Custom Dialog Demo

main.dart

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Custom Dialog Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Custom Dialog Demo'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);
  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  void _showDialog() {
    var height = MediaQuery.of(context).size.height;
    var width = MediaQuery.of(context).size.width;

    var minWidth = (width > 720 ? width * 0.50 : width * 0.70);

    showDialog(
        context: context,
        builder: (_) => SimpleDialog(
              contentPadding:
                  EdgeInsets.symmetric(vertical: 8.0, horizontal: 16.0),
              children: <Widget>[
                CircleAvatar(
                    child: Icon(Icons.alarm, size: 48.0), minRadius: 36.0),
                SizedBox(height: 8.0),
                ConstrainedBox(
                  constraints: BoxConstraints(
                    minWidth: minWidth,
                  ),
                  child: Column(
                    children: [
                      Text('TitleTitleTitleTitleTitle',
                          style: Theme.of(context).textTheme.headline5),
                      SizedBox(height: 8.0),
                      Text(
                        'DescriptionDescriptionDescriptionDescriptionDescriptionDescription',
                        style: Theme.of(context).textTheme.bodyText1,
                      ),
                      SizedBox(height: 8.0),
                      Container(
                        padding: EdgeInsets.all(8.0),
                        width: 200.0,
                        color: Colors.lightBlue,
                        child: Column(
                          children: [
                            Row(
                              mainAxisAlignment: MainAxisAlignment.center,
                              children: [
                                SizedBox(width: 100.0, child: Text('height:')),
                                Expanded(
                                  child: Text('$height',
                                      textAlign: TextAlign.right),
                                ),
                              ],
                            ),
                            Row(
                              mainAxisAlignment: MainAxisAlignment.center,
                              children: [
                                SizedBox(width: 100.0, child: Text('width:')),
                                Expanded(
                                  child: Text('$width',
                                      textAlign: TextAlign.right),
                                ),
                              ],
                            ),
                            Row(
                              mainAxisAlignment: MainAxisAlignment.center,
                              children: [
                                SizedBox(
                                    width: 100.0, child: Text('minWidth:')),
                                Expanded(
                                  child: Text('${minWidth.toStringAsFixed(1)}',
                                      textAlign: TextAlign.right),
                                ),
                              ],
                            ),
                          ],
                        ),
                      ),
                      SizedBox(height: 8.0),
                      Text(
                        'AnnotationAnnotation',
                        style: Theme.of(context).textTheme.headline4,
                      ),
                      RaisedButton(
                        onPressed: () {},
                        child: Text('OK'),
                        shape: RoundedRectangleBorder(
                          borderRadius: BorderRadius.all(Radius.circular(45.0)),
                        ),
                      ),
                    ],
                  ),
                ),
              ],
            ));
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text(widget.title)),
      body: Container(),
      floatingActionButton: FloatingActionButton(
        onPressed: _showDialog,
        tooltip: 'ShowDialog',
        child: Icon(Icons.send),
      ),
    );
  }
}