<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"    android:paddingBottom="@dimen/activity_vertical_margin"    android:paddingLeft="@dimen/activity_horizontal_margin"    android:paddingRight="@dimen/activity_horizontal_margin"    android:paddingTop="@dimen/activity_vertical_margin"    tools:context="com.example.logindemo.MainActivity" >    <TextView        android:layout_width="fill_parent"        android:layout_height="wrap_content"        android:text="请输入用户名" />    <EditText         android:layout_width="fill_parent"        android:layout_height="wrap_content"        android:id="@+id/et_username"        />     <TextView                android:layout_width="fill_parent"        android:layout_height="wrap_content"        android:text="请输入密码" />    <EditText         android:inputType="textPassword"        android:layout_width="fill_parent"        android:layout_height="wrap_content"        android:id="@+id/et_password"        />    <RelativeLayout         android:layout_width="fill_parent"        android:layout_height="wrap_content"                >        <CheckBox             android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:id="@+id/cb_remember"            android:text="记住密码"            android:checked="true"            />        <Button            android:onClick="login"            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:layout_alignParentRight="true"            android:text="登录"            android:id="@+id/btn_login" />    </RelativeLayout></LinearLayout>

package com.example.logindemo;import java.util.Map;import android.os.Bundle;import android.support.v7.app.ActionBarActivity;import android.text.TextUtils;import android.view.Menu;import android.view.MenuItem;import android.view.View;import android.widget.CheckBox;import android.widget.EditText;import android.widget.Toast;import com.example.logindemo.service.LoginService;public class MainActivity extends ActionBarActivity {        private EditText et_username;    private EditText et_pwd;    private CheckBox cb_remember;        @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        et_username = (EditText)this.findViewById(R.id.et_username);        et_pwd = (EditText)this.findViewById(R.id.et_password);        cb_remember = (CheckBox)this.findViewById(R.id.cb_remember);                Map<String,String> map = LoginService.getUserInfo(this);        if(map!=null)        {            et_username.setText(map.get("username"));            et_pwd.setText(map.get("password"));        }    }        public void login(View v){                String username = et_username.getText().toString();        String pwd = et_pwd.getText().toString();                if(TextUtils.isEmpty(username) || TextUtils.isEmpty(pwd)){                        Toast.makeText(MainActivity.this, "username or password is empty", Toast.LENGTH_SHORT).show();            return;        }        else        {                        if(cb_remember.isChecked())            {                boolean result = LoginService.saveUserInfo(this, username, pwd);                if(result)                {                    Toast.makeText(MainActivity.this, "save user info success", Toast.LENGTH_SHORT).show();                }            }                        if("test".equals(username) && "123".equals(pwd))            {                Toast.makeText(MainActivity.this, "login success", Toast.LENGTH_SHORT).show();            }            else            {                                Toast.makeText(MainActivity.this, "username or password is error", Toast.LENGTH_SHORT).show();            }        }            }}

package com.example.logindemo.service;import java.io.BufferedReader;import java.io.File;import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.InputStreamReader;import java.util.HashMap;import java.util.Map;import android.content.Context;public class LoginService {        public static boolean saveUserInfo(Context context,String username,String pwd)    {        try        {            File file = new File(context.getFilesDir(),"info.txt");            FileOutputStream fos = new FileOutputStream(file);            fos.write((username+"##"+pwd).getBytes());            fos.close();            return true;        }        catch(Exception e)        {            e.printStackTrace();            return false;        }            }        public static Map<String,String> getUserInfo(Context context)    {        try        {            File file = new File(context.getFilesDir(),"info.txt");            FileInputStream fis = new FileInputStream(file);            BufferedReader br = new BufferedReader(new InputStreamReader(fis));            String strs = br.readLine();            String arr[] = strs.split("##");            Map<String,String> map = new HashMap<String,String>();            map.put("username", arr[0]);            map.put("password", arr[1]);            return map;                    }        catch(Exception e)        {            e.printStackTrace();            return null;        }        }}