Fix for Issue #61

example/ios/Runner.xcworkspace/xcshareddata/WorkspaceSettings.xcsettings

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>BuildSystemType</key>
+	<string>Original</string>
+	<key>PreviewsEnabled</key>
+	<false/>
+</dict>
+</plist>

ios/Classes/BarcodeScannerViewController.m

@@ -10,6 +10,35 @@
 @implementation BarcodeScannerViewController {
 }
 
+- (void)viewWillTransitionToSize:(CGSize)size withTransitionCoordinator:(id<UIViewControllerTransitionCoordinator>)coordinator
+{
+    CGRect bounds = [UIScreen mainScreen].bounds;
+    CGRect reversedBounds = CGRectMake(bounds.origin.x, bounds.origin.y, bounds.size.height, bounds.size.width);
+    self.previewView.bounds = reversedBounds;
+    self.previewView.frame = reversedBounds;
+    [self.scanRect stopAnimating];
+    [self.scanRect removeFromSuperview];
+    [self setupScanRect:reversedBounds];
+    [super viewWillTransitionToSize:size withTransitionCoordinator:coordinator];
+}
+
+- (void)setupScanRect:(CGRect)bounds {
+    self.scanRect = [[ScannerOverlay alloc] initWithFrame:bounds];
+    self.scanRect.translatesAutoresizingMaskIntoConstraints = NO;
+    self.scanRect.backgroundColor = UIColor.clearColor;
+    [self.view addSubview:_scanRect];
+    [self.view addConstraints:[NSLayoutConstraint
+                               constraintsWithVisualFormat:@"V:[scanRect]"
+                               options:NSLayoutFormatAlignAllBottom
+                               metrics:nil
+                               views:@{@"scanRect": _scanRect}]];
+    [self.view addConstraints:[NSLayoutConstraint
+                               constraintsWithVisualFormat:@"H:[scanRect]"
+                               options:NSLayoutFormatAlignAllBottom
+                               metrics:nil
+                               views:@{@"scanRect": _scanRect}]];
+    [_scanRect startAnimating];
+}
 
 - (void)viewDidLoad {
     [super viewDidLoad];
@@ -26,21 +55,7 @@ - (void)viewDidLoad {
                                 options:NSLayoutFormatAlignAllBottom
                                 metrics:nil
                                   views:@{@"previewView": _previewView}]];
-  self.scanRect = [[ScannerOverlay alloc] initWithFrame:self.view.bounds];
-  self.scanRect.translatesAutoresizingMaskIntoConstraints = NO;
-  self.scanRect.backgroundColor = UIColor.clearColor;
-  [self.view addSubview:_scanRect];
-  [self.view addConstraints:[NSLayoutConstraint
-                             constraintsWithVisualFormat:@"V:[scanRect]"
-                             options:NSLayoutFormatAlignAllBottom
-                             metrics:nil
-                             views:@{@"scanRect": _scanRect}]];
-  [self.view addConstraints:[NSLayoutConstraint
-                             constraintsWithVisualFormat:@"H:[scanRect]"
-                             options:NSLayoutFormatAlignAllBottom
-                             metrics:nil
-                             views:@{@"scanRect": _scanRect}]];
-  [_scanRect startAnimating];
+    [self setupScanRect:self.view.bounds];
     self.scanner = [[MTBBarcodeScanner alloc] initWithPreviewView:_previewView];
     self.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemCancel target:self action:@selector(cancel)];
   [self updateFlashButton];

ios/Classes/ScannerOverlay.m

@@ -83,19 +83,31 @@ - (void)stopAnimating {
   }
 
   - (CGRect)scanRect {
-    CGRect rect = self.frame;
-    CGFloat heightMultiplier = 3.0/4.0; // 4:3 aspect ratio
-    CGFloat scanRectWidth = rect.size.width * 0.8f;
-    CGFloat scanRectHeight = scanRectWidth * heightMultiplier;
-    CGFloat scanRectOriginX = (rect.size.width / 2) - (scanRectWidth / 2);
-    CGFloat scanRectOriginY = (rect.size.height / 2) - (scanRectHeight / 2);
-    return CGRectMake(scanRectOriginX, scanRectOriginY, scanRectWidth, scanRectHeight);
+      CGRect rect = self.frame;
+
+      CGFloat frameWidth = rect.size.width;
+      CGFloat frameHeight = rect.size.height;
+
+      BOOL isLandscape = frameWidth > frameHeight;
+      CGFloat widthOnPortrait = isLandscape ? frameHeight : frameWidth;
+      CGFloat scanRectWidth = widthOnPortrait * 0.8f;
+      CGFloat aspectRatio = 3.0/4.0;
+      CGFloat scanRectHeight = scanRectWidth * aspectRatio;
+
+      if(isLandscape) {
+          CGFloat navbarHeight = 32;
+          frameHeight += navbarHeight;
+      }
+
+      CGFloat scanRectOriginX = (frameWidth - scanRectWidth) / 2;
+      CGFloat scanRectOriginY = (frameHeight - scanRectHeight) / 2;
+      return CGRectMake(scanRectOriginX, scanRectOriginY, scanRectWidth, scanRectHeight);
   }
 
   - (CGRect)scanLineRect {
     CGRect scanRect = [self scanRect];
-    CGRect rect = self.frame;
-    return CGRectMake(scanRect.origin.x, rect.size.height / 2, scanRect.size.width, 1);
+    CGFloat positionY = scanRect.origin.y + (scanRect.size.height / 2);
+    return CGRectMake(scanRect.origin.x, positionY, scanRect.size.width, 1);
   }
 
 @end