What causes "Unknown error occurred." in MuntashirAkon/AppManager?

Inspect the cause (th) stack trace — the message is intentionally generic

MuntashirAkon/AppManager · error · BackupException

Unknown error occurred.

Error message

Unknown error occurred.

What it means

SBConverter.convert's catch-all converts any Throwable that is not already a BackupException into BackupException('Unknown error occurred.', th). It guarantees callers always receive a BackupException from convert, while the cause retains the original unexpected failure (NPE, ClassCastException, RuntimeException, Error, etc.).

Solutions

Inspect the cause (th) stack trace — the message is intentionally generic
Check that all converter fields (mBackupItem, mDestMetadata, mChecksum, mCachedApk) are initialized before use
Re-run with debug logging to find which conversion stage threw
Report/fix the underlying bug; this catch-all indicates an unanticipated failure path

Defensive patterns

Strategy: try-catch

Validate before calling

// guard converter state before calling convert
if (packageName == null || userId < 0) {
    throw new IllegalArgumentException("packageName and userId must be set before conversion");
}

Try / catch

try {
    converter.convert(...);
} catch (BackupException e) {
    Throwable root = e.getCause();
    if (root != null) {
        Log.e(TAG, "Conversion failed with unexpected error", root);
    }
}

Prevention

Always inspect getCause() — the top message is a generic catch-all
Initialize all converter fields before invoking convert
Run conversion in debug mode to capture the original stack trace
Handle large backups carefully to avoid runtime Errors (OOM)

When it happens

Trigger: Any unexpected Throwable inside the conversion pipeline not covered by the specific IOException/CryptoException handlers — e.g. NullPointerException on uninitialized fields (mBackupItem, mDestMetadata), ClassCastException, or runtime errors from metadata/icon/APK backup helpers.

Common situations: Programming errors in converter state (fields used before assignment), unexpected nulls from parsed source metadata, library bugs, or OOM/other Errors during large APK backups.

Understand the failure class

Background: "This is a bug, please report it": internal invariant violations, unreachable panics, and SNH errors explained — this error's family across 47 libraries.

Related errors

AI-assisted analysis of MuntashirAkon/AppManager@0152f468fc (2026-09-12). Data as JSON: /api/errors/a19df8f3fc4f0c49. Report an issue: GitHub.

Appendix: source

Thrown at app/src/main/java/io/github/muntashirakon/AppManager/backup/convert/SBConverter.java:153

            }
            mChecksum.close();
            // Encrypt checksum
            try {
                mBackupItem.encrypt(new Path[]{mChecksum.getFile()});
            } catch (IOException e) {
                throw new BackupException("Failed to encrypt checksums.txt");
            }
            // Replace current backup
            try {
                mBackupItem.commit();
            } catch (IOException e) {
                throw new BackupException("Could not finalise backup.", e);
            }
            backupSuccess = true;
        } catch (BackupException e) {
            throw e;
        } catch (Throwable th) {
            throw new BackupException("Unknown error occurred.", th);
        } finally {
            mBackupItem.cleanup();
            mCachedApk.requireParent().delete();
            if (backupSuccess) {
                BackupUtils.putBackupToDbAndBroadcast(ContextUtils.getContext(), mDestMetadata);
            }
        }
    }

    @Override
    public void cleanup() {
        for (Path file : mFilesToBeDeleted) {
            file.delete();
        }
    }

    private void backupApkFile() throws BackupException {
        Path sourceDir = mCachedApk.requireParent();

View on GitHub (pinned to 0152f468fc)