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Description:

flow builder

Flutter Flows made easy!

Usage #
Define a Flow State #
The flow state will be the state which drives the flow. Each time this state changes, a new navigation stack will be generated based on the new flow state.
class Profile {
const Profile({this.name, this.age, this.weight});

final String? name;
final int? age;
final int? weight;

Profile copyWith({String? name, int? age, int? weight}) {
return Profile(
name: name ?? this.name,
age: age ?? this.age,
weight: weight ?? this.weight,
);
}
}
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Create a FlowBuilder #
FlowBuilder is a widget which builds a navigation stack in response to changes in the flow state. onGeneratePages will be invoked for each state change and must return the new navigation stack as a list of pages.
FlowBuilder<Profile>(
state: const Profile(),
onGeneratePages: (profile, pages) {
return [
MaterialPage(child: NameForm()),
if (profile.name != null) MaterialPage(child: AgeForm()),
];
},
);
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Update the Flow State #
The state of the flow can be updated via context.flow<T>().update.
class NameForm extends StatefulWidget {
@override
_NameFormState createState() => _NameFormState();
}

class _NameFormState extends State<NameForm> {
var _name = '';

void _continuePressed() {
context.flow<Profile>().update((profile) => profile.copyWith(name: _name));
}

@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: const Text('Name')),
body: Center(
child: Column(
children: <Widget>[
TextField(
onChanged: (value) => setState(() => _name = value),
decoration: InputDecoration(
labelText: 'Name',
hintText: 'John Doe',
),
),
RaisedButton(
child: const Text('Continue'),
onPressed: _name.isNotEmpty ? _continuePressed : null,
)
],
),
),
);
}
}
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Complete the Flow #
The flow can be completed via context.flow<T>().complete.
class AgeForm extends StatefulWidget {
@override
_AgeFormState createState() => _AgeFormState();
}

class _AgeFormState extends State<AgeForm> {
int? _age;

void _continuePressed() {
context
.flow<Profile>()
.complete((profile) => profile.copyWith(age: _age));
}

@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: const Text('Age')),
body: Center(
child: Column(
children: <Widget>[
TextField(
onChanged: (value) => setState(() => _age = int.parse(value)),
decoration: InputDecoration(
labelText: 'Age',
hintText: '42',
),
keyboardType: TextInputType.number,
),
RaisedButton(
child: const Text('Continue'),
onPressed: _age != null ? _continuePressed : null,
)
],
),
),
);
}
}
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FlowController #
A FlowBuilder can also be created with a custom FlowController in cases where the flow can be manipulated outside of the sub-tree.
class MyFlow extends StatefulWidget {
@override
State<MyFlow> createState() => _MyFlowState();
}

class _MyFlowState extends State<MyFlow> {
late FlowController<Profile> _controller;

@override
void initState() {
super.initState();
_controller = FlowController(const Profile());
}

@override
Widget build(BuildContext context) {
return FlowBuilder(
controller: _controller,
onGeneratePages: ...,
);
}

@override dispose() {
_controller.dispose();
super.dispose();
}
}
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