Android登录时密码保护功能

<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"
 android:background="#e6e6e6"
  android:orientation="vertical">
  <imageview 
   android:id="@+id/iv_head"
   android:layout_width="150dp"
   android:layout_height="150dp"
   android:layout_centerhorizontal="true"
   android:layout_margintop="40dp"
   android:src="@drawable/ic_launcher"/>
  <linearlayout 
   android:id="@+id/layout"
   android:layout_width="match_parent"
   android:layout_height="wrap_content"
   android:layout_below="@+id/iv_head"
   android:layout_margin="10dp"
   android:background="#ffffff"
   android:orientation="vertical">
   <relativelayout 
    android:id="@+id/rl_username"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_margin="10dp">
    <textview 
     android:id="@+id/tv_name"
     android:layout_width="wrap_content"
     android:layout_height="wrap_content"
     android:layout_centervertical="true"
     android:text="账号"/>
    <edittext 
     android:id="@+id/et_number"
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
     android:layout_marginleft="5dp"
     android:layout_torightof="@+id/tv_name"
     android:background="@null"/>
   </relativelayout>
   <view 
    android:layout_width="match_parent"
    android:layout_height="2dp"
    android:background="#e6e6e6"/>
   <relativelayout 
    android:id="@+id/rl_userpsd"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_margin="10dp">
    <textview 
     android:id="@+id/tv_psw"
     android:layout_width="wrap_content"
     android:layout_height="wrap_content"
     android:layout_centervertical="true"
     android:text="密码"/>
    <edittext 
     android:id="@+id/et_password"
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
     android:layout_marginleft="5dp"
     android:layout_torightof="@+id/tv_psw"
     android:inputtype="textpassword"
     android:background="@null"/>
   </relativelayout>
   
  </linearlayout>
  <button 
   android:id="@+id/login"
   android:onclick="login"
   android:layout_width="match_parent"
   android:layout_height="40dp"
   android:layout_below="@+id/layout"
   android:layout_centerhorizontal="true"
   android:layout_marginleft="10dp"
   android:layout_marginright="10dp"
   android:layout_margintop="20dp"
   android:background="#3c8dc4"
   android:text="登录"
   android:textcolor="#ffffff"/>
  <button 
   android:id="@+id/signup"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:text="注册"
   android:background="#e6e6e6"
   android:textcolor="#000000"
   android:layout_margintop="21dp"
   android:layout_centerhorizontal="true"
   android:layout_marginright="10dp"
   android:layout_below="@+id/login"
   android:layout_alignparentright="true"/>

  <checkbox
   android:id="@+id/save"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_alignbaseline="@+id/signup"
   android:layout_alignbottom="@+id/signup"
   android:layout_alignleft="@+id/login"
   android:layout_marginleft="14dp"
   android:text="记住密码" />
 
</relativelayout>

package com.itcast.test03;
import java.io.bufferedreader;
import java.io.ioexception;
import java.io.inputstream;
import java.io.inputstreamreader;
import java.io.unsupportedencodingexception;
import java.security.messagedigest;
import java.security.nosuchalgorithmexception;
import java.util.arraylist;
import java.util.list;
import org.apache.http.httpentity;
import org.apache.http.httpresponse;
import org.apache.http.namevaluepair;
import org.apache.http.parseexception;
import org.apache.http.client.clientprotocolexception;
import org.apache.http.client.httpclient;
import org.apache.http.client.entity.urlencodedformentity;
import org.apache.http.client.methods.httppost;
import org.apache.http.impl.client.defaulthttpclient;
import org.apache.http.message.basicnamevaluepair;
import org.apache.http.util.entityutils;
import org.json.jsonarray;
import org.json.jsonobject;
import android.os.build;
import android.os.bundle;
import android.os.strictmode;
import android.annotation.suppresslint;
import android.annotation.targetapi;
import android.app.activity;
import android.content.intent;
import android.content.sharedpreferences;
import android.text.textutils;
import android.util.log;
import android.view.menu;
import android.view.view;
import android.view.view.onclicklistener;
import android.view.view.onfocuschangelistener;
import android.widget.button;
import android.widget.checkbox;
import android.widget.edittext;
import android.widget.toast;


public class mainactivity extends activity implements onclicklistener {
 private edittext et_username;
 private edittext et_userpsd;
 private button login;
 private button signup;
 private checkbox save;
 private string user,pass;
 @override
 protected void oncreate(bundle savedinstancestate) {
  super.oncreate(savedinstancestate);  
  setcontentview(r.layout.activity_main);
  et_username = (edittext)findviewbyid(r.id.et_number);
  et_userpsd = (edittext)findviewbyid(r.id.et_password);
  login=(button)findviewbyid(r.id.login);
  signup=(button)findviewbyid(r.id.signup);
  save = (checkbox)findviewbyid(r.id.save);
  save.setonclicklistener(new checkbox.onclicklistener(){
   public void onclick(view v) {
    sharedpreferences pre = getsharedpreferences("loginvalue",
             mode_world_writeable);
    pass = md5( et_userpsd.gettext().tostring());
    user = et_username.gettext().tostring();
    if (!pass.equals("") && !user.equals("")) {
       pre.edit().putstring("username",
         et_username.gettext().tostring())
         .putstring("password", encryptmd5(pass)).commit();
    toast.maketext(getapplicationcontext(),"保存成功!",
    toast.length_short).show();
    } else{
    toast.maketext(getapplicationcontext(),"密码不能为空！",
    toast.length_long).show();
  }
    }
  });
  login.setonclicklistener(new button.onclicklistener() {
    
