缺少StatelessWidget的具体实现

Question

这个页面是我的PhotoPreviewScreen，单击下面代码中的按钮后，我将来自相机屏幕的照片发送到主页。

我得到了一些有趣的错误，我以前没有见过，在文档中很少，在屏幕截图中。以前有没有人见过这些？我该怎么纠正呢？

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

class PhotoPreviewScreen extends StatelessWidget {
  Function setData;
  PhotoPreviewScreen({Key key, this.setData}) : super(key: key);
}

class _PhotoPreviewScreenState extends State<PhotoPreviewScreen> {
  final String imagePath;
  var image;

  Future _openGallery() async {}


  @override
  Widget build(BuildContext context) {
    return Scaffold(
      floatingActionButton: FloatingActionButton(
        onPressed: () => Navigator.pop(
            context), // Go back to the camera to take the picture again
        child: Icon(Icons.camera_alt),
      ),
      appBar: AppBar(title: Text('Photo Preview')),
      body: Column(children: [
        Expanded(child: Image.file(File(imagePath))),
        const SizedBox(height: 16.0),
        OutlineButton(
          onPressed: () {
            _openGallery();
            Navigator.pop(context);
          },
          child: Text('Okay'),
          borderSide: BorderSide(
              color: Color(
                  0xff33333D)), 
        ),
      ]),
    );
  }
}

错误

​

​

Answer 1

class PhotoPreviewScreen extends StatefulWidget {Function setData;   PhotoPreviewScreen({Key key, this.setData}) : super(key: key); }

我想应该是"StatefulWidget“而不是"StatelesWidget”。

Answer 2

试试下面的代码片段：

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

class PhotoPreviewScreen extends StatefulWidget {
  Function setData;
  PhotoPreviewScreen({Key key, this.setData}) : super(key: key);

_PhotoPreviewScreenState createState() => _PhotoPreviewScreenState();
}

class _PhotoPreviewScreenState extends State<PhotoPreviewScreen> {
  final String imagePath = ' ';
  var image;

  Future _openGallery() async {}


  @override
  Widget build(BuildContext context) {
    return Scaffold(
      floatingActionButton: FloatingActionButton(
        onPressed: () => Navigator.pop(
            context), // Go back to the camera to take the picture again
        child: Icon(Icons.camera_alt),
      ),
      appBar: AppBar(title: Text('Photo Preview')),
      body: Column(children: [
        Expanded(child: Image.file(File(imagePath))),
        const SizedBox(height: 16.0),
        OutlineButton(
          onPressed: () {
            _openGallery();
            Navigator.pop(context);
          },
          child: Text('Okay'),
          borderSide: BorderSide(
              color: Color(
                  0xff33333D)), 
        ),
      ]),
    );
  }
}