use optional generic function to access fragment

Signed-off-by: alperozturk96 <alper_ozturk@proton.me>

Author: alperozturk96

app/src/main/java/com/owncloud/android/ui/activity/DrawerActivity.java

@@ -691,14 +691,20 @@ public void replaceAlbumFragment() {
         transaction.commit();
     }
 
+    public <T extends Fragment> Optional<T> getFragment(String tag, Class<T> clazz) {
+        return Optional.ofNullable(getSupportFragmentManager().findFragmentByTag(tag))
+            .filter(clazz::isInstance)
+            .map(clazz::cast);
+    }
+
     public boolean isAlbumsFragment() {
-        Fragment albumsFragment = getSupportFragmentManager().findFragmentByTag(AlbumsFragment.Companion.getTAG());
-        return albumsFragment instanceof AlbumsFragment && albumsFragment.isVisible();
+        final var fragment = getFragment(AlbumsFragment.Companion.getTAG(), AlbumsFragment.class);
+        return fragment.map(AlbumsFragment::isVisible).orElse(false);
     }
 
     public boolean isAlbumItemsFragment() {
-        Fragment albumItemsFragment = getSupportFragmentManager().findFragmentByTag(AlbumItemsFragment.Companion.getTAG());
-        return albumItemsFragment instanceof AlbumItemsFragment && albumItemsFragment.isVisible();
+        final var fragment = getFragment(AlbumItemsFragment.Companion.getTAG(), AlbumItemsFragment.class);
+        return fragment.map(AlbumItemsFragment::isVisible).orElse(false);
     }
 
     private void startAssistantScreen() {

app/src/main/java/com/owncloud/android/ui/activity/FileActivity.java

@@ -109,7 +109,6 @@
 
 import java.lang.ref.WeakReference;
 import java.util.ArrayList;
-import java.util.Objects;
 
 import javax.inject.Inject;
 
@@ -841,18 +840,25 @@ private void onUpdateShareInformation(RemoteOperationResult result, @StringRes i
     }
 
     public void refreshList() {
-        // first check for album fragments
         if (isAlbumsFragment()) {
-            ((AlbumsFragment) Objects.requireNonNull(getSupportFragmentManager().findFragmentByTag(AlbumsFragment.Companion.getTAG()))).refreshAlbums();
-        } else if (isAlbumItemsFragment()) {
-            ((AlbumItemsFragment) Objects.requireNonNull(getSupportFragmentManager().findFragmentByTag(AlbumItemsFragment.Companion.getTAG()))).refreshData();
-        } else {
-            final Fragment fragment = getSupportFragmentManager().findFragmentByTag(FileDisplayActivity.TAG_LIST_OF_FILES);
-            if (fragment instanceof OCFileListFragment listFragment) {
-                listFragment.onRefresh();
-            } else if (fragment instanceof FileDetailFragment detailFragment) {
-                detailFragment.goBackToOCFileListFragment();
-            }
+            getFragment(AlbumsFragment.Companion.getTAG(), AlbumsFragment.class)
+                .ifPresent(AlbumsFragment::refreshAlbums);
+            return;
+        }
+
+        if (isAlbumItemsFragment()) {
+            getFragment(AlbumItemsFragment.Companion.getTAG(), AlbumItemsFragment.class)
+                .ifPresent(AlbumItemsFragment::refreshData);
+            return;
+        }
+
+        final var fragment =
+            getSupportFragmentManager().findFragmentByTag(FileDisplayActivity.TAG_LIST_OF_FILES);
+
+        if (fragment instanceof OCFileListFragment listFragment) {
+            listFragment.onRefresh();
+        } else if (fragment instanceof FileDetailFragment detailFragment) {
+            detailFragment.goBackToOCFileListFragment();
         }
     }