Question

当有SocketException时，我想返回CircularProgressIndicator，但这不起作用，并且由于此异常，需要互联网运行的完整代码无法运行。

我该如何解决？如果有人知道，请提前谢谢：

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
        home: Scaffold(
      body: StreamBuilder(
          stream: Firestore.instance.collection('images').snapshots(),
          builder: (context, snapshot) {
            try {
              if (!snapshot.hasData)
                return Center(child: CircularProgressIndicator());
              for (int i = 0; i < snapshot.data.documents.length; i++) {
                listOfUrls.add(snapshot.data.documents[i]['url']);
                listOfPics.add(Card(
                    color: Colors.black12,
                    shape: RoundedRectangleBorder(
                        borderRadius: BorderRadius.circular(10)),
                    child: Image.network(listOfUrls[i])));
              }
              return Bar();
            } on SocketException catch (_) {
              return Center(
                child: Text('Connect to the internet'),
              );
            }
          }),
    ));
  }
}

Answer 1

try..catch中的任何代码都无法触发SocketException。您应该尝试使用snapshot.hasError getter：

@override
  Widget build(BuildContext context) {
    return MaterialApp(
        home: Scaffold(
      body: StreamBuilder(
          stream: Firestore.instance.collection('images').snapshots(),
          builder: (context, snapshot) {
            if (snapshot.hasError && snapshot.error is SocketException)
              return Center(
                child: Text('Connect to the internet'),
              );
            if (!snapshot.hasData)
              return Center(child: CircularProgressIndicator());
            for (int i = 0; i < snapshot.data.documents.length; i++) {
              listOfUrls.add(snapshot.data.documents[i]['url']);
              listOfPics.add(Card(
                  color: Colors.black12,
                  shape: RoundedRectangleBorder(
                      borderRadius: BorderRadius.circular(10)),
                  child: Image.network(listOfUrls[i])));
            }
            return Bar();
          }),
    ));
  }

为什么捕获此异常无效？

1 个答案: