如何解析Android中的JSON？

Question

如何解析Android中的JSON提要？

Answer 1

注意:这个答案自2013年以来一直没有更新.建议的下载json的方法不再推荐用于android了,因为从api 23开始已经从sdk中删除了http客户端.
但是,下面的解析逻辑仍然适用

Android拥有解析内置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:

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

现在你有了JSON,那又怎样？

创建一个JSONObject:

JSONObject jObject = new JSONObject(result);

获取特定字符串

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

获取特定的布尔值

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

获取特定的整数

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

得到一个特定的长

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

获得特定的双倍

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

要获取特定的JSONArray:

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

从阵列中获取项目

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

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,下一步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(在此示例中使用).

2.1.存储在变量所有这些节点名称:在接触JSON我们有像姓名,电子邮件地址,性别和电话号码的项目.首先,将所有这些节点名称存储在变量中.打开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.下面我创建一个JSONParser类的实例并使用for循环我循环遍历每个json项目,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

我为你编写了一个简单的例子并注明了源代码.该示例显示了如何抓取实时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();
}

获得JSONObject后,请参阅SDK以获取有关如何提取所需数据的详细信息.