapter-pattern

byAnton Shumikhin·Aug 26, 2024

Quick and efficient way: retrieve the Context directly from the ViewHolder's itemView with the getContext() method:

Context context = holder.itemView.getContext();

Diverse paths to retrieve context

Constructor injection: "Hello, Context here"

The Context diamond can be delivered right into the hands of your adapter at birth (aka initialization). Here's how:

public class MyAdapter extends RecyclerView.Adapter<MyViewHolder> {
    private final Context context; // Context partying in Adapter's constructor (No code party is complete without Context)

    public MyAdapter(Context context) {
        this.context = context; // Handing over the party invite
    }
    // ... rest of the party-goers (methods) ...
}

The perk here is the surety that your Context arrives at the party as soon as it begins!

Get it from ViewHolder: "Contact Context through itemView"

Another popular club to meet Context is in the onBindViewHolder method, and it's as easy as:

@Override
public void onBindViewHolder(MyViewHolder holder, int position) {
    Context context = holder.itemView.getContext(); // "Hey itemView, is Context there?"
    // Context found and ready to paint the town red
}

Chit-chat with RecyclerView: "Hey, wait, I'm your RecyclerView"

onAttachedToRecyclerView allows you for some quality time with Context without any third parties involved:

@Override
public void onAttachedToRecyclerView(@NonNull RecyclerView recyclerView) {
    Context context = recyclerView.getContext(); // Whispering to RecyclerView "Trust me with your Context"
    // Context at your service for a wild ride in RecyclerView
}

Pssst, if you're spending a night out with Context, don't forget to take it home (onDetachedFromRecyclerView) to avoid any memory hangovers!

Responsible parenting of Context

Preventing Memory Leaks: "Context is not a stray cat"

Avoid storing Context too freely or it might end up haunting your memory (quite literally!):

Scoping: Keep its presence as local as possible. Avoid static clutches.
WeakReferences: Use WeakReference<Context> wraps if custody is necessary.

Context Lifecycle: "It’s not you, it’s your lifespan"

Adapters and their Context live different lifespans. Be mindful of this relationship to avoid run-ins with null or unexpected termination.

Performance Nightmares: "Context is not a free lunch"

While Context is friendly, do not feed it too much in onBindViewHolder. Overeating can lead to performance sluggishness.

Loading Images: Picasso to the Rescue

If loading images, call in Picasso – Context's buddy:

Picasso.with(context).load("image_url").into(holder.imageView); // Picasso: "Say no more, I got this"

Advanced Tips: Dependency Injection and Performance

Dependency Injection: Dagger does the magic

If Dagger is at your service, injecting Context comes with added elegance:

@Module
public class MyModule {
    @Provides
    @Singleton
    Context providesApplicationContext() {
        return myApplication.getApplicationContext();
    }
}

This trick does away with manual handling, and gives Context a royal entrance.

Revisiting onAttachedToRecyclerView: One Call Wonder

onAttachedToRecyclerView calls are less frequent making it a Context hotline. Ensure to check for null entities and have fallbacks ready.

Code Optimization: Less is More

Minimize Context use in onBindViewHolder by using efficient operations:

@Override
public void onBindViewHolder(MyViewHolder holder, int position) {
    holder.textView.setText(myDataSet[position]);
    // Picasso might pop in to load images, if invited
}