Android JSON data parsing_PHP tutorial

Android JSON data parsing

Software and hardware environment

• Macbook Pro MGX 72
• Android Studio 1.3.2
• Genymotion Simulator

Preface

There are very few apps today that do not deal with servers. Among them, in lightweight communication interactions, JSON (JavaScript Object Notation) and XML is also known as the Heavenly Sword and Dragon-Slaying Sword of client-server interaction solutions. This article mainly introduces JSON-related knowledge.

JSON object

The object in JSON is included in a pair of curly brackets. Each item in the object is a "key:value" data pair, and the data pairs are separated by commas . The key of a JSON object can only be of String type, and the value may be of other types such as number, boolean, or null. As shown below

<code class="none" style="-webkit-print-color-adjust:exact;margin:0px;padding:0px;border:none;border-radius:3px;background-color:transparent;">{    "Name" : "Alex",    "Sex"  : "Male",    "Age"  : "20",}</code>

JSON array

The JSON array is included in a pair of square brackets. Each element is a JSON object and is also separated by commas. The example is as follows

<code class="none" style="-webkit-print-color-adjust:exact;margin:0px;padding:0px;border:none;border-radius:3px;background-color:transparent;">[    {    "Name" : "Alex",    "Sex"  : "Male",    "Age"  : "20",    },    {    "Name" : "May",    "Sex"  : "Female",    "Age"  : "19",    },    {    "Name" : "Mike",    "Sex"  : "Male",    "Age"  : "21",    }]</code>

Basic usage of FastJSON

FastJSON is a framework developed by Alibaba that specializes in parsing JSON. According to their own tests, it is very fast and efficient, and there is no other framework. Let's take a JSON data query for Suzhou city weather forecast from an aggregated data website as an example. The obtained URL address is http://v.juhe.cn/weather/index?format=2&cityname=Suzhou&key=6f9276e4d79c5d102bbfb28717beba93. To ensure there is no problem with the data source, you can open the URL in a browser to see if there is data. Here is another tool for Mac, JSON Accelerator, which can not only crawl from the Internet, but also add http request header information, which is very convenient to use.

创建工程

新建工程取名为FastJSONDemo，由于要访问网络，所以需要在AndroidManifest.xml中添加相应权限

<code class="none" style="-webkit-print-color-adjust:exact;margin:0px;padding:0px;border:none;border-radius:3px;background-color:transparent;"><uses-permission android:name="android.permission.INTERNET"></uses-permission></code>

代码部分

网络请求部分，这里我们使用volley这个库，Google出品，使用简单。源码下载地址https://android.googlesource.com/platform/frameworks/volley/，jar包的下载地址http://download.csdn.net/detail/djstava/8793421。下载后把volley的库导入到工程中，UI的话，用了一个TextView来显示接收到的json数据

为了建立一个全局的请求队列，需要在实现一个继承自Application的子类，叫VolleyApplication

<code class="none" style="-webkit-print-color-adjust:exact;margin:0px;padding:0px;border:none;border-radius:3px;background-color:transparent;">package com.djstava.fastjsondemo;import android.app.Application;import com.android.volley.RequestQueue;import com.android.volley.toolbox.Volley;/*** 包名称: com.djstava.fastjsondemo* 创建人: djstava* 创建时间: 15/9/23 下午3:44*/public class VolleyApplication extends Application{    public static RequestQueue requestQueue;    @Override    public void onCreate() {    super.onCreate();    requestQueue =  Volley.newRequestQueue(getApplicationContext());}public static RequestQueue getVolleyQueue() {    return requestQueue;    }}</code>

