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/