Flutter_bloc框架使用笔记，后续估计都不太会用了，android界面开发工具

body: BlocProvider(
create: (_) => _registerBloc,
child: RegisterScreen(widget.phone),
)

这里是为后续的节点注册了一个RegisterBloc, 从这个节点下级的widget就可以通过Provider.of<RegisterBloc>来获取。 当然也可以有其他的方式比如context.read<RegisterBloc>来获取。

这里也可以把bloc传给screen,可以方便在screen里面获取bloc。而不是通过在配置树里查找bloc。能稍微减少些性能消耗。

2. screen

screen主要是构建配置页面内容用。

class RegisterScreen extends StatelessWidget {
const RegisterScreen(
this.phone, {

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Key? key,
}) : super(key: key);

final String phone;

@override
Widget build(BuildContext context) {
return BlocListener<RegisterBloc, RegisterState>(
listener: (ctx, state) {
if (state.status.isSubmissionInProgress) {
EasyLoading.show(
maskType: EasyLoadingMaskType.clear, dismissOnTap: false);
return;
}
if (state.status.isSubmissionFailure) {
EasyLoading.dismiss();
var message = LS.of(context, “register_error”);
EasyLoading.showError(’$message:${state.errMessage ?? ‘’}’);
return;
}
if (state.status.isSubmissionSuccess) {
EasyLoading.dismiss();
showCupertinoDialog(
context: context,
builder: (context) {
return
AlertDialog(
content: Text(LS.of(context, “register_success”)),
actions: [TextButton(onPressed: (){
Navigator.of(context).popUntil(ModalRoute.withName("/"));
}, child: Text(LS.of(context, “confirm”)))],
);
});
}
},
child: Align(
alignment: Alignment(0, -1),
child: Padding(
padding: const EdgeInsets.only(top: 31, left: 36, right:36),
child: Column(children: [
_UsernameInput(),
_PasswordInput(),
_ConfirmPasswordInput(),
const SizedBox(
height: 20,
),
_RegisterButton()
]),
),
));
}
}

class _RegisterButton extends StatelessWidget {
@override
Widget build(BuildContext context) {
return BlocBuilder<RegisterBloc, RegisterState>(builder: (context, state) {
return CircleRectButton(
child: Text(LS.of(context, “register”), style: TextStyle(letterSpacing: 20)),
onPressed: state.status.isValidated
? () async {
context.read().add(RegisterSubmitEvent());
}
: null);
});
}
}

BlocListener： 通过BlocListener来监听状态消息，收到消息child不会rebuild。适合拿来弹出加载页，错误信息等。

BlocBuilder 通过BlocBuilder来包装需要修改的内容。 这里的在组装页面的时候尽量在涉及到更新的地方使用 BlocBuilder,也尽可能的考虑buildwhen 属性。保持当必须要更新时才重新build的思路。

3. bloc

bloc 在封装后没什么逻辑，他的思路就是接受页面的事件，转为状态变更返回给页面。

class RegisterBloc extends Bloc<RegisterEvent, RegisterState> {

RegisterBloc(RegisterState initialState) : super(initialState);

@override
Stream mapEventToState(
RegisterEvent event,
) async* {
try {
yield* event.applyAsync(currentState: state, bloc: this);
} catch (, stackTrace) {
developer.log(’$’, name: ‘RegisterBloc’, error: _, stackTrace: stackTrace);
yield state;
}
}
}

将对应的事件处理放在event里面去执行显然更符合设计模式。代码也会更清晰，而不用做很多判断

if(event is event){
do()
} else if (event is event) {
do()
}

4. event

@immutable
abstract class RegisterEvent {
const RegisterEvent();
Stream applyAsync({required RegisterState currentState, required RegisterBloc bloc});
}

class UsernameChangeEvent extends RegisterEvent {
const UsernameChangeEvent(this.username);
final String username;

Stream applyAsync({required RegisterState currentState, required RegisterBloc bloc}) async* {
var input = UsernameInput.dirty(username);
var status = Formz.validate([input, currentState.password, currentState.confirmPassword]);
yield currentState.copyWith(username: input, status: status);
}

}

抽象event，定义事件接口。 子类event来接收参数，实现事件接口并抛出新的状态给页面。

5. state

class RegisterState extends Equatable {
final UsernameInput username;
final PasswordTwoInput password;
final PasswordTwoInput confirmPassword;
final FormzStatus status;
final String? errMessage;
RegisterState({
this.username = const UsernameInput.pure(),
this.password = const PasswordTwoInput.pure(),
this.confirmPassword = const PasswordTwoInput.pure(),
this.status = FormzStatus.pure,
this.errMessage
});

@override
List get props => [username, password, confirmPassword, status];

RegisterState copyWith({
UsernameInput? username,
PasswordTwoInput? password,
PasswordTwoInput? confirmPassword,
FormzStatus? status,
}) {
return RegisterState(
username: username ?? this.username,
password: password ?? this.password,
confirmPassword: confirmPassword ?? this.confirmPassword,