如何使警报对话框在颤振中工作

Question

>我正在使用以下代码来注册用户，有一个上传图像的选项，如果为空，则用户不会被注册，这是正常工作的，我唯一面临的是，如果图像null它应该向用户发出警报对话框，但警报对话框根本不起作用。 我应该如何实现警报对话框？

if (avatarImageFile != null ) {
FirebaseAuth.instance
.createUserWithEmailAndPassword(
email: emailInputController.text,
password: pwdInputController.text)
.then((currentUser) =>
Firestore.instance
.collection("users")
.document(currentUser.user.uid)
.setData({
"username": userNameInputController.text,
"email": emailInputController.text,
})
.then((result) =>
{
uploadFile(currentUser.user.uid),
print(currentUser.user.getIdToken()),
currentUser.user.sendEmailVerification(),
Navigator.pushAndRemoveUntil(
context,
MaterialPageRoute(
builder: (context) =>
MainScreen(
)),
(_) => false),
})
.catchError((err) => print(err)))
.catchError((err) => print(err));
}
else {
print("Please Upload the Image");
AlertDialog(
title: Text("Image Required"),
content: Text("Please upload the image"),
actions: <Widget>[
FlatButton(
child: Text("Close"),
onPressed: () {
Navigator.of(context).pop();
},
)
],
);
}

Answer 1

您需要使用该函数showDialog以便显示对话框：

else {
print("Please Upload the Image");
showDialog(
context: context,
builder: (BuildContext context) {
return AlertDialog(
title: Text("Image Required"),
content: Text("Please upload the image"),
actions: <Widget>[
FlatButton(
child: Text("Close"),
onPressed: () {
Navigator.of(context).pop();
},
)
],
);
};
);
}

Answer 2

Peter Haddad的回答解决了这个问题，但我建议将AlertDialog放在一个小部件中，以便再次重用AlertDialog。以下是我为我的项目所做的：

Dialogs.dart：

import 'package:flutter/material.dart';
enum alertDialogAction { cancel, save }
class Dialogs {
static Future<alertDialogAction> alertDialog(
BuildContext context,
String title,
String body,
String cancel,
String save,
) {
Future<alertDialogAction> action = showDialog(
context: context,
barrierDismissible: true,
builder: (BuildContext context) {
return AlertDialog(
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(10),
),
title: Text(title),
content: Text(body),
actions: <Widget>[
FlatButton(
onPressed: () =>
Navigator.pop(context, alertDialogAction.cancel),
child: Text(cancel)),
RaisedButton(
color: Colors.orange,
onPressed: () =>
Navigator.of(context).pop(alertDialogAction.save),
child: Text(
save,
style: TextStyle(color: Colors.white),
)),
],
);
});
return (action != null) ? action : alertDialogAction.cancel;
}

以下是您可以如何称呼它：

onPressed:() async {
final action= await Dialogs.alertDialog(context,"Title","Body","Cancel","Save");
//cancel and save are the button text for cancel and save operation
if(action==alertDialogAction.save){
//do something
Navigator.pop(context);
}
}

Answer 3

您还可以使用基架显示对话框，例如，

Scaffold.of(context).showSnackBar(SnackBar(content: AlertDialog(content: Text('Alert!!!'))));

但你必须记住，上下文应该是当前的脚手架。 因此，您可能希望将 body 属性(在 Scaffold 中(包装在构建器小部件中，然后在该构建器小部件中使用上下文时，该上下文将是当前基架。

Answer 4

showDialog(
context: context,
builder: (BuildContext context) {
return AlertDialog(
title: Text("Your Title!!!"),
content: Text("Your Content!!!"),
actions: <Widget>[
FlatButton(
child: Text("Close"),
onPressed: () {
Navigator.of(context).pop();
},
)
],
);
};
);