Add banner at top of library when downloaded only mode is enabled

app/src/main/java/eu/kanade/tachiyomi/ui/library/LibraryController.kt

@@ -35,6 +35,7 @@ import eu.kanade.tachiyomi.ui.main.MainActivity
 import eu.kanade.tachiyomi.ui.manga.MangaController
 import eu.kanade.tachiyomi.util.system.getResourceColor
 import eu.kanade.tachiyomi.util.system.toast
+import eu.kanade.tachiyomi.util.view.visible
 import java.io.IOException
 import kotlinx.android.synthetic.main.main_activity.tabs
 import kotlinx.coroutines.flow.filter
@@ -172,6 +173,10 @@ class LibraryController(
                 is LibrarySettingsSheet.Display.BadgeGroup -> onDownloadBadgeChanged()
             }
         }
+
+        if (preferences.downloadedOnly().get()) {
+            binding.downloadedOnly.visible()
+        }
     }
 
     override fun onChangeStarted(handler: ControllerChangeHandler, type: ControllerChangeType) {

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

@@ -4,10 +4,34 @@
     android:layout_width="match_parent"
     android:layout_height="match_parent">
 
-    <androidx.viewpager.widget.ViewPager
-        android:id="@+id/library_pager"
+    <LinearLayout
         android:layout_width="match_parent"
-        android:layout_height="match_parent" />
+        android:layout_height="match_parent"
+        android:orientation="vertical">
+
+        <FrameLayout
+            android:id="@+id/downloaded_only"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:background="?attr/colorSecondary"
+            android:visibility="gone">
+
+            <TextView
+                android:layout_width="wrap_content"
+                android:layout_height="wrap_content"
+                android:layout_gravity="center"
+                android:padding="4dp"
+                android:text="@string/label_downloaded_only"
+                android:textColor="?attr/colorOnSecondary" />
+
+        </FrameLayout>
+
+        <androidx.viewpager.widget.ViewPager
+            android:id="@+id/library_pager"
+            android:layout_width="match_parent"
+            android:layout_height="match_parent" />
+
+    </LinearLayout>
 
     <eu.kanade.tachiyomi.widget.ActionToolbar
         android:id="@+id/action_toolbar"