如何在Android中解析JSON数据?
如何在Android中解析JSON数据?
Android内置了解析JSON所需的所有工具。以下是示例,无需使用GSON或类似工具。
获取JSON:
假设您有一个JSON字符串
String result = "{\"someKey\":\"someValue\"}";
创建一个JSONObject:
JSONObject jObject = new JSONObject(result);
如果您的JSON字符串是一个数组,例如:
String result = "[{\"someKey\":\"someValue\"}]"
如果您需要获取一个数组,应该使用下面演示的JSONArray
而不是JSONObject
要获取特定字符串
String aJsonString = jObject.getString("STRINGNAME");
获取特定布尔值:
boolean aJsonBoolean = jObject.getBoolean("BOOLEANNAME");
获取特定整数
int aJsonInteger = jObject.getInt("INTEGERNAME");
获取特定的长整型数
long aJsonLong = jObject.getLong("LONGNAME");
获取特定的double数值
double aJsonDouble = jObject.getDouble("DOUBLENAME");
获取特定的JSONArray:
JSONArray jArray = jObject.getJSONArray("ARRAYNAME");
获取数组中的项目
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
}
}
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;
}
}
解析 JSON 数据
一旦你创建了解析器类,下一步就是了解如何使用该类。以下是我解释如何使用解析器类解析 JSON(在此示例中)。
2.1.将所有这些节点名称存储在变量中:在联系人的json中,我们有诸如姓名、电子邮件、地址、性别和电话号码之类的项目。因此,首先要做的是将所有这些节点名称存储在变量中。打开你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(parser class
)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();
}
我已经为您编写了一个简单的示例,并对源代码进行了注释。该示例展示了如何获取实时的JSON并将其解析为JSONObject
以进行详细提取:
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();
}
一旦您拥有了您的JSONObject
,请参阅SDK获取有关如何提取所需数据的详细信息。
readLine()
会失败。 - kazinix