java - 没有来自 JSON 的值

Question

我想显示 JSON 中的值只是为了测试目的，但我实际上什么也没收到。哪里可能有问题？ Utils 中的链接肯定是正确的，我已经在浏览器上运行了它，一切都很好。

这是代码

实用程序类

public class WeatherUtils {
public WeatherUtils(){}

public static ArrayList<Weather> getHourlyData (double minTemp, double maxTemp, double currentTemp, double airPressure){

    ArrayList<Weather> weatherList = new ArrayList<>();

    try {
        JSONObject reader = new JSONObject("https://api.openweathermap.org/data/2.5/forecast?q=London,us&units=metric&appid=ID...");
        JSONArray array = reader.getJSONArray("list");
        for (int i = 0; i<array.length(); i++){

            JSONObject secondReader = array.getJSONObject(i);
            JSONObject dataObject = secondReader.getJSONObject("main");
            for (int j = 0; j<dataObject.length(); j++){
                currentTemp = dataObject.getDouble("temp");
                minTemp = dataObject.getDouble("temp_min");
                maxTemp = dataObject.getDouble("temp_max");
                airPressure = dataObject.getDouble("pressure");
            }
            weatherList.add(new Weather(currentTemp,minTemp,maxTemp,airPressure));
        }

    } catch (JSONException e) {
        e.printStackTrace();
    }
    return weatherList;
 }
}

主要 Activity 双 a、b、c、d；

    a = 0.0;
    b = 0.0;
    c = 0.0;
    d = 0.0;

    ArrayList<Weather> weathers = WeatherUtils.getHourlyData(a,b,c,d);
    System.out.println(weathers);

JSON 结构

 {
  "cod": "200",
  "message": 0.0074,
  "cnt": 40,
  "list": [
    {
      "dt": 1559131200,
      "main": {
        "temp": 22.1,
        "temp_min": 21.32,
        "temp_max": 22.1,
        "pressure": 1012.31,
        "sea_level": 1012.31,
        "grnd_level": 976.84,
        "humidity": 92,
        "temp_kf": 0.78
      },
      "weather": [
        {
          "id": 500,
          "main": "Rain",
          "description": "light rain",
          "icon": "10d"
        }
      ],
      "clouds": {
        "all": 89
      },
      "wind": {
        "speed": 3.08,
        "deg": 213.025
      },
      "rain": {
        "3h": 0.875
      },
      "sys": {
        "pod": "d"
      },
      "dt_txt": "2019-05-29 12:00:00"
    },
    {

当然，还有更多数据。我发布了一个“区 block ”

我该如何解决这个问题？

Answer 1

好吧，考虑到您只是想“测试”json 解析，您几乎没有什么选择，但让我们选择一个简单的。但首先，我想说提取解析器并将其放入自己的类/方法中，以便更容易测试，如下所示:

public class WeatherUtils {
public WeatherUtils(){}

public static ArrayList<Weather> getHourlyData (double minTemp, double maxTemp, double currentTemp, double airPressure){

    final ArrayList<Weather> weatherList = new ArrayList<>();

    try {
        final JSONObject response = httpCall();
        weatherList = mapWeatherResponse(response);
    } catch (JSONException e) {
        e.printStackTrace();
    }
    return weatherList;
 }

public static List<Weather> mapWeatherResponse(JSONObject reader){
    final ArrayList<Weather> weatherList = new ArrayList<>();
    JSONArray array = reader.getJSONArray("list");
    for (int i = 0; i<array.length(); i++){
        JSONObject secondReader = array.getJSONObject(i);
        JSONObject dataObject = secondReader.getJSONObject("main");
        for (int j = 0; j<dataObject.length(); j++){
            currentTemp = dataObject.getDouble("temp");
            minTemp = dataObject.getDouble("temp_min");
            maxTemp = dataObject.getDouble("temp_max");
            airPressure = dataObject.getDouble("pressure");
        }
        weatherList.add(new Weather(currentTemp,minTemp,maxTemp,airPressure));
    }
}
}

使用 junit 测试测试响应解析器:

您可以像这样创建 junit 测试:

public class WeatherUtilsTest {
    @Test
    public void parserResponseTEst() {
        final List<String> expectedResponse = new ArrayList<>();
        //fill the expectedResponse with the correspondent values

        final String json = "{\n" +
                "  \"cod\": \"200\",\n" +
                "  \"message\": 0.0074,\n" +
                "  \"cnt\": 40,\n" +
                "  \"list\": [\n" +
                "    {\n" +
                "      \"dt\": 1559131200,\n" +
                "      \"main\": {\n" +
                "        \"temp\": 22.1,\n" +
                "        \"temp_min\": 21.32,\n" +
                "        \"temp_max\": 22.1,\n" +
                "        \"pressure\": 1012.31,\n" +
                "        \"sea_level\": 1012.31,\n" +
                "        \"grnd_level\": 976.84,\n" +
                "        \"humidity\": 92,\n" +
                "        \"temp_kf\": 0.78\n" +
                "      },\n" +
                "      \"weather\": [\n" +
                "        {\n" +
                "          \"id\": 500,\n" +
                "          \"main\": \"Rain\",\n" +
                "          \"description\": \"light rain\",\n" +
                "          \"icon\": \"10d\"\n" +
                "        }\n" +
                "      ],\n" +
                "      \"clouds\": {\n" +
                "        \"all\": 89\n" +
                "      },\n" +
                "      \"wind\": {\n" +
                "        \"speed\": 3.08,\n" +
                "        \"deg\": 213.025\n" +
                "      },\n" +
                "      \"rain\": {\n" +
                "        \"3h\": 0.875\n" +
                "      }\n" +
                "    }]\n" +
                "    }";

        final List<String> response = WeatherUtils.mapWeatherResponse(new JSONObject(json));
        assertEquals(expectedResponse, response);
    }
}

您正在执行的 JSONObject 解析器没有任何问题。您提到您在Utils中使用的链接是正确的，当您在浏览器、 postman 、失眠中测试它时，您是否得到正确的响应？

OBS JSONObject reader = new JSONObject("https://api..."); 不会获取任何内容，您所做的是从给定的 String 创建一个 JSONObject，即“https://...”。要获取数据，您需要实现一些 http 客户端。这是一个例子https://stackoverflow.com/a/4457526/761668