Android基础——JSON数据的全方位解析

本篇文章包括以下内容：

JSON是什么

JSONObject的解析和存储

JSONObject的解析和存储（抽象）

JSONArray的解析和存储

模拟周边加油站JSON数据实战

JSON是什么

JSON：JavaScript对象表示法（JavaScript Object Notation）

JSON是存储和交换文本信息的语法
JSON是轻量级的文本数据交换格式
JSON独立于语言和平台
JSON具有自我描述性，更易理解

类似XML，比XML更小、更快、更易解析

没有结束标签
更短
读写的速度更快
使用数组
不使用保留字

JSON语法是JavaScript对象表示法语法的子集

数据在名称/值对中
数据由逗号分割
花括号保存对象
方括号保存数据

JSON值可以是

数字（整数或浮点数）
字符串（在双引号中）
逻辑值（true或false）
数组（在方括号中）
对象（在花括号中）
null

JSONObject的解析和存储

JSONObject数据是用key-value来存储的，中间使用冒号隔开，外层的花括号表示一个对象

{"username":"Hensen","qq":"510402535"
}

首先创建一个存储数据的Bean类

public class User {private String username;private int qq;public User(String username, int qq) {this.username = username;this.qq = qq;}
}

下面我们使用将服务器获取的JSON数据放进一个JSON对象中，获取其对象中的值

//模拟服务器传来的JSON数据
String str ="{\n" +"\t\"username\":\"Hensen\",\n" +"\t\"qq\":\"510402535\""+"\n}";
JSONObject json = new JSONObject(str);
String username = json.getString("username");
int qq = json.getInt("qq");
//使用对象的形式进行保存
User user = new User(username, qq);

JSONObject的解析和存储（抽象）

我们会碰到在一个JSON中嵌套有其他JSON对象，而这个嵌套的JSON对象中可以抽象出共同的属性，看例子

"price":{"E90":"5.36","E93":"5.77","E97":"6.25","E0":"5.34"
}
"gastprice":{"92#":"5.58","0#车柴":"5.15"
}

这个时候我们就不用创建两个对象了，创建一个对象抽取他们的属性即可

首先创建一个存储数据的Bean类

public class FourthLevelObject {private String type;private String price;public FourthLevelObject(String type, String price) {this.type = type;this.price = price;}@Overridepublic String toString() {return "FourthLevelObject{" +"type='" + type + '\'' +", price='" + price + '\'' +'}';}
}

然后我们解析并存储

JSONObject price = data_json.getJSONObject("price");
JSONObject gastprice = data_json.getJSONObject("gastprice");
Iterator<String> keys_price = price.keys();
while (keys_price.hasNext()) {String key = keys_price.next();String value = price.getString(key);//使用对象的形式进行保存FourthLevelObject fourthLevelObject = new FourthLevelObject(key, value);
}
Iterator<String> keys_gastprice = gastprice.keys();
while (keys_gastprice.hasNext()) {String key = keys_gastprice.next();String value = gastprice.getString(key);//使用对象的形式进行保存FourthLevelObject fourthLevelObject = new FourthLevelObject(key, value);
}

JSONArray的解析和存储

"data":[{"id":"59797","name":"太洋加油站"},{"id":"11083","name":"中石化麻子岗加油站"}]

通过遍历JSONArray，剩下的跟JSONObject一样，

JSONArray data = result.getJSONArray("data");
for (int i = 0; i < data.length(); i++) {String id = data_json.getString("id");String name = data_json.getString("name");//使用对象的形式进行保存User user = new User(id, name);//如果User为嵌套对象，应该添加到集合中//list.add(user);
}

