JsonObject JsonArray解析问题

Question

我是JSON的新手，但已成功从其他JSON请求中提取数据。这一个给我带来麻烦。任何帮助或指针，将不胜感激。

这是JSON请求：http://api.wunderground.com/api/95e20de6002dc6f0/currenthurricane/view.json

，上面拉下我想要的数据。

下面是我遇到的麻烦我的代码：

public static ArrayList<CycloneData> extractFeatureFromJson(String cycloneJSON) { 

    // Create an empty ArrayList to start adding Cyclones to 
    ArrayList<CycloneData> cyclones = new ArrayList<>(); 

    // try to parse the cycloneJSON response string. If there's a problem with the way the JSON 
    // is formatted, a JSONException exception object will be thrown. 
    // Catch the exception, and print the error message to the logs. 

    try { 

     JSONObject rootJsonObject = new JSONObject(cycloneJSON); 

     // Create JSONArray associated with the key called "currenthurricane", which represents 
     // a list of cyclones from JSON response. 
     JSONArray currentHurricaneArray = rootJsonObject.getJSONArray("currenthurricane"); 

     //Loop through each section in the currentHurricaneArray array & create an 
     //{@link CycloneData} object for each one 
     for (int i = 0; i < currentHurricaneArray.length(); i++) { 
      //Get cyclone JSONObject at position i in the array 
      JSONObject cycloneProperties = currentHurricaneArray.getJSONObject(i); 
      //Extract “stormName_Nice” for Cyclone's name 
      String name = cycloneProperties.optString("stormName_Nice"); 
      // Extract the value for the key called "url" 
      String url = cycloneProperties.optString("url"); 
      int category = cycloneProperties.optInt("SaffirSimpsonCategory"); 
      CycloneData cyclone = new CycloneData(category, name, url); 
      //Add new cyclone to list 
      cyclones.add(cyclone); 
     } 

    } catch (JSONException e) { 
     // If an error is thrown when executing any of the above statements in the "try" block, 
     // catch the exception here, so the app doesn't crash. Print a log message 
     // with the message from the exception. 
     Log.e("Utils", "Problem parsing the cyclone JSON results", e); 
    } 

    // Return the list of cyclones 
    return cyclones; 
} 

使用Android Studio中的调试器，我可以看到，在currentHurricaneArray：JSONArray currentHurricaneArray = rootJsonObject.getJSONArray("currenthurricane");

越来越预期的JSON数组数据。

当for循环开始的JSONObject：JSONObject cycloneProperties = currentHurricaneArray.getJSONObject(i);

有我在寻找，以及正确的阵列信息。

但是，之后，它开始提取字符串。 String name = cycloneProperties.optString("stormName_Nice");

它什么也没有返回。

调试表明：name = ""

我能够得到我想要，如果我使用JSON查询工具的信息，但我无法弄清楚如何得到它在我的代码工作。

我敢肯定我的字符串提取是错误的，我只是无法弄清楚如何使它正确。或者也许我错了。

*************良好的代码下面*******************

确定的Gaetan Maisse让我去。以下是我所做的工作。

for (int i = 0; i < currentHurricaneArray.length(); i++) { 
      //Get cyclone JSONObject at position i in the array 
      JSONObject cycloneProperties = currentHurricaneArray.getJSONObject(i); 

      // Extract "stormInfo" object 
      JSONObject stormInfo = cycloneProperties.optJSONObject("stormInfo"); 
      //Extract “stormName_Nice” & "requesturl" for Cyclone's name and url 
      String name = stormInfo.optString("stormName_Nice"); 
      String url = stormInfo.optString("requesturl"); 

      // Extract "Current" object 
      JSONObject Current = cycloneProperties.optJSONObject("Current"); 
      // Extract "SaffirSimpsonCategory" key 
      int category = Current.optInt("SaffirSimpsonCategory"); 

      CycloneData cyclone = new CycloneData(category, name, url); 
      //Add new cyclone to list 
      cyclones.add(cyclone); 
     } 

Answer 1

你缺少JSON关键stormInfo在分析过程stormName_Nice：

{ 
    "response": { 
     "version": "0.1", 
     "termsofService": "http://www.wunderground.com/weather/api/d/terms.html", 
     "features": { 
      "currenthurricane": 1 
     } 
    }, 
    "currenthurricane": [{ 
     "stormInfo": { 
      "stormName": "Daniel", 
      "stormName_Nice": "Hurricane Daniel", 
      "stormNumber": "ep201204" 
     }, 
     ..., 
     "SaffirSimpsonCategory": 1, 
     "url":"URL", 
     ... 
    }] 
} 

它应该更好地与这个工程：

JSONObject rootJsonObject = new JSONObject(cycloneJSON); 

// Create JSONArray associated with the key called "currenthurricane", which represents 
// a list of cyclones from JSON response. 
JSONArray currentHurricaneArray = rootJsonObject.getJSONArray("currenthurricane"); 

//Loop through each section in the currentHurricaneArray array & create an 
//{@link CycloneData} object for each one 
for (int i = 0; i < currentHurricaneArray.length(); i++) { 
    //Get cyclone JSONObject at position i in the array 
    JSONObject cycloneProperties = currentHurricaneArray.getJSONObject(i); 

    // Extract "stormInfo" object 
    JSONObject stormInfo = cycloneProperties.getJSONObject("stormInfo"); 
    //Extract “stormName_Nice” for Cyclone's name 
    String name = stormInfo.optString("stormName_Nice"); 

    // Extract other values from cycloneProperties 
    String url = cycloneProperties.optString("url"); 
    int category = cycloneProperties.optInt("SaffirSimpsonCategory"); 
    CycloneData cyclone = new CycloneData(category, name, url); 
    //Add new cyclone to list 
    cyclones.add(cyclone); 
} 

Answer 2

optString（字符串名称，字符串回退），如果它存在，如果需要的话它胁迫，或者如果没有这样的映射存在回退到返回通过名称映射的值。打印后备测试。如果回退被触发，则没有键。这表明您的json结构格式不正确，或者您的解析逻辑不适合您正在使用的已定义结构。