use MediaQuery.sizeOf() instead of the topmost layout builder

@@ -232,8 +232,8 @@ class _MobileScannerState extends State<MobileScanner>
 
   @override
   Widget build(BuildContext context) {
-    return LayoutBuilder(
-      builder: (context, constraints) {
+    final Size size = MediaQuery.sizeOf(context);
+
     return ValueListenableBuilder<MobileScannerArguments?>(
       valueListenable: _controller.startArguments,
       builder: (context, value, child) {
@@ -246,7 +246,7 @@ class _MobileScannerState extends State<MobileScanner>
             widget.fit,
             widget.scanWindow!,
             value.size,
-                constraints.biggest,
+            size,
           );
 
           _controller.updateScanWindow(scanWindow);
@@ -272,8 +272,6 @@ class _MobileScannerState extends State<MobileScanner>
         );
       },
     );
-      },
-    );
   }
 
   @override