Android中JSON的解析-JSONObject和JSONArray

JSON解析

无可奈何花落去,似曾相识燕归来 – 晏殊

JSON语法

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json语法是JavaScript对象表示法语法的子集

• 数据在名称/值对中
• 数据由逗号分隔
• 花括号保持对象
• 方括号保存数组

JSON的值可以是：

• 数字（整数或者浮点数）
• 字符串（在双引号内）
• 逻辑值(true 或 false)
• 数组(使用方括号[]包围)
• 对象( 使用花括号{}包围)
• null

JSON中有且只有两种结构：对象和数组。

1、对象：对象在js中表示为“{}”括起来的内容，数据结构为
{key：value,key：value,…}的键值对的结构，在面向对象的语言中，key为对象的属性，value为对应的属性值，所以很容易理解，取值方法为
对象.key 获取属性值，这个属性值的类型可以是 数字、字符串、数组、对象几种。

2、数组：数组在js中是中括号“[]”括起来的内容，数据结构为
[“java”,”javascript”,”vb”,…]，取值方式和所有语言中一样，使用索引获取，字段值的类型可以是 数字、字符串、数组、对象几种。

本地json文件的解析

本地的json数据

我们先解析本地的json文件 ,之后再解析网络的json文件
程序要解析的数据都放在项目的assets目录下

我们将新建三个json文件,来依次解析不同的数据类型
下面就三个json文件的源码
注意三个json文件的不同

• get_data1.json

{"name":"baoqiang", "age":"18", "address":"ganzhou"}

• get_data2.json

[  {"id":1,"ide":"Eclipse","name":"java"},  {"id":2,"ide":"XCode","name":"Swift"},  {"id":3,"ide":"Visual Studio","name":"C##"}]

• get_data3.json

{"name":"baoqiang", "age":"18", "address":"ganzhou",  "languages":[    {"id":1,"ide":"Eclipse","name":"java"},    {"id":2,"ide":"XCode","name":"Swift"},    {"id":3,"ide":"Visual Studio","name":"C##"}  ] }

解析实现方法

一. 解析get_data1.json的数据,代码直接放在onCreate方法下执行

 try {            //InputStreamReader 将字节输入流转换为字符流            InputStreamReader isr = new InputStreamReader(getAssets().open("get_data1.json"), "UTF-8");            //包装字符流,将字符流放入缓存里            BufferedReader br = new BufferedReader(isr);            String line;            //StringBuilder和StringBuffer功能类似,存储字符串            StringBuilder builder = new StringBuilder();            while ((line = br.readLine()) != null) {                //append 被选元素的结尾(仍然在内部)插入指定内容,缓存的内容依次存放到builder中                builder.append(line);            }            br.close();            isr.close();            //builder.toString()返回表示此序列中数据的字符串            JSONObject root = new JSONObject(builder.toString());            System.out.println("name=  " + root.getString("name") +                    ";age=  " + root.getInt("age") +                    ";address=  " + root.getString("address"));        } catch (IOException e) {            e.printStackTrace();        } catch (JSONException e) {            e.printStackTrace();        }

结果

二. 解析get_data2.json的数据

try {            InputStreamReader isr = new InputStreamReader(getAssets().open("get_data2.json"), "UTF-8");            BufferedReader br = new BufferedReader(isr);            String line;            StringBuilder builder = new StringBuilder();            while ((line = br.readLine()) != null) {                builder.append(line);            }            br.close();            isr.close();            JSONArray array = new JSONArray(builder.toString());            for (int i = 0; i < array.length(); i++) {                JSONObject lan = array.getJSONObject(i);                System.out.println("-----------------");                System.out.println("id= " + lan.getInt("id"));                System.out.println("ide= " + lan.getString("ide"));                System.out.println("name= " + lan.getString("name"));            }        } catch (IOException e) {            e.printStackTrace();        } catch (JSONException e) {            e.printStackTrace();        }

结果

三.解析get_data3.json数据

try {            InputStreamReader isr = new InputStreamReader(getAssets().open("get_data3.json"), "UTF-8");            BufferedReader br = new BufferedReader(isr);            String line;            StringBuilder builder = new StringBuilder();            while ((line = br.readLine()) != null) {                builder.append(line);            }            br.close();            isr.close();            JSONObject root = new JSONObject(builder.toString());            System.out.println("name= " + root.getString("name") +                    " age= " + root.getInt("age") +                    " address= " + root.getString("address"));            //读取多个数据            JSONArray array = root.getJSONArray("languages");            for (int i = 0; i < array.length(); i++) {                JSONObject lan = array.getJSONObject(i);                System.out.println("-----------------");                System.out.println("id= " + lan.getInt("id"));                System.out.println("name= " + lan.getString("name"));                System.out.println("ide= " + lan.getString("ide"));            }        } catch (IOException e) {            e.printStackTrace();        } catch (JSONException e) {            e.printStackTrace();        }

