Fix 8 critical/high resilience issues across camera, preview, logger, settings, and admin

src/screens/AdminScreen.tsx

@@ -65,6 +65,7 @@ export default function AdminScreen({ currentSettings, onSave, onClose }: AdminS
   const [countdown, setCountdown] = useState<string>(String(currentSettings.countdownDuration));
   const [printerIp, setPrinterIp] = useState<string>(currentSettings.printerIp);
   const [password, setPassword] = useState<string>(currentSettings.adminPassword);
+  const [isTogglingKiosk, setIsTogglingKiosk] = useState<boolean>(false);
   const [logs, setLogs] = useState<string | null>(null);
   const scrollViewRef = useRef<ScrollView>(null);
   
@@ -98,7 +99,9 @@ export default function AdminScreen({ currentSettings, onSave, onClose }: AdminS
     return () => clearInterval(interval);
   }, []);
 
-  const handleKioskToggle = (enable: boolean) => {
+  const handleKioskToggle = async (enable: boolean) => {
+    if (isTogglingKiosk) return;
+    setIsTogglingKiosk(true);
     try {
       if (enable) {
         const success = KioskMode.startKiosk();
@@ -124,6 +127,8 @@ export default function AdminScreen({ currentSettings, onSave, onClose }: AdminS
       }
     } catch (e: any) {
       Alert.alert('Nativer Fehler', e.message || 'Fehler im Kiosk-Modul');
+    } finally {
+      setIsTogglingKiosk(false);
     }
   };
 
@@ -298,6 +303,7 @@ export default function AdminScreen({ currentSettings, onSave, onClose }: AdminS
               placeholder="Standard: 1234"
               placeholderTextColor={THEME.colors.textMuted}
               secureTextEntry
+              maxLength={20}
               value={password}
               onChangeText={setPassword}
               keyboardType="number-pad"

src/screens/CameraScreen.tsx

@@ -129,10 +129,10 @@ export default function CameraScreen({
 
   // 1. Request built-in camera permission on mount (just in case we fallback)
   useEffect(() => {
-    if (!permission || !permission.granted) {
+    if (permission && !permission.granted && permission.canAskAgain) {
       requestPermission();
     }
-  }, [permission]);
+  }, []);
 
   // 2. Check if a USB camera is connected.
   useEffect(() => {
@@ -251,7 +251,7 @@ export default function CameraScreen({
     return () => {
       if (countdownTimerRef.current) clearTimeout(countdownTimerRef.current);
     };
-  }, [countdownDuration, isIdle, pictureSize, isUsbConnected]);
+  }, [countdownDuration, isIdle, pictureSize, isUsbConnected, burstCount, burstIntervalSec]);
 
   const startCountdown = () => {
     isCancelledRef.current = false;

src/screens/PreviewScreen.tsx

@@ -217,8 +217,9 @@ export default function PreviewScreen({
     }
   };
 
-  // Triggers the view capture and the print job
+  // ── Actions ──
   const handlePrint = async () => {
+    if (idleTimerRef.current) clearTimeout(idleTimerRef.current);
     if (!mountedRef.current) return;
     if (isProcessing) return;
     setIsProcessing(true);
@@ -253,6 +254,7 @@ export default function PreviewScreen({
 
   // Saves to gallery without printing
   const handleSaveOnly = async () => {
+    if (idleTimerRef.current) clearTimeout(idleTimerRef.current);
     if (!mountedRef.current) return;
     if (isProcessing) return;
     setIsProcessing(true);
@@ -281,6 +283,7 @@ export default function PreviewScreen({
 
   // Auto-save and exit
   const handleExit = useCallback(async () => {
+    if (idleTimerRef.current) clearTimeout(idleTimerRef.current);
     if (!mountedRef.current) return;
     if (isProcessing) return;
     const state = stateRef.current;
@@ -326,6 +329,7 @@ export default function PreviewScreen({
   }, [resetIdleTimer]);
 
   const handleRetakeClick = async () => {
+    if (idleTimerRef.current) clearTimeout(idleTimerRef.current);
     if (!mountedRef.current) return;
     if (isProcessing) return;
     if (stickers.length > 0 || layout !== 'single' || activeFrame || dateOverlay !== 'off') {

src/services/logger.ts

@@ -3,15 +3,23 @@ import * as FileSystem from 'expo-file-system/legacy';
 const logFileUri = FileSystem.documentDirectory + 'app_logs.txt';
 
 // Queue to serialize file operations and prevent race conditions
-let writeQueue = Promise.resolve();
+const logQueue: string[] = [];
+let isWriting = false;
 
-const enqueueWrite = (logLine: string) => {
-  writeQueue = writeQueue.then(async () => {
+const processLogQueue = async () => {
+  if (isWriting) return;
+  isWriting = true;
+  
+  while (logQueue.length > 0) {
+    const logLine = logQueue.shift();
+    if (!logLine) continue;
+    
     try {
-      const fileInfo = await FileSystem.getInfoAsync(logFileUri);
-      if (!fileInfo.exists) {
-        await FileSystem.writeAsStringAsync(logFileUri, logLine, { encoding: FileSystem.EncodingType.UTF8 });
-      } else {
+      if (logFileUri) {
+        const fileInfo = await FileSystem.getInfoAsync(logFileUri);
+        if (!fileInfo.exists) {
+          await FileSystem.writeAsStringAsync(logFileUri, '', { encoding: FileSystem.EncodingType.UTF8 });
+        }
         const current = await FileSystem.readAsStringAsync(logFileUri, { encoding: FileSystem.EncodingType.UTF8 });
         let newContent = current + logLine;
         if (newContent.length > 100000) {
@@ -21,12 +29,15 @@ const enqueueWrite = (logLine: string) => {
       }
     } catch (e) {
       console.warn('Failed to write to log file:', e);
-      // We catch here so the queue is not broken for subsequent logs
     }
-  }).catch((e) => {
-    console.error('Queue error:', e);
-  });
-  return writeQueue;
+  }
+  
+  isWriting = false;
+};
+
+const enqueueWrite = async (logLine: string) => {
+  logQueue.push(logLine);
+  processLogQueue(); // Intentionally unawaited to run in background
 };
 
 export const logger = {

src/services/settings.ts

@@ -61,7 +61,7 @@ export async function loadSettings(): Promise<AppSettings> {
 export async function saveSettings(settings: AppSettings): Promise<void> {
   try {
     const content = JSON.stringify(settings, null, 2);
-    await FileSystem.writeAsStringAsync(settingsFile.uri, content);
+    await settingsFile.write(content);
     console.log('Settings saved successfully:', content);
   } catch (e) {
     console.error('Failed to save settings:', e);