Android studio-SharedPreferences

1.SharedPreferences的使用
–SharedPreferences是Android平台上一个轻量级的存储类，用于存储一些应用程序的配置参数，例如用户名、密码、自定义参数的设置等。

–SharedPreferences中存储的数据是以key/value键值对的形式保存在XML文件中，该文件位于“data/data/<packagename>/shared_prefs”文件夹中。

2.SharedPreferences的使用–存储数据
•SharedPreferences sp = getSharedPreferences("data",MODE_PRIVATE);
•Editor editor = sp.edit();
•editor.putString("name", "传智播客");
•editor.putInt("age", 8);
•editor.commit();
–取出数据
•SharedPreferences sp = context.getSharedPreferences();
•String data = sp.getString("name","");
–编辑数据
•SharedPreferences sp = context.getSharedPreferences ();
•Editor editor = sp.edit();
•editor.remove("name");
•editor.clear();

•editor.commit();

3.应用：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#E6E6E6"
    android:orientation="vertical" >

    <ImageView
        android:id="@+id/iv_head"
        android:layout_width="50dp"
        android:layout_height="50dp"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="40dp"
        android:src="@drawable/dddss" />

    <LinearLayout
        android:id="@+id/layout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@+id/iv_head"
        android:layout_margin="10dp"
        android:background="#ffffff"
        android:orientation="vertical" >

        <RelativeLayout
            android:id="@+id/rl_username"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_margin="10dp" >

            <TextView
                android:id="@+id/tv_name"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_centerVertical="true"
                android:text="账号" />

            <EditText
                android:id="@+id/et_number"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginLeft="5dp"
                android:layout_toRightOf="@+id/tv_name"
                android:background="@null" />
        </RelativeLayout>

        <View
            android:layout_width="match_parent"
            android:layout_height="2dp"
            android:background="#E6E6E6" />

        <RelativeLayout
            android:id="@+id/rl_userpsw"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_margin="10dp" >

            <TextView
                android:id="@+id/tv_psw"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_centerVertical="true"
                android:text="密码" />

            <EditText
                android:id="@+id/et_password"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginLeft="5dp"
                android:layout_toRightOf="@+id/tv_psw"
                android:inputType="textPassword"
                android:background="@null" />
        </RelativeLayout>
    </LinearLayout>

    <Button
        android:id="@+id/btn_login"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@+id/layout"
        android:layout_centerHorizontal="true"
        android:layout_marginLeft="10dp"
        android:layout_marginRight="10dp"
        android:layout_marginTop="20dp"
        android:background="#3C8DC4"
        android:text="登录"
        android:textColor="#ffffff" />

</RelativeLayout>

MainActivity.java代码

package com.example.zlf.demo51sharepreferences;

        import android.icu.text.IDNA;
        import android.support.v7.app.AppCompatActivity;
        import android.os.Bundle;
        import android.text.TextUtils;
        import android.util.Log;
        import android.view.View;
        import android.widget.Button;
        import android.widget.EditText;
        import android.widget.Toast;

        import java.util.Map;
        import java.util.concurrent.TimeUnit;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
    private EditText etNumber;
    private  EditText etPassword;
    //private Button   btn_login;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initView();//初始化，下面有此方法
        //取出号码
        Map<String,String> userInfo=Utils.getUserInfo(this);
        if (userInfo!=null){
            etNumber.setText(userInfo.get("number"));
            etPassword.setText(userInfo.get("password"));
        }

    }
    private void initView() {
        etNumber=(EditText)findViewById(R.id.et_number);
        etPassword=(EditText)findViewById(R.id.et_password);
        //因为没有定义login，这里直接用findViewById
        findViewById(R.id.btn_login).setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        //点击登陆时，获取QQ号和密码
        String number=etNumber.getText().toString().trim();
        String password=etPassword.getText().toString();
        //判断你输入的QQ号和密码是否正确
        if(TextUtils.isEmpty(number)){
            Toast.makeText(this,"请输入QQ号",Toast.LENGTH_SHORT).show();
            return;
        }
        if(TextUtils.isEmpty(password)){
            Toast.makeText(this,"请输入密码",Toast.LENGTH_SHORT).show();
            return;
        }
        //登陆成功
        Toast.makeText(this,"登陆成功",Toast.LENGTH_SHORT).show();
        Log.i("MainActivity","记住密码："+number+","+password);
        //保存用户信息
        boolean isSaveSuccess=Utils.saveUserInfo(this,number,password);
        if (isSaveSuccess){
            Toast.makeText(this,"保存成功",Toast.LENGTH_SHORT).show();

        }else {
            Toast.makeText(this,"保存失败",Toast.LENGTH_SHORT).show();
        }


    }
}

Utils.java代码

package com.example.zlf.demo51sharepreferences;

import android.content.Context;
import android.content.SharedPreferences;

import java.util.HashMap;
import java.util.Map;

public class Utils {
    public static boolean saveUserInfo(Context context, String number,
                                       String password) {
        SharedPreferences sp = context.getSharedPreferences("data", Context.MODE_PRIVATE);//数据自己可用
        SharedPreferences.Editor edit = sp.edit();
        edit.putString("userName", number);
        edit.putString("pwd", password);
        edit.commit();
        return true;//存储成功
    }

    // 从data.xml中获取QQ号码和密码
    public static Map<String, String> getUserInfo(Context context) {
        SharedPreferences sp = context.getSharedPreferences("data", Context.MODE_PRIVATE);

        String number = sp.getString("userName", null);
        String password = sp.getString("pwd", null);
        Map<String,String> userMap = new HashMap<String, String>();
        userMap.put("number", number);
        userMap.put("password", password);

        return userMap;
    }
}

结果：