Android 隐藏后如何显示工具栏（通过在 RecyclerView 中向下滚动）

Question

I have BottomNavigationView with three fragments. First one has a RecyclerView and I implemented to hide Toolbar after scrolling this RecyclerView and it works. When I change fragment I would like to show it again (actionbar) - but actionbar.isShowing() returns true and actionbar.show() doesn't work. Maybe somebody has an idea?

activity_main.xml

<androidx.coordinatorlayout.widget.CoordinatorLayout
     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"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:background="@android:color/white"
     tools:context=".main.MainActivity">

<com.google.android.material.appbar.AppBarLayout
    android:layout_width="match_parent"
    android:layout_height="?attr/actionBarSize">

    <androidx.appcompat.widget.Toolbar
        android:id="@+id/mainToolbar"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_scrollFlags="scroll|enterAlways|snap"
        app:title="@string/app_name"/>

</com.google.android.material.appbar.AppBarLayout>

<com.google.android.material.bottomnavigation.BottomNavigationView
    android:id="@+id/mainNav"
    android:layout_width="match_parent"
    android:layout_height="56dp"
    android:background="@android:color/white"
    app:layout_behavior="com.google.android.material.bottomsheet.BottomSheetBehavior"
    app:menu="@menu/user_tabs_menu" />

<FrameLayout
    android:id="@+id/mainFrameLayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:layout_behavior="@string/appbar_scrolling_view_behavior" />

</androidx.coordinatorlayout.widget.CoordinatorLayout>

Answer 1

When you change fragments you should call AppBarLayout.setExpanded(true)

Answer 2

Can you show us some code on how are you making the toolbar disappear?