MainActivity: Show bottom nav when the tab page is changed (#4914)

* MainActivity: Show bottom nav when the tab page is changed

* Revert "MainActivity: Show bottom nav when the tab page is changed"

This reverts commit 27fd73db

* MainActivity: Show bottom nav when the app bar is fully expanded

(cherry picked from commit d0bf93ebb7)

app/src/main/java/eu/kanade/tachiyomi/ui/main/MainActivity.kt

@@ -155,6 +155,15 @@ class MainActivity : BaseViewBindingActivity<MainActivityBinding>() {
         tabAnimator = ViewHeightAnimator(binding.tabs, 0L)
         bottomNavAnimator = ViewHeightAnimator(binding.bottomNav)
 
+        // If bottom nav is hidden, make it visible again when the app bar is expanded
+        binding.appbar.addOnOffsetChangedListener(
+            AppBarLayout.OnOffsetChangedListener { _, verticalOffset ->
+                if (verticalOffset == 0) {
+                    showBottomNav(true)
+                }
+            }
+        )
+
         // Set behavior of bottom nav
         preferences.hideBottomBar()
             .asImmediateFlow { setBottomNavBehaviorOnScroll() }