模拟周边加油站JSON数据实战

这里以周边加油站数据为例，其解析步骤有

分析数据中的成员变量（花括号为对象，方括号为数组，使用List存储数组）
根据分析后的结果，创建对应的对象
解析JSON数据、存储JSON数据

大家可以尝试一下自己写解析，发现哪里不对时，直接运行程序，系统会自动给你提示哪一行解析出错的

{"resultcode":"200","reason":"Successed!","result":{"data":[{"id":"59797","name":"太洋加油站","area":"514000","areaname":"广东省 梅州市 梅江区","address":"广东省梅州市梅江区环市北路家乐广场附近,路南侧","brandname":"不详","type":"其他","discount":"非打折加油站","exhaust":"国Ⅲ","position":"116.104117014,24.3286227908","lon":"116.11066877213","lat":"24.33427865799","price":{"E90":"5.36","E93":"5.77","E97":"6.25","E0":"5.34"},"gastprice":{"92#":"5.58","0#车柴":"5.15"},"fwlsmc":"","distance":2462},{"id":"11083","name":"中石化麻子岗加油站","area":"516000","areaname":"广东省 梅州市","address":"广东省梅州市205国道与梅松路交叉口东南方向，嘉应大学附近","brandname":"中石化","type":"直营店","discount":"打折加油站","exhaust":"国Ⅲ","position":"116.124168,24.32516","lon":"116.13067098935","lat":"24.331051295968","price":{"E90":"5.36","E93":"5.77","E97":"6.25","E0":"5.34"},"gastprice":{"92#":"5.58","95#":"6.05","0#车柴":"5.15"},"fwlsmc":"银联卡,信用卡支付,加油卡,便利店,93#自助加油,柴油自助加油,97#自助加油,发卡充值网点,银联卡充值,加油卡充值业务","distance":439},{"id":"51175","name":"月梅加油站","area":"514000","areaname":"广东省 梅州市 梅江区","address":"广东省梅州市梅江区月梅路月梅农贸批发市场北,路西侧","brandname":"不详","type":"其他","discount":"非打折加油站","exhaust":"国Ⅲ","position":"116.1250119928,24.3291280115","lon":"116.1315112916","lat":"24.335033948452","price":{"E90":"5.36","E93":"5.77","E97":"6.25","E0":"5.34"},"gastprice":{"92#":"5.58","0#车柴":"5.15"},"fwlsmc":"","distance":465},{"id":"29356","name":"中石化嘉华加油站","area":"514700","areaname":"广东省 梅州市 梅县","address":"广东省梅州市梅江区月梅路与碧桂路交叉路口,路东","brandname":"中石化","type":"直营店","discount":"打折加油站","exhaust":"国Ⅲ","position":"116.1192494629,24.3272616485","lon":"116.132454","lat":"24.339033","price":{"E90":"5.36","E93":"5.77","E97":"6.25","E0":"5.34"},"gastprice":{"92#":"5.58","95#":"6.05","0#车柴":"5.15"},"fwlsmc":"加油卡,便利店,发卡充值网点,卫生间,银联卡充值,加油卡充值业务","distance":804},{"id":"51077","name":"东郊加油站","area":"514000","areaname":"广东省 梅州市 梅江区","address":"广东省梅州市梅江区东山大道金山龙丰卫生站附近","brandname":"不详","type":"其他","discount":"非打折加油站","exhaust":"国Ⅲ","position":"116.1357199618,24.3121215949","lon":"116.14218687436","lat":"24.31822136463","price":{"E90":"5.36","E93":"5.77","E97":"6.25","E0":"5.34"},"gastprice":{"92#":"5.58","0#车柴":"5.15"},"fwlsmc":"","distance":1720}],"pageinfo":{"pnums":20,"current":1,"allpage":1}},"error_code":0
}

一、分析数据中的成员变量

在JSON中，只有两种语法，JSONObject（花括号内）和JSONArray（方括号内）

JSONObject：可以理解为一个Map集合，通过get获取value

JSONArray：可以理解为一个数组，通过循环获取对应的JSONObject

从上面的数据可以发现其中有五个JSON对象，一个JSON数组，从外到里分析

对象1~4：

对象5：在最后面

二、根据分析后的结果，创建对应的对象（按循序从1~5）

在JSONObject中，左边是属性，右边是值

如果右边的值为一个JSONArray，则在对象中使用List< Object>来存储，简单的说就是对象中的List嵌套另一个对象

记住：花括号用对象，方括号用集合

根据上面的分析，创建第一个对象

public class FirstLevelObject {private String resultcode;private String reason;private List<Result> result;private String error_code;public FirstLevelObject(String resultcode, String reason, List<Result> result, String error_code) {this.resultcode = resultcode;this.reason = reason;this.result = result;this.error_code = error_code;}@Overridepublic String toString() {return "FirstLevelObject{" +"resultcode='" + resultcode + '\'' +", reason='" + reason + '\'' +", result=" + result +", error_code='" + error_code + '\'' +'}';}
}

创建第二个对象

public class Result {private List<Data> data;private List<PageInfo> pageinfo;public Result(List<Data> data, List<PageInfo> pageinfo) {this.data = data;this.pageinfo = pageinfo;}@Overridepublic String toString() {return "Result{" +"data=" + data +", pageinfo=" + pageinfo +'}';}
}

