public boolean onOptionsItemSelected(MenuItem item) {

         // TODO Auto-generated method stub

         switch(item.getItemId()){

         case 1:

             Intent intent = new Intent();

             intent.setAction(Intent.ACTION_MAIN);

             intent.addCategory(Intent.CATEGORY_HOME);

             startActivity(intent);

             break;

         case 2:

             Toast.makeText(MainActivity.this, "POWER BY BOF", Toast.LENGTH_LONG).show();

             break;

         case 3:

             login();

             break;

         }

         return super.onOptionsItemSelected(item);

     }

     //用户注册

     public void login(){

         /*

          * 此段代码为重点内容

          *

          */

         LayoutInflater factory = LayoutInflater.from(MainActivity.this);

         final View v1 = factory.inflate(R.layout.login, null);

         //创建对话框

         final Builder alertDialog = new AlertDialog.Builder(this);

         alertDialog.setTitle("用户登陆");

         alertDialog.setView(v1);

         alertDialog.setPositiveButton("登录", new DialogInterface.OnClickListener() {

             @Override

             public void onClick(DialogInterface dialog, int which) {

                 /*

                  * 下面两行代码为获取dialog中的控件对象，

                  * 和UI布局获取控件对象略有不同，只能在用到alertDialog的地方进行实现

                  */

                 EditText user = (EditText)v1.findViewById(R.id.user);

                 EditText passwd = (EditText)v1.findViewById(R.id.passwd);

                 String userStr = user.getText().toString();

                 String passwdStr = passwd.getText().toString();

                 if(userStr.equals("android") && passwdStr.equals("asdf123..")){

                     Intent intent1 = new Intent(MainActivity.this,HandproActivity.class);

                     startActivity(intent1);

                 }else{

                     Toast.makeText(MainActivity.this, "账号或密码错误，请重新输入", Toast.LENGTH_LONG).show();

                 }

                 //Toast.makeText(MainActivity.this, "haha", Toast.LENGTH_LONG).show();

             }

         });

         alertDialog.setNegativeButton("去注册", new DialogInterface.OnClickListener() {

             @Override

             public void onClick(DialogInterface dialog, int which) {

                 // TODO Auto-generated method stub

             }

         });

         alertDialog.create().show();

     }