RaisedButton已弃用，已替换为ElevatedButton：
替换：

RaisedButton(/*...*/),

与：

ElevatedButton(/*...*/),

在此处检查所有新迁移：
https://docs.flutter.dev/release/breaking-changes/buttons#context

已弃用，已被ElevatedButton取代。新按钮和按钮主题

不推荐使用RaisedButton。请将其替换为ElevatedButton

return MaterialApp(
      home: Scaffold(
          body: Column(
            children: <Widget>[
              Text('question'),
              ElevatedButton(
                child: Text('answer1'),
                onPressed: null,
              ),
            ],
          ),
      ),
    );

Raised button已过时，请使用Elevated Button

return MaterialApp(
      home: Scaffold(
          body: Column(children:[
              Text('question'),
              ElevatedButton(child: Text('answer1'),onPressed: null),
            ],),
      ),
    );