java - Changing mainactivity inner layout background from preference activity in android -

i have preferences activity. activity want able change background color of 1 of layouts in main activity.

right when try run settings activity "if" loops carry change in background color, app crashes.

the click listener opens settings activity:

        settings.setonclicklistener(new view.onclicklistener() {              @override              public void onclick(view view) {                  intent intentpreferences = new intent(getapplicationcontext(),                          settingsactivity.class);                  startactivity(intentpreferences);                    //startactivityforresult(intentpreferences);              }          });

the preferencescreen layout:

<?xml version="1.0" encoding="utf-8"?>  <preferencescreen xmlns:android="http://schemas.android.com/apk/res/android">        <switchpreference          android:key="pref_sync"          android:id="@+id/prefswitch"          android:defaultvalue="false"          android:title="you want yellow or white background?"          />    </preferencescreen>

my preferences activity:

public class settingsactivity extends preferenceactivity {        private static final boolean always_simple_prefs = false;      private switchpreference settingsswitch;        @suppresswarnings("deprecation")      @override      protected void oncreate(bundle savedinstancestate) {          super.oncreate(savedinstancestate);          addpreferencesfromresource(r.xml.preferences);          preferencemanager mpreferencemanager = getpreferencemanager();          relativelayout rl = (relativelayout) findviewbyid(r.id.newdeliverylayout);          if (mpreferencemanager.getsharedpreferences().getboolean("pref_sync", true)){              rl.setbackgroundcolor(color.yellow);          } else{              rl.setbackgroundcolor(color.white);          }        }        @override      protected void onpostcreate(bundle savedinstancestate) {          super.onpostcreate(savedinstancestate);      }    }

the preferences screen opens if comment out rl.setbackgroundcolor lines in if loop

you each time main activity loads checks shared preferences , loads color ever in preferences. if preferences null set default color?

so example on can set color this. (ive put hex color reference can change whatever wish.

public void setbackgroundcolor() {     sharedpreferences sharedpreferences = getpreferences(context.mode_private);     sharedpreferences.editor editor = sharedpreferences.edit();     editor.putstring("color", "#ffffff");     editor.commit() } 

then in main activity make sure call method every time loads / reloads

public void getbackgroundcolor() {     sharedpreferences sharedpreferences = getpreferences(context.mode_private);     if (sharedpreferences.contains("color")) {         string mycolor = sharedpreferences.getstring("color", null);         mybackground.setbackgroundcolor(color.parsecolor(mycolor));     } }