android - DataBinding: cannot find symbol class -

i've got problem databinding in android. above xml file , activity class:

activity_main.xml ( binding in android:enabled="@{logininfo.existinguser}")

 <layout xmlns:android="http://schemas.android.com/apk/res/android"     xmlns:tools="http://schemas.android.com/tools"     xmlns:app="http://schemas.android.com/apk/res-auto">    <data>   <variable    name="logininfo"     type="com.example.android.loginapplication.logininfo"/>   </data>  <linearlayout android:layout_width="match_parent"     android:layout_height="match_parent"     android:orientation="vertical"     android:padding="16dp">      <radiogroup         android:layout_width="match_parent"         android:layout_height="wrap_content"         android:orientation="vertical">          <radiobutton             android:layout_width="wrap_content"             android:layout_height="wrap_content"             android:text="@string/new_customer"             android:enabled="@{logininfo.existinguser}"/>          <radiobutton             android:layout_width="wrap_content"             android:layout_height="wrap_content"             android:text="@string/i_have_a_password"/>     </radiogroup>      <edittext     android:id="@+id/password"     android:layout_width="match_parent"     android:layout_height="wrap_content"     android:inputtype="textpassword"/>   </linearlayout>    </layout> 

logininfoactivity.java

public class logininfoactivity extends appcompatactivity {  private logininfo logininfo; @override protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     logininfobinding binding = databindingutil.setcontentview(             this, r.layout.activity_main);       binding.setlogininfo(logininfo); } } 

it can't find generated class logininfobinding in logininfoactivity...

is xml correct? or depends other things?

the binding class named after layout resource default. layout resource activity_main.xml, binding activitymainbinding.