android - case expressions must be constant expressions. Getting Error on R.id.* -

i got stuck on project; , unable understand error. kindly me on that. getting case expressions must constant expressions on every r.id , sharing code here.

i getting error on every case r.id ; kindly suggest

public void onclick(view v) {     int currentbgcolor = preferencesutils.getbgcolor(this);     switch (v.getid()) {     case r.id.btn_home:         if (isshowbgselect) {             hidebgselector(false);             isshowbgselect = false;         }         dismissmaincling(v);         toggle();         break;     case r.id.btn_bookmark:         if (isshowbgselect) {             hidebgselector(false);             isshowbgselect = false;         }         boolean isbookmarked = false;         (bookmark bm : mbookmarklist) {             if (bm.partid == mcurrentpart && bm.chapid == mcurrentchap) {                 isbookmarked = true;                 break;             }         }         if (isbookmarked) {             showunbookmarkdialog(mcurrentpart, mcurrentchap);         } else {             showsavebookmarkdialog(mcurrentpart, mcurrentchap);         }         break;     case r.id.btn_bm_list:         if (isshowbgselect) {             hidebgselector(false);             isshowbgselect = false;         }         // togglesecondary();         break;     case r.id.btn_background:         if (!isshowbgselect) {             showbgselector();             isshowbgselect = true;         } else {             hidebgselector(true);             isshowbgselect = false;         }         mbtnbgselect.setenabled(false);         mbtnbgselect.setselected(true);         break;     case r.id.btn_fullscreen:         if (isshowbgselect) {             hidebgselector(false);             isshowbgselect = false;         }         if (isfullscreen) {             showcontroller();             mfullscreenbutton.setenabled(false);             isfullscreen = false;         } else {             hidecontroller();             isfullscreen = true;         }         break;     case r.id.btn_home_slidingmenu_left:         toggle();         break;     case r.id.btn_home_slidingmenu_right:         // togglesecondary();         break;     case r.id.btn_bg_white:         if (isshowbgselect) {             hidebgselector(false);             isshowbgselect = false;         }         if (currentbgcolor != constants.bg_color_white) {             preferencesutils.savebgcolor(this, constants.bg_color_white);             loadpart(mcurrentpart, mcurrentchap);         }         break;     case r.id.btn_bg_khaki:         if (isshowbgselect) {             hidebgselector(false);             isshowbgselect = false;         }         if (currentbgcolor != constants.bg_color_khaki) {             preferencesutils.savebgcolor(this, constants.bg_color_khaki);             loadpart(mcurrentpart, mcurrentchap);         }         break;     case r.id.btn_bg_sepia:         if (isshowbgselect) {             hidebgselector(false);             isshowbgselect = false;         }         if (currentbgcolor != constants.bg_color_sepia) {             preferencesutils.savebgcolor(this, constants.bg_color_sepia);             loadpart(mcurrentpart, mcurrentchap);         }         break;     case r.id.btn_about:         showaboutdialog();         break;     case r.id.tv_contact_us:         intent email = new intent(intent.action_send);         email.putextra(intent.extra_email, new string[] { getresources()                 .getstring(r.string.dialog_about_email) });         email.putextra(intent.extra_subject,                 gettext(r.string.contact_prefix) + " "                         + gettext(r.string.app_name));         email.settype("message/rfc822");         startactivity(intent.createchooser(email,                 gettext(r.string.contact_chooser)));         break;     } }  @override public boolean onoptionsitemselected(menuitem item) {     int currentbgcolor = preferencesutils.getbgcolor(this);     switch (item.getitemid()) {     case android.r.id.home:         toggle();         return true;     case r.id.menu_bookmark:         boolean isbookmarked = false;         (bookmark bm : mbookmarklist) {             if (bm.partid == mcurrentpart && bm.chapid == mcurrentchap) {                 isbookmarked = true;                 break;             }         }         if (isbookmarked) {             showunbookmarkdialog(mcurrentpart, mcurrentchap);         } else {             showsavebookmarkdialog(mcurrentpart, mcurrentchap);         }         return true;     case r.id.menu_bookmarked_chap:         // togglesecondary();         return true;     case r.id.menu_bg_white:         if (currentbgcolor != constants.bg_color_white) {             preferencesutils.savebgcolor(this, constants.bg_color_white);             loadpart(mcurrentpart, mcurrentchap);         }         return true;     case r.id.menu_bg_khaki:         if (currentbgcolor != constants.bg_color_khaki) {             preferencesutils.savebgcolor(this, constants.bg_color_khaki);             loadpart(mcurrentpart, mcurrentchap);         }         return true;     case r.id.menu_bg_sepia:         if (currentbgcolor != constants.bg_color_sepia) {             preferencesutils.savebgcolor(this, constants.bg_color_sepia);             loadpart(mcurrentpart, mcurrentchap);         }         return true;     case r.id.menu_about:         showaboutdialog();         return true;     }     return super.onoptionsitemselected(item); }  @override public boolean oncreateoptionsmenu(menu menu) {     getmenuinflater().inflate(r.menu.activity_main, menu);     return true; }  @override public boolean onprepareoptionsmenu(menu menu) {     // todo auto-generated method stub     if (isshowbgselect) {         hidebgselector(false);         isshowbgselect = false;     }     return super.onprepareoptionsmenu(menu);  }  @override protected void ondestroy() {     super.ondestroy();  }