结果

注意

lan.getInt(“id”)和getJSONObject();还可以用lan.optInt(“id”)和optJSONObject()表示,功能相同,返回值不同,,get会有null值异常抛出
如果解析数组和对象类型数不正确,则会报错
System.err: org.json.JSONException …….type org.json.JSONObject cannot be converted to JSONArray
System.err: at org.json.JSON.typeMismatch(JSON.java:111)

网络 json文件的解析

网络上的json数据

网络服务器选用Tomcat服务器
我们把get_data3.json文件放在C:\Program Files\Apache Software Foundation\Tomcat 7.0\webapps\ROOT目录下,并开启Tomcat服务器
大可不必用eclipse建立动态网站来发布文件
下图是开启后从浏览器查看发布的数据

• get_data3.json

{"name":"baoqiang", "age":"18", "address":"ganzhou",  "languages":[    {"id":1,"ide":"Eclipse","name":"java"},    {"id":2,"ide":"XCode","name":"Swift"},    {"id":3,"ide":"Visual Studio","name":"C##"}  ] }

联网权限

<uses-permission android:name="android.permission.INTERNET"/>

代码

注意

联网需要开子线程,如果要更新UI,还需要在子线程中用runOnUiThread()或者Handler来处理

@Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        System.out.println("开始");        new Thread() {            @Override            public void run() {                try {                    //注意填写自己的IPv4路径,不能用localhost                    String path = "http://192.168.1.44:8080/get_data3.json";                    URL url = new URL(path);                    System.out.println(path);                    HttpURLConnection conn = (HttpURLConnection) url.openConnection();                    conn.setRequestMethod("GET");                    conn.setConnectTimeout(5000);                    if (conn.getResponseCode() == 200) {                        System.out.println("连接成功");                        InputStream in = conn.getInputStream();                        InputStreamReader isr = new InputStreamReader(in);                        //InputStreamReader isr = new InputStreamReader(getAssets().open("get_data.json"),"UTF-8");                        BufferedReader br = new BufferedReader(isr);                        String line;                        //StringBuilder 缓存区 StringBuffer                        StringBuilder builder = new StringBuilder();                        while ((line = br.readLine()) != null) {                            builder.append(line);                        }                        br.close();                        isr.close();                        JSONObject root = new JSONObject(builder.toString());                        System.out.println("name= " + root.getString("name") +                                " age= " + root.getInt("age") +                                " address= " + root.getString("address"));                        //读取多个数据                        JSONArray array = root.getJSONArray("languages");                        for (int i = 0; i < array.length(); i++) {                            JSONObject lan = array.getJSONObject(i);                            System.out.println("-----------------");                            System.out.println("id= " + lan.getInt("id"));                            System.out.println("name= " + lan.getString("name"));                            System.out.println("ide= " + lan.getString("ide"));                        }                    } else {                        System.out.println("连接失败");                    }                } catch (IOException e) {                    e.printStackTrace();                } catch (JSONException e) {                    e.printStackTrace();                }            }        }.start();    }

结果

JSON文本的编写

需要编写的格式文件

{"name":"baoqiang", "age":"18", "address":"ganzhou",  "languages":[    {"id":1,"ide":"Eclipse","name":"java"},    {"id":2,"ide":"XCode","name":"Swift"},    {"id":3,"ide":"Visual Studio","name":"C##"}  ]}

编写代码

 try {            JSONObject root = new JSONObject();            root.put("name", "baoqiang");            root.put("age", "12");            root.put("adress", "guanzhou");            /**             * languages三行值             */            JSONObject lan1 = new JSONObject();            lan1.put("id", "1");            lan1.put("ide", "Eclipse");            lan1.put("name", "java");            JSONObject lan2 = new JSONObject();            lan2.put("id", "2");            lan2.put("ide", "Xcode");            lan2.put("name", "swift");            JSONObject lan3 = new JSONObject();            lan3.put("id", "3");            lan3.put("ide", "Studio");            lan3.put("name", "C#");            JSONArray array = new JSONArray();            array.put(lan1);            array.put(lan2);            array.put(lan3);            root.put("languages", array);            System.out.println(root.toString());        } catch (JSONException e) {            e.printStackTrace();        }

结果

源码下载

json本地解析-源码:https://github.com/PengHongfu/Json_Local.git
json网络解析-源码:https://github.com/PengHongfu/Json_net.git

参考

http://blog.isming.me/blog/2014/06/04/parse-json-in-android/