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);

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

/
**
 * RecyclerView适配器
 */
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;
  }

  /**
   * 相当于getView方法中View和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) {
    //根据position得到对应的数据
    String data = datas.get(position);
    holder.tvTitle.setText(data);
  }

  /**
   * 得到总条数
   *
   * @return
   */
  @Override
  public int getItemCount() {
    return datas.size();
  }
}

    //添加Android自带的分割线
    recyclerView.addItemDecoration(new DividerItemDecoration(this,DividerItemDecoration.VERTICAL));

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

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

  <gradient
    android:centerColor="#ff00ff00" //绿色
    android:endColor="#ff0000ff"  //蓝色
    android:startColor="#ffff0000" //红色
    android:type="linear" />
  <size android:height="3dp" />

</shape>

    //添加自定义分割线
    DividerItemDecoration divider = new DividerItemDecoration(this,DividerItemDecoration.VERTICAL);
    divider.setDrawable(ContextCompat.getDrawable(this,R.drawable.custom_divider));
    recyclerView.addItemDecoration(divider);