Avoid SMB rename checks on the UI thread

The rename completion path in MainActivityHelper re-checked success by calling newFile.exists(context) on the UI thread because SAF-backed renames can report false negatives. For SMB targets that fallback routes into HybridFile.exists() and performs synchronous network I/O on the main thread. Limit the fallback probe to SAF-backed targets and cover it with a focused regression test.

Constraint: Preserve the post-rename verification workaround for SAF-backed rename targets
Rejected: Change HybridFile.exists() semantics for all SMB callers | too broad and would affect background operations that legitimately rely on it
Confidence: high
Scope-risk: narrow
Directive: Keep rename completion fallbacks off the UI thread for remote backends; only use exists(context) as a SAF-specific verification path
Tested: ./gradlew :app:testFdroidDebugUnitTest --tests com.amaze.filemanager.utils.MainActivityHelperTest -x kaptFdroidDebugUnitTestKotlin
Tested: ./gradlew :app:compileFdroidDebugJavaWithJavac
Tested: ./gradlew :app:compileFdroidDebugUnitTestJavaWithJavac -x kaptFdroidDebugUnitTestKotlin
Not-tested: Full :app:testFdroidDebugUnitTest (blocked by existing kaptFdroidDebugUnitTestKotlin failure in unrelated tests referencing missing ShadowMultiDex)

Author: venkyqz

app/src/main/java/com/amaze/filemanager/utils/MainActivityHelper.java

@@ -80,6 +80,7 @@
 
 import androidx.annotation.NonNull;
 import androidx.annotation.StringRes;
+import androidx.annotation.VisibleForTesting;
 import androidx.appcompat.widget.AppCompatEditText;
 import androidx.appcompat.widget.AppCompatImageView;
 import androidx.appcompat.widget.AppCompatTextView;
@@ -388,7 +389,8 @@ public void done(final HybridFile hFile, final boolean b) {
                    * DocumentFile.renameTo() may return false even when rename is successful. Hence we need an extra check
                    * instead of merely looking at the return value
                    */
-                  if (b || newFile.exists(context)) {
+                  if (b
+                      || (shouldVerifyRenameWithExists(newFile) && newFile.exists(context))) {
                     Intent intent = new Intent(MainActivity.KEY_INTENT_LOAD_LIST);
 
                     intent.putExtra(
@@ -435,6 +437,11 @@ public void invalidName(final HybridFile file) {
         });
   }
 
+  @VisibleForTesting
+  static boolean shouldVerifyRenameWithExists(HybridFile file) {
+    return file.isDocumentFile() || file.isOtgFile();
+  }
+
   public @FolderState int checkFolder(final @NonNull File folder, Context context) {
     return checkFolder(folder.getAbsolutePath(), OpenMode.FILE, context);
   }

app/src/test/java/com/amaze/filemanager/utils/MainActivityHelperTest.java

@@ -0,0 +1,28 @@
+package com.amaze.filemanager.utils;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+import com.amaze.filemanager.fileoperations.filesystem.OpenMode;
+import com.amaze.filemanager.filesystem.HybridFile;
+
+import org.junit.Test;
+
+public class MainActivityHelperTest {
+  @Test
+  public void testPostRenameExistenceCheckIsLimitedToSafBackedTargets() {
+    assertTrue(
+        MainActivityHelper.shouldVerifyRenameWithExists(
+            new HybridFile(OpenMode.DOCUMENT_FILE, "content://example/tree/primary:test")));
+    assertTrue(
+        MainActivityHelper.shouldVerifyRenameWithExists(
+            new HybridFile(OpenMode.OTG, "otg:/example")));
+
+    assertFalse(
+        MainActivityHelper.shouldVerifyRenameWithExists(
+            new HybridFile(OpenMode.SMB, "smb://server/share/file")));
+    assertFalse(
+        MainActivityHelper.shouldVerifyRenameWithExists(
+            new HybridFile(OpenMode.FILE, "/storage/emulated/0/file")));
+  }
+}