如何在Flutter中使用CircularProgressIndicator
嗨，我设计了“忘记密码”屏幕，并在单击按钮时集成了Firebase。我想显示CircularProgressIndicator用户单击按钮的时间，并在Firebase执行完成时将其关闭。
有谁知道如何做到这一点 ？我想CircularProgressIndicator放在设备的中央。
class ForgotPasswordScreen extends StatelessWidget { final emailController = new TextEditingController();
final authHandler = new Auth();
@override
Widget build(BuildContext context) {
return new Scaffold(body: Container(
height: MediaQuery.of(context).size.height,
decoration: BoxDecoration(
color: Colors.white,
),
child: new Column(
crossAxisAlignment: CrossAxisAlignment.center,
mainAxisSize: MainAxisSize.max,
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
new Row(
children: <Widget>[
new Expanded(
child: new Padding(
padding: const EdgeInsets.only(left: 40.0),
child: new Text(
"EMAIL",
style: TextStyle(
fontWeight: FontWeight.bold,
color: Colors.redAccent,
fontSize: 15.0,
),
),
),
),
],
),
new Container(
width: MediaQuery.of(context).size.width,
margin: const EdgeInsets.only(left: 40.0, right: 40.0, top: 10.0),
alignment: Alignment.center,
decoration: BoxDecoration(
border: Border(
bottom: BorderSide(
color: Colors.redAccent,
width: 0.5,
style: BorderStyle.solid),
),
),
padding: const EdgeInsets.only(left: 0.0, right: 10.0),
child: new Row(
crossAxisAlignment: CrossAxisAlignment.center,
mainAxisAlignment: MainAxisAlignment.start,
children: <Widget>[
new Expanded(
child: TextField(
controller: emailController,
textAlign: TextAlign.left,
decoration: InputDecoration(
border: InputBorder.none,
hintText: 'PLEASE ENTER YOUR EMAIL',
hintStyle: TextStyle(color: Colors.grey),
),
),
),
],
),
),
Divider(
height: 24.0,
),
new Container(
width: MediaQuery.of(context).size.width,
margin: const EdgeInsets.only(left: 30.0, right: 30.0, top: 20.0),
alignment: Alignment.center,
child: new Row(
children: <Widget>[
new Expanded(
child: new FlatButton(
shape: new RoundedRectangleBorder(
borderRadius: new BorderRadius.circular(30.0),
),
color: Colors.redAccent,
onPressed: () => authHandler.sendPasswordResetEmail(emailController.text).then((void nothing) {
print("done");
}).catchError((e) => print(e)),
child: new Container(
padding: const EdgeInsets.symmetric(
vertical: 20.0,
horizontal: 20.0,
),
child: new Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
new Expanded(
child: Text(
"FORGOT PASSWORD",
textAlign: TextAlign.center,
style: TextStyle(
color: Colors.white,
fontWeight: FontWeight.bold),
),
),
],
),
),
),
),
],
),
),
],
),
));
}
}
回答：
好的，首先您必须稍微更改代码。
从更改Stateless为Stateful来管理小部件的状态，并放置一个名为的全局变量isLoading。您可以使用该变量，isLoading在按下按钮时将其设置为true，在按钮isLoading完成后将其设置为false。
在您的build方法内添加一个验证，以在isLoading为true 时显示循环进度，否则显示您的字段。
class ForgotPasswordScreen extends StatefulWidget { @override
ForgotPasswordScreenState createState() {
return new ForgotPasswordScreenState();
}
}
class ForgotPasswordScreenState extends State<ForgotPasswordScreen> {
final emailController = new TextEditingController();
final authHandler = new Auth();
bool isLoading = false;
@override
Widget build(BuildContext context) {
return new Scaffold(
body: Container(
height: MediaQuery.of(context).size.height,
decoration: BoxDecoration(
color: Colors.white,
),
child: isLoading
? Center(
child: CircularProgressIndicator(),
)
: new Column(
crossAxisAlignment: CrossAxisAlignment.center,
mainAxisSize: MainAxisSize.max,
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
new Row(
children: <Widget>[
new Expanded(
child: new Padding(
padding: const EdgeInsets.only(left: 40.0),
child: new Text(
"EMAIL",
style: TextStyle(
fontWeight: FontWeight.bold,
color: Colors.redAccent,
fontSize: 15.0,
),
),
),
),
],
),
new Container(
width: MediaQuery.of(context).size.width,
margin: const EdgeInsets.only(
left: 40.0, right: 40.0, top: 10.0),
alignment: Alignment.center,
decoration: BoxDecoration(
border: Border(
bottom: BorderSide(
color: Colors.redAccent,
width: 0.5,
style: BorderStyle.solid),
),
),
padding: const EdgeInsets.only(left: 0.0, right: 10.0),
child: new Row(
crossAxisAlignment: CrossAxisAlignment.center,
mainAxisAlignment: MainAxisAlignment.start,
children: <Widget>[
new Expanded(
child: TextField(
controller: emailController,
textAlign: TextAlign.left,
decoration: InputDecoration(
border: InputBorder.none,
hintText: 'PLEASE ENTER YOUR EMAIL',
hintStyle: TextStyle(color: Colors.grey),
),
),
),
],
),
),
Divider(
height: 24.0,
),
new Container(
width: MediaQuery.of(context).size.width,
margin: const EdgeInsets.only(
left: 30.0, right: 30.0, top: 20.0),
alignment: Alignment.center,
child: new Row(
children: <Widget>[
new Expanded(
child: new FlatButton(
shape: new RoundedRectangleBorder(
borderRadius: new BorderRadius.circular(30.0),
),
color: Colors.redAccent,
onPressed: () {
setState(() {
isLoading = true;
});
authHandler
.sendPasswordResetEmail(
emailController.text)
.then((void nothing) {
print("done");
setState(() {
isLoading = false;
});
}).catchError((e) => print(e));
},
child: new Container(
padding: const EdgeInsets.symmetric(
vertical: 20.0,
horizontal: 20.0,
),
child: new Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
new Expanded(
child: Text(
"FORGOT PASSWORD",
textAlign: TextAlign.center,
style: TextStyle(
color: Colors.white,
fontWeight: FontWeight.bold),
),
),
],
),
),
),
),
],
),
),
],
)));
}
}
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