since startSyncFolderOperation called onResume and startSyncFolderOperation runs on main thread it must be run on background thread thus executor is used.

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

Author: alperozturk96

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

@@ -66,7 +66,6 @@
 import com.nextcloud.utils.extensions.BundleExtensionsKt;
 import com.nextcloud.utils.extensions.FileExtensionsKt;
 import com.nextcloud.utils.extensions.IntentExtensionsKt;
-import com.nextcloud.utils.extensions.ViewExtensionsKt;
 import com.nextcloud.utils.fileNameValidator.FileNameValidator;
 import com.nextcloud.utils.view.FastScrollUtils;
 import com.owncloud.android.MainApp;
@@ -146,6 +145,9 @@
 import java.util.Collection;
 import java.util.List;
 import java.util.Optional;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
 
 import javax.inject.Inject;
 
@@ -252,6 +254,8 @@ public class FileDisplayActivity extends FileActivity
      */
     private long fileIDForImmediatePreview = -1;
 
+    private final ScheduledExecutorService executor = Executors.newScheduledThreadPool(Runtime.getRuntime().availableProcessors());
+
     public void setFileIDForImmediatePreview(long fileIDForImmediatePreview) {
         this.fileIDForImmediatePreview = fileIDForImmediatePreview;
     }
@@ -2180,35 +2184,36 @@ public void startSyncFolderOperation(OCFile folder, boolean ignoreETag) {
      * @param ignoreFocus reloads file list even without focus, e.g. on tablet mode, focus can still be in detail view
      */
     public void startSyncFolderOperation(final OCFile folder, final boolean ignoreETag, boolean ignoreFocus) {
-
         // the execution is slightly delayed to allow the activity get the window focus if it's being started
         // or if the method is called from a dialog that is being dismissed
-        if (TextUtils.isEmpty(searchQuery) && getUser().isPresent()) {
-            getHandler().postDelayed(() -> {
-                Optional<User> user = getUser();
-
-                if (!ignoreFocus && !hasWindowFocus() || !user.isPresent()) {
-                    // do not refresh if the user rotates the device while another window has focus
-                    // or if the current user is no longer valid
-                    return;
-                }
+        if (!TextUtils.isEmpty(searchQuery) || getUser().isEmpty()) {
+            Log_OC.w(TAG,"Cannot startSyncFolderOperation, search query is empty or user not present");
+            return;
+        }
+
+        executor.schedule(() -> {
+            Optional<User> user = getUser();
+            if (!ignoreFocus && !hasWindowFocus() || user.isEmpty()) {
+                Log_OC.w(TAG,"do not refresh if the user rotates the device while another window has focus or if the current user is no longer valid");
+                return;
+            }
 
-                long currentSyncTime = System.currentTimeMillis();
-                mSyncInProgress = true;
+            long currentSyncTime = System.currentTimeMillis();
+            mSyncInProgress = true;
 
-                // perform folder synchronization
-                RemoteOperation refreshFolderOperation = new RefreshFolderOperation(folder, currentSyncTime, false, ignoreETag, getStorageManager(), user.get(), getApplicationContext());
-                refreshFolderOperation.execute(getAccount(), MainApp.getAppContext(), FileDisplayActivity.this, null, null);
+            // perform folder synchronization on background thread
+            final var refreshFolderOperation = new RefreshFolderOperation(folder, currentSyncTime, false, ignoreETag, getStorageManager(), user.get(), getApplicationContext());
+            refreshFolderOperation.execute(getAccount(), MainApp.getAppContext(), FileDisplayActivity.this, null, null);
 
+            // switch back to main thread
+            getHandler().post(() -> {
                 OCFileListFragment fragment = getListOfFilesFragment();
-
                 if (fragment != null && !(fragment instanceof GalleryFragment)) {
                     fragment.setLoading(true);
                 }
-
                 setBackgroundText();
-            }, DELAY_TO_REQUEST_REFRESH_OPERATION_LATER);
-        }
+            });
+        }, DELAY_TO_REQUEST_REFRESH_OPERATION_LATER, TimeUnit.MILLISECONDS);
     }
 
     private void requestForDownload(OCFile file, String downloadBehaviour, String packageName, String activityName) {
@@ -2600,6 +2605,7 @@ public void onReceive(Context context, Intent intent) {
 
     @Override
     protected void onDestroy() {
+        executor.shutdown();
         LocalBroadcastManager.getInstance(this).unregisterReceiver(refreshFolderEventReceiver);
         super.onDestroy();
     }