GSON实例详解

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GSON是Google提供的用来在Java对象和JSON数据之间进行映射的Java类库，GSON可以很容易的将一个java对象转换成json文本，也可以很容易的将json文本转换为java对象，两种转换方式分别对应的方法是：toJson()和fromJson()。

一：toJson()详解（将一个java对象转换成json文本）
1,生成生成数组类型的json文本，效果图：
（点击按钮 toJsonArray）
这里写图片描述
代码:
首先新建一个类：GsonInfo;

public class GsonInfo {    private String name;    private int age;    private String gender;    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;    }    @Override    public String toString() {        return "GsonInfo{" +                "name='" + name + '\'' +                ", age=" + age +                ", gender='" + gender + '\'' +                '}';    }    public GsonInfo(String name, int age, String gender) {        this.name = name;        this.age = age;        this.gender = gender;    }}

layout布局:

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical">    <LinearLayout        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:orientation="horizontal">        <Button            android:id="@+id/btn_tojson"            android:layout_width="1dp"            android:layout_height="wrap_content"            android:layout_weight="1"            android:text="toJsonArray"/>        <Button            android:id="@+id/btn_fromjson"            android:layout_width="1dp"            android:layout_height="wrap_content"            android:layout_weight="1"            android:text="fromJsonArray"/>    </LinearLayout>    <TextView        android:id="@+id/branch1"        android:layout_width="wrap_content"        android:layout_height="wrap_content" />    <TextView        android:id="@+id/branch2"        android:layout_width="wrap_content"        android:layout_height="wrap_content" />    <LinearLayout        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:orientation="horizontal">        <Button            android:id="@+id/btn_tojson2"            android:layout_width="1dp"            android:layout_height="wrap_content"            android:layout_weight="1"            android:text="toJsonMix"/>        <Button            android:id="@+id/btn_fromjson2"            android:layout_width="1dp"            android:layout_height="wrap_content"            android:layout_weight="1"            android:text="fromJsonMix"/>    </LinearLayout>    <TextView        android:id="@+id/branch3"        android:layout_width="wrap_content"        android:layout_height="wrap_content" />    <TextView        android:id="@+id/branch4"        android:layout_width="wrap_content"        android:layout_height="wrap_content" />    <TextView        android:id="@+id/branch5"        android:layout_width="wrap_content"        android:layout_height="wrap_content" /></LinearLayout>

MainActivity代码：

import android.annotation.TargetApi;import android.app.Activity;import android.app.Notification;import android.app.NotificationManager;import android.app.PendingIntent;import android.content.Context;import android.content.Intent;import android.os.Build;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.view.View;import android.widget.TextView;import com.google.gson.Gson;import org.json.JSONObject;import java.util.ArrayList;import java.util.LinkedList;import java.util.List;public class MainActivity extends Activity implements View.OnClickListener{    private TextView tv_branch1;    private TextView tv_branch2;    private TextView tv_branch3;    private TextView tv_branch4;    private TextView tv_branch5;    private Gson gson = new Gson();//初始化Gson    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        findViewById(R.id.btn_tojson).setOnClickListener(this);        findViewById(R.id.btn_tojson2).setOnClickListener(this);        tv_branch1 = (TextView) findViewById(R.id.branch1);        tv_branch2 = (TextView) findViewById(R.id.branch2);        tv_branch3 = (TextView) findViewById(R.id.branch3);        tv_branch4 = (TextView) findViewById(R.id.branch4);        tv_branch5 = (TextView) findViewById(R.id.branch5);    }    @Override    public void onClick(View v) {        switch (v.getId()){            case R.id.btn_tojson:                toJson();//生成数组类型的json文本                break;        }    }    /**     * 格式类似于：     * [{     "name": "小琛",     "gender": "男",     "age": "21"     },     {     "name": "中琛",     "gender": "未知",     "age": "22"     },     {     "name": "大琛",     "gender": "男",     "age": "23"     }]     */    private StringtoJson(){        List<GsonInfo> list = new ArrayList<GsonInfo>();        GsonInfo info1 = new GsonInfo("小琛",21,"男");        list.add(info1);        GsonInfo info2 = new GsonInfo("中琛",22,"未知");        list.add(info2);        GsonInfo info3 = new GsonInfo("大琛",23,"男");        list.add(info3);        tv_branch1.setText(gson.toJson(list));        return gson.toJson(list);    }}

