【发布时间】：2018-06-13 09:42:10
【问题描述】：
我有以下工作代码：
class Submit extends StatefulWidget {
@override
_SubmitState createState() => new _SubmitState();
}
class _SubmitState extends State<Submit> {
final scaffoldKey = new GlobalKey<ScaffoldState>();
final formKey = new GlobalKey<FormState>();
final myController = new TextEditingController();
double _w;
@override
void dispose() {
// Clean up the controller when the Widget is removed from the Widget tree
myController.dispose();
super.dispose();
}
void _submit() {
final form = formKey.currentState;
if (form.validate()) {
form.save();
_performSubmit();
}
}
void _performSubmit() {
final double data = double.parse(myController.text)*(2);
var route = new MaterialPageRoute(builder: (BuildContext context) =>
new NextPage(w1: data.toStringAsFixed(3)),
);
Navigator.of(context).push(route);
}
@override
Widget build(BuildContext context) {
void _restart() {
Navigator.of(context).push(new MaterialPageRoute(
builder: (BuildContext context) => new HomePage()));
}
return new Scaffold(
key: scaffoldKey,
appBar: new AppBar(
actions: <Widget>[
],
title: new Text('Next Page'),
),
body: new Form(
key: formKey,
child: new Column(
children: [
new TextFormField(
controller: myController,
keyboardType: TextInputType.numberWithOptions(decimal: true),
onSaved: (val) => _w = double.parse(val),
),
new RaisedButton(
onPressed: _submit,
child: new Text(
'Next Page',
),
)
],
),
),
);
}
}
class NextPage extends StatefulWidget {
final String w1;
NextPage({Key key, this.w1}) : super (key: key);
@override
_NextPageState createState() => _NextPageState();
}
class _NextPageState extends State<NextPage> {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: new AppBar(
title: new Text("Second page")
),
body: new Text("${widget.w1}")
);
}
}
在这里，我传递了一个乘以 2 的变量（称为 w1），然后在下一个屏幕上显示它（NextScreen）和 Text。但我想要一个列表中的结果，该列表与我接下来展示的其他类一起定义。我想显示变量w1 的值，其中文本1.1 是（在List<Entry> 内）。接下来我有完整的代码，但我不知道如何传递变量。如果我写new Entry('${widget.w1}',),，我会得到undefined name widget。
如何将我的变量传递给该列表？
class Submit extends StatefulWidget {
@override
_SubmitState createState() => new _SubmitState();
}
class _SubmitState extends State<Submit> {
final scaffoldKey = new GlobalKey<ScaffoldState>();
final formKey = new GlobalKey<FormState>();
final myController = new TextEditingController();
double _w;
@override
void dispose() {
// Clean up the controller when the Widget is removed from the Widget tree
myController.dispose();
super.dispose();
}
void _submit() {
final form = formKey.currentState;
if (form.validate()) {
form.save();
_performSubmit();
}
}
void _performSubmit() {
final double data = double.parse(myController.text)*(2);
var route = new MaterialPageRoute(builder: (BuildContext context) =>
new NextPage(w1: data.toStringAsFixed(3)),
);
Navigator.of(context).push(route);
}
@override
Widget build(BuildContext context) {
void _restart() {
Navigator.of(context).push(new MaterialPageRoute(
builder: (BuildContext context) => new HomePage()));
}
return new Scaffold(
key: scaffoldKey,
appBar: new AppBar(
actions: <Widget>[
],
title: new Text('Next Page'),
),
body: new Form(
key: formKey,
child: new Column(
children: [
new TextFormField(
controller: myController,
keyboardType: TextInputType.numberWithOptions(decimal: true),
onSaved: (val) => _w = double.parse(val),
),
new RaisedButton(
onPressed: _submit,
child: new Text(
'Next Page',
),
)
],
),
),
);
}
}
class NextPage extends StatefulWidget {
final String w1;
NextPage({Key key, this.w1}) : super (key: key);
@override
_NextPageState createState() => _NextPageState();
}
class _NextPageState extends State<NextPage> {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: new AppBar(
title: new Text("Second page")
),
body: new ListView.builder(
itemBuilder: (BuildContext context, int index) =>
new EntryItem(data[index]),
itemCount: data.length,
),
);
}
}
// One entry in the multilevel list displayed by this app.
class Entry {
Entry(this.title, [this.children = const <Entry>[]]);
final String title;
final List<Entry> children;
}
// The entire multilevel list displayed by this app.
List<Entry> data = <Entry>[
new Entry(
'First',
<Entry>[
new Entry(
'1.1',
),
],
),
];
// Displays one Entry. If the entry has children then it's displayed
// with an ExpansionTile.
class EntryItem extends StatelessWidget {
const EntryItem(this.entry);
final Entry entry;
Widget _buildTiles(Entry root) {
if (root.children.isEmpty)
return new ListTile(
title: new Text(root.title));
return new ExpansionTile(
key: new PageStorageKey<Entry>(root),
title: new Text(root.title,),
children: root.children.map(_buildTiles).toList(),
);
}
@override
Widget build(BuildContext context) {
return _buildTiles(entry);
}
}
【问题讨论】：
-
这里的代码太多了。你能提供一个minimal功能的例子吗？
-
@RémiRousselet 我已经编辑了帖子，并在不破坏它的情况下尽可能地最小化了代码。请注意，第二个代码是第一个带有可扩展列表的代码