问题
I am learning to build apps in Flutter. Now I have come to alert dialogs. I have done them before in Android and iOS, but how do I make an alert in Flutter?
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I'd like to make a more general canonical Q&A so my answer is below.
回答1:
One Button
showAlertDialog(BuildContext context) {
// set up the button
Widget okButton = FlatButton(
child: Text("OK"),
onPressed: () { },
);
// set up the AlertDialog
AlertDialog alert = AlertDialog(
title: Text("My title"),
content: Text("This is my message."),
actions: [
okButton,
],
);
// show the dialog
showDialog(
context: context,
builder: (BuildContext context) {
return alert;
},
);
}
Two Buttons
showAlertDialog(BuildContext context) {
// set up the buttons
Widget cancelButton = FlatButton(
child: Text("Cancel"),
onPressed: () {},
);
Widget continueButton = FlatButton(
child: Text("Continue"),
onPressed: () {},
);
// set up the AlertDialog
AlertDialog alert = AlertDialog(
title: Text("AlertDialog"),
content: Text("Would you like to continue learning how to use Flutter alerts?"),
actions: [
cancelButton,
continueButton,
],
);
// show the dialog
showDialog(
context: context,
builder: (BuildContext context) {
return alert;
},
);
}
Three Buttons
showAlertDialog(BuildContext context) {
// set up the buttons
Widget remindButton = FlatButton(
child: Text("Remind me later"),
onPressed: () {},
);
Widget cancelButton = FlatButton(
child: Text("Cancel"),
onPressed: () {},
);
Widget launchButton = FlatButton(
child: Text("Launch missile"),
onPressed: () {},
);
// set up the AlertDialog
AlertDialog alert = AlertDialog(
title: Text("Notice"),
content: Text("Launching this missile will destroy the entire universe. Is this what you intended to do?"),
actions: [
remindButton,
cancelButton,
launchButton,
],
);
// show the dialog
showDialog(
context: context,
builder: (BuildContext context) {
return alert;
},
);
}
Handling button presses
The onPressed callback for the buttons in the examples above were empty, but you could add something like this:
Widget launchButton = FlatButton(
child: Text("Launch missile"),
onPressed: () {
Navigator.of(context).pop(); // dismiss dialog
launchMissile();
},
);
If you make the callback null, then the button will be disabled.
onPressed: null,
Supplemental code
Here is the code for main.dart in case you weren't getting the functions above to run.
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter',
home: Scaffold(
appBar: AppBar(
title: Text('Flutter'),
),
body: MyLayout()),
);
}
}
class MyLayout extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Padding(
padding: const EdgeInsets.all(8.0),
child: RaisedButton(
child: Text('Show alert'),
onPressed: () {
showAlertDialog(context);
},
),
);
}
}
// replace this function with the examples above
showAlertDialog(BuildContext context) { ... }
回答2:
Or you can use RFlutter Alert library for that. It is easily customizable and easy-to-use. Its default style includes rounded corners and you can add buttons as much as you want.
Basic Alert:
Alert(context: context, title: "RFLUTTER", desc: "Flutter is awesome.").show();
Alert with Button:
Alert(
context: context,
type: AlertType.error,
title: "RFLUTTER ALERT",
desc: "Flutter is more awesome with RFlutter Alert.",
buttons: [
DialogButton(
child: Text(
"COOL",
style: TextStyle(color: Colors.white, fontSize: 20),
),
onPressed: () => Navigator.pop(context),
width: 120,
)
],
).show();
You can also define generic alert styles.
*I'm one of developer of RFlutter Alert.
回答3:
You can use this code snippet for creating a two buttoned Alert box,
import 'package:flutter/material.dart';
class BaseAlertDialog extends StatelessWidget {
//When creating please recheck 'context' if there is an error!
Color _color = Color.fromARGB(220, 117, 218 ,255);
String _title;
String _content;
String _yes;
String _no;
Function _yesOnPressed;
Function _noOnPressed;
BaseAlertDialog({String title, String content, Function yesOnPressed, Function noOnPressed, String yes = "Yes", String no = "No"}){
this._title = title;
this._content = content;
this._yesOnPressed = yesOnPressed;
this._noOnPressed = noOnPressed;
this._yes = yes;
this._no = no;
}
@override
Widget build(BuildContext context) {
return AlertDialog(
title: new Text(this._title),
content: new Text(this._content),
backgroundColor: this._color,
shape:
RoundedRectangleBorder(borderRadius: new BorderRadius.circular(15)),
actions: <Widget>[
new FlatButton(
child: new Text(this._yes),
textColor: Colors.greenAccent,
onPressed: () {
this._yesOnPressed();
},
),
new FlatButton(
child: Text(this._no),
textColor: Colors.redAccent,
onPressed: () {
this._noOnPressed();
},
),
],
);
}
}
OUTPUT WILL BE LIKE THIS
回答4:
If you want beautiful and responsive alert dialog then you can use flutter packages like
rflutter alert ,fancy dialog,rich alert,sweet alert dialogs,easy dialog & easy alert
These alerts are good looking and responsive. Among them rflutter alert is the best. currently I am using rflutter alert for my apps.
回答5:
Check out Flutter Dropdown Banner to easily alert users of events and prompt action without having to manage the complexity of presenting, delaying, and dismissing the component.
To set it up:
import 'packages:dropdown_banner/dropdown_banner.dart';
...
class MainApp extends StatelessWidget {
...
@override
Widget build(BuildContext context) {
final navigatorKey = GlobalKey<NavigatorState>();
...
return MaterialApp(
...
home: DropdownBanner(
child: Scaffold(...),
navigatorKey: navigatorKey,
),
);
}
}
To use it:
import 'packages:dropdown_banner/dropdown_banner.dart';
...
class SomeClass {
...
void doSomethingThenFail() {
DropdownBanner.showBanner(
text: 'Failed to complete network request',
color: Colors.red,
textStyle: TextStyle(color: Colors.white),
);
}
}
来源：https://stackoverflow.com/questions/53844052/how-to-make-an-alertdialog-in-flutter