将SingleChildScrollView的位置更改为列的顶部可以正常工作

return AlertDialog(
            contentPadding: EdgeInsets.only(left: 25, right: 25),
            title: Center(child: Text("Information")),
            shape: RoundedRectangleBorder(
                borderRadius: BorderRadius.all(Radius.circular(20.0))),
            content: Container(
              height: 200,
              width: 300,
              child: SingleChildScrollView(
                child: Column(
                  crossAxisAlignment: CrossAxisAlignment.stretch,
                  children: <Widget>[
                    SizedBox(
                      height: 20,
                    ),
                    Text(
                        'Name of requestor: }'
                    ),
                    Text(
                      'Description:' * 20,
                    ),
                    Text(
                      'Help_Description',
                    ),
                    Text(
                      'Type of help needed:Help_TypeNeeded',
                    )
                  ],
                ),
              ),
            ),

全测试码

import 'package:flutter/material.dart';
import 'package:flutter/cupertino.dart';

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

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

class StatelessWidgetDemo extends StatefulWidget {
  @override
  _StatelessWidgetDemoState createState() => _StatelessWidgetDemoState();
}

class _StatelessWidgetDemoState extends State<StatelessWidgetDemo> {
  @override
  Widget build(BuildContext context) {
    return SafeArea(
        child: Scaffold(
            appBar: AppBar(
              title: Text('Dialog Demo'),
            ),
            body: Center(
              child: Column(
                mainAxisAlignment: MainAxisAlignment.center,
                children: <Widget>[
                  RaisedButton(
                    onPressed: () {
                      _showTestDialog();
                    },
                    child: Text('Show Test Dialog'),
                  ),
                  SizedBox(
                    height: 20,
                  ),
                  RaisedButton(
                    onPressed: () {
                      _showCupertinoDialog();
                    },
                    child: Text('Show Cupertino Dialog'),
                  ),
                  SizedBox(
                    height: 20,
                  ),
                  RaisedButton(
                    onPressed: () {
                      _showSimpleDialog();
                    },
                    child: Text('Show Simple Dialog'),
                  )
                ],
              ),
            )));
  }

  void _showTestDialog() {
    showDialog(
        context: context,
        barrierDismissible: false,
        //context: _scaffoldKey.currentContext,
        builder: (context) {
          return AlertDialog(
            contentPadding: EdgeInsets.only(left: 25, right: 25),
            title: Center(child: Text("Information")),
            shape: RoundedRectangleBorder(
                borderRadius: BorderRadius.all(Radius.circular(20.0))),
            content: Container(
              height: 200,
              width: 300,
              child: SingleChildScrollView(
                child: Column(
                  crossAxisAlignment: CrossAxisAlignment.stretch,
                  children: <Widget>[
                    SizedBox(
                      height: 20,
                    ),
                    Text(
                        'Name of requestor: }'
                    ),
                    Text(
                      'Description:' * 20,
                    ),
                    Text(
                      'Help_Description',
                    ),
                    Text(
                      'Type of help needed:Help_TypeNeeded',
                    )
                  ],
                ),
              ),
            ),
            actions: <Widget>[
              Row(
                mainAxisAlignment: MainAxisAlignment.center,
                children: <Widget>[
                  Container(
                    width: MediaQuery.of(context).size.width * 0.20,
                    child: RaisedButton(
                      child: new Text(
                        'Fund',
                        style: TextStyle(color: Colors.white),
                      ),
                      color: Color(0xFF121A21),
                      shape: new RoundedRectangleBorder(
                        borderRadius: new BorderRadius.circular(30.0),
                      ),
                      onPressed: () {
                        //saveIssue();
                        Navigator.of(context).pop();
                      },
                    ),
                  ),
                  SizedBox(
                    width: MediaQuery.of(context).size.width * 0.01,
                  ),
                  Padding(
                    padding: const EdgeInsets.only(right: 70.0),
                    child: Container(
                      width: MediaQuery.of(context).size.width * 0.20,
                      child: RaisedButton(
                        child: new Text(
                          'Cancel',
                          style: TextStyle(color: Colors.white),
                        ),
                        color: Color(0xFF121A21),
                        shape: new RoundedRectangleBorder(
                          borderRadius: new BorderRadius.circular(30.0),
                        ),
                        onPressed: () {
                          Navigator.of(context).pop();
                        },
                      ),
                    ),
                  ),
                  SizedBox(
                    height: MediaQuery.of(context).size.height * 0.02,
                  ),
                ],
              )
            ],
          );
        });
  }

