android - shared preferences is throughing Exception -

i getting problem , not know how find out , adding code getting

  caused by: java.lang.nullpointerexception             @ android.preference.preferencemanager.getdefaultsharedpreferencesname(preferencemanager.java:376)             @ android.preference.preferencemanager.getdefaultsharedpreferences(preferencemanager.java:371)             @ com.example.mine4.accelerometergpsmaster.mainapplication.onpreferencechange(mainapplication.java:100)             @ com.example.mine4.accelerometergpsmaster.mainactivity.onresume(mainactivity.java:108)             @ android.app.instrumentation.callactivityonresume(instrumentation.java:1259)             @ android.app.activity.performresume(activity.java:5200)             @ android.app.activitythread.performresumeactivity(activitythread.java:2931)             at android.app.activitythread.handleresumeactivity(activitythread.java:2973)             at android.app.activitythread.handlelaunchactivity(activitythread.java:2408)             at android.app.activitythread.access$600(activitythread.java:165)             at android.app.activitythread$h.handlemessage(activitythread.java:1373)             at android.os.handler.dispatchmessage(handler.java:107)             at android.os.looper.loop(looper.java:194)             at android.app.activitythread.main(activitythread.java:5391)             at java.lang.reflect.method.invokenative(native method)             at java.lang.reflect.method.invoke(method.java:525)             at com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:833)             at com.android.internal.os.zygoteinit.main(zygoteinit.java:600)             at dalvik.system.nativestart.main(native method) 

my code:

 public static void onpreferencechange() {         sharedpreferences sp = preferencemanager.getdefaultsharedpreferences(mainapplication.getinstance());         //  latest settings, , update accordingly         boolean newstate = sp.getboolean("pref_onoff", false); // false off/not-running          prefinterval = integer.parseint( sp.getstring("pref_interval", "60") );         preftimeout = integer.parseint( sp.getstring("pref_timeout", "30") );          mainapplication.prefthreshold = double.parsedouble( sp.getstring("pref_threshold", "0.30") );         mainapplication.prefthreshold2 = mainapplication.prefthreshold + 9.80;          // if turned off service, handle change         togglestate( newstate );     } 

now please me out setting problem

i think because mainapplication.getinstance() null. maybe forgot assign value mainapplication.getinstance() or onpreferencechange called before assigned code.