SharedPreferences

<?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:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="com.example.yz.sharedpreferences.MainActivity">
    <TextView
            android:layout_width="match_parent"
            android:layout_height="50dp"
            android:gravity="center"
            android:text="登录界面"
            android:textSize="22sp" />

    <EditText
            android:id="@+id/ev_userName"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="请输入用户名" />
    <EditText
            android:id="@+id/ev_password"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="请输入密码" />
    <Button
            android:id="@+id/btn_login"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:gravity="center"
            android:text="写入"
            android:textSize="20sp"
            android:onClick="onClick"
            android:layout_gravity="center"/>
    <Button
            android:id="@+id/btn_b"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:gravity="center"
            android:text="读取"
            android:textSize="20sp"
            android:onClick="onClick"
            android:layout_gravity="center"/>

    </LinearLayout>

 

package com.example.yz.sharedpreferences;

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.Toast;

public class MainActivity extends AppCompatActivity {
private  EditText  ev_userName;
    private   EditText ev_password;
    private Button btn_login;
    private  Button  btn_b;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

       ev_userName = (EditText) findViewById(R.id.ev_userName);
       ev_password = (EditText) findViewById(R.id.ev_password);
        btn_login = (Button) findViewById(R.id.btn_login);
        btn_b=(Button)findViewById(R.id.btn_b);
            }
            public void onClick(View view){
                switch (view.getId()){
                    case R.id.btn_login:
                        String username = ev_userName.getText().toString();
                        String password = ev_password.getText().toString();
                        write(username,password);
                        break;
                    case R.id.btn_b:
                        read();
                        break;

                }
            }
            private void read() {
                SharedPreferences prefs = getSharedPreferences("data.text", MODE_PRIVATE); //获取对象，读取data文件
                String username = prefs.getString("username", ""); //获取文件中的数据
                String password = prefs.getString("password", "");
                Toast.makeText(MainActivity.this, "用户名："+username+"密码："+password, Toast.LENGTH_LONG).show();
            }

            private void write(String username, String password) {
                SharedPreferences.Editor editor = getSharedPreferences("data.text", MODE_PRIVATE).edit();//获取对象，并且命名文件的名称
                editor.putString("username",username );  //保存数据
                editor.putString("password",password);
                editor.commit();
                editor.clear();
                Toast.makeText(MainActivity.this, "保存成功!", Toast.LENGTH_LONG).show();
            }
        }