Flutter /如何在Statefulwidget之间传递和获取数据[重复]

这个问题在这里已有答案：

• Controlling State from outside of a StatefulWidget 3个答案

我是一名初级（或不到1个月的学习者）dart / flutter开发人员 . 我尝试创建一个示例proflie应用程序 - 在主屏幕上显示用户的配置文件图像 . - 用户可以使用应用程序内相机拍照或从相册中选择并显示为 Profiles 照片 .

我创建了2个主viewController .

• main.dart

void main() {
 runApp(new MaterialApp(
 home: new MyApp(),
 routes: <String, WidgetBuilder>{
  '/screen1': (BuildContext context) => new MyApp(),
  '/screen3': (BuildContext context) => new UploadAvatarButton()
  },
 ));
}

 class MyApp extends StatefulWidget {
  final String _images =  "";
  MyApp(String _images, {Key key}) : super(key: key);
  @override
  State<StatefulWidget> createState() {
   return new MyHomePage();
  }
 }

 class MyHomePage extends State<MyApp> {
 @override
 Widget build(BuildContext context) {

 Widget myPhoto = new Container(
 //Attribute
 child: new FlatButton(
  child: new Container(
   decoration: new BoxDecoration(
    shape: BoxShape.circle,
    image: new DecorationImage(
     fit: BoxFit.cover, image: new AssetImage('images/sample.jpg')),
    ),
   ),
 onPressed: _showPersBottomSheetCallBack,
  ),
 );

 return new MaterialApp(
 home: new Scaffold(
 //Header
 body: new Center(
  child: new Column(
    crossAxisAlignment: CrossAxisAlignment.center,
    children: [
      new Container(child: myPhoto),

和2. cameraView.dart

class UploadAvatarButton extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return new MakeUploadAvatarButtonState();
  }
class MakeUploadAvatarButtonState extends State<UploadAvatarButton> {
  File _image;
  Future getImage() async {
    var image = await ImagePicker.pickImage(source: ImageSource.camera);
    setState(() {
      _image = image;
//Try to send data or image back to main screen
      List<int> imageBytes = image.readAsBytesSync();
      String base64Image = BASE64.encode(imageBytes);
//send data back
      Navigator.push(context, new MaterialPageRoute(builder: (_) => 
  new MyApp(_image.)));
    });
  }

如您所见，我使用方法从相机发回图像

List<int> imageBytes = image.readAsBytesSync();
  String base64Image = BASE64.encode(imageBytes);
  Navigator.push(context, new MaterialPageRoute(builder: (_) => 
  new MyApp(_image.)));

在主要

final String _images =  "";
MyApp(String _images, {Key key}) : super(key: key);

但是，我收到了错误

[dart] The constructor returns type 'dynamic' that isn't of expected type 'Widget'.

你能告诉我吗？

祝您好运