rename onDetect to onBarcodeDetected; remove typedefs; add placeholder builder; …

…fix bug with media query; replace onSTart with onScannerRestarted

@@ -6,39 +6,38 @@ import 'package:mobile_scanner/src/mobile_scanner_controller.dart';
 import 'package:mobile_scanner/src/objects/barcode_capture.dart';
 import 'package:mobile_scanner/src/objects/barcode_capture.dart';
 import 'package:mobile_scanner/src/objects/mobile_scanner_arguments.dart';
 import 'package:mobile_scanner/src/objects/mobile_scanner_arguments.dart';
 
 
-typedef MobileScannerCallback = void Function(BarcodeCapture barcodes);
-typedef MobileScannerArgumentsCallback = void Function(
-  MobileScannerArguments? arguments,
-);
-
-/// A widget showing a live camera preview.
+/// The [MobileScanner] widget displays a live camera preview.
 class MobileScanner extends StatefulWidget {
 class MobileScanner extends StatefulWidget {
   /// The controller that manages the barcode scanner.
   /// The controller that manages the barcode scanner.
   final MobileScannerController controller;
   final MobileScannerController controller;
 
 
-  /// Function that gets called when a Barcode is detected.
+  /// The [BoxFit] for the camera preview.
   ///
   ///
-  /// [barcode] The barcode object with all information about the scanned code.
-  /// [startInternalArguments] Information about the state of the MobileScanner widget
-  final MobileScannerCallback onDetect;
+  /// Defaults to [BoxFit.cover].
+  final BoxFit fit;
 
 
-  /// Function that gets called when the scanner is started.
-  ///
-  /// [arguments] The start arguments of the scanner. This contains the size of
-  /// the scanner which can be used to draw a box over the scanner.
-  final MobileScannerArgumentsCallback? onStart;
+  /// The function that signals when new barcodes were detected by the [controller].
+  final void Function(BarcodeCapture barcodes) onBarcodeDetected;
 
 
-  /// Handles how the widget should fit the screen.
-  final BoxFit fit;
+  /// The function that signals when the barcode scanner is restarted,
+  /// due to coming back to the foreground.
+  final void Function(MobileScannerArguments? arguments)? onScannerRestarted;
 
 
-  /// Whether to automatically resume the camera when the application is resumed
-  final bool autoResume;
+  /// The function that builds a placeholder widget when the scanner
+  /// is not yet displaying its camera preview.
+  ///
+  /// If this is null, a black [ColoredBox] is used as placeholder.
+  final Widget Function(BuildContext, Widget?)? placeholderBuilder;
 
 
-  /// Create a [MobileScanner] with a [controller].
-  /// The [controller] must have been initialized, using [MobileScannerController.start].
+  /// Create a new [MobileScanner] using the provided [controller]
+  /// and [onBarcodeDetected] callback.
   const MobileScanner({
   const MobileScanner({
     required this.controller,
     required this.controller,
     this.fit = BoxFit.cover,
     this.fit = BoxFit.cover,
+    required this.onBarcodeDetected,
+    this.onScannerRestarted,
+    this.placeholderBuilder,
+    super.key,
   });
   });
 
 
   @override
   @override
@@ -100,20 +99,19 @@ class _MobileScannerState extends State<MobileScanner>
 
 
   @override
   @override
   Widget build(BuildContext context) {
   Widget build(BuildContext context) {
-    return ValueListenableBuilder(
-      valueListenable: controller.startArguments,
+    return ValueListenableBuilder<MobileScannerArguments?>(
+      valueListenable: widget.controller.startArguments,
       builder: (context, value, child) {
       builder: (context, value, child) {
-        value = value as MobileScannerArguments?;
         if (value == null) {
         if (value == null) {
-          return const ColoredBox(color: Colors.black);
-        } else {
-          controller.barcodes.listen((barcode) {
-            widget.onDetect(barcode);
-          });
+          return widget.placeholderBuilder?.call(context, child) ??
+              const ColoredBox(color: Colors.black);
+        }
+
         return ClipRect(
         return ClipRect(
-            child: SizedBox(
-              width: MediaQuery.of(context).size.width,
-              height: MediaQuery.of(context).size.height,
+          child: LayoutBuilder(
+            builder: (_, constraints) {
+              return SizedBox.fromSize(
+                size: constraints.biggest,
                 child: FittedBox(
                 child: FittedBox(
                   fit: widget.fit,
                   fit: widget.fit,
                   child: SizedBox(
                   child: SizedBox(
@@ -124,9 +122,10 @@ class _MobileScannerState extends State<MobileScanner>
                         : Texture(textureId: value.textureId!),
                         : Texture(textureId: value.textureId!),
                   ),
                   ),
                 ),
                 ),
+              );
+            },
           ),
           ),
         );
         );
-        }
       },
       },
     );
     );
   }
   }