Question

我是JSON的新手，但已成功从其他几个JSON请求中提取数据。这个给我带来了麻烦。任何帮助或指示将不胜感激。

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

上面提到了我想要的数据。

以下是我遇到问题的代码：

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;
}

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

获取预期的JSON数组数据。

当for循环启动JSONObject时：JSONObject cycloneProperties = currentHurricaneArray.getJSONObject(i);

我也正在寻找正确的数组信息。

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

它什么都不返回。

调试显示：name = ""

如果我使用JSON查询工具，我可以获得我想要的信息，但我无法弄清楚如何在我的代码中使用它。

我确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。或者也许我错了他们。

*************好的代码在*******************以下

好的GaëtanMaisse让我走了。以下是我为使其工作所做的工作。

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

optString（String name，String fallback），返回按名称映射的值（如果存在），必要时强制转换，如果不存在此映射，则返回。打印回退到test.if回退被触发然后没有键。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。

Answer 2

您在stormInfo的解析过程中缺少JSON密钥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",
        ... 
    }]
}

最好使用它：

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);
}

JsonObject JsonArray解析问题

2 个答案: