如何在 Android 中解析 JSON？ [复制]

Question

如何在 Android 中解析 JSON 提要？

Answer 1

Android 内置了解析 json 所需的所有工具。示例如下，不需要 GSON 或类似的东西。

获取您的 JSON：

假设你有一个 json 字符串

String result = "{\"someKey\":\"someValue\"}";

创建JSONObject：

JSONObject jObject = new JSONObject(result);

如果你的 json 字符串是一个数组，例如：

String result = "[{\"someKey\":\"someValue\"}]"

那么您应该使用JSONArray，如下所示，而不是JSONObject

获取特定字符串

String aJsonString = jObject.getString("STRINGNAME");

获取特定的布尔值

boolean aJsonBoolean = jObject.getBoolean("BOOLEANNAME");

获取特定整数

int aJsonInteger = jObject.getInt("INTEGERNAME");

获取特定的多头

long aJsonLong = jObject.getLong("LONGNAME");

获取特定的双精度

double aJsonDouble = jObject.getDouble("DOUBLENAME");

获取具体的JSONArray：

JSONArray jArray = jObject.getJSONArray("ARRAYNAME");

从数组中获取项目

for (int i=0; i < jArray.length(); i++)
{
    try {
        JSONObject oneObject = jArray.getJSONObject(i);
        // Pulling items from the array
        String oneObjectsItem = oneObject.getString("STRINGNAMEinTHEarray");
        String oneObjectsItem2 = oneObject.getString("anotherSTRINGNAMEINtheARRAY");
    } catch (JSONException e) {
        // Oops
    }
}

Answer 2

1. 编写 JSON 解析器类

   public class JSONParser {
   
       static InputStream is = null;
       static JSONObject jObj = null;
       static String json = "";
   
       // constructor
       public JSONParser() {}
   
       public JSONObject getJSONFromUrl(String url) {
   
           // Making HTTP request
           try {
               // defaultHttpClient
               DefaultHttpClient httpClient = new DefaultHttpClient();
               HttpPost httpPost = new HttpPost(url);
   
               HttpResponse httpResponse = httpClient.execute(httpPost);
               HttpEntity httpEntity = httpResponse.getEntity();
               is = httpEntity.getContent();
   
           } catch (UnsupportedEncodingException e) {
               e.printStackTrace();
           } catch (ClientProtocolException e) {
               e.printStackTrace();
           } catch (IOException e) {
               e.printStackTrace();
           }
   
           try {
               BufferedReader reader = new BufferedReader(new InputStreamReader(
                       is, "iso-8859-1"), 8);
               StringBuilder sb = new StringBuilder();
               String line = null;
               while ((line = reader.readLine()) != null) {
                   sb.append(line + "\n");
               }
               is.close();
               json = sb.toString();
           } catch (Exception e) {
               Log.e("Buffer Error", "Error converting result " + e.toString());
           }
   
           // try parse the string to a JSON object
           try {
               jObj = new JSONObject(json);
           } catch (JSONException e) {
               Log.e("JSON Parser", "Error parsing data " + e.toString());
           }
   
           // return JSON String
           return jObj;
   
       }
   }
   

2. 解析 JSON 数据
   一旦你创建了解析器类，接下来的事情就是知道如何使用该类。下面我将解释如何使用解析器类解析 json（在本例中）。

   2.1。将所有这些节点名称存储在变量中：在联系人 json 中，我们有姓名、电子邮件、地址、性别和电话号码等项目。所以第一件事是将所有这些节点名称存储在变量中。打开您的主活动类并声明将所有节点名称存储在静态变量中。

   // url to make request
   private static String url = "http://api.9android.net/contacts";
   
   // JSON Node names
   private static final String TAG_CONTACTS = "contacts";
   private static final String TAG_ID = "id";
   private static final String TAG_NAME = "name";
   private static final String TAG_EMAIL = "email";
   private static final String TAG_ADDRESS = "address";
   private static final String TAG_GENDER = "gender";
   private static final String TAG_PHONE = "phone";
   private static final String TAG_PHONE_MOBILE = "mobile";
   private static final String TAG_PHONE_HOME = "home";
   private static final String TAG_PHONE_OFFICE = "office";
   
   // contacts JSONArray
   JSONArray contacts = null;
   

   2.2。使用解析器类获取 JSONObject 并循环遍历每个 json 项。下面我创建了一个JSONParser 类的实例，并使用for 循环遍历每个json 项，最后将每个json 数据存储在变量中。

   // Creating JSON Parser instance
   JSONParser jParser = new JSONParser();
   
   // getting JSON string from URL
   JSONObject json = jParser.getJSONFromUrl(url);
   
       try {
       // Getting Array of Contacts
       contacts = json.getJSONArray(TAG_CONTACTS);
   
       // looping through All Contacts
       for(int i = 0; i < contacts.length(); i++){
           JSONObject c = contacts.getJSONObject(i);
   
           // Storing each json item in variable
           String id = c.getString(TAG_ID);
           String name = c.getString(TAG_NAME);
           String email = c.getString(TAG_EMAIL);
           String address = c.getString(TAG_ADDRESS);
           String gender = c.getString(TAG_GENDER);
   
           // Phone number is agin JSON Object
           JSONObject phone = c.getJSONObject(TAG_PHONE);
           String mobile = phone.getString(TAG_PHONE_MOBILE);
           String home = phone.getString(TAG_PHONE_HOME);
           String office = phone.getString(TAG_PHONE_OFFICE);
   
       }
   } catch (JSONException e) {
       e.printStackTrace();
   }
   

Answer 3

我已经为您编写了一个简单的示例并注释了源代码。该示例展示了如何抓取实时 json 并解析为 JSONObject 以进行详细信息提取：

try{
    // Create a new HTTP Client
    DefaultHttpClient defaultClient = new DefaultHttpClient();
    // Setup the get request
    HttpGet httpGetRequest = new HttpGet("http://example.json");

    // Execute the request in the client
    HttpResponse httpResponse = defaultClient.execute(httpGetRequest);
    // Grab the response
    BufferedReader reader = new BufferedReader(new InputStreamReader(httpResponse.getEntity().getContent(), "UTF-8"));
    String json = reader.readLine();

    // Instantiate a JSON object from the request response
    JSONObject jsonObject = new JSONObject(json);

} catch(Exception e){
    // In your production code handle any errors and catch the individual exceptions
    e.printStackTrace();
}

拥有JSONObject 后，请参阅SDK，了解有关如何提取所需数据的详细信息。