RecyclerView is a popular widget used in Android development to display large sets of data efficiently.

When working with RecyclerView, it’s often necessary to get the ID of the item that was clicked or interacted with.

Here’s a detailed guide on how to get item ID in RecyclerView Android.

Why Get Item ID in RecyclerView?

There are a few key reasons you may need to get the ID of an item in RecyclerView:

• To detect which item was clicked and take action on that specific item
• To retrieve data or perform lookups based on the ID to update the UI
• To pass the ID to other parts of the app for further processing when an item is selected
• To differentiate between items and determine each item’s identity

Approaches to Get Item ID in RecyclerView

There are a couple common approaches to get the ID of the clicked item in RecyclerView:

• Using click listener interface in adapter
• Using click listener interface in view holder

Using Click Listener Interface in Adapter

One way is to define a click Listener interface in the RecyclerView adapter class and set an on click listener on the ViewHolder. Here are the steps:

• Define an interface like OnItemClickListener in adapter with a callback method
• Pass an instance of OnItemClickListener when constructing adapter
• Implement onClick() in ViewHolder to call the interface callback method
• Override the callback method in Activity/Fragment to handle click

This allows the activity/fragment to get notified of click events and receive the position or ID.

Using Click Listener Interface in ViewHolder

Another approach is to define the click Listener Interface in the ViewHolder class instead and invoke a callback passed from adapter. Here are the steps:

• Define OnItemClickListener interface in ViewHolder
• Pass click listener object from adapter to ViewHolder
• Set click listener on itemView in ViewHolder
• Invoke callback interface when item is clicked
• Implement callback in Activity/Fragment to handle click

This also allows the activity to get click events and ID like the previous approach.

Example Code

Here is some sample code to demonstrate implementing a click listener in the adapter to get the ID:

// OnItemClickListener interface
public interface OnItemClickListener {

  void onItemClick(int position);

}

// In RecyclerView adapter

private OnItemClickListener listener;

public void setOnItemClickListener(OnItemClickListener listener) {
  this.listener = listener; 
}

// In ViewHolder

@Override
public void onClick(View view) {
  if (listener != null) {
    int position = getAdapterPosition();
    if (position != RecyclerView.NO_POSITION) {
      listener.onItemClick(position);
    }
  }
}

// In Activity

adapter.setOnItemClickListener(new OnItemClickListener() {

  @Override
  public void onItemClick(int position) {
    // Handle click, use position or map to ID
  }
});

This provides a clean way to get callbacks in the activity and access the item ID on clicks.

Pros

• Loosely couples view holders from activity/fragment code
• Cleaner code separation and flow
• Easy to pass data like ID or position
• Flexible for item click handling

Cons

• Slightly more code needed for interfaces
• Need to ensure callbacks and listeners are set properly

FAQs

This covers the main approaches for getting item ID on click events in RecyclerView. By leveraging click listener interfaces and callbacks, you can easily implement item click handling and get access to the ID or other data you need on clicks.