android - 为什么 org.json.JSONObject getLong 和 getString 不相等

Question

代码如下:

     JSONObject contentObject = new JSONObject(content);
     JSONObject params = contentObject.getJSONObject("response_params");
     Log.d("onTest", "channel_id:" + params.getString("channel_id"));
     Log.d("onTest", "channel_id:" + params.getLong("channel_id"));

日志打印:

   08-21 12:46:21.470: DEBUG/onTest(25228): onMessage: content : {"response_params":{"appid":"1071410","channel_id":"3537275240990320342","user_id":"714893193627619861"},"request_id":1293438498}
   08-21 12:46:21.480: DEBUG/onTest(25228): channel_id:3537275240990320342
   08-21 12:46:21.480: DEBUG/onTest(25228): channel_id:3537275240990320128

为什么 getLong 的值为 3537275240990320128，而 String 的值为 3537275240990320342？

Answer 1

根据文档 here ,

public long getLong (String name)

Returns the value mapped by name if it exists and is a long or can be coerced to a long. Note that JSON represents numbers as doubles, so this is lossy; use strings to transfer numbers via JSON.

编辑: 要亲自查看，您可以这样做

JSONObject json = new JSONObject();
try {
    json.put("test", "3537275240990320342");
    String str = json.getString("test");
    double dou = Double.parseDouble(str);
    long lo = (long) dou;
} catch (JSONException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}

您会看到 lo 的值正是您执行 getLong 时得到的值