Add scroll to top button to the lists screen

app/app/src/main/java/com/github/livingwithhippos/unchained/lists/view/ListsTabFragment.kt

@@ -175,6 +175,10 @@ class ListsTabFragment : UnchainedFragment() {
             findNavController().navigate(action)
         }
 
+        binding.fabScrollToTop.setOnClickListener {
+            viewModel.postScrollToTop(binding.tabs.selectedTabPosition)
+        }
+
         // an external link has been shared with the app
         activityViewModel.externalLinkLiveData.observe(
             viewLifecycleOwner,
@@ -624,6 +628,15 @@ class DownloadsListFragment : UnchainedFragment(), DownloadListListener {
             },
         )
 
+        // scroll the list to the top when the parent fragment fab is clicked on this tab
+        viewModel.scrollToTopLiveData.observe(viewLifecycleOwner) { event ->
+            if (event?.peekContent() == DOWNLOADS_TAB) {
+                event.getContentIfNotHandled()?.let {
+                    if (_binding != null) binding.rvDownloadList.layoutManager?.scrollToPosition(0)
+                }
+            }
+        }
+
         // starts the Transformations.switchMap(queryLiveData) which otherwise won't trigger the
         // Paging
         // request
@@ -835,6 +848,15 @@ class TorrentsListFragment : UnchainedFragment(), TorrentListListener {
             },
         )
 
+        // scroll the list to the top when the parent fragment fab is clicked on this tab
+        viewModel.scrollToTopLiveData.observe(viewLifecycleOwner) { event ->
+            if (event?.peekContent() == TORRENTS_TAB) {
+                event.getContentIfNotHandled()?.let {
+                    if (_binding != null) binding.rvTorrentList.layoutManager?.scrollToPosition(0)
+                }
+            }
+        }
+
         return binding.root
     }
 

app/app/src/main/java/com/github/livingwithhippos/unchained/lists/viewmodel/ListTabsViewModel.kt

@@ -79,6 +79,9 @@ constructor(
 
     val eventLiveData = MutableLiveData<Event<ListEvent>>()
 
+    // tab index of the list to be scrolled to the top, see ListsTabFragment fabScrollToTop
+    val scrollToTopLiveData = MutableLiveData<Event<Int>>()
+
     /**
      * Un restrict a torrent and move it to the download section
      *
@@ -178,6 +181,10 @@ constructor(
         eventLiveData.postEvent(event)
     }
 
+    fun postScrollToTop(tab: Int) {
+        scrollToTopLiveData.postEvent(tab)
+    }
+
     companion object {
         const val KEY_SELECTED_TAB = "selected_tab_key"
         const val TORRENT_DELETED = -1

app/app/src/main/res/drawable/icon_arrow_upward.xml

@@ -0,0 +1,10 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24"
+    android:tint="?attr/colorControlNormal">
+  <path
+      android:fillColor="@android:color/white"
+      android:pathData="M4,12l1.41,1.41L11,7.83V20h2V7.83l5.58,5.59L20,12l-8,-8L4,12z"/>
+</vector>

app/app/src/main/res/layout/fragment_tab_lists.xml

@@ -24,6 +24,18 @@
         app:layout_constraintStart_toStartOf="parent"
         app:layout_constraintTop_toBottomOf="@id/tabs" />
 
+    <com.google.android.material.floatingactionbutton.FloatingActionButton
+        android:id="@+id/fabScrollToTop"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_marginBottom="15dp"
+        android:contentDescription="@string/scroll_to_top"
+        app:fabSize="mini"
+        app:layout_constraintBottom_toTopOf="@id/fabNewDownload"
+        app:layout_constraintEnd_toEndOf="@id/fabNewDownload"
+        app:layout_constraintStart_toStartOf="@id/fabNewDownload"
+        app:srcCompat="@drawable/icon_arrow_upward" />
+
     <com.google.android.material.floatingactionbutton.FloatingActionButton
         android:id="@+id/fabNewDownload"
         android:layout_width="wrap_content"

app/app/src/main/res/values/strings.xml

@@ -25,6 +25,7 @@
     <string name="premium_days_format">Remaining days: %1$d</string>
     <string name="user">User</string>
     <string name="new_download">New Download</string>
+    <string name="scroll_to_top">Scroll to the top</string>
     <string name="remote_traffic">Remote Traffic</string>
     <string name="password_optional">Password [Optional]</string>
     <string name="yes">Yes</string>