   @override
   public void onclick(view v) {
    
   sharedpreferences sp = getsharedpreferences("loginvalue",mode_world_readable);
   string loginuser = sp.getstring("username",null);
   string loginpass = sp.getstring("password",null);
    
   user = et_username.gettext().tostring();
   pass = et_userpsd.gettext().tostring();
    
   string passmd5 = md5(pass);
   string encryptmd5 = encryptmd5(passmd5);
    
   system.out.println("username="+ loginuser
   + "-------------password="+ loginpass);
   system.out.println("user=="+ user
   + "-------------encryptmd5=="+ encryptmd5);
   if (!user.equals("") && !pass.equals("")) {
   if (user.equals(loginuser) && encryptmd5.equals(loginpass)) {
   intent intent = new intent();
   intent.setclass(mainactivity.this, studentmainactivity.class);
   mainactivity.this.startactivity(intent);
   finish();
   } else{
   toast.maketext(getapplicationcontext(),"密码是错误的！",
   toast.length_long).show();
   }
   } else{
   toast.maketext(getapplicationcontext(),"密码不能为空！",
   toast.length_long).show();
   }
    
   }
    
   });
  initwidget();//
  }
 private void initwidget()
 {
  
  login.setonclicklistener(this);
  signup.setonclicklistener(this);
  et_username.setonfocuschangelistener(new onfocuschangelistener()
  {

   @override
   public void onfocuschange(view v, boolean hasfocus) {
    // todo auto-generated method stub
    if(!hasfocus){
     string username=et_username.gettext().tostring().trim();
     if(username.length()<4){
      toast.maketext(mainactivity.this, "用户名不能小于4个字符", toast.length_short);
     }
    }
   }
   
  });
  et_userpsd.setonfocuschangelistener(new onfocuschangelistener()
  {

   @override
   public void onfocuschange(view v, boolean hasfocus) {
    // todo auto-generated method stub
    if(!hasfocus){
     string password=et_userpsd.gettext().tostring().trim();
     if(password.length()<4){
      toast.maketext(mainactivity.this, "密码不能小于4个字符", toast.length_short);
     }
    }
   }
   
  });
 }
 

 public void onclick(view v) {
  // todo auto-generated method stub
  switch(v.getid())
  {
  case r.id.login:
   if(checkedit())
   {
    login();
   }   
   break;
  case r.id.signup:
   intent intent2=new intent(mainactivity.this,signup.class);
   startactivity(intent2);
   break;
  }
 }
 
 private boolean checkedit(){
  if(et_username.gettext().tostring().trim().equals("")){
   toast.maketext(mainactivity.this, "用户名不能为空", toast.length_short).show();
   intent intent=new intent(mainactivity.this,studentmainactivity.class);
   startactivity(intent);
  }else if(et_userpsd.gettext().tostring().trim().equals("")){
   toast.maketext(mainactivity.this, "密码不能为空", toast.length_short).show();
  }else{
   return true;
  }
  return false;
 }
 
 private void login(){
  //这个网址需要改动
  string httpurl="http://192.168.1.102:8080/web-test/login.jsp";
  httppost httprequest=new httppost(httpurl);
  list<namevaluepair> params=new arraylist<namevaluepair>();
  params.add(new basicnamevaluepair("username",et_username.gettext().tostring().trim()));
  params.add(new basicnamevaluepair("password",et_userpsd.gettext().tostring().trim()));
  httpentity httpentity = null;
  try {
   httpentity = new urlencodedformentity(params,"utf8");
  } catch (unsupportedencodingexception e) {
   // todo auto-generated catch block
   e.printstacktrace();
  }
  httprequest.setentity(httpentity);
  httpclient httpclient=new defaulthttpclient();
  httpresponse httpresponse = null;
  try {
   httpresponse = httpclient.execute(httprequest);
  } catch (clientprotocolexception e) {
   // todo auto-generated catch block
   e.printstacktrace();
  } catch (ioexception e) {
   // todo auto-generated catch block
   e.printstacktrace();
  }
  if(httpresponse.getstatusline().getstatuscode()==200)
  {
   string strresult = null;
   try {
    strresult = entityutils.tostring(httpresponse.getentity());
   } catch (parseexception e) {
    // todo auto-generated catch block
    e.printstacktrace();
   } catch (ioexception e) {
    // todo auto-generated catch block
    e.printstacktrace();
   }
   toast.maketext(mainactivity.this, strresult, toast.length_short).show();
   intent intent=new intent(mainactivity.this,studentmainactivity.class);
   startactivity(intent);
  }
  else
   
  {
   toast.maketext(mainactivity.this, "登录失败！", toast.length_short).show();
  }
  
 }
 public static string md5(string str){ 
  messagedigest md5 = null; 
 try {
  md5 = messagedigest.getinstance("md5");
 } catch (nosuchalgorithmexception e) {
  // todo auto-generated catch block
  e.printstacktrace();
  return "";
 }
  char[] chararray = str.tochararray();
  byte[] bytearray = new byte[chararray.length];
  for (int i = 0; i < chararray.length; i++) {
  bytearray[i] = (byte)chararray[i];
 }
  byte[] md5bytes = md5.digest(bytearray);
  stringbuffer hexvalue = new stringbuffer();
  for (int i = 0; i < md5bytes.length; i++) {
  int val = ((int)md5bytes[i])&0xff;
  if(val<16){
   hexvalue.append("0");
  }
  hexvalue.append(integer.tohexstring(val));
 }
  return hexvalue.tostring();  
 }
 public static string encryptmd5(string str){
  char[] a = str.tochararray();
  for (int i = 0; i < a.length; i++) {
  a[i] = (char)(a[i]^'1');
 }
  string s = new string(a);
  return s;
 }
 }

<uses-permission android:name="android.permission.write_external_storage" />
<uses-permission android:name="android.permission.internet" />