From 692d2e2b1af3ab08d5b1ae523eca2a650fb57faf Mon Sep 17 00:00:00 2001
From: ibrahim-iqbal <ibrahim-iqbal@users.noreply.github.com>
Date: Mon, 21 Sep 2026 13:04:19 +0530
Subject: [PATCH] fix: guard startSyncFolderOperation against a null folder
 (#4738)
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`ReceiveExternalFilesViewModel.refreshFolderUseCase(folderToSync: OCFile)`
is a Kotlin function with a non-null parameter. `ReceiveExternalFilesActivity`
was passing the result of `getCurrentDir()` — which returns null whenever
the storage manager cannot resolve the current folder — straight through
without a null check, so the Kotlin platform-type check tripped the NPE
that shows up in the Play console stack in issue #4738.

Short-circuit `startSyncFolderOperation` when the folder is null and log
the skip via Timber. All other callers already null-check the folder they
pass in; the crash path was the `getCurrentDir()` handoff.

Signed-off-by: ibrahim-iqbal <ibrahim-iqbal@users.noreply.github.com>
---
 changelog/unreleased/4738                              | 10 ++++++++++
 .../ui/activity/ReceiveExternalFilesActivity.java      |  8 ++++++++
 2 files changed, 18 insertions(+)
 create mode 100644 changelog/unreleased/4738

diff --git a/changelog/unreleased/4738 b/changelog/unreleased/4738
new file mode 100644
index 00000000000..1b500d52d7b
--- /dev/null
+++ b/changelog/unreleased/4738
@@ -0,0 +1,10 @@
+Bugfix: Prevent NullPointerException when returning from external-file receive screen
+
+The share-into flow's `ReceiveExternalFilesActivity` forwarded a folder to
+`ReceiveExternalFilesViewModel.refreshFolderUseCase` without guarding for null,
+so any code path where `getCurrentDir()` resolved to `null` — such as leaving
+the screen before the storage manager had loaded the parent folder — crashed
+with a Kotlin platform-type NPE. The activity now skips the sync when the
+folder cannot be resolved and logs the reason instead of crashing.
+
+https://github.com/owncloud/android/issues/4738
diff --git a/owncloudApp/src/main/java/com/owncloud/android/ui/activity/ReceiveExternalFilesActivity.java b/owncloudApp/src/main/java/com/owncloud/android/ui/activity/ReceiveExternalFilesActivity.java
index 2d0af9aeca0..c585e2f7ff2 100644
--- a/owncloudApp/src/main/java/com/owncloud/android/ui/activity/ReceiveExternalFilesActivity.java
+++ b/owncloudApp/src/main/java/com/owncloud/android/ui/activity/ReceiveExternalFilesActivity.java
@@ -628,6 +628,14 @@ public void onSavedCertificate() {
     }
 
     private void startSyncFolderOperation(OCFile folder) {
+        // getCurrentDir() and other callers can hand us a null folder when the
+        // storage manager cannot resolve the parent path yet; forwarding that
+        // to the Kotlin use case would trip the platform-type null check and
+        // crash as reported in issue #4738.
+        if (folder == null) {
+            Timber.w("startSyncFolderOperation called with a null folder; skipping sync");
+            return;
+        }
 
         mSyncInProgress = true;