<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#E6E6E6"
    android:orientation="vertical">
 
    <ImageView
        android:id="@+id/iv"
        android:layout_width="70dp"
        android:layout_height="70dp"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="40dp"
        android:src="@drawable/head"
        />
    <LinearLayout
        android: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_marginBottom="5dp"
        android:layout_marginLeft="10dp"
        android:layout_marginRight="10dp"
        android:layout_marginTop="15dp"
        android:background="#ffffff">
 
        <TextView
            android: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"/>
        <EditText
            android: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>
 
    <LinearLayout
        android: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_marginLeft="10dp"
        android:layout_marginRight="10dp"
        android:background="#ffffff">
 
        <TextView
            android: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"/>
        <EditText
            android:id="@+id/et_password"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginLeft="5dp"
            android:background="@null"
            android:inputType="textPassword"
            android:padding="10dp"/>
    </LinearLayout>
 
    <Button
        android: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="50dp"
        android:background="#3c8dc4"
        android:text="登录"
        android:textColor="#ffffff"
        android:textSize="20sp"
        />
</RelativeLayout>

package com.example.saveqq;
 
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 user;
    private EditText password;
    private Button button;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //1.初始化view
        initView();
 
        //2.若用户保存了信息，进行数据回写
        //I/O流方法
        Map<String,String> userInfo = FileSaveQQ.getUserInfo(this);
        
        //SharedPreferences的方法
/*        Map<String,String> userInfo = SpSaveQQ.getUserInfo(this);*/
            if ((userInfo!=null)){
                user.setText(userInfo.get("user"));
                password.setText(userInfo.get("password"));
            }
    }
 
    private void initView() {
        //控件的初始化
        user = (EditText)findViewById(R.id.et_number);
        password = (EditText)findViewById(R.id.et_password);
        button = (Button) findViewById(R.id.btn_login);
        //2.设置按钮点击事件
        button.setOnClickListener(this);
    }
 
    @Override
    public void onClick(View v) {
        //1.点击获取账号密码
        String  s_user = user.getText().toString().trim();
        String  s_password = password.getText().toString().trim();
        //2.检查用户名和密码是否为空
        if (TextUtils.isEmpty(s_user)){
            Toast.makeText(this,"请输入QQ账号",Toast.LENGTH_LONG).show();
            return;
        }
        if (TextUtils.isEmpty(s_password)){
            Toast.makeText(this,"请输入QQ密码",Toast.LENGTH_LONG).show();
            return;
        }
        Toast.makeText(this,"登陆成功",Toast.LENGTH_LONG).show();
 
        //3.保存用户信息
        //I/O流的方法
        boolean isSaveSuccess = FileSaveQQ.saveUserInfo(this,s_user,s_password);
        //用SharedPreferences的方法
/*        boolean isSaveSuccess = SpSaveQQ.saveUserInfo(this,s_user,s_password);*/
        if (isSaveSuccess){
            Toast.makeText(this,"保存成功",Toast.LENGTH_LONG).show();
        }else{
            Toast.makeText(this,"保存失败",Toast.LENGTH_LONG).show();
        }
    }
}

package com.example.saveqq;
 
import android.content.Context;
 
 
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
 
public class FileSaveQQ {
    //保存QQ账号和密码到data.txt
    public static  boolean saveUserInfo(Context context,String user,String password){
        try {
            //1.通过上下文获取文件输出流
            FileOutputStream fos = context.openFileOutput("data.txt",context.MODE_APPEND);
            //2.把数据写到文件中
            fos.write((user+":"+password).getBytes());
            fos.close();
            return true;
        } catch (IOException e) {
            e.printStackTrace();
            return false;
        }
    }
 
    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);
            Map<String,String> userMap = new HashMap<String, String>();
            content = new String(buffer);
            String[] infos = content.split(":");
            userMap.put("user",infos[0]);
            userMap.put("password",infos[1]);
            fis.close();
            return userMap;
        } catch (IOException e ) {
            return  null;
        }
 
 
    }
}

package com.example.saveqq;
 
import android.annotation.SuppressLint;
import android.content.Context;
import android.content.SharedPreferences;
 
import java.util.HashMap;
import java.util.Map;
 
//保存QQ账号和密码到data.xml中
public class SpSaveQQ {
    public static boolean saveUserInfo(Context context,String username,String password){
        SharedPreferences sp = context.getSharedPreferences("data",context.MODE_PRIVATE);
        SharedPreferences.Editor editor = sp.edit();
        editor.putString("username",username);
        editor.putString("password",password);
        editor.commit();
        return true;
    }
 
    //从data.xml文件中获取存储的QQ账号和密码
    public static Map<String,String> getUserInfo(Context context){
        SharedPreferences sp = context.getSharedPreferences("data",context.MODE_PRIVATE);
        String username = sp.getString("username","");
        String password = sp.getString("password","");
        Map<String,String> userMap = new HashMap<>();
        userMap.put("username",username);
        userMap.put("password",password);
        return  userMap;
    }
}