Flutter调用贷款模拟接口报FormatException: Unexpected end of input如何解决

数据老陈

2026-10-20

错误根源

你错误地对字符串类型的response.body直接取下标[0]，导致传给jsonDecode的内容只有单个字符[，完全不符合JSON格式，才触发了格式异常。你之前不加[0]报错是因为接口返回的是JSON数组，解码后是List类型，无法直接传给接收Map参数的fromJson方法，操作顺序完全搞反了。

修复方案

1. 修正LoanModel.simulators方法

因为你需要把数据渲染到ListView，接口本身也返回了多期还款数据，所以直接解析为List<LoanModel>返回即可：

static Future<List<LoanModel>> simulators({String periodtime, String interestpermonth, String loanamountrequest, String idUser, String url}) async  {
  var url = "http://192.168.0.23/edufund-api/Api/loansimulation.php?periodtime=" + periodtime + "&interestpermonth=" + interestpermonth + "&loanamountrequest=" +loanamountrequest;
  final response = await http.get(url,headers:{"Content-Type":"application/json"});
  // 先解码整个响应字符串得到数组
  List<dynamic> jsonList = jsonDecode(response.body);
  // 遍历数组把每一项转成LoanModel对象
  List<LoanModel> resList = jsonList.map((item) => LoanModel.fromJson(item)).toList();
  print(response.body);
  return resList;
}

2. 修正贷款模拟处理逻辑

适配返回的列表数据，同时增加异常捕获避免崩溃：

void result() async {
  try {
    List<LoanModel> loanList = await LoanModel.simulators(
        periodtime: periodtime,
        interestpermonth: interestpermonth,
        loanamountrequest: loanamountrequest,
        url: BaseURL.kLoanSimulationUrl2
    );
    // 取第一条的状态判断请求是否成功
    if (loanList.isNotEmpty && loanList.first.status == true) {
      // 把列表传到Simulator页面用于渲染ListView
      Navigator.pushReplacementNamed(context, Simulator.id, arguments: loanList);
    } else {
      _scaffoldKey.currentState.showSnackBar(SnackBar(
        content: Text("获取贷款模拟数据失败"),
        duration: Duration(seconds: 3),
      ));
    }
  } catch(e) {
    _scaffoldKey.currentState.showSnackBar(SnackBar(
      content: Text("请求出错：${e.toString()}"),
      duration: Duration(seconds: 3),
    ));
  }
}

3. Simulator页面渲染ListView示例

在Simulator页面接收传递的列表，直接构建列表即可：

class Simulator extends StatefulWidget {
  static const String id = "Simulator";
  @override
  _SimulatorState createState() => _SimulatorState();
}

class _SimulatorState extends State<Simulator> {
  @override
  Widget build(BuildContext context) {
    // 接收传入的还款计划列表
    List<LoanModel> loanList = ModalRoute.of(context).settings.arguments as List<LoanModel>;
    return Scaffold(
      appBar: AppBar(title: Text("贷款模拟结果")),
      body: ListView.builder(
        itemCount: loanList.length,
        itemBuilder: (context, index) {
          final item = loanList[index];
          return ListTile(
            title: Text("第${item.no}期"),
            subtitle: Column(
              crossAxisAlignment: CrossAxisAlignment.start,
              children: [
                Text("月供：${item.installment}"),
                Text("利息：${item.interest}，本金：${item.principal}"),
                Text("剩余本金：${item.balance}"),
              ],
            ),
          );
        },
      ),
    );
  }
}

注意事项

你的LoanModel中定义的message字段，接口返回的JSON里没有对应值，需要后端在请求失败的场景下补充返回该字段才能正常使用
Android高版本默认禁止HTTP请求，需要在安卓配置文件中添加HTTP允许规则，同时确保测试手机和服务端在同一个局域网，能正常访问192.168.0.23的接口

内容的提问来源于stack exchange，提问作者user15043474