java - Get value from strings.xml in Facebook SDK -

i setting app facebook login , trying of pre set strings , colors facebook sdk , use them in activity_login.xml. this

<button     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:layout_gravity="center_horizontal"     android:layout_margintop="100dp"      android:text="@string/com_facebook_loginview_log_in_button"     android:textcolor="@color/com_facebook_loginview_text_color"     android:textsize="@dimen/com_facebook_loginview_text_size"     android:textstyle="bold"      android:background="@drawable/com_facebook_button_blue"     android:drawableleft="@drawable/com_facebook_inverse_icon"     android:drawablepadding="@dimen/com_facebook_likebutton_compound_drawable_padding"     android:paddingleft="@dimen/com_facebook_loginview_padding_left"     android:paddingtop="@dimen/com_facebook_loginview_padding_top"     android:paddingright="@dimen/com_facebook_loginview_padding_right"     android:paddingbottom="@dimen/com_facebook_loginview_padding_bottom"     android:onclick="onloginclick"/> 

but error cant resolve symbol @string/com_facebook_loginview_log_in_button , have imported facebook sdk correctly , good, can't seem use values?

thanks in advance. :)

is there reason can't use facebook button?

<com.facebook.widget.loginbutton     android:id="@+id/facebook_button"     android:layout_width="wrap_content"     android:layout_height="wrap_content"/> 

make sure import facebook sdk project work.