<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"     android:layout_width="match_parent"     android:layout_height="match_parent"     android:orientation="vertical">     <EditText         android:id="@+id/et_1"         android:layout_width="match_parent"         android:layout_height="wrap_content"         android:hint="输入你想写入的内容："         android:layout_margin="20dp"/>     <Button         android:id="@+id/bt_1"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:text="写入"         android:layout_margin="5dp"         android:onClick="click1"/>     <EditText         android:id="@+id/et_2"         android:layout_width="match_parent"         android:layout_height="wrap_content"         android:hint="显示读取的内容"         android:layout_margin="20dp"/>     <Button         android:id="@+id/bt_2"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:text="读取"         android:layout_margin="5dp"         android:onClick="click2"/> </LinearLayout>

　　

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package com.example.zy;   import androidx.appcompat.app.AppCompatActivity; import android.os.Bundle; import android.view.View; import android.widget.EditText; import android.widget.Toast; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; public class MainActivity extends AppCompatActivity {     @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_main);         findViewById(R.id.bt_1);         findViewById(R.id.bt_2);         EditText editText1=findViewById(R.id.et_1);         EditText editText2=findViewById(R.id.et_2);     }     public void click1(View view){         EditText editText1=findViewById(R.id.et_1);         EditText editText2=findViewById(R.id.et_2);         String fileName="data.txt";         String content=editText1.getText().toString();         FileOutputStream fos=null;         try {             fos=openFileOutput(fileName,MODE_PRIVATE);             fos.write(content.getBytes());         } catch (Exception e) {             e.printStackTrace();         }finally {             if (fos!=null){                 try {                     fos.close();                 } catch (IOException e) {                     e.printStackTrace();                 }             }         }         Toast.makeText(MainActivity.this,"保存成功",Toast.LENGTH_SHORT).show();     }  public void click2(View view){         EditText editText2=findViewById(R.id.et_2);         String content="";         FileInputStream fis=null;         try {             fis=openFileInput("data.txt");             byte[] buffer=new byte[fis.available()];             fis.read(buffer);             content=new String(buffer);         } catch (Exception e) {             e.printStackTrace();         } finally {             if (fis!=null){                 try {                     fis.close();                 } catch (IOException e) {                     e.printStackTrace();                 }             }         }         Toast.makeText(MainActivity.this,"读取成功",Toast.LENGTH_SHORT).show();         editText2.setText(content);     } }

　　

 2.使用sharedpreference实现记住密码功能

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<?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" tools:context=".MainActivity" android:orientation="vertical"> <LinearLayout     android:layout_width="match_parent"     android:layout_height="wrap_content"     android:orientation="horizontal">     <TextView         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:text="账号:"         android:textSize="25sp"         android:textColor="#000"         android:layout_marginTop="40dp"         android:layout_marginLeft="10dp"/>     <EditText         android:id="@+id/et_3"         android:layout_width="match_parent"         android:layout_height="wrap_content"         android:hint="请输入用户名:"         android:layout_marginTop="40dp"         android:textSize="25sp"/> </LinearLayout> <LinearLayout     android:layout_width="match_parent"     android:layout_height="wrap_content"     android:orientation="horizontal">     <TextView         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:text="密码:"         android:textSize="25sp"         android:textColor="#000"         android:layout_marginTop="15dp"         android:layout_marginLeft="10dp"/>     <EditText         android:id="@+id/et_4"         android:layout_width="match_parent"         android:layout_height="wrap_content"         android:hint="请输入密码"         android:layout_marginTop="15dp"         android:textSize="25sp"/> </LinearLayout> <LinearLayout     android:layout_width="match_parent"     android:layout_height="wrap_content"     android:orientation="horizontal">     <CheckBox         android:id="@+id/cb_1"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:text="记住密码"         android:textSize="20sp"         android:layout_marginTop="15dp"/>     <CheckBox         android:id="@+id/cb_2"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:text="自动登录"         android:textSize="20sp"         android:layout_marginTop="15dp"/>     <Button         android:id="@+id/bt_3"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:text="登陆"         android:textSize="20sp"         android:layout_marginTop="15dp"         android:layout_marginLeft="35dp"         android:onClick="clickQQ"         tools:ignore="OnClick" /> </LinearLayout> </LinearLayout>

　　

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package com.example.dierti;   import androidx.appcompat.app.AppCompatActivity;   import android.content.SharedPreferences; import android.os.Bundle; import android.view.View; import android.widget.CheckBox; import android.widget.EditText; import android.widget.Toast;   public class MainActivity extends AppCompatActivity {       private EditText yonghuming,mima;     private CheckBox box;     @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_main);           yonghuming=findViewById(R.id.et_3);         mima=findViewById(R.id.et_4);         box=findViewById(R.id.cb_1);         load();     }       public void clickQQ(View view){         String yhm=yonghuming.getText().toString();         String mm=mima.getText().toString();         if (box.isChecked()){             SharedPreferences sp=getSharedPreferences("info",MODE_PRIVATE);             SharedPreferences.Editor et=sp.edit();             et.putString("YHM",yhm);             et.putString("MM",mm);             et.commit();             Toast.makeText(this,"登陆成功",Toast.LENGTH_SHORT).show();         }else{             Toast.makeText(this,"登陆成功",Toast.LENGTH_SHORT).show();         }     }       private void load() {         SharedPreferences sp=getSharedPreferences("info",MODE_PRIVATE);         String yhmString=sp.getString("YHM","");         String mmString=sp.getString("MM","");         yonghuming.setText(yhmString);         mima.setText(mmString);     } }