  void _showMaterialDialog() {
    showDialog(
        context: context,
        builder: (context) {
          return AlertDialog(
            title: Text('Material Dialog'),
            content: Text('This is the content of the material dialog'),
            actions: <Widget>[
              FlatButton(
                  onPressed: () {
                    _dismissDialog();
                  },
                  child: Text('Close')),
              FlatButton(
                onPressed: () {
                  print('HelloWorld!');
                  _dismissDialog();
                },
                child: Text('HelloWorld!'),
              )
            ],
          );
        });
  }

  _dismissDialog() {
    Navigator.pop(context);
  }

  void _showCupertinoDialog() {
    showDialog(
        context: context,
        builder: (context) {
          return CupertinoAlertDialog(
            title: Text('Cupertino Dialog'),
            content: Text('This is the content of the cupertino dialog'),
            actions: <Widget>[
              FlatButton(
                  onPressed: () {
                    _dismissDialog();
                  },
                  child: Text('Close')),
              FlatButton(
                onPressed: () {
                  print('HelloWorld!');
                  _dismissDialog();
                },
                child: Text('HelloWorld!'),
              )
            ],
          );
        });
  }

  void _showSimpleDialog() {
    showDialog(
        context: context,
        builder: (context) {
          return SimpleDialog(
            title: Text('Chosse an Option'),
            children: <Widget>[
              SimpleDialogOption(
                onPressed: () {
                  _dismissDialog();
                },
                child: const Text('Option 1'),
              ),
              SimpleDialogOption(
                onPressed: () {
                  _dismissDialog();
                },
                child: const Text('Option 2'),
              ),
              SimpleDialogOption(
                onPressed: () {
                  _dismissDialog();
                },
                child: const Text('Option 3'),
              ),
              SimpleDialogOption(
                onPressed: () {
                  _dismissDialog();
                },
                child: const Text('Option 4'),
              ),
            ],
          );
        });
  }
}

只需将AlertDialog的scrollable参数设置为true，即可将title和content小部件都包含在滚动视图中，从而在显示按钮栏的同时可以看到所有溢出的内容。

OutlinedButton(
  onPressed: () => showDialog(
    context: context,
    builder: (_) => AlertDialog(
      title: const Text('Reason'),
      shape: const RoundedRectangleBorder(
          borderRadius:
              BorderRadius.all(Radius.circular(20))),
      scrollable: true,
      content: Text('Super long content here'),
      actionsAlignment: MainAxisAlignment.center,
      actions: [
        OutlinedButton(
          onPressed: () => Navigator.pop(context),
          child: Text('I have done reading ✓'),
        )
      ],
    ),
  ),
  child: Text('View reason for visit'),
)

定义未来对话框

Future<bool>_loadForm(BuildContext context) async {
  return await showDialog<bool>(
    context: context,
    builder: (context) {
      return Dialog(child: MyWidget(params));
    });
  }

从onPressed事件的列表视图调用对话框中的卡片

onPressed: () => 
  _loadChecklistForm(context).then((values)=>{})

在构建的myWidget中返回对话框

final _formKey = GlobalKey<FormState>();
 List<Widget> formWidgetList = new List();

 formWidgetList.add(new Text('Hello world'));  

 return Dialog(
      shape: RoundedRectangleBorder(
        borderRadius: BorderRadius.circular(20),
      ),
      elevation: 0.0,
      child: SingleChildScrollView(
        child:     Column(children:formWidgetList) ));