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// 间隔为1
mRecyclerView.addItemDecoration(new VerticalItemDecoration(DP.dp2px(getContext(), 1)));

import android.graphics.Rect;
import android.support.v7.widget.RecyclerView;
import android.view.View;

/**
 * Created by twiceYuan on 3/30/16.
 * Email: i@twiceyuan.com
 * Site: http://twiceyuan.com
 *
 * RecyclerView 分割线高度设定
 */
public class VerticalItemDecoration extends RecyclerView.ItemDecoration {
    private final int mVerticalSpaceHeight;

    public VerticalItemDecoration(int mVerticalSpaceHeight) {
        this.mVerticalSpaceHeight = mVerticalSpaceHeight;
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent,
                               RecyclerView.State state) {
        outRect.bottom = mVerticalSpaceHeight;
    }
}