Updated barcode check to inline check. Updated README.md.

example/lib/main.dart

@@ -148,10 +148,10 @@ class _QRViewExampleState extends State<QRViewExample> {
 
   Widget _buildQrView(BuildContext context) {
     // For this example we check how width or tall the device is and change the scanArea and overlay accordingly.
-    double scanArea = (MediaQuery.of(context).size.width < 500 ||
+    var scanArea = (MediaQuery.of(context).size.width < 500 ||
             MediaQuery.of(context).size.height < 400)
-        ? 150
-        : 300;
+        ? 150.0
+        : 300.0;
     // To ensure the Scanner view is properly sizes after rotation
     // we need to listen for Flutter SizeChanged notification and update controller
     return NotificationListener<SizeChangedLayoutNotification>(