Question

我的第一个问题。我对android和json有点新鲜。

我有一个带有一些值的.json文件（见下文）。我需要解析它，我试过但我得到了一个nullpointer异常。任何帮助都会很棒！

{
  "i": 475,
  "lp": "NEW",
  "c": "tlf",
  "dmc": 0,
  "hfg": false,
  "b": [
    "No",
    "Yes"
  ],
  "t": [
    {
      "i": 131321,
      "d": [
        {
          "d": "2014-07-01T08:32:08",
          "lm": 1,
          "s": 0,
          "b": 33,
          "i": 1,
          "sS": 63,
          "bV": 14.1,
          "h": 0.9,
          "mi": 137385101,
          "x": 0,
          "de": 0
        },
        {
          "d": "2014-07-01T08:39:08",
          "lm": 1,
          "s": 0,
          "b": 34,
          "i": 1,
          "sS": 63,
          "bV": 14.1,
          "h": 0.9,
          "mi": 137385102,
          "x": 0,
          "de": 0
        }
      ],
      "m": [
        {
          "a": 44.409315,
          "o": 26.204476,
          "b": 239,
          "f": 1,
          "i": 137385102
        },
        {
          "a": 44.409175,
          "o": 26.203828,
          "b": 255,
          "f": 2,
          "i": 137385103
        }
      ],
      "p": {
        "a": 0,
        "o": 0
      }
    }
  ],
  "e": [

  ]
}

代码：

 StringBuffer sb = new StringBuffer();
        BufferedReader br = null;
        try {
            br = new BufferedReader(new InputStreamReader(getAssets().open(
                    "Chart-data-source.json")));
            String temp;
            while ((temp = br.readLine()) != null)
                sb.append(temp);
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                br.close(); // stop reading
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        String myjsonstring = sb.toString();

错误：引起：java.lang.NullPointerException 在com.chartdata.Main.onCreate（Main.java:47） - （br.close（）;这是第47行）

Answer 1

要从文件中读取json，请尝试使用此方法

    public static String readFile(String path, Charset encoding) 
          throws IOException 
        {
          byte[] encoded = Files.readAllBytes(Paths.get(path));
          return encoding.decode(ByteBuffer.wrap(encoded)).toString();
     }

调用方法如：

String myJsonString = readFile("C:/pathToJsonFile/folderjsonFlex.json", StandardCharsets.UTF_8);

然后创建json，只需使用

JSONObject myCoolJson = new JSONObject(myJsonString);

Json解析给出nullpointer异常（android）

1 个答案: