从 dart 访问 json 中的数组值元素

Question

我在 flutter 中有这个 const 变量：

static const questions = [
    {
      "question": "question",
      "answers": ["1", "2"],
      "message":
          "message",
    }, 
]

如何从 dart 访问“1”？

我尝试使用 QuestionContent.questions[0]["answers"][0]. 但是我得到了错误 "The method '[]' can't be unconditionally invoked because the receiver can be 'null'"

Answer 1

尝试使用：

Text((QuestionContent.questions[0] as Map<String, dynamic>)['answers'][0] ?? '')

或：

Text((questions[0]['answers'] as List<String>)[0]),

Answer 2

试试下面的代码：

const questions = [
  {
    "question": "question",
    "answers": ["1", "2"],
    "message":
    "message",
  },
];
Map<String, Object> question = questions[0];
List<String> answers = question["answers"] as List<String>;
String firstAnswer = answers.elementAt(0);

您收到错误的原因是编译器无法判断您的 QuestionContent.questions[0]["answers"] 是否为空：

从 dart 访问 json 中的数组值元素

Access to a element of array value in json from dart

json

dart

flutter