flutter how to fix permission handler error-CodePudding

I dont know how to resolve this red error part. I copied this from internet then i got this error. please help me to solve this.

This is my full code.

import 'package:flutter/material.dart';
import 'package:permission_handler/permission_handler.dart';
import 'package:android_intent/android_intent.dart';
import 'package:geolocator/geolocator.dart';
class AskForPermission extends StatefulWidget {
  @override
  _AskForPermissionState createState() => _AskForPermissionState();
}
class _AskForPermissionState extends State<AskForPermission> {
  final PermissionHandler permissionHandler = PermissionHandler();
  Map<PermissionGroup, PermissionStatus>? permissions;
  void initState() {
    super.initState();
    requestLocationPermission();
    _gpsService();
  }
  Future<bool> _requestPermission(PermissionGroup permission) async {
    final PermissionHandler _permissionHandler = PermissionHandler();
    var result = await _permissionHandler.requestPermissions([permission]);
    if (result[permission] == PermissionStatus.granted) {
      return true;
    }
    return false;
  }
/*Checking if your App has been Given Permission*/
  Future<bool> requestLocationPermission({Function? onPermissionDenied}) async {
    var granted = await _requestPermission(PermissionGroup.location);
    if (granted!=true) {
      requestLocationPermission();
    }
    debugPrint('requestContactsPermission $granted');
    return granted;
  }
/*Show dialog if GPS not enabled and open settings location*/
  Future _checkGps() async {
    if (!(await Geolocator.isLocationServiceEnabled())) {
      if (Theme.of(context).platform == TargetPlatform.android) {
        showDialog(
            context: context,
            builder: (BuildContext context) {
              return AlertDialog(
                title: Text("Can't get gurrent location"),
                content:const Text('Please make sure you enable GPS and try again'),
                actions: <Widget>[
                  FlatButton(child: Text('Ok'),
                      onPressed: () {
                        final AndroidIntent intent = AndroidIntent(
                            action: 'android.settings.LOCATION_SOURCE_SETTINGS');
                        intent.launch();
                        Navigator.of(context, rootNavigator: true).pop();
                        _gpsService();
                      })],
              );
            });
      }
    }
  }

/*Check if gps service is enabled or not*/
  Future _gpsService() async {
    if (!(await Geolocator.isLocationServiceEnabled())) {
      _checkGps();
      return null;
    } else
      return true;
  }
  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: Text('Ask for permisions'),
          backgroundColor: Colors.red,
        ),
        body: Center(
            child: Column(
              children: <Widget>[
                Text("All Permission Granted"),
              ],
            ))
    );
  }
}

CodePudding user response：

Install permission handler package from here. Then in your .dart file add import and call permission asking function somewhere. E.g. function like this asks for storage permission.

import 'package:permission_handler/permission_handler.dart';

  Future<void> getStoragePermission() async {
    if (await Permission.manageExternalStorage.request().isGranted) {
      setState(() {});
    } else if (await Permission.storage.request().isPermanentlyDenied) {
      await openAppSettings();
    } else if (await Permission.storage.request().isDenied) {
      setState(() {});
    }
  }

CodePudding user response：

Please refer to below code

https://pub.dev/packages/permission_handler/install permission_handler: ^5.0.1 1

import 'package:permission_handler/permission_handler.dart';
import 'package:google_fonts/google_fonts.dart';

class MyApp extends StatelessWidget {
  MyApp({Key key}) : super(key: key);

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primaryColor: Color(0xfff00B074),
        textTheme: const TextTheme(
          bodyText1: TextStyle(
              fontSize: 18.0,
              fontFamily: 'Barlow-Medium',
              color: Color(0xff464255)),
        ),
      ),
      home: PermissionHandlerScreen(),
    );
  }
}

class PermissionHandlerScreen extends StatefulWidget {
  @override
  _PermissionHandlerScreenState createState() =>
      _PermissionHandlerScreenState();
}

class _PermissionHandlerScreenState extends State<PermissionHandlerScreen> {
  @override
  void initState() {
    super.initState();
    permissionServiceCall();
  }

  permissionServiceCall() async {
    await permissionServices().then(
      (value) {
        if (value != null) {
          if (value[Permission.storage].isGranted &&
              value[Permission.camera].isGranted &&
              value[Permission.microphone].isGranted) {
            /* ========= New Screen Added  ============= */

            Navigator.pushReplacement(
              context,
              MaterialPageRoute(builder: (context) => SplashScreen()),
            );
          }
        }
      },
    );
  }

  /*Permission services*/
  Future<Map<Permission, PermissionStatus>> permissionServices() async {
    // You can request multiple permissions at once.
    Map<Permission, PermissionStatus> statuses = await [
      Permission.storage,
      Permission.camera,
      Permission.microphone,
      //add more permission to request here.
    ].request();

    if (statuses[Permission.storage].isPermanentlyDenied) {
      openAppSettings();
      setState(() {});
    } else {
      if (statuses[Permission.storage].isDenied) {
        permissionServiceCall();
      }
    }
    if (statuses[Permission.microphone].isPermanentlyDenied) {
      openAppSettings();
      setState(() {});
    } else {
      if (statuses[Permission.microphone].isDenied) {
        permissionServiceCall();
        
      }
    }

    if (statuses[Permission.camera].isPermanentlyDenied) {
      openAppSettings();
      setState(() {});
    } else {
      if (statuses[Permission.camera].isDenied) {
        permissionServiceCall();
      }
    }
    /*{Permission.camera: PermissionStatus.granted, Permission.storage: PermissionStatus.granted}*/
    return statuses;
  }

  @override
  Widget build(BuildContext context) {
    permissionServiceCall();
    return WillPopScope(
      onWillPop: () {
        SystemNavigator.pop();
      },
      child: Scaffold(
        body: Container(
          child: Center(
            child: InkWell(
                onTap: () {
                  permissionServiceCall();
                },
                child: Text("Click here to enable Enable Permission Screen")),
          ),
        ),
      ),
    );
  }
}

class SplashScreen extends StatelessWidget {
  const SplashScreen({Key key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return WillPopScope(
      onWillPop: () {
        SystemNavigator.pop();
      },
      child: Scaffold(
        body: Center(
          child: Text(
            "Splash Screen",
          ),
        ),
      ),
    );
  }
}