Is there any way to enable scrollbars for RecyclerView in code?

As we saw, RecyclerView is more effective than ListView, so I prefer to use it in my project. But recently I have a trouble when put it in my custom ViewGroup. RecyclerView is easy to set scrollbars in xml like this:

<android.support.v7.widget.RecyclerView
    android:id="@+id/recycler_view"
    android:scrollbars="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

But I really can't find any method to set the scrollbars in code for RecyclerView, what I have tried is:

mRecyclerView.setVerticalScrollBarEnabled(true);

and then I saw this in Android's document.

So I tried to make my own LayoutManager and override the functions which I thought I need. But finally I failed. So can anyone tell me how should I make my own LayoutManager or just show me an other solution. Thank you!

At the moment it seems to be impossible to enable scroll bars programmatically. The reason for that behaviour is that Android does not call either View.initializeScrollbarsInternal(TypedArray a) or View.initializeScrollbars(TypedArray a). Both methods are only called if you instantiate your RecyclerView with an AttributeSet.
As a workaround I would suggest, that you create a new layout file with your RecyclerView only: vertical_recycler_view.xml

<android.support.v7.widget.RecyclerView
xmlns:android="http://schemas.android.com/apk/res/android"
android:scrollbars="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent" />

Now you can inflate and add the RecyclerView with scrollbars everywhere you want: MyCustomViewGroup.java

public class MyCustomViewGroup extends FrameLayout
{
    public MyCustomViewGroup(Context context)
    {
        super(context);

        RecyclerView verticalRecyclerView = (RecyclerView) LayoutInflater.from(context).inflate(R.layout.vertical_recycler_view, null);
        verticalRecyclerView.setLayoutManager(new LinearLayoutManager(context, LinearLayoutManager.VERTICAL, false));
        addView(verticalRecyclerView);
    }
}

Set the vertical scrollbar in the xml layout

<android.support.v7.widget.RecyclerView
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:scrollbars="vertical" />

Just in xml properties

<android.support.v7.widget.RecyclerView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/recyclerView"
    android:scrollbars="vertical" <!-- type of scrollbar -->
    android:scrollbarThumbVertical="@android:color/darker_gray"  <!--color of scroll bar-->
    android:scrollbarSize="5dp"> <!--width of scroll bar-->

</android.support.v7.widget.RecyclerView>

I would prefer to use ContextThemeWrapper for that, because it can be used dynamically from code.

First define in Style.xml:

<style name="ScrollbarRecyclerView" parent="android:Widget">
    <item name="android:scrollbars">vertical</item>
</style>

And then whenever you initialize your RecyclerView use ContextThemeWrapper:

RecyclerView recyclerView = new RecyclerView(new ContextThemeWrapper(context, R.style.ScrollbarRecyclerView));

You can do it without inflating an XML layout, but you'll need to declare a custom theme attribute and a style:

<resources>
    <attr name="verticalRecyclerViewStyle" format="reference"/>

    <style name="VerticalRecyclerView" parent="android:Widget">
        <item name="android:scrollbars">vertical</item>
    </style>
</resources>

Then set the value of the attribute to the style in your theme:

<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">

    <item name="verticalRecyclerViewStyle">@style/VerticalRecyclerView</item>
</style>

Now you can create the RecyclerView programmatically with a vertical scrollbar:

RecyclerView recyclerView = new RecyclerView(context, null, R.attr.verticalRecyclerViewStyle);

Use a code like:

<androidx.recyclerview.widget.RecyclerView
 android:id="@+id/categoryRecyclerLayout"
 android:layout_width="414dp"
 android:layout_height="652dp"
 android:scrollbars="vertical" .... />