2,一个对象嵌套一个对象的json文本,效果图：
(点击按钮 toJsonMix)
这里写图片描述
代码：
除了 GsonInfo类，还要新建一个类：GsonInfo2:

public class GsonInfo2 {    private String boyFriend;    private String grilFriend;    public GsonInfo2() {        super();    }    public GsonInfo2(String boyFriend, String grilFriend) {        super();        this.boyFriend = boyFriend;        this.grilFriend = grilFriend;    }    public String getBoyFriend() {        return boyFriend;    }    public void setBoyFriend(String boyFriend) {        this.boyFriend = boyFriend;    }    public String getGrilFriend() {        return grilFriend;    }    public void setGrilFriend(String grilFriend) {        this.grilFriend = grilFriend;    }    @Override    public String toString() {        return "GsonInfo2{" +                "boyFriend='" + boyFriend + '\'' +                ", grilFriend='" + grilFriend + '\'' +                '}';    }}

布局不用修改，MainActivity:

import android.annotation.TargetApi;import android.app.Activity;import android.app.Notification;import android.app.NotificationManager;import android.app.PendingIntent;import android.content.Context;import android.content.Intent;import android.os.Build;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.view.View;import android.widget.TextView;import com.google.gson.Gson;import org.json.JSONObject;import java.util.ArrayList;import java.util.LinkedList;import java.util.List;public class MainActivity extends Activity implements View.OnClickListener{    private TextView tv_branch1;    private TextView tv_branch2;    private TextView tv_branch3;    private TextView tv_branch4;    private TextView tv_branch5;    private Gson gson = new Gson();//初始化Gson    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        findViewById(R.id.btn_tojson).setOnClickListener(this);        findViewById(R.id.btn_fromjson).setOnClickListener(this);        findViewById(R.id.btn_tojson2).setOnClickListener(this);        findViewById(R.id.btn_fromjson2).setOnClickListener(this);        tv_branch1 = (TextView) findViewById(R.id.branch1);        tv_branch2 = (TextView) findViewById(R.id.branch2);        tv_branch3 = (TextView) findViewById(R.id.branch3);        tv_branch4 = (TextView) findViewById(R.id.branch4);        tv_branch5 = (TextView) findViewById(R.id.branch5);    }    @Override    public void onClick(View v) {        switch (v.getId()){            case R.id.btn_tojson2:                toJson2();//一个对象嵌套一个对象的json文本                break;        }    }    /**     * 格式类似于：     * {     "friend": {     "grilFriend": "小花",     "bogFriend": "小美"     },     "name": "小明",     "gender": "男",     "age": 11     }     */    private void toJson2(){        GsonInfo info = new GsonInfo("小明",11,"男");        GsonInfo2 info2 = new GsonInfo2("小美","小花");        String infoStr = gson.toJson(info);        String info2Str = gson.toJson(info2);        tv_branch3.setText(infoStr);        tv_branch4.setText(info2Str);        JSONObject object = null;        try {            JSONObject infoObject = new JSONObject(info2Str);            object = new JSONObject(infoStr);            object.put("friend",infoObject);//键值对        }catch (Exception e){            e.printStackTrace();        }        tv_branch5.setText(object.toString());    }}

二：fromJson()详解(将json文本转换为java对象)

 private void fromJson() {        //获得toJson()中的JSON的字符串        String fromData = toJson();        Type type = new TypeToken<GsonInfo>() {        }.getType();        GsonInfo gsonInfo = new GsonInfo();        gsonInfo = gson.fromJson(fromData, type);        tv_branch2.setText(gsonInfo.toString());    }

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