来自服务器的数据没有进入 android 中的微调器？

Question

我正在尝试将服务器数据放入我的微调器中，但是当我尝试使用此代码时，我什么也没得到，它没有在微调器中显示任何数据。 这是我的 Home.java 文件：

   public class Home extends AppCompatActivity implements AdapterView.OnItemClickListener, AdapterView.OnItemSelectedListener {

    private Spinner countrySpinner, locationSpinner, citySpinner;
    private TextView cityCodeTextView;
    private Button submitButton;
    private ArrayList<String> country_list, location_list, city_list;
    private JSONArray result;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_home);

        countrySpinner = (Spinner) findViewById(Country);
        //citySpinner = (Spinner) findViewById(City);
        //locationSpinner = (Spinner) findViewById(R.id.Location);
        countrySpinner.setOnItemSelectedListener(this);

        country_list = new ArrayList<String>();
        //location_list = new ArrayList<String>();
        // city_list = new ArrayList<String>();

        getData();
    }
    private void getData(){
        StringRequest
                stringRequest = new StringRequest(Config.DATA_URL,
                new Response.Listener<String>() {
                    @Override
                    public void onResponse(String response) {
                        JSONObject j = null;
                        try {
                            Log.d("Test",response);
                            j = new JSONObject(response);

                            //Storing the Array of JSON String to our JSON Array
                            result = j.getJSONArray(Config.JSON_ARRAY);

                            //Calling method getStudents to get the students from the JSON Array
                            getCountry(result);
                        } catch (JSONException e) {
                            e.printStackTrace();
                        }
                    }
                },new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {

            }
        });
                RequestQueue requestQueue = Volley.newRequestQueue(this);

        //Adding request to the queue
        requestQueue.add(stringRequest);
    }

    private void   getCountry(JSONArray  jsonArrayCountry){
        //Traversing through all the items in the json array
        List<Country> countries = new ArrayList<>();

        try {

            String country_name, country_code;
            JSONObject countries_object;


            for (int i = 0; i < jsonArrayCountry.length(); i++) {
                countries_object = jsonArrayCountry.getJSONObject(i);
                country_code = countries_object.getString("id");
                country_name = countries_object.getString("country");
                countries.add(new Country(country_code, country_name));
            }
            ArrayAdapter countryAdapter = new ArrayAdapter<>(this, android.R.layout.simple_spinner_dropdown_item, countries);
            countrySpinner.setAdapter(countryAdapter);
            countrySpinner.setOnItemSelectedListener(this);
        } catch (JSONException e) {
            Log.e("Home", e.getLocalizedMessage(), e);
        }



    }

    //Method to get student name of a particular position

    //Doing the same with this method as we did with getName()


    //Doing the same with this method as we did with getName()



    //this method will execute when we pic an item from the spinner
    @Override
    public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
        //Setting the values to textviews for a selected item
        //textViewName.setText(getName(position));
        //textViewCourse.setText(getCourse(position));
        //textViewSession.setText(getSession(position));
    }

    //When no item is selected this method would execute
    @Override
    public void onNothingSelected(AdapterView<?> parent) {
       // textViewName.setText("");
      //  textViewCourse.setText("");
        //textViewSession.setText("");
    }

    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {

    }
}

这是 conig.java 文件：

public class Config {
    //JSON URL
    public static final String DATA_URL = "http://..../get_country.php";


    //JSON array name
    public static final String JSON_ARRAY = "result";
}

这是我的json：

[
  {
    "id": "1",
    "country": "UAE"
  },
  {
    "id": "2",
    "country": "UK"
  },
  {
    "id": "3",
    "country": "SAUDI ARABIA"
  },
  {
    "id": "4",
    "country": "OMAN"
  },
  {
    "id": "5",
    "country": "BAHRAIN"
  }
]

我在 logcat 中没有收到任何错误...我不知道为什么它不显示？？

Answer 1

根据您的附加 JSON，您的 JSON 数组没有任何名称，您正在尝试解析

result = j.getJSONArray(Config.JSON_ARRAY); // Config.JSON_ARRAY = "results";

