Android RecyclerView

Once you determine your layout, you need to implement your Adapter and ViewHolder. These two classes work together to define how your data is displayed. The ViewHolder is a wrapper around a View that contains the layout for an individual item in the list. The Adapter creates ViewHolder objects as needed and also sets the data for those views. The process of associating views to their data is called binding.

1. 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.

    /*** 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 ViewtextView = (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)@Overridepublic ViewHolder onCreateViewHolder(ViewGroup viewGroup, int viewType) {// Create a new view, which defines the UI of the list itemView view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.text_row_item, viewGroup, false);return new ViewHolder(view);}

2. 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.

    // Replace the contents of a view (invoked by the layout manager)@Overridepublic void onBindViewHolder(ViewHolder viewHolder, final int position) {// Get element from your dataset at this position and replace the// contents of the view with that elementviewHolder.getTextView().setText(localDataSet[position]);}

3. getItemCount(): RecyclerView calls this method to get the size of the dataset. 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.

    // Return the size of your dataset (invoked by the layout manager)@Overridepublic int getItemCount() {return localDataSet.length;}