flutter - 如何解决 “Expected a value of type ' int'，但在Flutter中得到了 'String'类型之一

Question

我有一个本地JSON文件，如下所示:

[
    {
        "1": [
            {
                "mode": "text",
                "value": "text exapple1"
            },
            {
                "mode": "latex",
                "value": "\frac00"
            },
            {
                "mode": "text",
                "value": "text exapple2"
            },
            {
                "mode": "latex",
                "value": "\frac00"
            },
            {
                "mode": "text",
                "value": "text exapple3"
            }
        ]
    },
    {
        "2": [
            {
                "mode": "text",
                "value": "text exapple4"
            }
        ]
    }
]

我试图在我的代码中使用FutureBuilder解析它:

return FutureBuilder(
    future:
        DefaultAssetBundle.of(context).loadString("assets/paragraph.json"),
    builder: (context, snapshot) {
      var mydata = json.decode(snapshot.data.toString());
      if (mydata != null) {
        return SizeTransition(
            axis: Axis.vertical,
            sizeFactor: animation,
            child: Center(child: Text(mydata["1"][0].toString()))
            );
      } else {
        return SizeTransition(
            axis: Axis.vertical,
            sizeFactor: animation,
            child: Center(child: CircularProgressIndicator())
            );
      }
    });

这是我收到的错误消息:

══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════ The following TypeErrorImpl was thrown building FutureBuilder(dirty, state: _FutureBuilderState#4fb8d): Expected a value of type 'int', but got one of type 'String'

如果我这样做:

mydata[1][1]

它给了我一个空输出!
该代码有什么问题以及如何解决？

Answer 1

您的JSON在顶层表示一个数组，因为它以[开头。因此，您必须使用整数索引而不是字符串来访问元素。在第二层，您拥有的对象是 map 。因此，我认为mydata[2]["2"]["mode"]应该给您“文本”。或者，您期望使用特定访问权限从JSON输出什么？