如何在不重启fluter的情况下，在添加到firebase后立即显示图像

import 'package:flutter/material.dart';
import 'package:firebase_storage/firebase_storage.dart';
import 'package:image_picker/image_picker.dart';

class ImageUploadScreen extends StatefulWidget {
  @override
  _ImageUploadScreenState createState() => _ImageUploadScreenState();
}

class _ImageUploadScreenState extends State<ImageUploadScreen> {
  FirebaseStorage _storage = FirebaseStorage.instance;
  String _imageUrl;

  Future<void> _uploadImage() async {
    final picker = ImagePicker();
    final pickedFile = await picker.getImage(source: ImageSource.gallery);

    if (pickedFile != null) {
      // 上传图像文件到Firebase Storage
      Reference storageRef = _storage.ref().child('images/${DateTime.now()}.png');
      UploadTask uploadTask = storageRef.putFile(File(pickedFile.path));

      // 监听上传任务的状态
      uploadTask.snapshotEvents.listen((TaskSnapshot snapshot) {
        print('Upload progress: ${snapshot.bytesTransferred}/${snapshot.totalBytes}');
      }, onError: (Object e) {
        print('Upload error: $e');
      });

      // 等待上传完成，并获取图像文件的下载URL
      TaskSnapshot snapshot = await uploadTask.whenComplete(() {});
      String downloadUrl = await snapshot.ref.getDownloadURL();

      setState(() {
        _imageUrl = downloadUrl;
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Image Upload'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            if (_imageUrl != null)
              Image.network(_imageUrl),
            RaisedButton(
              child: Text('Upload Image'),
              onPressed: _uploadImage,
            ),
          ],
        ),
      ),
    );
  }
}