我正在尝试验证自己的字段，然后再提交flutter。但是由于字段始终为空，因此验证始终为真，因此无法验证。
这是我尝试过的。有人可以帮助我确定我做错了什么吗？
如下所示，我什至设置了validators和controller。但是，即使字段为空，仍会提交
class _AddNewsState extends State<AddNews> {
GlobalKey<FormState> _key = GlobalKey<FormState>();
TextEditingController _headlineController;
TextEditingController _descriptionController;
String _dropDownActivity;
// get current date
static var now = new DateTime.now();
static var formatter = new DateFormat('yyyy-MM-dd');
String formattedDate = formatter.format(now);
// get current timie
dynamic currentTime = DateFormat.jm().format(DateTime.now());
@override
void initState() {
super.initState();
_headlineController = TextEditingController();
_descriptionController = TextEditingController();
_dropDownActivity = "";
}
@override
Widget build(BuildContext context) {
File _image;
String image_url = "";
FileImage _getImage() {
var img = (File(widget.imgPath));
setState(() {
_image = img;
});
return FileImage(_image);
}
Future _showToastMsg(String msgType, String msg) {
if (msgType == "success") {
return Fluttertoast.showToast(
msg: msg,
textColor: Colors.white,
toastLength: Toast.LENGTH_SHORT,
timeInSecForIosWeb: 1,
gravity: ToastGravity.BOTTOM,
backgroundColor: Colors.green,
);
} else if (msgType == "error") {
return Fluttertoast.showToast(
msg: msg,
textColor: Colors.white,
toastLength: Toast.LENGTH_SHORT,
timeInSecForIosWeb: 1,
gravity: ToastGravity.BOTTOM,
backgroundColor: Colors.red,
);
} else {
return Fluttertoast.showToast(
msg: msg,
textColor: Colors.white,
toastLength: Toast.LENGTH_SHORT,
timeInSecForIosWeb: 1,
gravity: ToastGravity.BOTTOM,
backgroundColor: Colors.black,
);
}
}
get_image_url_from_uploadPicture(String url) {
image_url = url;
return image_url;
}
showLoadingWhileSaving(BuildContext context) {
AlertDialog alert = AlertDialog(
content: new Row(
children: [
CircularProgressIndicator(),
Container(margin: EdgeInsets.only(left: 5), child: Text("Loading")),
],
),
);
showDialog(
barrierDismissible: false,
context: context,
builder: (BuildContext context) {
return alert;
},
);
}
Future _uploadPicture(BuildContext context) async {
String fileName = basename(_image.path);
StorageReference storageReference =
FirebaseStorage.instance.ref().child(fileName);
StorageUploadTask storageUploadTask = storageReference.putFile(_image);
showLoadingWhileSaving(context);
StorageTaskSnapshot storageTaskSnapshot =
await storageUploadTask.onComplete;
image_url =
await (await storageUploadTask.onComplete).ref.getDownloadURL();
get_image_url_from_uploadPicture(image_url);
Navigator.pop(context);
setState(() {
_showToastMsg("success", "News Successfully Saved!");
});
}
return Scaffold(
appBar: AppBar(
leading: Builder(
builder: (BuildContext context) {
return IconButton(
icon: const Icon(null),
color: Colors.white,
onPressed: () {},
);
},
),
centerTitle: true,
title: Text(
"Report a News",
),
backgroundColor: Colors.blueGrey,
),
body: Container(
child: SingleChildScrollView(
padding: const EdgeInsets.all(26.0),
child: Form(
key: _key,
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
mainAxisAlignment: MainAxisAlignment.start,
children: <Widget>[
Align(
alignment: Alignment.center,
child: GFImageOverlay(
border: Border.all(color: Colors.blueGrey, width: 4.0),
height: 200,
width: 200,
color: Colors.red,
shape: BoxShape.circle,
boxFit: BoxFit.fill,
image: (widget.imgPath != null)
? _getImage()
: AssetImage("images/default_news_image.png"),
)),
SizedBox(
height: 30.0,
),
TextFormField(
textInputAction: TextInputAction.next,
controller: _headlineController,
validator: (headline) {
if (headline == null || headline.isEmpty) {
