Flutter: Unhandled Exception: ServicesBinding.defaultBinaryMessenger was accessed before the binding was initialized

Question

Any solution to solve this problem?

Stacktrace:

[VERBOSE-2:ui_dart_state.cc(148)] Unhandled Exception: ServicesBinding.defaultBinaryMessenger was accessed before the binding was initialized.
If you're running an application and need to access the binary messenger before `runApp()` has been called (for example, during plugin initialization), then you need to explicitly call the `WidgetsFlutterBinding.ensureInitialized()` first.
If you're running a test, you can call the `TestWidgetsFlutterBinding.ensureInitialized()` as the first line in your test's `main()` method to initialize the binding.
#0      defaultBinaryMessenger.<anonymous closure> (package:flutter/src/services/binary_messenger.dart:73:7)
#1      defaultBinaryMessenger (package:flutter/src/services/binary_messenger.dart:86:4)
#2      MethodChannel.binaryMessenger (package:flutter/src/services/platform_channel.dart:140:62)
#3      MethodChannel.invokeMethod (package:flutter/src/services/platform_channel.dart:314:35)
<asynchronous suspension>
#4      MethodChannel.invokeMapMethod (package:f<…>

Answer 1

This problem is introduced when you upgrade Flutter. The reason behind this is you are waiting for some data or running an async function inside main().

I was initialising ScopedModel inside main() and inside that I was awaiting for some data.

There is a very small fix. Just run WidgetsFlutterBinding.ensureInitialized() inside void main() , before you do runApp(). Works like a charm!!

void main() {
  WidgetsFlutterBinding.ensureInitialized();
  runApp(Delta(
    model: ProductDataModel(),
  ));
}

Answer 2

This generally happens if you are awaiting on main() method. So, the solution would be:

void main() {
  // add this, and it should be the first line in main method
  WidgetsFlutterBinding.ensureInitialized(); 

  // rest of your app code
  runApp(
    MaterialApp(...),
  );
}

Answer 3

Not sure if I have the correct answer, but I got the same error after a recent flutter upgrade, and managed to get it to work, so I'm sharing my findings.

Looks like the error might be caused by a recent breaking change: https://groups.google.com/forum/#!msg/flutter-announce/sHAL2fBtJ1Y/mGjrKH3dEwAJ.

As a result, we need to manually change the code as follows:

• If you're running an application and need to access the binary messenger before runApp() has been called (for example, during plugin initialization), then you need to explicitly call the WidgetsFlutterBinding.ensureInitialized() first.
• If you're running a test, you can call the TestWidgetsFlutterBinding.ensureInitialized() as the first line in your test's main() method to initialize the binding.

Alternatively, if you are a newbie like me and struggling to understand the above and #38464, you can temporarily avoid this problem by switching to the beta channel. Just run "flutter channel beta". The breaking change is not in beta channel yet, so after switching to beta channel you wouldn't get this error at least for now.

Answer 4

just add this line in main.dart

WidgetsFlutterBinding.ensureInitialized(); 

your code seems like

void main() {
  WidgetsFlutterBinding.ensureInitialized();
  return runApp(MultiProvider(
    providers: [
      ChangeNotifierProvider.value(
        value: AppState(),
      )
    ],
    child: MyApp(),
  ));
}

Answer 5

You could run into this if you're trying to execute plugin native code in an isolate. The isolate_handler documentation here explains this well:

Plugins use a mechanism called platform channel to communicate between the Dart and the native sides, a message passing mechanism using the MethodChannel type. This mechanism depends on elements of the underlying UI engine to function.

The catch here is that isolates will provide a performance boost only in the case of computationally expensive dart code. The plugin's platform code will again use the main(UI) thread again.

Calling WidgetsFlutterBinding.ensureInitialized inside an isolate will also fail because of the absence of an underlying UI engine in the isolate.

Answer 6

in my case when using orientation,

before solved :

void main() {
SystemChrome.setPreferredOrientations([DeviceOrientation.portraitUp]).then((_).{
runApp(MyApp());
});
}

solved use :

void main() {
WidgetsFlutterBinding.ensureInitialized();
SystemChrome.setPreferredOrientations([DeviceOrientation.portraitUp])
  .then((_) {
runApp(MyApp());
});
}

The point is to add WidgetsFlutterBinding.ensureInitialized() in the first line of the main class

Answer 7

Solution: Call WidgetsFlutterBinding.ensureInitialized(); before calling asynchronous functions.

void main() async {
  WidgetsFlutterBinding.ensureInitialized();   //  ADD THIS BEFORE YOUR ASYNC FUNCTION CALL.
  await Firestore.instance.settings(...);      //  NOW YOU CAN CALL ASYNC FUNCTION.   
  ...
  runApp(
    ...
  )

Answer 8

Before I had the version v1.12.13+hotfix.5, then I switched to version v1.14.4 and it worked.

The error says that you should add WidgetsFlutterBinding.ensureInitialized();, but since that didn't work for me I switched to the other version. One thing to keep in mind though is that you still have to add WidgetsFlutterBinding.ensureInitialized(); as the very first line in your main!

Answer 9

An answer posted on the GitHub issue 47033 solved my problem.

issue: https://github.com/flutter/flutter/issues/47033

the solution that worked for me: https://github.com/flutter/flutter/issues/47033#issuecomment-571936089

I think this is an issue regarding the flutter version 1.12.13+hotfix maybe downgrading the flutter may help as well.

Answer 10

It's worth nothing that if you are receiving this error from an isolate, then the accepted solution doesn't work.

WidgetsFlutterBinding.ensureInitialized();

only ensures the binding on the main thread.
There is work being done to be able to remove the restriction, you can follow that issue here

https://github.com/flutter/flutter/issues/13937