android:用Sharedpreferences保存对象实例

一，安装第三方库:

地址:

https://mvnrepository.com/artifact/com.google.code.gson/gson

build.gradle中dependencies添加:

implementation 'com.google.code.gson:gson:2.13.0'

然后点击 Sync Now

二，代码:

xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".activity.PreferenceActivity">

    <Button
        android:id="@+id/buttonsave"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="168dp"
        android:layout_marginTop="30dp"
        android:layout_marginEnd="155dp"
        android:layout_marginBottom="653dp"
        android:text="保存"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/buttonread"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="174dp"
        android:layout_marginTop="65dp"
        android:layout_marginEnd="149dp"
        android:layout_marginBottom="539dp"
        android:text="读取"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/buttonsave" />
</androidx.constraintlayout.widget.ConstraintLayout>

java

Goodsinfo.java

package com.example.okdemo1.model;

public class GoodsInfo {
    //商品id
    private int id;
    //商品图片
    private String pic;

    public GoodsInfo(int id, String pic) {
        this.id = id;
        this.pic = pic;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getPic() {
        return pic;
    }

    public void setPic(String pic) {
        this.pic = pic;
    }
}

PreferenceActivity.java

package com.example.okdemo1.activity;

import android.app.ActivityOptions;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;

import androidx.activity.EdgeToEdge;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.graphics.Insets;
import androidx.core.view.ViewCompat;
import androidx.core.view.WindowInsetsCompat;

import com.example.imagelib.ImageListActivity;
import com.example.okdemo1.MainActivity;
import com.example.okdemo1.R;
import com.example.okdemo1.model.GoodsInfo;
import com.google.gson.Gson;

public class PreferenceActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        EdgeToEdge.enable(this);
        setContentView(R.layout.activity_preference);

        //给按钮增加点击事件
        Button myButton = findViewById(R.id.buttonsave);
        myButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                GoodsInfo gi = new GoodsInfo(123,"桂林山水图片");

                // 处理点击事件
                //获取一个文件名为userInfo、权限为private的xml文件的SharedPreferences对象
                SharedPreferences sharedPreferences = getSharedPreferences("userInfo", MODE_PRIVATE);
                //得到SharedPreferences.Editor对象，并保存数据到该对象中
                SharedPreferences.Editor editor = sharedPreferences.edit();
                //保存key-value对到文件中
                Gson gson = new Gson();
                String goodsStr = gson.toJson(gi);
                editor.putString("goodsOne", goodsStr);
                editor.commit();
            }
        });

        //给按钮增加点击事件
        Button readButton = findViewById(R.id.buttonread);
        readButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // 处理点击事件
                SharedPreferences sharedPreferences = getSharedPreferences("userInfo", MODE_PRIVATE);
                //读取数据
                String goodsOne = sharedPreferences.getString("goodsOne", "");
                if (goodsOne != null) {
                    Gson gson = new Gson();
                    GoodsInfo obj = gson.fromJson(goodsOne, GoodsInfo.class);
                    //打印已读取数据
                    Log.d("id",String.valueOf(obj.getId()));
                    Log.d("pic",obj.getPic());
                }
            }
        });
    }
}

三，测试效果:

四，查看文件内容:

<?xml version='1.0' encoding='utf-8' standalone='yes' ?>
<map>
    <string name="name">总统秘书王富贵</string>
    <int name="id" value="12345" />
    <string name="goodsOne">{&quot;id&quot;:123,&quot;pic&quot;:&quot;桂林山水图片&quot;}</string>
</map>