Android JSON解析類 - JsonReader

在Android 3.0 honeycomb開始提供了新的JSON解析類 - android.util.JsonReader，下面android123以下面的JSON為例子

[
   {
     "id": 912345678901,
     "text": "How do I read JSON on android?",
     "geo": null,
     "user": {
       "name": "android_newb",
       "followers_count": 41
      
   },
   {
     "id": 912345678902,
     "text": "@android_newb just use android.util.JSonReader!",
     "geo": [50.454722, -104.606667],
     "user": {
       "name": "jesse",
       "followers_count": 2
     }
   }
 ]}

 則解析上面的JSON，使用下面代碼即可，整個處理方法和解析XML差不多，最終使用List數組保存，不過android開發網提示大家，下面的編碼為UTF-8如果遇到中文，服務器默認按GBK編碼，下面的UTF-8改為GB2312可以解決亂碼問題。

 public List readJSonStream(InputStream in) throws IOException {
     JsonReader reader = new JSonReader(new InputStreamReader(in, "UTF-8"));
     return readMessagesArray(reader);
   
 
   public List readMessagesArray(JSonReader reader) throws IOException {
     List messages = new ArrayList();
 
     reader.beginArray();
     while (reader.hasNext()) {
       messages.add(readMessage(reader));
     }
     reader.endArray();
     return messages;
   }
 
   public Message readMessage(JSonReader reader) throws IOException {
     long id = -1;
     String text = null;
     User user = null;
     List geo = null;
 
     reader.beginObject();
     while (reader.hasNext()) {
       String name = reader.nextName();
       if (name.equals("id")) {
         id = reader.nextLong();
       } else if (name.equals("text")) {
         text = reader.nextString();
       } else if (name.equals("geo") && reader.peek() != JSonToken.NULL) {
         geo = readDoublesArray(reader);
       } else if (name.equals("user")) {
         user = readUser(reader);
       } else {
         reader.skipValue();
       }
     }
     reader.endObject();
     return new Message(id, text, user, geo);
   }
 
   public List readDoublesArray(JSonReader reader) throws IOException {
     List doubles = new ArrayList();
 
     reader.beginArray();
     while (reader.hasNext()) {
       doubles.add(reader.nextDouble());
     }
     reader.endArray();
     return doubles;
   }
 
   public User readUser(JSonReader reader) throws IOException {
     String username = null;
     int followersCount = -1;
 
     reader.beginObject();
     while (reader.hasNext()) {
       String name = reader.nextName();
       if (name.equals("name")) {
         username = reader.nextString();
       } else if (name.equals("followers_count")) {
         followersCount = reader.nextInt();
       } else {
         reader.skipValue();
       }
     }
     reader.endObject();
     return new User(username, followersCount);
   }}

   最終android123再次提醒大家，JSonReader是android 3.0引入的新解析類，必須在API Level為honeycomb中的SDK以及固件在3.0上才能使用，完整的成員如下

Public Constructors
 JSonReader(Reader in)  公共構造方法
 
void  beginArray()
Consumes the next token from the JSON stream and asserts that it is the beginning of a new array.
void  beginObject()
Consumes the next token from the JSON stream and asserts that it is the beginning of a new object.
void  close()
Closes this JSON reader and the underlying Reader.
void  endArray()
Consumes the next token from the JSON stream and asserts that it is the end of the current array.
void  endObject()
Consumes the next token from the JSON stream and asserts that it is the end of the current array.
boolean  hasNext()
Returns true if the current array or object has another element.
boolean  isLenIEnt()
Returns true if this parser is liberal in what it accepts.
boolean  nextBoolean()
Returns the boolean value of the next token, consuming it.
double  nextDouble()
Returns the double value of the next token, consuming it.
int  nextInt()
Returns the int value of the next token, consuming it.
long  nextLong()
Returns the long value of the next token, consuming it.
String  nextName()
Returns the next token, a property name, and consumes it.
void  nextNull()
Consumes the next token from the JSON stream and asserts that it is a literal null.
String  nextString()
Returns the string value of the next token, consuming it.
JSonToken  peek()
Returns the type of the next token without consuming it.
void  setLenient(boolean lenIEnt)
Configure this parser to be be liberal in what it accepts.
void  skipValue()
Skips the next value recursively.
String  toString()
Returns a string containing a concise, human-readable description of this object.