thewckd / blocfromzerotohero Goto Github PK

Hi WCKD,
I use route access method to locally provide bloc just like how you do in the youtube tutorial. However the situation is a bit weird. The thing is that after exception the program does not shutdown and the widget depending on the bloc(DatesBloc) seems to work correctly, which means it finds the bloc and give the correct responses to the widget just causing exception earlier. What's more, if I provide the bloc in homepage wrapping DatesPage instead of providing it by route, the exception is just gone. And, if I exchange the order of DatesPage and ChatsPage in HomePage, it turns out to be that it is ChatsBloc causes the exception instead of DatesBloc. Is there any possible reason to this phenomenon or any possible solution to resolve this issue?

I am trying to run the code with null safety enabled in the project. I keep getting the following error when I run the test on counter_cubit_test.dart:

Null check operator used on a null value

This is the code in the counter_cubit.dart file:

import 'package:bloc/bloc.dart';
import 'package:equatable/equatable.dart';

part 'counter_state.dart';

class CounterCubit extends Cubit<CounterState> {
  CounterCubit() : super(CounterState(counterValue: 0));

  void increment() => emit(
      CounterState(counterValue: state.counterValue! + 1, wasIncremented: true));

  void decrement() => emit(CounterState(
      counterValue: state.counterValue! - 1, wasIncremented: false));
}

This is the code in the counter_state.dart file:

part of 'counter_cubit.dart';

class CounterState extends Equatable {
  final int? counterValue;
  final bool? wasIncremented;

  CounterState({required this.counterValue, this.wasIncremented});

  @override
  List<Object> get props => [this.counterValue!, this.wasIncremented!];
}

This is the code in the main.dart file:

import 'package:flutter/material.dart';
import 'package:flutter_bloc/flutter_bloc.dart';
import 'package:flutter_counter_bloc/cubits/counter_cubit.dart';

void main() => runApp(MyApp());

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: "Flutter Demo",
      theme: ThemeData(
        primaryColor: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: BlocProvider<CounterCubit>(
        create: (context) => CounterCubit(),
        child: MyHomePage(title: "Flutter Demo Home Page"),
      ),
    );
  }
}

///Used a stateless widget since state is handled by the Bloc library in this case. I referred the
///following link: https://stackoverflow.com/questions/58864869/flutter-state-management-bloc-stateless-vs-stateful-widget
class MyHomePage extends StatelessWidget {
  final String? title;

  const MyHomePage({Key? key, this.title}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(title!),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            Text("You have pushed this button this many times:"),
            BlocConsumer<CounterCubit, CounterState>(
              ///Refactored the if...else block into a function to show the SnackBar Widget
                listener: (context, state) => snackBarFunction(state.wasIncremented!, context),
                ///Refactored the if...else block into a function that returns a Text widget
                builder: (context, state) => counterText(state.counterValue!, context)),
            SizedBox(height: 24),
            Row(
              mainAxisAlignment: MainAxisAlignment.spaceEvenly,
              children: [
                FloatingActionButton(
                  onPressed: () => BlocProvider.of<CounterCubit>(context).decrement(),
                  heroTag: Text("$title"),
                  tooltip: "Decrement",
                  child: Icon(Icons.remove),
                ),
                FloatingActionButton(
                  onPressed: () => BlocProvider.of<CounterCubit>(context).increment(),
                  heroTag: Text("$title #2"),
                  tooltip: "Increment",
                  child: Icon(Icons.add),
                ),
              ],
            )
          ],
        ),
      ),
    );
  }
}

///This function is used to show the snack bar widget depending on whether the counter was incremented
///or decremented
void snackBarFunction(bool counterState, context) {
  if (counterState == true) {
    ///Scaffold.of(context).showSnackBar(snackBar) is deprecated
    ///Using ScaffoldMessenger.of(context).showSnackBar(snackBar) instead
    ScaffoldMessenger.of(context).showSnackBar(SnackBar(
      content: Text("Incremented!"),
      duration: Duration(milliseconds: 300),
    ));
  } else {
    ScaffoldMessenger.of(context).showSnackBar(SnackBar(
      content: Text("Decremented!"),
      duration: Duration(milliseconds: 300),
    ));
  }
}

///This function is used to change the returned Text widget in accordance with the value of the counter
Text counterText(int counterValue, context) {
  if (counterValue < 0) {
    return Text("BRR, Negative $counterValue",
        style: Theme.of(context).textTheme.headline4);
  } else if (counterValue % 2 == 0) {
    return Text("YAAAY $counterValue",
        style: Theme.of(context).textTheme.headline4);
  } else if (counterValue == 5) {
    return Text("HMM, NUMBER 5", style: Theme.of(context).textTheme.headline4);
  } else {
    return Text("$counterValue",
        style: Theme.of(context).textTheme.headline4);
  }
}

This is the code in the counter_cubit_test.dart file:

import 'package:flutter_counter_bloc/cubits/counter_cubit.dart';
import 'package:test/test.dart';
import 'package:bloc_test/bloc_test.dart';

void main() {
  group("CounterCubit", (){

    CounterCubit? counterCubit;

    setUp((){
      counterCubit = CounterCubit();
    });
    tearDown((){
      counterCubit!.close();
    });

    test("Initial state of CounterCubit is CounterState(counterValue: 0)", () {
      expect(counterCubit!.state, CounterState(counterValue: 0));
    });

    blocTest<CounterCubit, CounterState>(
      'the CounterCubit should emit a CounterState(counterValue:1, wasIncremented:true) when the increment function is called',
      build: () => counterCubit!,
      act: (cubit) => cubit.increment(),
      expect: () => <CounterState>[CounterState(counterValue: 1, wasIncremented: true)],
    );

    blocTest<CounterCubit, CounterState>(
      'the CounterCubit should emit a CounterState(counterValue:-1, wasIncremented:false) when the decrement function is called',
      build: () => counterCubit!,
      act: (cubit) => cubit.decrement(),
      expect: () => <CounterState>[CounterState(counterValue: -1, wasIncremented: false)],
    );
  });
}

I am following your tutorial and for some reason when I am just pushing the second screen , it does not crash and works as intended. I am using bloc 8.1 and Flutter 3.10. Has there been an update that now supports Flutter anonymous routes or now the two pages share a context?

