Android Recycler View Tutorial: Part 2

In Part 1, we created recycler view without any model or view holder. In this part, we will create data model and a view holder and bind both these to the recycler view.

Previous part: http://www.androidlearner.com/2017/07/android-recycler-view-tutorial.html

Now let's first create a simple data model: DummyModel.java

This class does nothing special, it just generates some dummy data.

public class DummyModel {
    //text
    String textData = "not set yet !!";
    public DummyModel() {
    }
    /**
     * constructor to set the dummy text
     * @param data
     */
    public DummyModel(String data) {
        textData = data;
    }
    static public List<DummyModel> getDummyModel(int length) {
        List<DummyModel> dummyModelsList = new ArrayList<>();
        for (int i = 0; i < length; i++) {
            dummyModelsList.add(new DummyModel("This is the model "+i));
        }
        return dummyModelsList;
    }
    /**
     * just a setter method !Not used!
     * @param text
     */
    public void setText(String text) {
        this.textData = text;
    }
}

Now let's create our view holder which will set the data to the view: DummyVH.java

We are creating a separate class for our view holder. This enables to reuse the component with different recycler view or one recycler view to have different components.

public class DummyVH extends RecyclerView.ViewHolder {
    TextView textView;
    /**
     * Constructor to set the items
     * @param itemView
     */
    public DummyVH(View itemView) {
        super(itemView);
        textView = (TextView)itemView.findViewById(R.id.textView);
        textView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(RecylerActivity.context, 
                "yooo "+textView.getText(), Toast.LENGTH_SHORT).show();
            }
        });
    }
    /**
     * function to set the data
     * @param dummyModel
     */
    public void bindVH(DummyModel dummyModel)
    {
        textView.setText(dummyModel.textData);
    }
}

Now let's create our adapter which will bind or view and the data model. RvDataAdpt2.java

This class is the same as the previous dataAdapter created in the previous tutorial. Recycler layout item is also the same. The view holder is just initiated from a different class.

/**
 * THis class will be the data adapter for the recycler view
 * This class must extend the Recycler view adapter.
 */
public class RvDataAdpt2 extends RecyclerView.Adapter {
    List<DummyModel> dummyModelsList;
    public RvDataAdpt2(List<DummyModel> listDummyModels)
    {
        dummyModelsList = listDummyModels;
    }
    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        //lets populate our recycler view with the item created;
        //get the view from the layout inflator
        //  third parameter is set to false to prevent viewgroup to attach to root
        View view = LayoutInflater.from(parent.getContext()).inflate
                   (R.layout.recycler_item,parent,false);
        return new DummyVH(view);
    }
    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
        //bind the view with the holder
        ((DummyVH)holder).bindVH(dummyModelsList.get(position));
    }
    @Override
    public int getItemCount() {
        return dummyModelsList.size(); // to display the 100 items
    }
}

Now let's bind this adapter to the recycler view. I have used the project created in the previous tutorial.

public class RecylerActivity extends AppCompatActivity {
        public static Context context;
    //Below are the components which are required by the Recycler view
    RecyclerView recyclerView; //this will hold the recycler view from the layout
    RecyclerView.Adapter   mAdapter; //this will hold the adapter for the recycler view
    RecyclerView.LayoutManager mLayoutmanager; //holds the layout manager
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        context = this;
        setContentView(R.layout.activity_recyler); //layout which contain the recycler view
        //Find the Recycler view
        recyclerView = (RecyclerView)findViewById
                       (R.id.my_recycler_view); //got the recycler view from the layout
        //set the layout manager for the recycler view
        //standard layout managers( LinearLayoutManager or GridLayoutManager) can be used, 
        //or implement your own.
        //Layout Manager tells how the item are shown in your Recycler View
        mLayoutmanager = new LinearLayoutManager(this);
        recyclerView.setLayoutManager(mLayoutmanager);
        //set the data adapter
        //Adapter contain the Data Which need to be shown in the view
        // mAdapter = new RvDataAdpt();
        mAdapter = new RvDataAdpt2(DummyModel.getDummyModel(100));
        recyclerView.setAdapter(mAdapter);
    }
}

Get the source fromhttps://github.com/sapandang/AndroidFeatures.

CodeProject