然后在MainActivity中的onStart方法编写请求部分，然后在onStop方法中取消请求

<code class="none" style="-webkit-print-color-adjust:exact;margin:0px;padding:0px;border:none;border-radius:3px;background-color:transparent;">private static final String JSON_URL = "http://v.juhe.cn/weather/index?format=2&cityname=%E8%8B%8F%E5%B7%9E&key=6f9276e4d79c5d102bbfb28717beba93";//字段key是从聚合数据网站上申请过来的，请自行替换@Overrideprotected void onStart() {    super.onStart();    JsonObjectRequest jsonObjectRequest = new JsonObjectRequest(Request.Method.GET, JSON_URL, null,            new Response.Listener<jsonobject>() {                @Override                public void onResponse(JSONObject jsonObject) {                    try {                        textView.setText(jsonObject.toString());                        Log.e(TAG,"result:" + jsonObject.getString("resultcode"));                    } catch (JSONException e) {                        e.printStackTrace();                    }                }            },            new Response.ErrorListener() {                @Override                public void onErrorResponse(VolleyError volleyError) {                    Log.e(TAG, volleyError.getMessage());                }            });    jsonObjectRequest.setTag("fastjson");    VolleyApplication.requestQueue.add(jsonObjectRequest);}@Overrideprotected void onStop() {    super.onStop();    VolleyApplication.requestQueue.cancelAll("fastjson");}</jsonobject></code>

别忘了在AndroiManifest.xml文件Application标签中加入

<code class="none" style="-webkit-print-color-adjust:exact;margin:0px;padding:0px;border:none;border-radius:3px;background-color:transparent;">android:name=".VolleyApplication"</code>

使用Genymotion模拟器运行程序，可以看到获取的数据

为了方便读者查看，利用JSON Accelerator格式化一下

<code class="none" style="-webkit-print-color-adjust:exact;margin:0px;padding:0px;border:none;border-radius:3px;background-color:transparent;">{"result" : {"sk" : {  "humidity" : "58%",  "wind_direction" : "西北风",  "temp" : "26",  "wind_strength" : "2级",  "time" : "17:27"},"today" : {  "temperature" : "22℃~27℃",  "dressing_index" : "舒适",  "dressing_advice" : "建议着长袖T恤、衬衫加单裤等服装。年老体弱者宜着针织长袖衬衫、马甲和长裤。",  "uv_index" : "弱",  "comfort_index" : "",  "wind" : "东北风3-4 级",  "weather" : "多云转阵雨",  "city" : "苏州",  "date_y" : "2015年09月24日",  "week" : "星期四",  "wash_index" : "不宜",  "weather_id" : {    "fa" : "01",    "fb" : "03"  },  "travel_index" : "较适宜",  "exercise_index" : "较适宜",  "drying_index" : ""},"future" : [  {    "temperature" : "22℃~27℃",    "weather_id" : {      "fa" : "01",      "fb" : "03"    },    "wind" : "东北风3-4 级",    "week" : "星期四",    "date" : "20150924",    "weather" : "多云转阵雨"  },  {    "temperature" : "21℃~26℃",    "weather_id" : {      "fa" : "03",      "fb" : "01"    },    "wind" : "东北风3-4 级",    "week" : "星期五",    "date" : "20150925",    "weather" : "阵雨转多云"  },  {    "temperature" : "21℃~27℃",    "weather_id" : {      "fa" : "01",      "fb" : "01"    },    "wind" : "东北风3-4 级",    "week" : "星期六",    "date" : "20150926",    "weather" : "多云"  },  {    "temperature" : "21℃~28℃",    "weather_id" : {      "fa" : "00",      "fb" : "00"    },    "wind" : "东北风3-4 级",    "week" : "星期日",    "date" : "20150927",    "weather" : "晴"  },  {    "temperature" : "22℃~28℃",    "weather_id" : {      "fa" : "01",      "fb" : "01"    },    "wind" : "东风3-4 级",    "week" : "星期一",    "date" : "20150928",    "weather" : "多云"  },  {    "temperature" : "22℃~28℃",    "weather_id" : {      "fa" : "01",      "fb" : "03"    },    "wind" : "东风3-4 级",    "week" : "星期二",    "date" : "20150929",    "weather" : "多云转阵雨"  },  {    "temperature" : "20℃~25℃",    "weather_id" : {      "fa" : "04",      "fb" : "04"    },    "wind" : "东南风4-5 级",    "week" : "星期三",    "date" : "20150930",    "weather" : "雷阵雨"    }    ]  },  "resultcode" : "200",  "reason" : "successed!",  "error_code" : 0}</code>