Improperly formatted define flag: Blocs

FAILURE: Build failed with an exception.

• Where:
  Script '/Users/a35850/development/flutter/packages/flutter_tools/gradle/flutter.gradle' line: 1035

• What went wrong:
  Execution failed for task ':app:compileFlutterBuildDebug'.

Process 'command '/Users/a35850/development/flutter/bin/flutter'' finished with non-zero exit value 1

• Try:
  Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.

• Get more help at https://help.gradle.org

BUILD FAILED in 1s
Exception: Gradle task assembleDebug failed with exit code 1

CounterState({@required this.counterValue, this.wasIncremented});

this shows an error and it works fine when i remove '@' from required, it also asks to add required to 'this.wasIncremented' .
means CounterState({required this.counterValue, required this.wasIncremented}); works fine ,
but in counter_cubit it asks to pass the required parameter of 'this.wasIncremented' in countercubit()

For those like me who found the repo but not a link to the course, here it is:
https://www.youtube.com/watch?v=w6XWjpBK4W8&list=PLptHs0ZDJKt_T-oNj_6Q98v-tBnVf-S_o

@flutterly, awesome course so far but i seem to be stuck at (1:21:00) my error is

The argument type 'List' can't be assigned to the parameter type 'dynamic Function()'. [29,17]
The argument type 'List' can't be assigned to the parameter type 'dynamic Function()'. [35,17]
so i went on to run the test and it FAILED... :'(

please could you or someone facing the same error/ OVERCAME this error kindly assist... thanks! :)

With current Dart (2.12.2 - I don't know how it worked in the past) this line is always called as break only jumps out of switch, not a method. Because of that, there is always an error returned and printed into the console:

D:\SDK\Flutter\flutter\bin\cache\dart-sdk\bin\dart.exe --enable-asserts D:\Projects\Tutorials\Flutter\blockhero\tryout\lib\main-bloc.dart
lib/main-bloc.dart: Warning: Interpreting this as package URI, 'package:streams/main-bloc.dart'.
1
Unhandled exception:
Unhandled error UnimplementedError occurred in Instance of 'CounterBloc'.
#0 CounterBloc.mapEventToState (package:streams/main-bloc.dart:18:5)

#0 BlocBase.onError. (package:bloc/src/bloc.dart:389:7)
#1 BlocBase.onError (package:bloc/src/bloc.dart:390:6)
#2 _RootZone.runBinaryGuarded (dart:async/zone.dart:1558:10)
#3 _BufferingStreamSubscription._sendError.sendError (dart:async/stream_impl.dart:360:15)
#4 _BufferingStreamSubscription._sendError (dart:async/stream_impl.dart:378:16)
#5 _BufferingStreamSubscription._addError (dart:async/stream_impl.dart:280:7)
#6 _SyncBroadcastStreamController._sendError. (dart:async/broadcast_stream_controller.dart:393:20)
#7 _BroadcastStreamController._forEachListener (dart:async/broadcast_stream_controller.dart:323:15)
#8 _SyncBroadcastStreamController._sendError (dart:async/broadcast_stream_controller.dart:392:5)
#9 _BroadcastStreamController._addError (dart:async/broadcast_stream_controller.dart:290:5)
#10 _RootZone.runBinaryGuarded (dart:async/zone.dart:1558:10)
#11 _BufferingStreamSubscription._sendError.sendError (dart:async/stream_impl.dart:360:15)
#12 _BufferingStreamSubscription._sendError (dart:async/stream_impl.dart:378:16)
#13 _BufferingStreamSubscription._addError (dart:async/stream_impl.dart:280:7)
#14 _ForwardingStreamSubscription._addError (dart:async/stream_pipe.dart:128:11)
#15 _ForwardingStream._handleError (dart:async/stream_pipe.dart:95:10)
#16 _ForwardingStreamSubscription._handleError (dart:async/stream_pipe.dart:157:13)
#17 _RootZone.runBinaryGuarded (dart:async/zone.dart:1558:10)
#18 _BufferingStreamSubscription._sendError.sendError (dart:async/stream_impl.dart:360:15)
#19 _BufferingStreamSubscription._sendError (dart:async/stream_impl.dart:378:16)
#20 _DelayedError.perform (dart:async/stream_impl.dart:602:14)
#21 _StreamImplEvents.handleNext (dart:async/stream_impl.dart:706:11)
#22 _PendingEvents.schedule. (dart:async/stream_impl.dart:663:7)
#23 _microtaskLoop (dart:async/schedule_microtask.dart:40:21)
#24 _startMicrotaskLoop (dart:async/schedule_microtask.dart:49:5)
#25 _runPendingImmediateCallback (dart:isolate-patch/isolate_patch.dart:120:13)
#26 _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:185:5)

Process finished with exit code 255

if navigate to second or third screen an press the increase or decrease button snackbar showing up one time and when you back to the previous screen snakbar showing up again same number of latest screen.