<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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"tools:context=".MainActivity"><ImageViewandroid:id="@+id/iv"android:layout_width="70dp"android:layout_height="70dp"android:layout_centerHorizontal="true"android:layout_marginTop="40dp"android:background="@drawable/dongman"/><LinearLayoutandroid:id="@+id/ll_number"android:layout_width="match_parent"android:layout_height="wrap_content"android:layout_below="@+id/iv"android:layout_centerVertical="true"android:layout_marginTop="15dp"android:layout_marginLeft="10dp"android:layout_marginRight="10dp"android:layout_marginBottom="5dp"android:background="#ffffff"><TextViewandroid:id="@+id/tv_number"android:layout_width="wrap_content"android:layout_height="wrap_content"android:padding="10dp"android:text="账号"android:textColor="#000"android:textSize="20sp"/><EditTextandroid:id="@+id/et_number"android:layout_width="match_parent"android:layout_height="wrap_content"android:layout_marginLeft="5dp"android:background="@null"android:padding="10dp"/></LinearLayout><LinearLayoutandroid:id="@+id/ll_password"android:layout_width="match_parent"android:layout_height="wrap_content"android:layout_below="@+id/ll_number"android:layout_centerVertical="true"android:layout_marginTop="15dp"android:layout_marginLeft="10dp"android:layout_marginRight="10dp"android:layout_marginBottom="5dp"android:background="#ffffff"><TextViewandroid:id="@+id/tv_password"android:layout_width="wrap_content"android:layout_height="wrap_content"android:padding="10dp"android:text="密码"android:textColor="#000"android:textSize="20sp"/><EditTextandroid:id="@+id/et_password"android:layout_width="match_parent"android:layout_height="wrap_content"android:layout_marginLeft="5dp"android:background="@null"android:padding="10dp"/></LinearLayout><Buttonandroid:id="@+id/btn_login"android:layout_width="match_parent"android:layout_height="wrap_content"android:layout_below="@+id/ll_password"android:layout_marginLeft="10dp"android:layout_marginRight="10dp"android:layout_marginTop="30dp"android:text="登录"android:background="#3C8DC4"android:textSize="20sp"/></RelativeLayout>

package com.example.remembernp;import androidx.appcompat.app.AppCompatActivity;import android.os.Bundle;
import android.text.TextUtils;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;import java.util.Map;public class MainActivity extends AppCompatActivity implements View.OnClickListener{private EditText etNumber;private EditText etPassword;private Button btnLogin;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);Button btn = (Button)findViewById(R.id.btn_login);Map<String,String> userInfo = SaveFile.getUserInfo(this);initView();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);btnLogin = (Button)findViewById(R.id.btn_login);btnLogin.setOnClickListener(this);}@Overridepublic void onClick(View view) {//单击事件，获取账号密码String number = etNumber.getText().toString().trim();String password = etPassword.getText().toString().trim();//检查账号密码是否正确if(TextUtils.isEmpty(number)){Toast.makeText(this, "请输入账号", Toast.LENGTH_SHORT).show();return;}if(TextUtils.isEmpty(password)){Toast.makeText(this, "请输入密码", Toast.LENGTH_SHORT).show();return;}//否则登录成功Toast.makeText(this, "登录成功", Toast.LENGTH_SHORT).show();//保存信息boolean isSaveSuccess = SaveFile.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();}}
}

package com.example.remembernp;import android.content.Context;import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.util.HashMap;
import java.util.Map;public class SaveFile {//把账号密码保存在data.txt文件中public static boolean saveUserInfo(Context context, String number, String password){try{FileOutputStream fos = context.openFileOutput("data.txt",Context.MODE_PRIVATE);fos.write((number + ":" + password).getBytes());fos.close();return true;}catch (Exception e){e.printStackTrace();return false;}}//从data.txt中去获取刚刚保存的账号密码public static Map<String,String> getUserInfo(Context context) {String content = "";try {FileInputStream fis = context.openFileInput("data.txt");byte[] buffer = new byte[fis.available()];fis.read(buffer);//读取content = new String(buffer);Map<String ,String > userMap = new HashMap<String, String>();String[] infos = content.split(":");userMap.put("number",infos[0]);userMap.put("password",infos[1]);fis.close();return userMap;}catch (Exception e){e.printStackTrace();return null;}}
}