Expected a value of type 'Map<String, String?>', but got one of type 'Null in f-CodePudding

I had Project, which was working very well. I upgraded it to null safety. Now I'm getting the Expected a value of type 'Map<String, String?>', but got one of type 'Null.

Here is the code before the upgrading to null safety:

final Map<String, String> args = ModalRoute.of(context).settings.arguments;

which is working fine.

And here is the code after upgrading to null safety.

final Map<String, String?> args =
        ModalRoute.of(context)!.settings.arguments as Map<String, String?>;

which gives the error Dose any know why? and how to fix it. Thanks in advance.

CodePudding user response：

Your ModalRoute.of(context) may be null for that reason you used ! on it so it may cause ModalRoute.of(context)!.settings.arguments be null but you expect non-null Map, so change this:

final Map<String, String?> args =
        ModalRoute.of(context)!.settings.arguments as Map<String, String?>;

to this:

 final Map<String, String?>? args =
    ModalRoute.of(context)?.settings.arguments as Map<String, String?>?;

CodePudding user response：

no need to use ? as you already initialize it you can try to use toString with json decode

final  args = json.decode(ModalRoute.of(context)!.settings.arguments.toString()) ;

CodePudding user response：

I changed the code:

final Map<String, String?> args =   ModalRoute.of(context)!.settings.arguments as Map<String, String?>;

Map? args = {};
args = ModalRoute.of(context)!.settings.arguments as Map?;

And it is working. Can someone please explain, what was the cause of the error? thank you