barcode_scanner_picklist.dart
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import 'dart:async';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:mobile_scanner/mobile_scanner.dart';
import 'package:mobile_scanner_example/picklist/classes/detect_collision.dart';
import 'package:mobile_scanner_example/picklist/widgets/crosshair.dart';
import 'package:mobile_scanner_example/scanner_error_widget.dart';
class BarcodeScannerPicklist extends StatefulWidget {
const BarcodeScannerPicklist({super.key});
@override
State<BarcodeScannerPicklist> createState() => _BarcodeScannerPicklistState();
}
class _BarcodeScannerPicklistState extends State<BarcodeScannerPicklist>
with WidgetsBindingObserver {
final _mobileScannerController = MobileScannerController(
autoStart: false,
);
StreamSubscription<Object?>? _barcodesSubscription;
final _scannerDisabled = ValueNotifier(false);
bool barcodeDetected = false;
@override
void initState() {
SystemChrome.setPreferredOrientations([DeviceOrientation.portraitUp]);
WidgetsBinding.instance.addObserver(this);
_barcodesSubscription = _mobileScannerController.barcodes.listen(
_handleBarcodes,
);
super.initState();
unawaited(_mobileScannerController.start());
}
@override
void didChangeAppLifecycleState(AppLifecycleState state) {
if (!_mobileScannerController.value.isInitialized) {
return;
}
switch (state) {
case AppLifecycleState.detached:
case AppLifecycleState.hidden:
case AppLifecycleState.paused:
return;
case AppLifecycleState.resumed:
_barcodesSubscription =
_mobileScannerController.barcodes.listen(_handleBarcodes);
unawaited(_mobileScannerController.start());
case AppLifecycleState.inactive:
unawaited(_barcodesSubscription?.cancel());
_barcodesSubscription = null;
unawaited(_mobileScannerController.stop());
}
}
@override
void dispose() {
WidgetsBinding.instance.removeObserver(this);
unawaited(_barcodesSubscription?.cancel());
_barcodesSubscription = null;
super.dispose();
_mobileScannerController.dispose();
}
void _handleBarcodes(BarcodeCapture capture) {
if (_scannerDisabled.value) {
return;
}
for (final barcode in capture.barcodes) {
if (isPointInPolygon(
Offset(
_mobileScannerController.value.size.width / 2,
_mobileScannerController.value.size.height / 2,
),
barcode.corners,
)) {
if (!barcodeDetected) {
barcodeDetected = true;
Navigator.of(context).pop(barcode);
}
return;
}
}
}
@override
Widget build(BuildContext context) {
const boxFit = BoxFit.contain;
return PopScope(
onPopInvokedWithResult: (didPop, result) {
if (didPop) {
SystemChrome.setPreferredOrientations([...DeviceOrientation.values]);
}
},
child: Scaffold(
appBar: AppBar(title: const Text('Picklist scanner')),
backgroundColor: Colors.black,
body: StreamBuilder(
stream: _mobileScannerController.barcodes,
builder: (context, snapshot) {
return Listener(
behavior: HitTestBehavior.opaque,
onPointerDown: (_) => _scannerDisabled.value = true,
onPointerUp: (_) => _scannerDisabled.value = false,
onPointerCancel: (_) => _scannerDisabled.value = false,
child: Stack(
fit: StackFit.expand,
children: [
MobileScanner(
controller: _mobileScannerController,
errorBuilder: (context, error, child) =>
ScannerErrorWidget(error: error),
fit: boxFit,
),
ValueListenableBuilder(
valueListenable: _scannerDisabled,
builder: (context, value, child) {
return Crosshair(
scannerDisabled: value,
);
},
),
],
),
);
},
),
),
);
}
}