构建小部件树时，Flutter AssetImage 无法首次加载

Question

我正在 Flutter 中构建一个 Hangman 应用程序，我希望主图像在寿命减少时更新为另一个图像。问题是，当我第一次运行应用程序时，我得到了这个错误：

I/flutter (21336): ══╡ EXCEPTION CAUGHT BY IMAGE RESOURCE SERVICE ╞════════════════════════════════════════════════════
I/flutter (21336): The following assertion was thrown resolving an image codec:
I/flutter (21336): Unable to load asset: assets/Hangman 10.png
I/flutter (21336): 
I/flutter (21336): When the exception was thrown, this was the stack:
I/flutter (21336): #0      PlatformAssetBundle.load (package:flutter/src/services/asset_bundle.dart:221:7)
I/flutter (21336): <asynchronous suspension>
I/flutter (21336): #1      AssetBundleImageProvider._loadAsync (package:flutter/src/painting/image_provider.dart:484:44)
I/flutter (21336): #2      AssetBundleImageProvider.load (package:flutter/src/painting/image_provider.dart:469:14) 
I/flutter (21336): #3      ImageProvider.resolve.<anonymous closure>.<anonymous closure>.<anonymous closure> (package:flutter/src/painting/image_provider.dart:327:17)
I/flutter (21336): #4      ImageCache.putIfAbsent (package:flutter/src/painting/image_cache.dart:160:22)
I/flutter (21336): #5      ImageProvider.resolve.<anonymous closure>.<anonymous closure> (package:flutter/src/painting/image_provider.dart:325:84)
I/flutter (21336): (elided 13 frames from package dart:async)
I/flutter (21336):
I/flutter (21336): Image provider: AssetImage(bundle: null, name: "assets/Hangman 10.png")
I/flutter (21336): Image key: AssetBundleImageKey(bundle: PlatformAssetBundle#133ec(), name: "assets/Hangman 10.png",
I/flutter (21336):   scale: 1.0)
I/flutter (21336): ════════════════════════════════════════════════════════════════════════════════════════════════════

然后，如果我只是热重新加载，图像会加载并且应用程序可以正常工作。 我的颤振医生说一切都很好：

Doctor summary (to see all details, run flutter doctor -v):
[√] Flutter (Channel stable, v1.12.13+hotfix.9, on Microsoft Windows [Version 10.0.18363.778], locale en-US)

[√] Android toolchain - develop for Android devices (Android SDK version 29.0.3)
[√] Android Studio (version 3.6)
[√] VS Code (version 1.44.2)
[√] Connected device (1 available)

• No issues found!

这是我的文件夹的结构 asset image name and location

还有我的 main.dart 文件

import 'package:flutter/material.dart';
import 'nouns.dart';
import 'keyboard_ws.dart';

void main() => runApp(MaterialApp(home: Home()));

String word = 'wordToBeGuessed'
int lives = 10;
List<String> lettersEntered = [];


class Home extends StatefulWidget {
  @override
  HomeState createState() => HomeState();
}

String word = 'savannah';
int lives = 10;
List<String> lettersEntered = [];
List<String> wordShowList = List.filled(word.length, '_');
String displayWord = wordShowList.join(' ');

class HomeState extends State<Home> {
@override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Hangman'),
        centerTitle: true,
      ),
      body: Column(
        crossAxisAlignment: CrossAxisAlignment.stretch,
        children: <Widget>[
          Expanded(
              child: Container(
            padding: EdgeInsets.symmetric(vertical: 30, horizontal: 20),
            child: Image(
              image: AssetImage('assets/Hangman $lives.png'),
              gaplessPlayback: true,
            ),
          )),
          Container(
            child: Text(
              displayWord,
              style: TextStyle(fontSize: 30),
            ),
          ),
          Keyboard(lettersEntered, sendKey)
        ],
      ),
    );
  }
}

我的资产文件夹在我的 pubspec.yaml 文件中被引用，如下所示：

flutter:
  assets:
  - assets/

Answer 1

原因：您的图片名称有空格
解决方案：Unable to load asset" when the asset path contains a space https://github.com/flutter/flutter/issues/47705#issuecomment-621728294
已在当前测试版 v1.17.0-3.2.pre 和开发版 v1.18.0-6.0.pre 中修复（但不是稳定版 v1.12.13+hotfix.9）
您可以考虑切换到新版本

工作演示

完整代码

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {  
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(       
        primarySwatch: Colors.blue,       
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {     
      _counter++;
    });
  }

  @override
  Widget build(BuildContext context) {    
    return Scaffold(
      appBar: AppBar(       
        title: Text(widget.title),
      ),
      body: Center(        
        child: Column(          
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Expanded(
                child: Container(
                  padding: EdgeInsets.symmetric(vertical: 30, horizontal: 20),
                  child: Image(
                    image: AssetImage('assets/images/alarm space.png'),
                    gaplessPlayback: true,
                  ),
                )),
            Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.headline4,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ),
    );
  }
}