How to make an AlertDialog in Flutter? - dart

Question

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?
Here are some related SO questions:
How to style AlertDialog Actions in Flutter
adding dropdown menu in alert dialog box in flutter
Show alert dialog on app main screen load automatically
how to refresh alertdialog in flutter
Alert Dialog with Rounded corners in flutter
I'd like to make a more general canonical Q&A so my answer is below.

Answer 1

One Button
showAlertDialog(BuildContext context) {
// set up the button
Widget okButton = TextButton(
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 = TextButton(
child: Text("Cancel"),
onPressed: () {},
);
Widget continueButton = TextButton(
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 = TextButton(
child: Text("Remind me later"),
onPressed: () {},
);
Widget cancelButton = TextButton(
child: Text("Cancel"),
onPressed: () {},
);
Widget launchButton = TextButton(
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 = TextButton(
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: ElevatedButton(
child: Text('Show alert'),
onPressed: () {
showAlertDialog(context);
},
),
);
}
}
// replace this function with the examples above
showAlertDialog(BuildContext context) { ... }

Answer 2

I used similar approach, but I wanted to
Keep the Dialog code as a widget in a separated file so I can reuse it.
Blurr the background when the dialog is shown.
Code:
1. alertDialog_widget.dart
import 'dart:ui';
import 'package:flutter/material.dart';
class BlurryDialog extends StatelessWidget {
String title;
String content;
VoidCallback continueCallBack;
BlurryDialog(this.title, this.content, this.continueCallBack);
TextStyle textStyle = TextStyle (color: Colors.black);
#override
Widget build(BuildContext context) {
return BackdropFilter(
filter: ImageFilter.blur(sigmaX: 6, sigmaY: 6),
child: AlertDialog(
title: new Text(title,style: textStyle,),
content: new Text(content, style: textStyle,),
actions: <Widget>[
new FlatButton(
child: new Text("Continue"),
onPressed: () {
continueCallBack();
},
),
new FlatButton(
child: Text("Cancel"),
onPressed: () {
Navigator.of(context).pop();
},
),
],
));
}
}
You can call this in main (or wherever you want) by creating a new method like:
_showDialog(BuildContext context)
{
VoidCallback continueCallBack = () => {
Navigator.of(context).pop(),
// code on continue comes here
};
BlurryDialog alert = BlurryDialog("Abort","Are you sure you want to abort this operation?",continueCallBack);
showDialog(
context: context,
builder: (BuildContext context) {
return alert;
},
);
}

Answer 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();
},
),
],
);
}
}
To show the dialog you can have a method that calls it NB after importing BaseAlertDialog class
_confirmRegister() {
var baseDialog = BaseAlertDialog(
title: "Confirm Registration",
content: "I Agree that the information provided is correct",
yesOnPressed: () {},
noOnPressed: () {},
yes: "Agree",
no: "Cancel");
showDialog(context: context, builder: (BuildContext context) => baseDialog);
}
OUTPUT WILL BE LIKE THIS

Answer 4

Here is a shorter, but complete code.
If you need a dialog with only one button:
await showDialog(
context: context,
builder: (context) => new AlertDialog(
title: new Text('Message'),
content: Text(
'Your file is saved.'),
actions: <Widget>[
new FlatButton(
onPressed: () {
Navigator.of(context, rootNavigator: true)
.pop(); // dismisses only the dialog and returns nothing
},
child: new Text('OK'),
),
],
),
);
If you need a dialog with Yes/No buttons:
onPressed: () async {
bool result = await showDialog(
context: context,
builder: (context) {
return AlertDialog(
title: Text('Confirmation'),
content: Text('Do you want to save?'),
actions: <Widget>[
new FlatButton(
onPressed: () {
Navigator.of(context, rootNavigator: true)
.pop(false); // dismisses only the dialog and returns false
},
child: Text('No'),
),
FlatButton(
onPressed: () {
Navigator.of(context, rootNavigator: true)
.pop(true); // dismisses only the dialog and returns true
},
child: Text('Yes'),
),
],
);
},
);
if (result) {
if (missingvalue) {
Scaffold.of(context).showSnackBar(new SnackBar(
content: new Text('Missing Value'),
));
} else {
saveObject();
Navigator.of(context).pop(_myObject); // dismisses the entire widget
}
} else {
Navigator.of(context).pop(_myObject); // dismisses the entire widget
}
}

Answer 5

Simply used this custom dialog class which field you not needed to leave it or make it null so this customization you got easily.
import 'package:flutter/material.dart';
class CustomAlertDialog extends StatelessWidget {
final Color bgColor;
final String title;
final String message;
final String positiveBtnText;
final String negativeBtnText;
final Function onPostivePressed;
final Function onNegativePressed;
final double circularBorderRadius;
CustomAlertDialog({
this.title,
this.message,
this.circularBorderRadius = 15.0,
this.bgColor = Colors.white,
this.positiveBtnText,
this.negativeBtnText,
this.onPostivePressed,
this.onNegativePressed,
}) : assert(bgColor != null),
assert(circularBorderRadius != null);
#override
Widget build(BuildContext context) {
return AlertDialog(
title: title != null ? Text(title) : null,
content: message != null ? Text(message) : null,
backgroundColor: bgColor,
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(circularBorderRadius)),
actions: <Widget>[
negativeBtnText != null
? FlatButton(
child: Text(negativeBtnText),
textColor: Theme.of(context).accentColor,
onPressed: () {
Navigator.of(context).pop();
if (onNegativePressed != null) {
onNegativePressed();
}
},
)
: null,
positiveBtnText != null
? FlatButton(
child: Text(positiveBtnText),
textColor: Theme.of(context).accentColor,
onPressed: () {
if (onPostivePressed != null) {
onPostivePressed();
}
},
)
: null,
],
);
}
}
Usage:
var dialog = CustomAlertDialog(
title: "Logout",
message: "Are you sure, do you want to logout?",
onPostivePressed: () {},
positiveBtnText: 'Yes',
negativeBtnText: 'No');
showDialog(
context: context,
builder: (BuildContext context) => dialog);
Output:

Answer 6

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.

