Android基础——JSON数据的全方位解析

时间：2022-10-16 20:40:12

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;
    }

    @Override
public 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：

Android基础——JSON数据的全方位解析

对象5：在最后面

Android基础——JSON数据的全方位解析

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;
    }

    @Override
public 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;
    }

    @Override
public 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;
    }

    @Override
public 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;
    }

    @Override
public 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;
    }

    @Override
public 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List
List<Result> result_list = new ArrayList<>();

//第二层读取
    JSONArray data = result.getJSONArray("data");
    JSONObject pageinfo = result.getJSONObject("pageinfo");
//第二层List
List<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List
List<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List
            FourthLevelObject 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List
            FourthLevelObject fourthLevelObject = new FourthLevelObject(key, value);
            gastprice_list.add(fourthLevelObject);
        }

//装载第二层List
Data 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List
    PageInfo pageInfo = new PageInfo(pnums, current, allpage);
    pageinfo_list.add(pageInfo);

//装载第一层List
    Result 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

Android基础——JSON数据的全方位解析
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