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Create dynamic lists with RecyclerView

RecyclerView makes it easy to efficiently display large sets of data. You supply the data and define how each item looks, and the RecyclerView library dynamically creates the elements when they're needed.

Key classes

Several different classes work together to build your dynamic list.

  • ViewGroup
  • RecyclerView.ViewHolder
  • RecyclerView.Adapter
  • LayoutManager

Steps for implementing your RecyclerView

  • First of all, decide what the list or grid is going to look like. Ordinarily you'll be able to use one of the RecyclerView library's standard layout managers.

  • Design how each element in the list is going to look and behave. Based on this design, extend the ViewHolder class. Your version of ViewHolder provides all the functionality for your list items. Your view holder is a wrapper around a View, and that view is managed by RecyclerView.

  • Define the Adapter that associates your data with the ViewHolder views.

When you define your adapter, you need to override three key methods:

  • onCreateViewHolder(): RecyclerView calls this method whenever it needs to create a new ViewHolder. The method creates and initializes the ViewHolder and its associated View, but does not fill in the view's contents—the ViewHolder has not yet been bound to specific data.

  • onBindViewHolder(): RecyclerView calls this method to associate a ViewHolder with data. The method fetches the appropriate data and uses the data to fill in the view holder's layout. For example, if the RecyclerView displays a list of names, the method might find the appropriate name in the list and fill in the view holder's TextView widget.

  • getItemCount(): RecyclerView calls this method to get the size of the data set. For example, in an address book app, this might be the total number of addresses. RecyclerView uses this to determine when there are no more items that can be displayed.

public class CustomAdapter extends RecyclerView.Adapter<CustomAdapter.ViewHolder> { private String[] localDataSet; /** * Provide a reference to the type of views that you are using * (custom ViewHolder). */ public static class ViewHolder extends RecyclerView.ViewHolder { private final TextView textView; public ViewHolder(View view) { super(view); // Define click listener for the ViewHolder's View textView = (TextView) view.findViewById(R.id.textView); } public TextView getTextView() { return textView; } } /** * Initialize the dataset of the Adapter. * * @param dataSet String[] containing the data to populate views to be used * by RecyclerView. */ public CustomAdapter(String[] dataSet) { localDataSet = dataSet; } // Create new views (invoked by the layout manager) @Override public ViewHolder onCreateViewHolder(ViewGroup viewGroup, int viewType) { // Create a new view, which defines the UI of the list item View view = LayoutInflater.from(viewGroup.getContext()) .inflate(R.layout.text_row_item, viewGroup, false); return new ViewHolder(view); } // Replace the contents of a view (invoked by the layout manager) @Override public void onBindViewHolder(ViewHolder viewHolder, final int position) { // Get element from your dataset at this position and replace the // contents of the view with that element viewHolder.getTextView().setText(localDataSet[position]); } // Return the size of your dataset (invoked by the layout manager) @Override public int getItemCount() { return localDataSet.length; } }