AlertDialog class Null safety

A material design alert dialog.

An alert dialog informs the user about situations that require acknowledgement. An alert dialog has an optional title and an optional list of actions. The title is displayed above the content and the actions are displayed below the content.

If the content is too large to fit on the screen vertically, the dialog will display the title and the actions and let the content overflow, which is rarely desired. Consider using a scrolling widget for content, such as SingleChildScrollView, to avoid overflow. (However, be aware that since AlertDialog tries to size itself using the intrinsic dimensions of its children, widgets such as ListView, GridView, and CustomScrollView, which use lazy viewports, will not work. If this is a problem, consider using Dialog directly.)

For dialogs that offer the user a choice between several options, consider using a SimpleDialog.

Typically passed as the child widget to showDialog, which displays the dialog.

This snippet shows a method in a State which, when called, displays a dialog box and returns a Future that completes when the dialog is dismissed.
Future<void> _showMyDialog() async {
  return showDialog<void>(
    context: context,
    barrierDismissible: false, // user must tap button!
    builder: (BuildContext context) {
      return AlertDialog(
        title: const Text('AlertDialog Title'),
        content: SingleChildScrollView(
          child: ListBody(
            children: const <Widget>[
              Text('This is a demo alert dialog.'),
              Text('Would you like to approve of this message?'),
            ],
          ),
        ),
        actions: <Widget>[
          TextButton(
            child: const Text('Approve'),
            onPressed: () {
              Navigator.of(context).pop();
            },
          ),
        ],
      );
    },
  );
}

This demo shows a TextButton which when pressed, calls showDialog. When called, this method displays a Material dialog above the current contents of the app and returns a Future that completes when the dialog is dismissed.
To create a local project with this code sample, run:
flutter create --sample=material.AlertDialog.2 mysample

See also:

Inheritance

Constructors

AlertDialog({Key? key, Widget? title, EdgeInsetsGeometry? titlePadding, TextStyle? titleTextStyle, Widget? content, EdgeInsetsGeometry contentPadding, TextStyle? contentTextStyle, List<Widget>? actions, EdgeInsetsGeometry actionsPadding, MainAxisAlignment? actionsAlignment, VerticalDirection? actionsOverflowDirection, double? actionsOverflowButtonSpacing, EdgeInsetsGeometry? buttonPadding, Color? backgroundColor, double? elevation, String? semanticLabel, EdgeInsets insetPadding, Clip clipBehavior, ShapeBorder? shape, bool scrollable})
Creates an alert dialog. [...]
const

Properties

actions List<Widget>?
The (optional) set of actions that are displayed at the bottom of the dialog with an OverflowBar. [...]
final
actionsAlignment MainAxisAlignment?
Defines the horizontal layout of the actions according to the same rules as for Row.mainAxisAlignment. [...]
final
actionsOverflowButtonSpacing double?
The spacing between actions when the OverflowBar switches to a column layout because the actions don't fit horizontally. [...]
final
actionsOverflowDirection VerticalDirection?
The vertical direction of actions if the children overflow horizontally. [...]
final
actionsPadding EdgeInsetsGeometry
Padding around the set of actions at the bottom of the dialog. [...]
final
backgroundColor Color?
The background color of the surface of this Dialog. [...]
final
buttonPadding EdgeInsetsGeometry?
The padding that surrounds each button in actions. [...]
final
clipBehavior Clip
Controls how the contents of the dialog are clipped (or not) to the given shape. [...]
final
content Widget?
The (optional) content of the dialog is displayed in the center of the dialog in a lighter font. [...]
final
contentPadding EdgeInsetsGeometry
Padding around the content. [...]
final
contentTextStyle TextStyle?
Style for the text in the content of this AlertDialog. [...]
final
elevation double?
The z-coordinate of this Dialog. [...]
final
hashCode int
The hash code for this object. [...]
@nonVirtual, read-only, inherited
insetPadding EdgeInsets
The amount of padding added to MediaQueryData.viewInsets on the outside of the dialog. This defines the minimum space between the screen's edges and the dialog. [...]
final
key Key?
Controls how one widget replaces another widget in the tree. [...]
final, inherited
runtimeType Type
A representation of the runtime type of the object.
read-only, inherited
scrollable bool
Determines whether the title and content widgets are wrapped in a scrollable. [...]
final
semanticLabel String?
The semantic label of the dialog used by accessibility frameworks to announce screen transitions when the dialog is opened and closed. [...]
final
shape ShapeBorder?
The shape of this dialog's border. [...]
final
title Widget?
The (optional) title of the dialog is displayed in a large font at the top of the dialog. [...]
final
titlePadding EdgeInsetsGeometry?
Padding around the title. [...]
final
titleTextStyle TextStyle?
Style for the text in the title of this AlertDialog. [...]
final

Methods

build(BuildContext context) Widget
Describes the part of the user interface represented by this widget. [...]
override
createElement() StatelessElement
Creates a StatelessElement to manage this widget's location in the tree. [...]
inherited
debugDescribeChildren() List<DiagnosticsNode>
Returns a list of DiagnosticsNode objects describing this node's children. [...]
@protected, inherited
debugFillProperties(DiagnosticPropertiesBuilder properties) → void
Add additional properties associated with the node. [...]
inherited
noSuchMethod(Invocation invocation) → dynamic
Invoked when a non-existent method or property is accessed. [...]
inherited
toDiagnosticsNode({String? name, DiagnosticsTreeStyle? style}) DiagnosticsNode
Returns a debug representation of the object that is used by debugging tools and by DiagnosticsNode.toStringDeep. [...]
inherited
toString({DiagnosticLevel minLevel = DiagnosticLevel.info}) String
A string representation of this object. [...]
inherited
toStringDeep({String prefixLineOne = '', String? prefixOtherLines, DiagnosticLevel minLevel = DiagnosticLevel.debug}) String
Returns a string representation of this node and its descendants. [...]
inherited
toStringShallow({String joiner = ', ', DiagnosticLevel minLevel = DiagnosticLevel.debug}) String
Returns a one-line detailed description of the object. [...]
inherited
toStringShort() String
A short, textual description of this widget.
inherited

Operators

operator ==(Object other) bool
The equality operator. [...]
@nonVirtual, inherited