Answer 7

Minumum code for alert dialog
showDialog(
context: context,
builder: (_) => AlertDialog(
title: Text('Title'),
content: Text(
'Content widget',
),
),
);

Answer 8

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.

Answer 9

showAlertDialog(BuildContext context, String message, String heading,
String buttonAcceptTitle, String buttonCancelTitle) {
// set up the buttons
Widget cancelButton = FlatButton(
child: Text(buttonCancelTitle),
onPressed: () {},
);
Widget continueButton = FlatButton(
child: Text(buttonAcceptTitle),
onPressed: () {
},
);
// set up the AlertDialog
AlertDialog alert = AlertDialog(
title: Text(heading),
content: Text(message),
actions: [
cancelButton,
continueButton,
],
);
// show the dialog
showDialog(
context: context,
builder: (BuildContext context) {
return alert;
},
);
}
called like:
showAlertDialog(context, 'Are you sure you want to delete?', "AppName" , "Ok", "Cancel");

Answer 10

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),
);
}
}
Click here to see an example

Answer 11

Just to add to the great answers - the best package I found is:
adaptive_dialog: ^1.8.0+1
For a one OK button the best thing I found is using showOkAlertDialog
Implementation:
import 'package:adaptive_dialog/adaptive_dialog.dart';
import 'package:flutter/material.dart';
Widget build(BuildContext context) {
return Container(
child: Center(
child: IconButton(
icon: Icon(
Icons.info,
),
onPressed: () => showOkAlertDialog(
context: context,
okLabel: 'OK',
title: 'Title',
message: 'This is the message',
),
)),
);
}
Clean and dismisses when you click 'Ok'.

Answer 12

If you need a dialog so this code for you. just use showDialog() onPress or any inside a function.
void showDialog() {
showDialog(
context: context,
builder: (ctx) => AlertDialog(
title: const Text("Login Failed!"),
content: const Text(
"Invalid credential !! Please check your email or password",
style: TextStyle(fontSize: 18, fontWeight: FontWeight.w400),
),
actions: <Widget>[
TextButton(
onPressed: () {
Navigator.of(ctx).pop();
},
child: Container(
child: const Text(
"Try again",
style: TextStyle(color: Colors.cyan, fontSize: 17),
),
),
),
],
),
)}
Demo dialog screenshots
hope its helpful😊😊😊

Answer 13

Simple and working solution that I used: Enjoy
// Sample can be used for exit dialog box on apps
showAlertDialog(BuildContext context) {
Widget okButton = TextButton(
child: const Text("Leave now",style: TextStyle(color: Colors.red),),
onPressed: () { SystemNavigator.pop(); },
);
Widget nopeButton = TextButton(
child: const Text("Stay here"),
onPressed: () { Navigator.pop(context); },
);
AlertDialog alert = AlertDialog(
title: const Text("Leave"),
content: const Text("Are you sure you want to leave?"),
actions: [
nopeButton,
okButton,
],
);
showDialog(
context: context,
builder: (BuildContext context) {
return alert;
},
);
}

Answer 14

Another easy option to show Dialog is to use stacked_services package
_dialogService.showDialog(
title: "Title",
description: "Dialog message Tex",
);
});

Answer 15

This code works and demonstrates how to obtain the button value pressed by the user:
import 'package:flutter/material.dart';
void main() => runApp(const MyApp());
class MyApp extends StatelessWidget {
const MyApp({Key? key}) : super(key: key);
static const String _title = 'Flutter Code Sample';
#override
Widget build(BuildContext context) {
return MaterialApp(
title: _title,
home: Scaffold(
appBar: AppBar(title: const Text(_title)),
body: const Center(
child: MyStatelessWidget(),
),
),
);
}
}
class MyStatelessWidget extends StatelessWidget {
const MyStatelessWidget({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
return TextButton(
onPressed: () {
// set up the buttons
Widget cancelButton = TextButton(
child: Text("Cancel"),
onPressed: () => Navigator.pop(context, 'Cancel'),
);
Widget continueButton = TextButton(
child: Text("Ok"),
onPressed: () => Navigator.pop(context, 'Ok'),
);
showDialog<String>(
context: context,
builder: (BuildContext context) => AlertDialog(
title: const Text('AlertDialog Title'),
content: const Text('AlertDialog description'),
actions: <Widget>[
cancelButton,
continueButton,
],
),
).then((value) => print(value));
},
child: const Text('Show Dialog'),
);
}
}
Pressing on Ok button. then on Cancel button print

Answer 16

`showDialog<String>(
context: context,
builder: (BuildContext context) =>
AlertDialog(
title: const Text(
'Invalid Password',
style: TextStyle(color: Colors.red),
),
content:
const Text('Create Strong Password'),
actions: <Widget>[
Center(
child: TextButton(
style: TextButton.styleFrom(
primary: Colors.white,
backgroundColor: Colors
.red, // Background Color
),
onPressed: () => Navigator.pop(
context, 'Cancel'),
child: const Text('Cancel'),
),
),
],
),
),`