Android基础——JSON数据的全方位解析
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：
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 + '\'' +
'}';
}
}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