A simple method of adding dividing lines in recyclerview

1、 Preface

Just beginning to learn RecyclerView When I learned it from a video , At that time, the dividing line was imported from the outside Java class , Then use the function inside to create the split line , So I have always done this . Until a few days ago, I accidentally found , original v7 One is provided in the package DividerItemDecoration class , Take advantage of it , We can easily realize RecyclerView Dividing line ！ What are you waiting for ？ Use it quickly .

2、 Create a simple RecyclerView

First of all, of course, there should be one RecyclerView, I won't go into that here , Just make some data . Go straight to the code ：

public class MainActivity extends AppCompatActivity {
    
    private RecyclerView recyclerView;
    private ArrayList<String> titles = new ArrayList<>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // initialization RecyclerView
        recyclerView = (RecyclerView) findViewById(R.id.recyclerView);
        recyclerView.setLayoutManager(new LinearLayoutManager(this,LinearLayoutManager.VERTICAL,false));
        for (int i = 0; i < 20; i++) {
            titles.add(" title "+i);
        }
        recyclerView.setAdapter(new RecyclerViewAdapter(this,titles));
    }
}

RecyclerViewAdapter Code for ：

**
 * RecyclerView Adapter 
 */
public class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerViewAdapter.ViewHolder> {
    

    private Context context;
    private ArrayList<String> datas;

    class ViewHolder extends RecyclerView.ViewHolder {
        ImageView ivIcon;
        TextView tvTitle;

        public ViewHolder(View itemView) {
            super(itemView);
            ivIcon = (ImageView) itemView.findViewById(R.id.iv_icon);
            tvTitle = (TextView) itemView.findViewById(R.id.tv_title);
        }
    }

    public RecyclerViewAdapter(Context context, ArrayList<String> datas) {
        this.context = context;
        this.datas = datas;
    }

    /** *  amount to getView In the method View and ViewHolder * * @param parent * @param viewType * @return */
    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View itemView = View.inflate(context, R.layout.item_recyclerview, null);
        RecyclerView.LayoutParams lp = new RecyclerView.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,
                ViewGroup.LayoutParams.WRAP_CONTENT);
        itemView.setLayoutParams(lp);
        return new ViewHolder(itemView);
    }

    /** * @param holder * @param position */
    @Override
    public void onBindViewHolder(ViewHolder holder, int position) {
        // according to position Get the corresponding data 
        String data = datas.get(position);
        holder.tvTitle.setText(data);
    }

    /** *  Get the total number  * * @return */
    @Override
    public int getItemCount() {
        return datas.size();
    }
}

After running, it's like this ：

Obviously , There is no dividing line at this time .

3、 Add default split line

Now let's add the dividing line , First, try the simplest , That is, Android's own split line . Just add a line of code .

        // add to Android Its own split line 
        recyclerView.addItemDecoration(new DividerItemDecoration(this,DividerItemDecoration.VERTICAL));

addItemDecoration Method requires a DividerItemDecoration The object of , When creating its object , We need to pass in the context and the direction of the divider . Run it again , You can see that the dividing line appears ：

4、 Custom split line

Sometimes the default light gray split line can't meet our requirements , Then we need ourselves “ Write ” A dividing line , How should I write it ？ open DividerItemDecoration Look at the source code , There is such a function ：

    public void setDrawable(@NonNull Drawable drawable) {
        if (drawable == null) {
            throw new IllegalArgumentException("Drawable cannot be null.");
        }
        mDivider = drawable;
    }

We just need to call this method , Then pass in a Drawable Function object is ok . Now we can use shape To write a divider style :

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android" android:shape="rectangle">

    <gradient  android:centerColor="#ff00ff00" // green  android:endColor="#ff0000ff" // Blue  android:startColor="#ffff0000" // Red  android:type="linear" />
    <size android:height="3dp" />

</shape>

What I got here is a coquettish gradient dividing line . Then the code of adding the dividing line is changed as follows ：

        // Add custom split lines 
        DividerItemDecoration divider = new DividerItemDecoration(this,DividerItemDecoration.VERTICAL);
        divider.setDrawable(ContextCompat.getDrawable(this,R.drawable.custom_divider));
        recyclerView.addItemDecoration(divider);

After running , You can see a colorful dividing line ：

In this way, the scope of use is much wider , such as item A certain interval is required between , Then we can add a transparent dividing line .

5、 summary

The code to add a divider is simple , You can do this when you need to add a simple dividing line in the future . Note, however, that this only applies to list layouts (LinearLayout) Of RecyclerView, Grid layout （GridLayout） And streaming layout （StaggeredGridLayout） It doesn't apply .