接下来该轮到fastjson登场了，，先到http://repo1.maven.org/maven2/com/alibaba/fastjson/下载对应版本的jar包，或者到https://github.com/alibaba/fastjson下载源码，再导入到工程中。

<code class="none" style="-webkit-print-color-adjust:exact;margin:0px;padding:0px;border:none;border-radius:3px;background-color:transparent;">JsonObjectRequest jsonObjectRequest = new JsonObjectRequest(Request.Method.GET, JSON_URL, null,            new Response.Listener<jsonobject>() {                @Override                public void onResponse(JSONObject jsonObject) {                    try {                        textView.setText(jsonObject.toString());                        com.alibaba.fastjson.JSONObject jsonObject1 = JSON.parseObject(jsonObject.toString());                        for (Map.Entry<string object> entry : jsonObject1.entrySet()) {                            System.out.println(entry.getKey() + ":" + entry.getValue());                        }                    } catch (Exception e) {                        e.printStackTrace();                    }                }            }, new Response.ErrorListener() {        @Override        public void onErrorResponse(VolleyError volleyError) {            Log.e(TAG, volleyError.getMessage());        }    });</string></jsonobject></code>

这样，简单的数据解析就完成了。

何为JavaBean?

JavaBean是符合某种规范的java组件，也就是java类，它必须满足如下特性:

• 有一个无参数的默认构造函数
• 有get和set方法

我们把公司员工抽象成一个类，然后利用fastjson来解析

<code class="none" style="-webkit-print-color-adjust:exact;margin:0px;padding:0px;border:none;border-radius:3px;background-color:transparent;">package com.djstava.fastjsondemo;/** * 包名称: com.djstava.fastjsondemo * 创建人: djstava * 创建时间: 15/9/28 上午11:07 */public class Employee {    private int num;    private String name;    private int age;    public Employee(int num, String name, int age) {        this.num = num;        this.name = name;        this.age = age;    }    public void setNum(int num) {        this.num = num;    }    public void setName(String name) {        this.name = name;    }    public void setAge(int age) {        this.age = age;    }    public int getNum() {        return num;    }    public String getName() {        return name;    }    public int getAge() {        return age;    }    @Override    public String toString() {        return "Employee{" +                "num=" + num +                ", name='" + name + '\'' +                ", age=" + age +                '}';    }}</code>

在Android Studio中，可以自动生成get、set、toString这些方法，Code->Generate，快捷键是Command + N。

<code class="none" style="-webkit-print-color-adjust:exact;margin:0px;padding:0px;border:none;border-radius:3px;background-color:transparent;">Employee employee  = new Employee(1,"djstava",20);Log.e(TAG,JSON.toJSONString(employee));</code>

可以看出输出的json格式与我们类中定义的属性的顺序不一致，其实没有关系，json都是通过key去获取其对应的value的。

如果仅仅是想解析JavaBean类中某几个字段时，可以使用SimplePropertyPreFilter这个类来实现，将需要解析的字段添加进来，如将Employee类中的"num"和"name"解析出来

<code class="none" style="-webkit-print-color-adjust:exact;margin:0px;padding:0px;border:none;border-radius:3px;background-color:transparent;">SimplePropertyPreFilter simplePropertyPreFilter = new SimplePropertyPreFilter(Employee.class,"num","name");Log.e(TAG,JSON.toJSONString(employee,simplePropertyPreFilter));</code>

源码下载

http://download.csdn.net/detail/djstavav/9144789

参考文献

1、http://www.json.org/
2、https://github.com/alibaba/fastjson/wiki
3、https://www.juhe.cn/docs/api/id/39

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