Android利用Gson解析嵌套多层的Json的简单方法

下面是“Android利用Gson解析嵌套多层的Json的简单方法”的完整攻略。

导入Gson库

首先需要在项目的build.gradle文件中添加Gson库的依赖：

dependencies {
    implementation 'com.google.code.gson:gson:2.8.6'
}

创建Java类

假设我们有以下json数据:

{
    "name": "张三",
    "age": 18,
    "gender": "male",
    "address": {
        "province": "广东省",
        "city": "深圳市",
        "district": "宝安区",
        "street": "西乡街道"
    },
    "phone_numbers": ["13888888888", "13999999999"]
}

我们需要定义Java类来保存这些数据。示例代码如下：

import java.util.List;

public class Person {
    private String name;
    private int age;
    private String gender;
    private Address address;
    private List<String> phone_numbers;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public Address getAddress() {
        return address;
    }

    public void setAddress(Address address) {
        this.address = address;
    }

    public List<String> getPhoneNumbers() {
        return phone_numbers;
    }

    public void setPhoneNumbers(List<String> phoneNumbers) {
        this.phone_numbers = phoneNumbers;
    }

    public static class Address {
        private String province;
        private String city;
        private String district;
        private String street;

        public String getProvince() {
            return province;
        }

        public void setProvince(String province) {
            this.province = province;
        }

        public String getCity() {
            return city;
        }

        public void setCity(String city) {
            this.city = city;
        }

        public String getDistrict() {
            return district;
        }

        public void setDistrict(String district) {
            this.district = district;
        }

        public String getStreet() {
            return street;
        }

        public void setStreet(String street) {
            this.street = street;
        }
    }
}

这里需要注意的是，Address类是定义在Person类内部的静态类。

使用Gson解析Json

Gson提供了解析Json数据的方法。在本例中，我们只需要使用如下代码即可解析：

Gson gson = new Gson();
Person person = gson.fromJson(jsonString, Person.class);

其中，jsonString是包含Json数据的字符串。解析结果是一个Person对象。

提取数据

Json数据中的数据可以通过Person对象的getter方法获取。示例如下：

String name = person.getName();
int age = person.getAge();
String gender = person.getGender();
Person.Address address = person.getAddress();
String province = address.getProvince();
String city = address.getCity();
String district = address.getDistrict();
String street = address.getStreet();
List<String> phoneNumbers = person.getPhoneNumbers();

以上代码将从Person对象中提取所有的数据。

示例1：解析嵌套多层的Json

假如我们有以下json数据：

{
    "name": "小明",
    "age": 18,
    "gender": "male",
    "address": {
        "province": "北京市",
        "city": "北京市",
        "district": "海淀区",
        "street": "中关村"
    },
    "hobbies": [
        {
            "name": "羽毛球",
            "level": "高手"
        },
        {
            "name": "游泳",
            "level": "菜鸟"
        }
    ]
}

我们需要定义Java类来保存这些数据。示例代码如下：

public class Person {
    private String name;
    private int age;
    private String gender;
    private Address address;
    private List<Hobby> hobbies;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public Address getAddress() {
        return address;
    }

    public void setAddress(Address address) {
        this.address = address;
    }

    public List<Hobby> getHobbies() {
        return hobbies;
    }

    public void setHobbies(List<Hobby> hobbies) {
        this.hobbies = hobbies;
    }

    public static class Address {
        private String province;
        private String city;
        private String district;
        private String street;

        public String getProvince() {
            return province;
        }

        public void setProvince(String province) {
            this.province = province;
        }

        public String getCity() {
            return city;
        }

        public void setCity(String city) {
            this.city = city;
        }

        public String getDistrict() {
            return district;
        }

        public void setDistrict(String district) {
            this.district = district;
        }

        public String getStreet() {
            return street;
        }

        public void setStreet(String street) {
            this.street = street;
        }
    }

    public static class Hobby {
        private String name;
        private String level;

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }

        public String getLevel() {
            return level;
        }

        public void setLevel(String level) {
            this.level = level;
        }
    }
}

我们可以使用以下代码解析Json：

Gson gson = new Gson();
Person person = gson.fromJson(jsonString, Person.class);

数据提取和上一个示例类似，这里不再赘述。

示例2：解析包含嵌套数组的Json

假设我们有以下json数据：

{
    "pages": [
        {
            "title": "主页",
            "url": "http://www.example.com/",
            "subpages": [
                {
                    "title": "新闻",
                    "url": "http://www.example.com/news"
                },
                {
                    "title": "产品",
                    "url": "http://www.example.com/products",
                    "subpages": [
                        {
                            "title": "手机",
                            "url": "http://www.example.com/products/mobile-phones"
                        },
                        {
                            "title": "电视",
                            "url": "http://www.example.com/products/tv"
                        }
                    ]
                },
                {
                    "title": "关于我们",
                    "url": "http://www.example.com/about-us"
                }
            ]
        }
    ]
}

我们需要定义Java类来保存这些数据。示例代码如下：

import java.util.List;

public class Website {
    private List<Page> pages;

    public List<Page> getPages() {
        return pages;
    }

    public void setPages(List<Page> pages) {
        this.pages = pages;
    }

    public static class Page {
        private String title;
        private String url;
        private List<Page> subpages;

        public String getTitle() {
            return title;
        }

        public void setTitle(String title) {
            this.title = title;
        }

        public String getUrl() {
            return url;
        }

        public void setUrl(String url) {
            this.url = url;
        }

        public List<Page> getSubpages() {
            return subpages;
        }

        public void setSubpages(List<Page> subpages) {
            this.subpages = subpages;
        }
    }
}

这里我们使用了递归的方式定义了Page类。我们可以使用以下代码解析Json：

Gson gson = new Gson();
Website website = gson.fromJson(jsonString, Website.class);

假设我们要打印所有子页面的标题，我们可以使用以下代码：

List<Website.Page> pages = website.getPages();

for (Website.Page page : pages) {
    printTitles(page);
}

private void printTitles(Website.Page page) {
    System.out.println(page.getTitle());

    if (page.getSubpages() != null) {
        for (Website.Page subpage : page.getSubpages()) {
            printTitles(subpage);
        }
    }
}

以上代码会打印出所有页面的标题，包括子页面的标题。

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