Fixed rotation on iOS.

example/lib/main.dart

@@ -29,21 +29,7 @@ class _QRViewExampleState extends State<QRViewExample> {
     return Scaffold(
       body: Column(
         children: <Widget>[
-          Expanded(
-            flex: 4,
-            child: QRView(
-              key: qrKey,
-              onQRViewCreated: _onQRViewCreated,
-              overlay: QrScannerOverlayShape(
-                borderColor: Colors.red,
-                borderRadius: 10,
-                borderLength: 30,
-                borderWidth: 10,
-                cutOutSize: 300,
-                cutOutBottomOffset: 24,
-              ),
-            ),
-          ),
+          Expanded(flex: 4, child: _buildQrView(context)),
           Expanded(
             flex: 1,
             child: FittedBox(
@@ -141,6 +127,29 @@ class _QRViewExampleState extends State<QRViewExample> {
     return backCamera == current;
   }
 
+  Widget _buildQrView(BuildContext context) {
+    // To ensure the Scanner view is properly sizes after rotation
+    // we need to listen for Flutter SizeChanged notifiation and update controller
+    return NotificationListener<SizeChangedLayoutNotification>(
+        onNotification: (notification) {
+          Future.microtask(() => controller?.updateDimensions(qrKey));
+          return false;
+        },
+        child: SizeChangedLayoutNotifier(
+            key: const Key('qr-size-notifier'),
+            child: QRView(
+              key: qrKey,
+              onQRViewCreated: _onQRViewCreated,
+              overlay: QrScannerOverlayShape(
+                borderColor: Colors.red,
+                borderRadius: 10,
+                borderLength: 30,
+                borderWidth: 10,
+                cutOutSize: 300,
+              ),
+            )));
+  }
+
   void _onQRViewCreated(QRViewController controller) {
     this.controller = controller;
     controller.scannedDataStream.listen((scanData) {

ios/Classes/QRView.swift

@@ -63,9 +63,16 @@ public class QRView:NSObject,FlutterPlatformView {
     }
     
     func setDimensions(width: Double, height: Double) -> Void {
-       previewView.frame = CGRect(x: 0, y: 0, width: width, height: height)
-       scanner = MTBBarcodeScanner(previewView: previewView)
-       MTBBarcodeScanner.requestCameraPermission(success: isCameraAvailable)
+        previewView.frame = CGRect(x: 0, y: 0, width: width, height: height)
+
+        if let sc: MTBBarcodeScanner = scanner {
+            if let previewLayer = sc.previewLayer {
+                previewLayer.frame = previewView.bounds;
+            }
+        } else {
+            scanner = MTBBarcodeScanner(previewView: previewView)
+            MTBBarcodeScanner.requestCameraPermission(success: isCameraAvailable)
+        }
     }
     
     func flipCamera(){

lib/src/qr_code_scanner.dart

@@ -100,11 +100,7 @@ class _CreationParams {
 class QRViewController {
   QRViewController._(int id, GlobalKey qrKey)
       : _channel = MethodChannel('net.touchcapture.qr.flutterqr/qrview_$id') {
-    if (defaultTargetPlatform == TargetPlatform.iOS) {
-      final RenderBox renderBox = qrKey.currentContext.findRenderObject();
-      _channel.invokeMethod('setDimensions',
-          {'width': renderBox.size.width, 'height': renderBox.size.height});
-    }
+    updateDimensions(qrKey);
     _channel.setMethodCallHandler(
       (call) async {
         switch (call.method) {
@@ -145,4 +141,12 @@ class QRViewController {
   void dispose() {
     _scanUpdateController.close();
   }
+
+  void updateDimensions(GlobalKey key) {
+    if (defaultTargetPlatform == TargetPlatform.iOS) {
+      final RenderBox renderBox = key.currentContext.findRenderObject();
+      _channel.invokeMethod('setDimensions',
+          {'width': renderBox.size.width, 'height': renderBox.size.height});
+    }
+  }
 }