_showToastMsg("error", "Please enter a Headline");
}
},
decoration: InputDecoration(
labelText: "Headline",
hintText: "Covid-19 new stats",
border: OutlineInputBorder(),
icon: Icon(Icons.add_box),
),
),
SizedBox(
height: 16.0,
),
TextFormField(
maxLines: 5,
textInputAction: TextInputAction.next,
controller: _descriptionController,
validator: (description) {
if (description == null || description.isEmpty) {
_showToastMsg("error", "Please provide a Headline");
}
},
decoration: InputDecoration(
labelText: "Description",
hintText: "Covid-19 new stats are sky-rock...",
border: OutlineInputBorder(),
icon: Icon(Icons.message),
),
),
SizedBox(
height: 16.0,
),
DropDownFormField(
titleText: 'Priority',
value: _dropDownActivity,
hintText: 'Select the priority',
onSaved: (value) {
setState(() {
_dropDownActivity = value;
});
},
onChanged: (value) {
setState(() {
_dropDownActivity = value;
});
},
validator: (value) {
if (value == null || value == "") {
_showToastMsg("error", "Please select a priority");
}
},
dataSource: [
{
"display": "High",
"value": "High",
},
{
"display": "Medium",
"value": "Medium",
},
{
"display": "Low",
"value": "Low",
},
],
textField: 'display',
valueField: 'value',
),
SizedBox(
height: 16.0,
),
Column(
mainAxisAlignment: MainAxisAlignment.start,
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
Row(
children: <Widget>[
GFButtonBadge(
size: GFSize.SMALL,
onPressed: () {
_showToastMsg(
"other", "Today is : ${formattedDate}");
},
icon: Icon(
Icons.calendar_today,
size: 16.0,
color: Colors.white,
),
text: '',
),
SizedBox(
width: 10.0,
),
Text(
"- ${formattedDate}",
style: TextStyle(fontSize: 18.0),
),
],
),
SizedBox(
height: 10.0,
),
Row(
children: <Widget>[
GFButtonBadge(
size: GFSize.SMALL,
onPressed: () {
_showToastMsg("other", "Time is : ${currentTime}");
},
icon: Icon(
Icons.alarm,
size: 16.0,
color: Colors.white,
),
text: '',
),
SizedBox(
width: 10.0,
),
Text(
"- ${currentTime}",
style: TextStyle(fontSize: 18.0),
),
],
),
SizedBox(
height: 14.0,
),
],
),
Align(
alignment: Alignment.center,
child: Text(
"Date and time will be saved automaticallt on \"Save\"",
textAlign: TextAlign.center,
style: TextStyle(
color: Colors.grey,
),
),
),
SizedBox(
height: 20.0,
),
Row(
crossAxisAlignment: CrossAxisAlignment.end,
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
children: <Widget>[
RaisedButton.icon(
icon: Icon(Icons.refresh),
color: Colors.orange,
textColor: Colors.white,
label: Text("Retake"),
onPressed: () async {
Navigator.of(context).pop();
},
),
RaisedButton.icon(
icon: Icon(Icons.add_a_photo),
color: Colors.green,
textColor: Colors.white,
label: Text("Snap"),
onPressed: () async {
try {
// first upload the photo
if (_key.currentState.validate()) {
_showToastMsg("other",
get_image_url_from_uploadPicture("cool"));
} else {
_showToastMsg("other",
get_image_url_from_uploadPicture("empty"));
}
// await FireStoreServiceApi().add_news(News(
// headline: _headlineController.text,
// description: _descriptionController.text,
// imageUrl: image_url,
// timeNews: currentTime.toString(),
// timeDate: formattedDate.toString(),
// priority: _dropDownActivity.toString(),
// ));
} catch (e) {
print(e);
}
},
),
],
),
],
),
),
),
),
);
}
}
告诉我我哪里出了问题以及如何解决
谢谢。
答案 0 :(得分：1)
无论何时要显示输入错误，都必须在String中返回一个validator。
TextFormField(
textInputAction: TextInputAction.next,
controller: _headlineController,
validator: (headline) {
if (headline == null || headline.isEmpty) {
return "Please enter a Headline";
}
return null;
},
decoration: InputDecoration(
labelText: "Headline",
hintText: "Covid-19 new stats",
border: OutlineInputBorder(),
icon: Icon(Icons.add_box),
),
),