网络通信——HTTP接口访问——移动数据格式JSON

Myth丶恋晨 2024-04-03 12:50 81阅读 0赞

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网络通信的交互数据格式有两大类，分别是JSON和XML 。

对于App来说，基本采用JSON格式与服务器通信。

JSON相比XML的优势主要有两个：(1)手机流量很贵，表达同样的信息，JSON串比XML串短很多。(2) JSON串解析得更快，也更省电，XML不但慢而且耗电。

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(1)整个JSON串由一对花括号包裹，并且内部的每个结构都以花括号包起来；(2)参数格式类似键值对，其中键名与键值之间以冒号分隔，形如“键名:键值”；(3)两个键值对之间以逗号分隔；(4)键名需要用双引号括起来，键值为数字的话则无需双引号，为字符串的话仍需双引号；(5)JSON数组通过方括号表达，方括号内部依次罗列各个元素，具体格式形如“数组的键名:\[元素1,元素2,元素3\]”；

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引入：

// https://mvnrepository.com/artifact/com.google.code.gson/gson
    implementation group: 'com.google.code.gson', name: 'gson', version: '2.8.8'

布局：

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UserInfo

package com.example.myapplication.bean;
    
    public class UserInfo 
    {
        public String name; // 姓名
        public int age; // 年龄
        public long height; // 身高
        public float weight; // 体重
        
        public UserInfo(String name, int age, long height, float weight) 
        {
            this.name = name;
            this.age = age;
            this.height = height;
            this.weight = weight;
        }
        
    }

主代码;

package com.example.myapplication;
    
    import android.os.Bundle;
    import android.view.View;
    import android.widget.TextView;
    
    import androidx.appcompat.app.AppCompatActivity;
    
    import com.example.myapplication.bean.UserInfo;
    import com.google.gson.Gson;
    
    public class MainActivity extends AppCompatActivity implements View.OnClickListener
    {
    
        private TextView tv_json; // 声明一个文本视图对象
        private UserInfo mUser; // 声明一个用户信息对象
        private String mJsonStr; // JSON格式的字符串
    
        @Override
        protected void onCreate(Bundle savedInstanceState)
        {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
    
            mUser = new UserInfo("asi", 25, 165L, 50.0f); // 创建用户实例
            mJsonStr = new Gson().toJson(mUser); // 把用户实例转换为JSON串
    
            tv_json = findViewById(R.id.tv_json);
    
            findViewById(R.id.btn_origin_json).setOnClickListener(this);
            findViewById(R.id.btn_convert_json).setOnClickListener(this);
        }
    
        @Override
        public void onClick(View v)
        {
            if (v.getId() == R.id.btn_origin_json)
            {
    
                mJsonStr = new Gson().toJson(mUser); // 把用户实例转换为JSON字符串
                tv_json.setText("JSON串内容如下：\n" + mJsonStr);
            }
            else if (v.getId() == R.id.btn_convert_json)
            {
    
                // 把JSON串转换为UserInfo类型的对象
                UserInfo newUser = new Gson().fromJson(mJsonStr, UserInfo.class);
    
                String desc = String.format("\n\t姓名=%s\n\t年龄=%d\n\t身高=%d\n\t体重=%f", newUser.name, newUser.age, newUser.height, newUser.weight);
    
                tv_json.setText("从JSON串解析而来的用户信息如下：" + desc);
            }
        }
    
    }

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