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 Android教程網 >> Android技術 >> 關於Android編程 >> Android基礎——JSON數據的全方位解析

Android基礎——JSON數據的全方位解析

編輯：關於Android編程

本篇文章包括以下內容：

JSON是什麼 JSONObject的解析和存儲 JSONObject的解析和存儲（抽象） JSONArray的解析和存儲 模擬周邊加油站JSON數據實戰

JSON是什麼

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

JSON是存儲和交換文本信息的語法 JSON是輕量級的文本數據交換格式 JSON獨立於語言和平台 JSON具有自我描述性，更易理解

類似XML，比XML更小、更快、更易解析

沒有結束標簽 更短 讀寫的速度更快 使用數組 不使用保留字

JSON語法是JavaScript對象表示法語法的子集

數據在名稱/值對中 數據由逗號分割 花括號保存對象 方括號保存數據

JSON值可以是

數字（整數或浮點數） 字符串（在雙引號中） 邏輯值（true或false） 數組（在方括號中） 對象（在花括號中） null

JSONObject的解析和存儲

JSONObject數據是用key-value來存儲的，中間使用冒號隔開，外層的花括號表示一個對象

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

首先創建一個存儲數據的Bean類

public class User {
    private String username;
    private int qq;

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

下面我們使用將服務器獲取的JSON數據放進一個JSON對象中，獲取其對象中的值

//模擬服務器傳來的JSON數據
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");
//使用對象的形式進行保存
User user = new User(username, qq);

JSONObject的解析和存儲（抽象）

我們會碰到在一個JSON中嵌套有其他JSON對象，而這個嵌套的JSON對象中可以抽象出共同的屬性，看例子

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

這個時候我們就不用創建兩個對象了，創建一個對象抽取他們的屬性即可

首先創建一個存儲數據的Bean類

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

然後我們解析並存儲

JSONObject price = data_json.getJSONObject("price");
JSONObject gastprice = data_json.getJSONObject("gastprice");
Iterator keys_price = price.keys();
while (keys_price.hasNext()) {
    String key = keys_price.next();
    String value = price.getString(key);
    //使用對象的形式進行保存
    FourthLevelObject fourthLevelObject = new FourthLevelObject(key, value);
}
Iterator keys_gastprice = gastprice.keys();
while (keys_gastprice.hasNext()) {
    String key = keys_gastprice.next();
    String value = gastprice.getString(key);
    //使用對象的形式進行保存
    FourthLevelObject fourthLevelObject = new FourthLevelObject(key, value);
}

JSONArray的解析和存儲

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

通過遍歷JSONArray，剩下的跟JSONObject一樣，

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");
     //使用對象的形式進行保存
     User user = new User(id, name);
     //如果User為嵌套對象，應該添加到集合中
     //list.add(user);
}

模擬周邊加油站JSON數據實戰

這裡以周邊加油站數據為例，其解析步驟有

分析數據中的成員變量（花括號為對象，方括號為數組，使用List存儲數組） 根據分析後的結果，創建對應的對象 解析JSON數據、存儲JSON數據

大家可以嘗試一下自己寫解析，發現哪裡不對時，直接運行程序，系統會自動給你提示哪一行解析出錯的

{
    "resultcode":"200",
    "reason":"Successed!",
    "result":{
        "data":[
            {
                "id":"59797",
                "name":"太洋加油站",
                "area":"514000",
                "areaname":"廣東省 梅州市 梅江區",
                "address":"廣東省梅州市梅江區環市北路家樂廣場附近,路南側",
                "brandname":"不詳",
                "type":"其他",
                "discount":"非打折加油站",
                "exhaust":"國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#車柴":"5.15"
                },
                "fwlsmc":"",
                "distance":2462
            },
            {
                "id":"11083",
                "name":"中石化麻子崗加油站",
                "area":"516000",
                "areaname":"廣東省 梅州市",
                "address":"廣東省梅州市205國道與梅松路交叉口東南方向，嘉應大學附近",
                "brandname":"中石化",
                "type":"直營店",
                "discount":"打折加油站",
                "exhaust":"國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#車柴":"5.15"
                },
                "fwlsmc":"銀聯卡,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,發卡充值網點,銀聯卡充值,加油卡充值業務",
                "distance":439
            },
            {
                "id":"51175",
                "name":"月梅加油站",
                "area":"514000",
                "areaname":"廣東省 梅州市 梅江區",
                "address":"廣東省梅州市梅江區月梅路月梅農貿批發市場北,路西側",
                "brandname":"不詳",
                "type":"其他",
                "discount":"非打折加油站",
                "exhaust":"國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#車柴":"5.15"
                },
                "fwlsmc":"",
                "distance":465
            },
            {
                "id":"29356",
                "name":"中石化嘉華加油站",
                "area":"514700",
                "areaname":"廣東省 梅州市 梅縣",
                "address":"廣東省梅州市梅江區月梅路與碧桂路交叉路口,路東",
                "brandname":"中石化",
                "type":"直營店",
                "discount":"打折加油站",
                "exhaust":"國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#車柴":"5.15"
                },
                "fwlsmc":"加油卡,便利店,發卡充值網點,衛生間,銀聯卡充值,加油卡充值業務",
                "distance":804
            },
            {
                "id":"51077",
                "name":"東郊加油站",
                "area":"514000",
                "areaname":"廣東省 梅州市 梅江區",
                "address":"廣東省梅州市梅江區東山大道金山龍豐衛生站附近",
                "brandname":"不詳",
                "type":"其他",
                "discount":"非打折加油站",
                "exhaust":"國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#車柴":"5.15"
                },
                "fwlsmc":"",
                "distance":1720
            }
        ],
        "pageinfo":{
            "pnums":20,
            "current":1,
            "allpage":1
        }
    },
    "error_code":0
}

