Android数据格式解析对象JSON用法

灰太狼 2022-06-12 00:16 210阅读 0赞

1.JSON概念：

一种轻量级的数据交换格式，具有良好的可读和便于快速编写的特性，从而可以在不同平台间进行数据交换。JSON采用兼容性很高的文本格式，同时也具备类似于C语言体系的行为。

JSON可以将Java对象转成json格式的字符串，可以将json字符串转换成Java。比XML更轻量级，Json使用起来比较轻便和简单。JSON数据格式，在Android中被广泛运用于客户端和服务器通信，在网络数据传输与解析时非常方便。

2.环境配置

[http://code.google.com/p/google-gson/][http_code.google.com_p_google-gson]里有一个名为Gson的类库，可以用它来解析Json数据，并且，Adroid 3.0平台里其实也就是把这一部分直接整合进Android里了。我们要解析Json数据，直接去网站上下载个jar包，导入到工程里，就可以解析Json数据了。

3.JSON应用

(1).JSON是一种轻量级的数据交换格式  
   (2).JSON基于两种数据结构：Object和Array。其中Object是“名称/值”对的集合。

（3）在Android中包含四个与JSON相关的类和一个Exceptions：

a.JSONObject

这是系统中有关JSON定义的基本单元，其包含一对儿(Key/Value)数值。

b.JSONArray

它代表一组有序的数值。将其转换为String输出(toString)所表现的形式是用方括号包裹，数值以逗号”,”分隔（例如：\[value1,value2,value3\]

c.JSONStringer

这个类可以帮助快速和便捷的创建JSONtext。其最大的优点在于可以减少由于格式的错误导致程序异常，引用这个类可以自动严格按照JSON语法规则（syntaxrules）创建JSON text。每个JSONStringer实体只能对应创建一个JSON text。例如：

String myString = new JSONStringer().object()   
    .key("name")  
    .value("小猪")   
    .endObject()  
    .toString();

myString =\{"name" : "小猪"\}

d.JSONTokener

这个是系统为JSONObject和JSONArray构造器解析JSON source string的类，它可以从source string中提取数值信息。

e.JSONException

（4）JSON格式举例

*a.Object实例：*

![复制代码][copycode.gif]

{
         "Image": {
          "Width":  800,
          "Height": 600,
          "Title":  "View from 15th Floor",
          "Thumbnail": {
              "Url":    "http://www.example.com/image/481989943",
              "Height": 125,
              "Width":  "100"
          },
          "IDs": [116, 943, 234, 38793]
        }
    }

![复制代码][copycode.gif]

*b.Array实例:*

![复制代码][copycode.gif]

[
       {
          "precision": "zip",
          "Latitude":  37.7668,
          "Longitude": -122.3959,
          "Address":   "",
          "City":      "SAN FRANCISCO",
          "State":     "CA",
          "Zip":       "94107",
          "Country":   "US"
       },
    
       {
          "precision": "zip",
          "Latitude":  37.371991,
          "Longitude": -122.026020,
          "Address":   "",
          "City":      "SUNNYVALE",
          "State":     "CA",
          "Zip":       "94085",
          "Country":   "US"
       }
    ]

![复制代码][copycode.gif]

4.JSON解析案例  
     (1)解析Object之一:

![复制代码][copycode.gif]

String jsonString ={"url":"http://www.cnblogs.com/qianxudetianxia"};
    
    解析方法：
    
    JSONObject demoJson = new JSONObject(jsonString);
    
    String url = demoJson.getString("url");

![复制代码][copycode.gif]

(2)解析Object之二:

![复制代码][copycode.gif]

String jsonString ={"name":"android"," version":"Beta1.0"};
    
    解析方法:
    
    JSONObject demoJson = new JSONObject(jsonString);
    
    String name = demoJson.getString("name");
    String version = demoJson.getString("version");
    
    System.out.println("name:"+name+",version:"+version);

![复制代码][copycode.gif]

(3).解析Array之一:

