Android中JSON数据的全方位解析

Android基础——JSON数据的全方位解析

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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

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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"
}

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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;
    }
}

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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);

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JSONObject的解析和存储（抽象）

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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"
}

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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 + '\'' +
                '}';
    }
}

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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);
}

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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"
            }
       ]

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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);
}

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模拟周边加油站JSON数据实战

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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
}

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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;
    }

    @Override
    public String toString() {
        return "FirstLevelObject{" +
                "resultcode='" + resultcode + '\'' +
                ", reason='" + reason + '\'' +
                ", result=" + result +
                ", error_code='" + error_code + '\'' +
                '}';
    }
}

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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 +
                '}';
    }
}

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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 +
                '}';
    }
}

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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 + '\'' +
                '}';
    }
}

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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 +
                '}';
    }
}

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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();
}

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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());

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效果图

来源：CSDN

作者：qq_32534441

链接：https://blog.csdn.net/qq_32534441/article/details/103588674