创建第三个对象

public class Data {private String id;private String name;private String area;private String areaname;private String address;private String brandname;private String type;private String discount;private String exhaust;private String position;private String lon;private String lat;private List<FourthLevelObject> price;private List<FourthLevelObject> gastprice;private String fwlsmc;private int distance;public Data(String id, String name, String area, String areaname, String address, String brandname, String type, String discount, String exhaust, String position, String lon, String lat, List<FourthLevelObject> price, List<FourthLevelObject> gastprice, String fwlsmc, int distance) {this.id = id;this.name = name;this.area = area;this.areaname = areaname;this.address = address;this.brandname = brandname;this.type = type;this.discount = discount;this.exhaust = exhaust;this.position = position;this.lon = lon;this.lat = lat;this.price = price;this.gastprice = gastprice;this.fwlsmc = fwlsmc;this.distance = distance;}@Overridepublic String toString() {return "Data{" +"id='" + id + '\'' +", name='" + name + '\'' +", area='" + area + '\'' +", areaname='" + areaname + '\'' +", address='" + address + '\'' +", brandname='" + brandname + '\'' +", type='" + type + '\'' +", discount='" + discount + '\'' +", exhaust='" + exhaust + '\'' +", position='" + position + '\'' +", lon='" + lon + '\'' +", lat='" + lat + '\'' +", price=" + price +", gastprice=" + gastprice +", fwlsmc='" + fwlsmc + '\'' +", distance=" + distance +'}';}
}

创建第四个对象

public class FourthLevelObject {private String type;private String price;public FourthLevelObject(String type, String price) {this.type = type;this.price = price;}@Overridepublic String toString() {return "FourthLevelObject{" +"type='" + type + '\'' +", price='" + price + '\'' +'}';}
}

创建第五个对象

public class PageInfo {private int pnums;private int current;private int allpage;public PageInfo(int pnums, int current, int allpage) {this.pnums = pnums;this.current = current;this.allpage = allpage;}@Overridepublic String toString() {return "PageInfo{" +"pnums=" + pnums +", current=" + current +", allpage=" + allpage +'}';}
}

三、解析JSON数据、存储JSON数据

由于数据对象是一层嵌套一层的，这个解析思想跟树的遍历是一个道理，从外层->内层->外层，所以我们在解析内层的时候是需要边解析边存储我们的数据

数据的解析和存储

try {//模拟服务器传来的JSON数据JSONObject json = new JSONObject(jsonString);//第一层读取String resultcode = json.getString("resultcode");String reason = json.getString("reason");JSONObject result = json.getJSONObject("result");String error_code = json.getString("error_code");//第一层ListList<Result> result_list = new ArrayList<>();//第二层读取JSONArray data = result.getJSONArray("data");JSONObject pageinfo = result.getJSONObject("pageinfo");//第二层ListList<Data> data_list = new ArrayList<>();List<PageInfo> pageinfo_list = new ArrayList<>();//第三层读取for (int i = 0; i < data.length(); i++) {//第三层ListList<FourthLevelObject> price_list = new ArrayList<>();List<FourthLevelObject> gastprice_list = new ArrayList<>();JSONObject data_json = (JSONObject) data.get(i);String id = data_json.getString("id");String name = data_json.getString("name");String area = data_json.getString("area");String areaname = data_json.getString("areaname");String address = data_json.getString("address");String brandname = data_json.getString("brandname");String type = data_json.getString("type");String discount = data_json.getString("discount");String exhaust = data_json.getString("exhaust");String position = data_json.getString("position");String lon = data_json.getString("lon");String lat = data_json.getString("lat");JSONObject price = data_json.getJSONObject("price");JSONObject gastprice = data_json.getJSONObject("gastprice");String fwlsmc = data_json.getString("fwlsmc");int distance = data_json.getInt("distance");//第四层读取Iterator<String> keys_price = price.keys();while (keys_price.hasNext()) {String key = keys_price.next();String value = price.getString(key);//装载第三层ListFourthLevelObject fourthLevelObject = new FourthLevelObject(key, value);price_list.add(fourthLevelObject);}Iterator<String> keys_gastprice = gastprice.keys();while (keys_gastprice.hasNext()) {String key = keys_gastprice.next();String value = gastprice.getString(key);//装载第三层ListFourthLevelObject fourthLevelObject = new FourthLevelObject(key, value);gastprice_list.add(fourthLevelObject);}//装载第二层ListData data1 = new Data(id, name, area, areaname, address, brandname, type, discount, exhaust, position, lon, lat, price_list, gastprice_list, fwlsmc, distance);data_list.add(data1);}//第五层读取int pnums = pageinfo.getInt("pnums");int current = pageinfo.getInt("current");int allpage = pageinfo.getInt("allpage");//装载第五层ListPageInfo pageInfo = new PageInfo(pnums, current, allpage);pageinfo_list.add(pageInfo);//装载第一层ListResult result1 = new Result(data_list, pageinfo_list);result_list.add(result1);//最后封装我们需要的得到的对象firstLevelObject = new FirstLevelObject(resultcode, reason, result_list, error_code);} catch (JSONException e) {e.printStackTrace();
}

由于我们第四个对象是嵌套在第三个对象数组中的，所以在里面再嵌套一层循环

由于第四个对象是同一性质的属性，所以我们抽象成一个属性为type和price的对象，其key是不确定的，需要自己通过keys遍历来获取value

接着我们输出我们解析的结果

tv.setText(firstLevelObject.toString());

效果图