<table style="border:1px solid silver; width:1027px; border-collapse:collapse; word-break:break-word; background:none!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; font-size:12px!important; min-height:auto!important"> 
 <tbody style="background:none!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important"> 
  <tr style="background:none!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important"> 
   <td style="color:rgb(69,69,69); border:1px solid silver; padding:3px; border-collapse:collapse; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; background:none!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; margin:0px!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important"> 
    <div style="background:none!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:relative!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important"> 
     <div style="background:none rgb(244,244,244)!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px 1em 0px 0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important"> 
      <code style="white-space:pre-wrap; background:none!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,0)!important">String jsonString ={ </code> 
      <code style="white-space:pre-wrap; background:none!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:blue!important">"number"</code> 
      <code style="white-space:pre-wrap; background:none!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,0)!important">:[1,2,3]};</code> 
     </div> 
     <div style="border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px 1em 0px 0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important">
       &nbsp; 
     </div> 
     <div style="background:none rgb(244,244,244)!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px 1em 0px 0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important"> 
      <code style="white-space:pre-wrap; background:none!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important">&nbsp;</code> 
      <code style="white-space:pre-wrap; background:none!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,0)!important">解析方法：</code> 
     </div> 
     <div style="border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px 1em 0px 0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important">
       &nbsp; 
     </div> 
     <div style="background:none rgb(244,244,244)!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px 1em 0px 0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important"> 
      <code style="white-space:pre-wrap; background:none!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,0)!important">JSONObject demoJson = </code> 
      <code style="white-space:pre-wrap; background:none!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important">new</code>&nbsp; 
      <code style="white-space:pre-wrap; background:none!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,0)!important">JSONObject(jsonString);</code> 
     </div> 
     <div style="border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px 1em 0px 0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important"> 
      <code style="white-space:pre-wrap; background:none!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,0)!important">JSONArray numberList = demoJson.getJSONArray(</code> 
      <code style="white-space:pre-wrap; background:none!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:blue!important">"number"</code> 
      <code style="white-space:pre-wrap; background:none!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,0)!important">);</code> 
     </div> 
     <div style="background:none rgb(244,244,244)!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px 1em 0px 0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important">
       &nbsp; 
     </div> 
     <div style="border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px 1em 0px 0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important"> 
      <code style="white-space:pre-wrap; background:none!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important">for</code> 
      <code style="white-space:pre-wrap; background:none!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,0)!important">(</code> 
      <code style="white-space:pre-wrap; background:none!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important">int</code>&nbsp; 
      <code style="white-space:pre-wrap; background:none!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,0)!important">i=0; i&lt;numberList.length(); i++){ </code> 
     </div> 
     <div style="background:none rgb(244,244,244)!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px 1em 0px 0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important"> 
      <code style="white-space:pre-wrap; background:none!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important">&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="white-space:pre-wrap; border:0px!important; background:none!important; padding:0px!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important; color:rgb(0,130,0)!important">//因为数组中的类型为int，所以为getInt，其他getString，getLong同用</code> 
     </div> 
     <div style="border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px 1em 0px 0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important"> 
      <code style="white-space:pre-wrap; background:none!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important">&nbsp;&nbsp;&nbsp;&nbsp;</code> 
      <code style="white-space:pre-wrap; background:none!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,0)!important">System.</code> 
      <code style="white-space:pre-wrap; background:none!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,255)!important">out</code> 
      <code style="white-space:pre-wrap; background:none!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,0)!important">.println(numberList.getInt(i));</code> 
     </div> 
     <div style="background:none rgb(244,244,244)!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px 1em 0px 0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; min-height:auto!important"> 
      <code style="white-space:pre-wrap; background:none!important; border:0px!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.8em!important; margin:0px!important; outline:0px!important; overflow:visible!important; padding:0px!important; position:static!important; right:auto!important; top:auto!important; vertical-align:baseline!important; width:auto!important; font-family:Consolas,&quot;Bitstream Vera Sans Mono&quot;,&quot;Courier New&quot;,Courier,monospace!important; min-height:auto!important; color:rgb(0,0,0)!important">}</code> 
     </div> 
    </div> </td> 
  </tr> 
 </tbody> 
</table>

(4).解析Array之二:

![复制代码][copycode.gif]

String jsonString ={"number":[[1],[2],[3]]};
    
    解析方法:
    
    //嵌套数组遍历
    JSONObject demoJson = new JSONObject(jsonString);
    JSONArray numberList = demoJson.getJSONArray("number");
    
    for(int i=0; i<numberList.length(); i++){
          //获取数组中的数组
          System.out.println(numberList.getJSONArray(i).getInt(0));
    }

![复制代码][copycode.gif]

*(5).解析Object和Array:*

![复制代码][copycode.gif]

String jsonString ={"mobile":[{"name":"android"},{"name":"iphone"}]};
    
    解析方法:
    
    JSONObject demoJson = new JSONObject(jsonString);
    JSONArray numberList = demoJson.getJSONArray("mobile");
    
    for(int i=0; i<numberList.length(); i++){
          System.out.println(numberList.getJSONObject(i).getString("name"));
    }

![复制代码][copycode.gif]

(6).使用optType:

上面的例子，使用getType在碰到查找不到节点的时候，会抛出异常。  
如果使用optType，找不到节点，则返回null或者默认值。

//无url节点，抛出异常
    String url = demoJson.getString("url");
    
    //无url节点，返回空，如果为基本类型，则返回默认值
    String url = demoJson.optString("url");

*(7).UTF-8的BOM头导致解析JSON异常的问题*  
      到json文件保存为utf-8的时候，在windows平台下，会产生bom头"EF BB EF"字节在文本的最前面（需要用十六进制工具打开才能看的到）。  
      有两种解决方法：  
      a.使用UltraEdit打开json文件， 另存为的时候，选择格式UTF-8,无BOM头，如果还不行，在用记事本打开，另存为UTF-8下，多试几次就可以了。  
      b.使用代码处理，截取json主体内容：

String jsonString = getJsonString();
    
    jsonString =jsonString.substring(jsonString.indexOf("{"),jsonString.lastIndexOf("}")+1);

[http_code.google.com_p_google-gson]: http://code.google.com/p/google-gson/
[copycode.gif]: /images/20220612/ffdd38a96f484dd28376b1db576ce455.png