Android开发——数据存储（一）SharedPreferences轻量级数据存储

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数据存储（一）SharedPreferences轻量级数据存储

代码示例

SharedPreferencesActivity的java代码

package com.example.administrator.exercise.datastorage;

import android.content.SharedPreferences;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

import com.example.administrator.exercise.R;
import com.example.administrator.exercise.util.ToastUtil;

public class SharedPreferencesActivity extends AppCompatActivity {

    private EditText editText;
    private Button button_save,button_display;
    private TextView textView;
    //读取数据
    private SharedPreferences sharedPreferences;
    //写入数据
    private SharedPreferences.Editor editor;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_shared_preferences);
        editText = (EditText) findViewById(R.id.sp_et_input);
        textView = (TextView) findViewById(R.id.sp_tv_display);
        //连接保存按钮
        button_save = (Button) findViewById(R.id.sp_btn_save);
        //连接显示按钮
        button_display = (Button) findViewById(R.id.sp_btn_display);

        //实例化sharedPreferences，参数：文件名称，模式（通常使用PRIVATE）
        sharedPreferences = getSharedPreferences("data",MODE_PRIVATE);
        //实例化editor
        editor = sharedPreferences.edit();
        
        button_save.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                //putString写入数据：键值对，参数：key,value
                editor.putString("data",editText.getText().toString());
                editor.apply();
                //这个是自定义的Toast工具，理解为一般的Toast提示即可。
                ToastUtil.showMsg(SharedPreferencesActivity.this,"保存成功");
            }
        });
        button_display.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                //getString读出数据，参数：key，default(缺省的值，设为空即可)
                textView.setText(sharedPreferences.getString("data",""));
                ToastUtil.showMsg(SharedPreferencesActivity.this,"读取成功");
            }
        });
    }
}

对应的布局文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_shared_preferences"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">
    <EditText
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:hint="请输入数据"
        android:id="@+id/sp_et_input"
        />
    <Button
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:text="保存"
        android:textSize="16sp"
        android:id="@+id/sp_btn_save"/>
    <Button
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:text="显示"
        android:textSize="16sp"
        android:id="@+id/sp_btn_display"/>
    <TextView
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:id="@+id/sp_tv_display"/>
</LinearLayout>

运行结果图

文件保存位置

data/data/applicationID（也就是工程包名）/shared_prefs

总结

//定义读写对象
SharedPreferences sharedPreferences = getSharedPreferences(“参数名”,MODE_PRIVATE)
SharedPreferences.Editor editor = sharedPreferences.edit()
//写入数据
editor.putString(“参数名”,editText.getText().toString())
editor.apply();
//读出数据
sharedPreferences.getString(“参数名”,"")