Android文件存储-将数据存储到内部文件

登录页面实现，数据存储将数据保存到内部文件，到再次加载页面，再从内部文件中获取

创建安卓项目

编写activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    tools:context=".MainActivity"
    android:padding="10dp"
    android:orientation="vertical">

    <ImageView
        android:layout_width="70dp"
        android:layout_height="70dp"

        android:layout_gravity="center_horizontal"
        android:layout_margin="30dp"
        android:src="@drawable/head"></ImageView>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="15dp"
        android:orientation="horizontal"
        android:background="@android:color/white">

        <TextView
            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_account"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginLeft="5dp"
            android:background="@null"
            android:padding="10dp" />

    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="15dp"
        android:orientation="horizontal"
        android:background="@android:color/white">

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:padding="10dp"
            android:text="密码"
            android:textColor="#000"
            android:textSize="20sp"></TextView>

        <EditText
            android: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>

    <Button
        android:id="@+id/btn_Login"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="25dp"
        android:background="#3C8DC4"
        android:text="登录"
        android:textColor="@android:color/white"
        android:textSize="20sp"
        />

</LinearLayout>

编写MainActivity：

package com.example.a2;

import androidx.appcompat.app.AppCompatActivity;

import android.content.SharedPreferences;
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.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    private EditText et_account;
    private EditText et_password;
    private Button btn_login;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        et_account =(EditText)findViewById(R.id.et_account);
        et_password =(EditText)findViewById(R.id.et_password);
        btn_login =(Button) findViewById(R.id.btn_Login);

        btn_login.setOnClickListener(this);//创建监听事件

        Map<String,String> map=getUserInfo();
        et_account.setText(map.get("账号"));
        et_password.setText(map.get("密码"));

    }

    @Override
    public void onClick(View v) {
        switch(v.getId()){
            case R.id .btn_Login:
                String account=et_account.getText().toString().trim();
                String password=et_password.getText().toString().trim();
                if (TextUtils.isEmpty(account)){
                    Toast.makeText(this,"账号为空",Toast.LENGTH_SHORT).show();
                    return;
                }
                if (TextUtils.isEmpty(password)){
                    Toast.makeText(this,"密码为空",Toast.LENGTH_SHORT).show();
                    return;
                }else{
                    Toast.makeText(this,"登录成功",Toast.LENGTH_SHORT).show();
                }
                //保存文件
                boolean issucess=SaveQQ(account,password);
                if(issucess==true){
                    Toast.makeText(this,"保存成功",Toast.LENGTH_SHORT).show();
                }else{
                    Toast.makeText(this,"保存失败",Toast.LENGTH_SHORT).show();
                }
                break;
        }
    }
//保存文件
    private boolean SaveQQ(String account, String password) {
        FileOutputStream fos=null;
        try{
            fos=openFileOutput("data.txt",MODE_PRIVATE);
            fos.write((account+"="+password).getBytes());
            fos.close();
            return true;
        }catch(IOException e){
            e.printStackTrace();
            return false;
        }
    }
//读取文件
    private Map<String,String> getUserInfo(){
        FileInputStream fis = null;
        try {
            fis = openFileInput("data.txt");
            byte[] buffer = new byte[fis.available()];
            fis.read(buffer);
            String info = new String(buffer);
            String[] infos = info.split("=");

            Map<String, String> map = new HashMap<>();
            map.put("账号", infos[0]);
            map.put("密码", infos[1]);

            fis.close();
            return map;
        }catch (Exception e){
            e.printStackTrace();
            return null;
        }
    }
}

 点击返回：

 另种方式：SharedPreferences存储 ，与上面只有MainActivity里内容不同：

package com.example.wenjianbaocun;

import androidx.appcompat.app.AppCompatActivity;

import android.content.SharedPreferences;
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.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    private EditText et_account;
    private EditText et_password;
    private Button btn_login;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        et_account =(EditText)findViewById(R.id.et_account);
        et_password =(EditText)findViewById(R.id.et_password);
        btn_login =(Button) findViewById(R.id.btn_Login);

        btn_login.setOnClickListener(this);//创建监听事件

        Map<String,String> map=getUserInfo();
        et_account.setText(map.get("账号"));
        et_password.setText(map.get("密码"));

    }
    @Override
    public void onClick(View v) {
        switch(v.getId()){
            case R.id .btn_Login:
                String account=et_account.getText().toString().trim();
                String password=et_password.getText().toString().trim();
                if (TextUtils.isEmpty(account)){
                    Toast.makeText(this,"账号为空",Toast.LENGTH_SHORT).show();
                    return;
                }
                if (TextUtils.isEmpty(password)){
                    Toast.makeText(this,"密码为空",Toast.LENGTH_SHORT).show();
                    return;
                }else{
                    Toast.makeText(this,"登录成功",Toast.LENGTH_SHORT).show();
                }
                //保存文件
                boolean issucess=SaveQQ(account,password);
                if(issucess==true){
                    Toast.makeText(this,"保存成功",Toast.LENGTH_SHORT).show();
                }else{
                    Toast.makeText(this,"保存失败",Toast.LENGTH_SHORT).show();
                }
                break;
        }
    }
    //内部存储 将数据保存到文件中
    private boolean SaveQQ(String account, String password){
        SharedPreferences sp=getSharedPreferences("data",MODE_PRIVATE);
        SharedPreferences.Editor editor=sp.edit();
        editor.putString("账号",account);
        editor.putString("密码",password);
        editor.commit();
        return true;

    }
    private Map<String,String> getUserInfo() {

        SharedPreferences SP=getSharedPreferences("data",MODE_PRIVATE);
        String account=SP.getString("账号","");
        String password=SP.getString("密码","");

        Map<String,String> map=new HashMap<>();
        map.put("账号",account);
        map.put("密码",password);
        return map;
    }
}