使用advance_pdf_viewer加载Firebase存储PDF时模拟器崩溃报错

从Firebase Storage获取PDF文件列表后，使用advance_pdf_viewer插件查看PDF，传递文件给阅读器时模拟器立即崩溃，出现以下错误日志：

E/AndroidRuntime(31096): java.lang.IllegalStateException: Reply already submitted
E/AndroidRuntime(31096): at io.flutter.embedding.engine.dart.DartMessenger$Reply.reply(DartMessenger.java:430)
E/AndroidRuntime(31096): at io.flutter.plugin.common.MethodChannel$IncomingMethodCallHandler$1.success(MethodChannel.java:267)
E/AndroidRuntime(31096): at pt.tribeiro.flutter_plugin_pdf_viewer.FlutterPluginPdfViewerPlugin$1$2.run(FlutterPluginPdfViewerPlugin.java:92)
E/AndroidRuntime(31096): at android.os.Handler.handleCallback(Handler.java:873)
E/AndroidRuntime(31096): at android.os.Handler.dispatchMessage(Handler.java:99)
E/AndroidRuntime(31096): at android.os.Looper.loop(Looper.java:214)
E/AndroidRuntime(31096): at android.app.ActivityThread.main(ActivityThread.java:7073)
E/AndroidRuntime(31096): at java.lang.reflect.Method.invoke(Native Method)
E/AndroidRuntime(31096): at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:494)
E/AndroidRuntime(31096): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:964)
E/flutter (31096): [ERROR:flutter/lib/ui/ui_dart_state.cc(198)] Unhandled Exception: MissingPluginException(No implementation found for method getPage on channel flutter_plugin_pdf_viewer)

相关代码如下：

class FilePage extends Stateful Widget {
  const FilePage({required this.file, this.isImage = false});
  final FirebaseFile file;
  final isImage;
  @override
  _FilePageState createState() => _FilePageState();
}

class _FilePageState extends State<FilePage> {
  @override
  void initState() {
    super.initState();
  }

  @override
  Widget build(BuildContext context) {

    //initState(){
    return WillPopScope(
      onWillPop: () async => true,
      child: Scaffold(
        appBar: AppBar(
          backgroundColor: Colors.indigo[900],
          title: Text(widget.file.name.split('.').first),
          centerTitle: true,
        ),
        body: widget.isImage
            ? loadImage(widget.file.url)
            : FutureBuilder(
            future: PDFDocument.fromURL(widget.file.url),
            builder: (context, snapshot) {
              switch (snapshot.connectionState) {
                case ConnectionState.waiting:
                case ConnectionState.active:
                  return Center(
                    child: CircularProgressIndicator(),
                  );
                default:
                  var pdf = snapshot.data as PDFDocument;
                  return PDFViewer(document: pdf);
              }
            }),
      ),
    );
  }

  Widget loadImage(String url) {
    return Image.network(
      url,
      loadingBuilder: (context, widget, event) {
        if (event == null) return widget;
        return Center(
          child: Column(
            crossAxisAlignment: CrossAxisAlignment.center,
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              CircularProgressIndicator(),
              SizedBox(
                height: 20,
              ),
              Text('Loading')
            ],
          ),
        );
      },
    );
  }
}

1. 修复FutureBuilder重复执行问题 #

将PDFDocument.fromURL的调用从build方法移到initState中，避免每次组件重建时重复发起PDF加载请求，导致插件方法通道重复回调：

class _FilePageState extends State<FilePage> {
  Future<PDFDocument>? _pdfFuture;

  @override
  void initState() {
    super.initState();
    if (!widget.isImage) {
      _pdfFuture = PDFDocument.fromURL(widget.file.url);
    }
  }

  @override
  Widget build(BuildContext context) {
    return WillPopScope(
      onWillPop: () async => true,
      child: Scaffold(
        appBar: AppBar(
          backgroundColor: Colors.indigo[900],
          title: Text(widget.file.name.split('.').first),
          centerTitle: true,
        ),
        body: widget.isImage
            ? loadImage(widget.file.url)
            : FutureBuilder(
                future: _pdfFuture,
                builder: (context, snapshot) {
                  switch (snapshot.connectionState) {
                    case ConnectionState.waiting:
                    case ConnectionState.active:
                      return Center(child: CircularProgressIndicator());
                    case ConnectionState.done:
                      if (snapshot.hasError) {
                        return Center(child: Text('加载PDF失败: ${snapshot.error}'));
                      }
                      var pdf = snapshot.data as PDFDocument;
                      return PDFViewer(document: pdf);
                    default:
                      return Center(child: Text('未知状态'));
                  }
                }),
      ),
    );
  }

  // loadImage方法保持不变
}

2. 处理插件兼容性问题 #

• 检查advance_pdf_viewer版本，若使用旧版本，尝试升级到最新稳定版；该插件底层依赖的flutter_plugin_pdf_viewer存在方法通道重复提交的bug，也可以考虑替换为维护更活跃的PDF插件（如pdfx）。
• 执行flutter clean和flutter pub get清理项目缓存，重新构建确保插件正确集成。

3. 验证文件访问权限 #

确认Firebase Storage中的PDF文件有公开访问权限，或应用已通过身份验证获取到有效访问URL，避免因URL无效、权限不足导致加载失败，间接触发插件错误。

内容的提问来源于stack exchange，提问作者learner