您的解析似乎不正确。

你必须像这样解析 JSON 数组 -

JSONArray result = new JSONArray(response);

也删除

j = new JSONObject(response);

Answer 2

嗨你能试试这样吗

for (int i = 0; i < jsonArrayCountry.length(); i++) {
           countries_object = jsonArrayCountry.getJSONObject(i);
           country_code = countries_object.getString("id");
           country_name = countries_object.getString("country");
           countries.add(new Country(country_code, country_name));
         }
ArrayAdapter countryAdapter = new ArrayAdapter<>(this, android.R.layout.simple_spinner_dropdown_item, countries);
countrySpinner.setAdapter(countryAdapter);

Answer 3

当您使用 API 时，第一步是检查 API 是否正常工作，您可以使用REST_CLIENT和POSTMAN Chekc - https://chrome.google.com/webstore/detail/postman/fhbjgbiflinjbdggehcddcbncdddomop?hl=en

输入您想要的 URL 和标题，然后检查响应是否完美
如果响应正确，则可以移至 android 端

我建议你使用 Gson Liabrary 来解析 gson - https://stackoverflow.com/a/41616005/4741746

您将直接获得需要为 Spinner 设置的 ArrayList

在响应部分你会得到你的 json 而不是在 android 端使用 Gson Lib BEST OF LUCK解析它

将此依赖项放在 app build.gradle 文件中

dependencies {
  compile 'com.google.code.gson:gson:2.6.2'
} 




public class Responce implements Serializable {

    @SerializedName("result")
    public ArrayList<Data>  result;

    public class Data implements Serializable {

     /*{
       "id": "1",
       "country": "UAE"
     },*/
    @SerializedName("country")
    public String  country;

    @SerializedName("id")
    public String  id;
    }
} 

稍微改变你的反应这是正确的方法

{
    "result": [
        {
            "id": "1",
            "country": "UAE"
        },
        {
            "id": "2",
            "country": "UK"
        },
        {
            "id": "3",
            "country": "SAUDI ARABIA"
        },
        {
            "id": "4",
            "country": "OMAN"
        },
        {
            "id": "5",
            "country": "BAHRAIN"
        }
    ]
}

现在你可以像这样访问它

             @Override
                public void onResponse(String response) {


                  Gson gson = new GsonBuilder().create();
                  Responce movie = gson.fromJson(response, Responce.class);
                  ArrayList<Data>  mCountryList=movie.result;

                }
            } 

第二种方式但不是正确的方式

@Override
   public void onResponse(String response) {


    try {
                    ArrayList<String> mStrings = new ArrayList<>();
                    JSONArray myArray = new JSONArray(response);
                    for(int i=0 ;i< myArray.length();i++){
                        JSONObject mObject = (JSONObject) myArray.get(i);
                        String id=  mObject.getString("id");
                        String country=  mObject.getString("country");
                        mStrings.add(country);
                    }
                    ArrayAdapter<String> spinnerArrayAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, mStrings); //selected item will look like a spinner set from XML
                    spinnerArrayAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
                    spinner.setAdapter(spinnerArrayAdapter);
                }catch (Exception e){

                }
      }
  } 

Answer 4

首先，您需要检查 json 是否正确解析。 为此，在获取国家代码和名称的 for 循环中放置一个Log 。

如果您发布的 JSON 与您从Log.d("Test",response);获得的相同Log.d("Test",response); ，那么你需要改变
从：

j = new JSONObject(response);
 //Storing the Array of JSON String to our JSON Array 
result = j.getJSONArray(Config.JSON_ARRAY);`

到：
result = new JSONArray(response);

否则，如果响应类似于{result:[...]} ，那么您是对的，您将解析 json。

接下来，如果您在 for 循环日志中获得了正确的值，则问题出在您的适配器上。 为简化起见，请使用扩展BaseAdapter而不是 ArrayAdapter 的自定义适配器。

Answer 5

添加

adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);

在 setAdapter 之前