查看此代码 - 获取数据并显示在列表上的小部件:
class _MyEventsFragmentState extends State <MyEventsFragment>{
var events;
@override
initState(){
super.initState();
events = fetchEvents(true);
}
@override
Widget build(BuildContext context) {
return new Center(
child: FutureBuilder<EventsResponse>(
future: events,
builder: (context, snapshot) {
if (snapshot.connectionState == ConnectionState.done) {
if (snapshot.hasError) {
helpers.logout(context, Strings.msg_session_expired);
return CircularProgressIndicator();
}
return new Container(color: Colors.white,
child: new ListControl().build(snapshot));
}
return CircularProgressIndicator();
},
)
);
}
}
fetchEvent
方法有参数来指示我需要获取哪些事件。如果设置为true, - 我的事件,如果设置为false - 返回所有事件。上面的代码加载我的事件,并在fetchEvents
覆盖内调用initState
以避免不必要的数据重新加载。
要获取所有事件,我定义了另一个类:
class EventsFragment extends StatefulWidget {
@override
_EventsFragmentState createState() => new _EventsFragmentState();
}
class _EventsFragmentState extends State <EventsFragment>{
var events;
@override
initState(){
super.initState();
events = fetchEvents(false);
}
@override
Widget build(BuildContext context) {
return new Center(
child: FutureBuilder<EventsResponse>(
future: events,
builder: (context, snapshot) {
if (snapshot.connectionState == ConnectionState.done) {
if (snapshot.hasError) {
helpers.logout(context, Strings.msg_session_expired);
return CircularProgressIndicator();
}
return new Container(color: Colors.white,
child: new ListControl().build(snapshot));
}
return CircularProgressIndicator();
},
)
);
}
}
但这是非常愚蠢的解决方案,因为代码几乎是一样的。所以我试图传递布尔值来指示要加载的事件,类似于:
@override
initState(){
super.initState();
events = fetchEvents(isMyEvents);
}
isMyEvents
应该来自EventsFragment
构造函数。但是,它不会在initState
内部访问。何正确通过?我可以在build
覆盖内访问它,但不能在initState
内访问它。如何正确传递它并确保每次创建窗口小部件实例时都会刷新它?
[编辑]
所以这就是我如何解决我的问题(看起来很好):
class EventsFragment extends StatefulWidget {
const EventsFragment({Key key, this.isMyEvent}) : super(key: key);
final bool isMyEvent;
@override
_EventsFragmentState createState() => new _EventsFragmentState();
}
class _EventsFragmentState extends State <EventsFragment>{
var events;
@override
initState(){
super.initState();
events = fetchEvents(widget.isMyEvent);
}
@override
void didUpdateWidget(EventsFragment oldWidget) {
if(oldWidget.isMyEvent != widget.isMyEvent)
events = fetchEvents(widget.isMyEvent);
super.didUpdateWidget(oldWidget);
}
@override
Widget build(BuildContext context) {
return new Center(
child: FutureBuilder<EventsResponse>(
future: events,
builder: (context, snapshot) {
if (snapshot.connectionState == ConnectionState.done) {
if (snapshot.hasError) {
helpers.logout(context, Strings.msg_session_expired);
return CircularProgressIndicator();
}
return new Container(color: Colors.white,
child: new ListControl().build(snapshot));
}
return CircularProgressIndicator();
},
)
);
}
}
将此参数传递给StatefulWidget
子类,然后使用该字段
class Foo extends StatefulWidget {
const Foo({Key key, this.isMyEvent}) : super(key: key);
final bool isMyEvent;
@override
_FooState createState() => _FooState();
}
class _FooState extends State<Foo> {
@override
void initState() {
super.initState();
print(widget.isMyEvent);
}
@override
Widget build(BuildContext context) {
return Container(
);
}
}