如何从底部应用程序栏布局隐藏浮动操作按钮

Question

I'm creating a Bottom App Bar with an Floating Action Button. The App Bar is part of my Main Activity and I want to hide the FAB for some Fragments within the Activity.

I already tried 'View.GONE' and 'fab.hide()'. Then I tried to hide the Fab with following function:

    private fun hideFloatingActionButton() {
        val params = fab.layoutParams as CoordinatorLayout.LayoutParams
        val behavior = params.behavior as FloatingActionButton.Behavior?

        if (behavior != null) {
            behavior.isAutoHideEnabled = false
        }

        params.anchorId = View.NO_ID;
        params.width = 0;
        params.height = 0;
        fab.layoutParams = params
        fab.hide()
    }

My layout.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"
        tools:context=".MainActivity"
        android:background="@color/backPrimary"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

    ...

         content
    ...

    <com.google.android.material.bottomappbar.BottomAppBar
            android:id="@+id/bar"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_gravity="bottom"
            style="@style/Widget.MaterialComponents.BottomAppBar"
            app:navigationIcon="@drawable/ic_burger_menu"
            app:fabAlignmentMode="end"
    />

    <com.google.android.material.floatingactionbutton.FloatingActionButton
            android:id="@+id/fab"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/start_project_day"
            app:srcCompat="@drawable/ic_next"
            app:layout_anchor="@id/bar"
    />

</androidx.coordinatorlayout.widget.CoordinatorLayout>

Answer 1

Just tested out with fab.hide() method and it works. The "logic" to hide the fab should occur in the activity and not in the fragment. The next logic is set in the activity and the hide part is inside the else branch at the end.

navController.addOnDestinationChangedListener { controller, destination, _ ->

        bar.animate().translationY(0f)


        // First page is main menu
        if(controller.graph.startDestination == destination.id){


            bar.navigationIcon = icon
            bar.fabAlignmentMode = BottomAppBar.FAB_ALIGNMENT_MODE_CENTER
            fab?.setImageDrawable(getDrawable(R.drawable.ic_local_wtf))

        }else{

            // Hide navigation drawer icon
            bar.navigationIcon = null

            // Move FAB from the center of BottomAppBar to the end of it
            bar.fabAlignmentMode = BottomAppBar.FAB_ALIGNMENT_MODE_END



            // Replace the action menu
            //bar.replaceMenu(bottomappbar_menu_secondary)
            invalidateOptionsMenu()

            // Change FAB icon
            fab?.setImageDrawable(getDrawable(R.drawable.ic_reply_white_24dp))
            fab.hide()
        }

    }