{"id":19611,"date":"2015-05-20T17:04:30","date_gmt":"2015-05-20T11:34:30","guid":{"rendered":"http:\/\/www.tothenew.com\/blog\/?p=19611"},"modified":"2015-05-20T17:04:30","modified_gmt":"2015-05-20T11:34:30","slug":"recyclerview-in-android","status":"publish","type":"post","link":"https:\/\/www.tothenew.com\/blog\/recyclerview-in-android\/","title":{"rendered":"RecyclerView in Android"},"content":{"rendered":"

Android\u00a0RecyclerView<\/span><\/a>\u00a0\u00a0was introduced in Android\u00a05.0 Lollipop<\/span><\/a>. It is much faster and memory efficient than Android ListView<\/span><\/a>.<\/p>\n

You can download sample application source code for this tutorial from here<\/strong><\/a>.<\/p>\n

\"recyclerViewDemoAppScreen\"<\/a><\/p>\n

A RecyclerView can cache previously used view for a specific adapter position for later reuse to display same type of data again later. This improves the performance of the RecyclerView drastically by skipping initial layout inflation or construction.<\/p>\n

We would have to learn about the following classes in order to use RecyclerView\u00a0in our apps:<\/p>\n

1.\u00a0RecyclerView.Adapter<\/a>: \u00a0<\/strong>It provides access to data sets items, creates views for items and binds items info to item view.\u00a0<\/strong>It is a placeholder for ListView Adapter classes. Just like \u00a0ListView adapter, it provides views to be fed to the RecyclerView. In onCreateViewHolder()<\/a>, we inflate \u00a0xml view\u00a0resources and wrap it inside a RecyclerView.ViewHolder instances and return it.<\/p>\n

[sourcecode language=”java” wraplines=”false” collapse=”false”]
\n@Override
\n public ListItemViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
\n View itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_recycler_view, parent, false);
\n return new ListItemViewHolder(itemView);
\n }
\n[\/sourcecode]<\/p>\n

In onBindViewHolder()<\/a>\u00a0we put the data in views. We access the views from ViewHolder supplied here:<\/p>\n

[sourcecode language=”java” wraplines=”false” collapse=”false”]
\n @Override
\n public void onBindViewHolder(ListItemViewHolder holder, int position) {
\n DataModel model = mDataModels.get(position);
\n holder.title.setText(model.getTitle());
\n }
\n[\/sourcecode]<\/p>\n

2.\u00a0RecyclerView.ViewHolder<\/a><\/strong>: ViewHolder class wraps the view instances inside it from where we can get child views directly. In this way we don’t need to inflate the view over and again every time we scroll the recycler view. It saves memory and make the scrolling fast and smooth. Here is the implementation of ViewHolder class which I subclassed:<\/p>\n

[sourcecode language=”java” wraplines=”false” collapse=”false”]
\n public class ListItemViewHolder extends ViewHolder {<\/p>\n

ImageView imgView;
\n TextView title;<\/p>\n

public ListItemViewHolder(View itemView) {
\n super(itemView);
\n title = (TextView) itemView.findViewById(R.id.textview_title);
\n imgView = (ImageView) itemView.findViewById(R.id.imageview_icon);
\n }
\n}<\/p>\n

[\/sourcecode]<\/p>\n

3.\u00a0RecyclerView.LayoutManager<\/a><\/strong>: \u00a0It is responsible for measuring and positioning item views within a RecyclerView. It is responsible for recycling out of screen views during scrolling. \u00a0 \u00a0 \u00a0 \u00a0 \u00a0RecyclerView.LayoutManager has three\u00a0subclasses.<\/p>\n