Error map
The argument type can't be assigned to the parameter type Dart: The argument type 'String?' can't be assigned to the parameter type 'String'
Flutter / Dart · layer 1, On your device
Centre: this error. First ring: errors it is linked with (12). Outer ring: what those are linked with. Colours show the layer of a request each error belongs to. Click any dot to re-centre the map on it; hover to follow its connections. The centre dot opens the error page.
Directly related (12)
Swift: Cannot convert value of type 'X' to expected argument type 'Y'
The value’s type doesn’t match what the function or property expects.
Dart/Flutter: Null check operator used on a null value
The ! operator was applied to a variable that was null at runtime.
Dart: LateInitializationError: Field 'controller' has not been initialized
A `late` variable was read before it was assigned.
Dart: Non-nullable instance field 'name' must be initialized. Try adding an initializer expression, or a generative constructor that initializes it, or mark it 'late'
With null safety every non-nullable field needs a value by the end of construction.
Dart: type '_InternalLinkedHashMap<String, dynamic>' is not a subtype of type 'List<dynamic>' in type cast
JSON decoded to a Map but your code expected a List (or the other way round).
Dart: Bad state: No element — .first, .last or .single on an empty list
You called `.first`, `.last`, `.single` or `.reduce` on an empty collection.
Dart: RangeError (index): Invalid value: Valid value range is empty: 0
A list or string was indexed outside its bounds, often an empty list or an off-by-one in `itemBuilder`.
Dart: FormatException: Unexpected character (at character 1) <!DOCTYPE html> — jsonDecode of an HTML page
`jsonDecode` received something that is not JSON, commonly an HTML error page, an empty string, or a plain-text message.
Dart: Bad state: Stream has already been listened to
A single-subscription stream was listened to twice, for instance by two `StreamBuilder`s or after a rebuild.
Dart: Error: Couldn't resolve the package 'x' in 'package:x/x.dart'
Code imports a package that is not in `pubspec.yaml` or `pub get` has not been run since adding it.
Dart: The property 'length' can't be unconditionally accessed because the receiver can be 'null'
With null safety you used `.` on a nullable value; Dart requires a null check first.
Dart: The getter 'name' isn't defined for the type 'User' / The method 'foo' isn't defined for the class
The analyzer cannot find that property or method on the object's static type.
Two steps away (15)
AttributeError: 'X' object has no attribute 'y'
You accessed an attribute or method that doesn’t exist on that object type.
java.lang.ClassCastException: class A cannot be cast to class B
An object was cast to a type it isn’t.
TS7016: Could not find a declaration file for module 'x'. 'x.js' implicitly has an 'any' type.
The JavaScript package has no TypeScript types bundled and no @types package installed.
Flutter: A RenderFlex overflowed by x pixels on the right/bottom
A Row or Column’s children need more space than available, so Flutter draws the yellow-black overflow stripes.
Flutter: setState() called after dispose(): _MyState#1a2b3 (lifecycle state: defunct, not mounted)
An async callback (network, timer, stream) finished after the widget was removed and then called setState.
TS2322: Type 'X' is not assignable to type 'Y'
You assigned a value whose type doesn’t match the declared type of the variable, property or return value.
Dart: type 'Null' is not a subtype of type 'String' in type cast
A value that was `null` at runtime was cast or used as a non-nullable type, most often when parsing JSON.
Dart: The named parameter 'key' is required, but there's no corresponding argument
A constructor or function marked `required` for a parameter was called without it.
Dart: Invalid argument(s): Illegal argument in isolate message: object is unsendable - Library:'dart:async' Class: _Future@4048458
You tried to send an object (closure, Future, socket, platform object) to another isolate that cannot be copied.
Flutter: Unhandled Exception: SocketException: Failed host lookup: 'api.example.com' (OS Error: No address associated with hostname, errno = 7)
The app could not resolve or reach the server: no internet, wrong host name, DNS failure, or missing network permission.
Flutter (Android): java.io.IOException: Cleartext HTTP traffic to api.example.com not permitted
Android 9+ blocks plain `http://` requests by default; the app must use HTTPS or explicitly allow cleartext for that host.
Flutter: setState() or markNeedsBuild() called during build. This widget cannot be marked as needing to build because the framework is already in the process of building widgets
State was changed while Flutter was building widgets, for example calling `setState` or a notifier from inside `build`.
Flutter: _HomeState#abc(ticker active) was disposed with an active Ticker. State.dispose() implementations must call dispose() on all their AnimationControllers
An `AnimationController` was still running when its `State` was disposed, because `dispose()` did not release it.
Dart pub: Because app depends on intl ^0.19.0 and flutter_localizations from sdk depends on intl 0.18.1, version solving failed
`flutter pub get` cannot find a set of package versions that satisfy every dependency's constraints.
Dart pub: The current Dart SDK version is 2.19.0. Because app requires SDK version >=3.0.0 <4.0.0, version solving failed
A package (or your own pubspec) requires a newer Dart SDK than the one your Flutter installation provides.
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