How can a divider line be added in an Android RecyclerView?

Solution 1:

In the October 2016 update, the support library v25.0.0 now has a default implementation of basic horizontal and vertical dividers available!

https://developer.android.com/reference/android/support/v7/widget/DividerItemDecoration.html

 recyclerView.addItemDecoration(new DividerItemDecoration(recyclerView.getContext(), DividerItemDecoration.VERTICAL));

Solution 2:

The Right way is to define ItemDecoration for the RecyclerView is as following

SimpleDividerItemDecoration.java

public class SimpleDividerItemDecoration extends RecyclerView.ItemDecoration {
    private Drawable mDivider;
 
    public SimpleDividerItemDecoration(Context context) {
        mDivider = ContextCompat.getDrawable(context, R.drawable.line_divider);
    }
 
    @Override
    public void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) {
        int left = parent.getPaddingLeft();
        int right = parent.getWidth() - parent.getPaddingRight();
 
        int childCount = parent.getChildCount();
        for (int i = 0; i < childCount; i++) {
            View child = parent.getChildAt(i);
 
            RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();
 
            int top = child.getBottom() + params.bottomMargin;
            int bottom = top + mDivider.getIntrinsicHeight();
 
            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(c);
        }
    }
}

Or If you are using kotlin: SimpleDividerItemDecoration.kt

class SimpleDividerItemDecoration(context: Context, @DrawableRes dividerRes: Int) : ItemDecoration() {

    private val mDivider: Drawable = ContextCompat.getDrawable(context, dividerRes)!!

    override fun onDrawOver(c: Canvas, parent: RecyclerView) {
        val left = parent.paddingLeft
        val right = parent.width - parent.paddingRight
        val childCount = parent.childCount
        for (i in 0 until childCount) {
            val child: View = parent.getChildAt(i)
            val params = child.layoutParams as RecyclerView.LayoutParams
            val top: Int = child.bottom + params.bottomMargin
            val bottom = top + mDivider.intrinsicHeight
            mDivider.setBounds(left, top, right, bottom)
            mDivider.draw(c)
        }
    }
}
    

line_divider.xml:

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
 
    <size
        android:width="1dp"
        android:height="1dp" />
 
    <solid android:color="@color/dark_gray" />
 
</shape>

Finally set it like this

recyclerView.addItemDecoration(new SimpleDividerItemDecoration(this));

Edit

As pointed by @Alan Solitar

context.getResources().getDrawable(R.drawable.line_divider); 

is depreciated instead of that you can use

ContextCompat.getDrawable(context,R.drawable.line_divider);