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samples/place_tracker/lib/app_model.dart

71 lines
1.7 KiB

import 'package:flutter/material.dart';
class _AppModelScope<T> extends InheritedWidget {
const _AppModelScope({
Key key,
this.appModelState,
Widget child,
}) : super(key: key, child: child);
final _AppModelState<T> appModelState;
@override
bool updateShouldNotify(_AppModelScope oldWidget) => true;
}
class AppModel<T> extends StatefulWidget {
AppModel({
Key key,
@required this.initialState,
this.child,
}) : assert(initialState != null),
super(key: key);
final T initialState;
final Widget child;
_AppModelState<T> createState() => _AppModelState<T>();
static Type _typeOf<T>() => T;
static T of<T>(BuildContext context) {
final Type appModelScopeType = _typeOf<_AppModelScope<T>>();
final _AppModelScope<T> scope = context
.inheritFromWidgetOfExactType(appModelScopeType) as _AppModelScope<T>;
return scope.appModelState.currentState;
}
static void update<T>(BuildContext context, T newState) {
final Type appModelScopeType = _typeOf<_AppModelScope<T>>();
final _AppModelScope<T> scope = context
.inheritFromWidgetOfExactType(appModelScopeType) as _AppModelScope<T>;
scope.appModelState.updateState(newState);
}
}
class _AppModelState<T> extends State<AppModel<T>> {
@override
void initState() {
super.initState();
currentState = widget.initialState;
}
T currentState;
void updateState(T newState) {
if (newState != currentState) {
setState(() {
currentState = newState;
});
}
}
@override
Widget build(BuildContext context) {
return _AppModelScope<T>(
appModelState: this,
child: widget.child,
);
}
}