Why does my vertical RecyclerView in my horizontal ViewPager2 not scroll?

Question

My RecyclerView in ViewPager2 does not scroll.

The documentation of ViewPager2 has a section about nested scrollable elements, but it is about elements having the same orientation as the ViewPager2. I have different orientations in ViewPager2 (horizontal) and RecyclerView (vertical).

How can I make the RecyclerView scroll? What am I doing wrong? Code from layout files:

RecyclerView-fragment code:

<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools">

     // ...

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/pieces_list"
        android:orientation="vertical"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager" />

</layout>

Code of fragment containing ViewPager2:

<androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <com.google.android.material.tabs.TabLayout xmlns:android="http://schemas.android.com/apk/res/android"
            xmlns:app="http://schemas.android.com/apk/res-auto"
            android:id="@+id/tabs"
            style="@style/AppTabLayout"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:tabGravity="fill"
            app:tabMaxWidth="0dp"
            app:tabMode="fixed"
            app:tabTextAppearance="@style/AppTabTextAppearance" />

        <androidx.viewpager2.widget.ViewPager2
            android:id="@+id/viewPager"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />

    </LinearLayout>

</androidx.coordinatorlayout.widget.CoordinatorLayout>

I connect them with FragmentStateAdapter and TabLayoutMediator in my fragment code, if this matters.

Likely it never receives any touch events. And the XML is also invalid. — Martin Zeitler, Apr 07 '20 at 20:40
@MartinZeitler I can click on items in the RecyclerView. So I guess it receives touch events. Why do you think the XML is invalid? (i put `// ...` only on stackoverflow to hide irrelevant code) — Zezi Reeds, Apr 07 '20 at 20:51

Zezi Reeds · Accepted Answer · 2020-04-09T20:43:39.690

The bug was not in my RecyclerView or ViewPager2 setup. I am also using the AppBarLayout. I did not put app:layout_scrollFlags="scroll|enterAlways" on the child layout which contained my ViewPager2 with RecyclerView. But each child of AppBarLayout must specify app:layout_scrollFlags in order for it to be scrollable.

Moreover, ViewPager2 and RecyclerView should not be a child of AppBarLayout, but be right below the AppBarLayout tag. I moved them out of the AppBarLayout and now everything works as expected.

Why does my vertical RecyclerView in my horizontal ViewPager2 not scroll?

1 Answers1