一、分析數據中的成員變量

在JSON中，只有兩種語法，JSONObject（花括號內）和JSONArray（方括號內）

JSONObject：可以理解為一個Map集合，通過get獲取value JSONArray：可以理解為一個數組，通過循環獲取對應的JSONObject

從上面的數據可以發現其中有五個JSON對象，一個JSON數組，從外到裡分析

對象1~4：

\

對象5：在最後面

二、根據分析後的結果，創建對應的對象（按循序從1~5）

在JSONObject中，左邊是屬性，右邊是值

如果右邊的值為一個JSONArray，則在對象中使用List< Object>來存儲，簡單的說就是對象中的List嵌套另一個對象

記住：花括號用對象，方括號用集合

根據上面的分析，創建第一個對象

public class FirstLevelObject {
    private String resultcode;
    private String reason;
    private List result;
    private String error_code;

    public FirstLevelObject(String resultcode, String reason, List 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 + '\'' +
                '}';
    }
}

創建第二個對象

public class Result {

    private List data;
    private List pageinfo;

    public Result(List data, List pageinfo) {
        this.data = data;
        this.pageinfo = pageinfo;
    }

    @Override
    public String toString() {
        return "Result{" +
                "data=" + data +
                ", pageinfo=" + pageinfo +
                '}';
    }
}

創建第三個對象

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 price;
    private List 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 price
            , List 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 +
                '}';
    }
}

創建第四個對象

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

創建第五個對象

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數據、存儲JSON數據

由於數據對象是一層嵌套一層的，這個解析思想跟樹的遍歷是一個道理，從外層->內層->外層，所以我們在解析內層的時候是需要邊解析邊存儲我們的數據

數據的解析和存儲

try {
    //模擬服務器傳來的JSON數據
    JSONObject json = new JSONObject(jsonString);
    //第一層讀取
    String resultcode = json.getString("resultcode");
    String reason = json.getString("reason");
    JSONObject result = json.getJSONObject("result");
    String error_code = json.getString("error_code");
    //第一層List
    List result_list = new ArrayList<>();

    //第二層讀取
    JSONArray data = result.getJSONArray("data");
    JSONObject pageinfo = result.getJSONObject("pageinfo");
    //第二層List
    List data_list = new ArrayList<>();
    List pageinfo_list = new ArrayList<>();

    //第三層讀取
    for (int i = 0; i < data.length(); i++) {
        //第三層List
        List price_list = new ArrayList<>();
        List 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");

        //第四層讀取
        Iterator keys_price = price.keys();
        while (keys_price.hasNext()) {
            String key = keys_price.next();
            String value = price.getString(key);
            //裝載第三層List
            FourthLevelObject fourthLevelObject = new FourthLevelObject(key, value);
            price_list.add(fourthLevelObject);
        }
        Iterator keys_gastprice = gastprice.keys();
        while (keys_gastprice.hasNext()) {
            String key = keys_gastprice.next();
            String value = gastprice.getString(key);
            //裝載第三層List
            FourthLevelObject fourthLevelObject = new FourthLevelObject(key, value);
            gastprice_list.add(fourthLevelObject);
        }

        //裝載第二層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);
    }

    //第五層讀取
    int pnums = pageinfo.getInt("pnums");
    int current = pageinfo.getInt("current");
    int allpage = pageinfo.getInt("allpage");
    //裝載第五層List
    PageInfo pageInfo = new PageInfo(pnums, current, allpage);
    pageinfo_list.add(pageInfo);

    //裝載第一層List
    Result result1 = new Result(data_list, pageinfo_list);
    result_list.add(result1);

    //最後封裝我們需要的得到的對象
    firstLevelObject = new FirstLevelObject(resultcode, reason, result_list, error_code);

} catch (JSONException e) {
    e.printStackTrace();
}

由於我們第四個對象是嵌套在第三個對象數組中的，所以在裡面再嵌套一層循環

由於第四個對象是同一性質的屬性，所以我們抽象成一個屬性為type和price的對象，其key是不確定的，需要自己通過keys遍歷來獲取value

接著我們輸出我們解析的結果

tv.setText(firstLevelObject.toString());

效果圖

\

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