问Flutter上传从multi_image_picker获取的多张图片失败

EN

import 'package:flutter/material.dart';
import 'dart:async';
import 'package:firebase_storage/firebase_storage.dart';
import 'package:flutter/services.dart';
import 'package:multi_image_picker/multi_image_picker.dart';
import 'package:mock_data/mock_data.dart';



class PageTwo extends StatefulWidget {
  @override
  _MyAppState createState() => new _MyAppState();
}

class _MyAppState extends State<PageTwo> {
  List<Asset> images = List<Asset>();
  String popop = mockString(50);

  @override
  void initState() {
    super.initState();
  }

  Widget buildGridView() {
    return GridView.count(
      crossAxisCount: 3,
      children: List.generate(images.length, (index) {
        Asset asset = images[index];
        return AssetThumb(
          asset: asset,
          width: 300,
          height: 300,
        );
      }),
    );
  }

  Future saveImage(Asset asset) async {
    String fileName = popop;
    ByteData byteData = await asset.requestOriginal();
    List<int> imageData = byteData.buffer.asUint8List();
    StorageReference ref = FirebaseStorage.instance.ref().child(fileName);
    StorageUploadTask uploadTask = ref.putData(imageData);

    return await (await uploadTask.onComplete).ref.getDownloadURL();
  }

  Future<void> loadAssets() async {
    List<Asset> resultList = List<Asset>();
    try {
      resultList = await MultiImagePicker.pickImages(
          maxImages: 300,
          enableCamera: true,
          selectedAssets: images,
          cupertinoOptions: CupertinoOptions(takePhotoIcon: "chat"),
          materialOptions: MaterialOptions(
            actionBarColor: "#abcdef",
            actionBarTitle: "Example App",
            allViewTitle: "All Photos",
            selectCircleStrokeColor: "#000000",
          ));
    } 
    }
    if (!mounted) return;

    setState(() {
      images = resultList;
      _error = error;
    });
  }

  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      home: new Scaffold(
        appBar: new AppBar(
          title: const Text('Getting pics'),
        ),
        body: Column(
          children: <Widget>[
            RaisedButton(
              child: Text("Pick images"),
              onPressed: loadAssets,
            ),
            RaisedButton(
              child: Text("Save Image"),
              onPressed: () => saveImage,
            ),
            Expanded(
              child: buildGridView(),
            )
          ],
        ),
      ),
    );
  }
}