sharedpreferences - Declared Shared Preferences in Android causes error when run on Android device? -

the ide doesn't seem detect error. when system run on physical device, system crashes when gets class. seems problem? shared preferences declared? how can fix this?

    package com.example.mobile_app;     import android.os.bundle;     import android.app.activity;     import android.content.sharedpreferences;     import android.view.menu;     import android.view.window;     import android.widget.textview;   public class post_4 extends activity {     static int time = post_1.gettime(), post_error = post_3.get_pos_err();     int percent;     float quotient_float = (float)post_error/(float)time;      float computation=0;     sharedpreferences value = getapplicationcontext().getsharedpreferences("values", mode_private);     sharedpreferences.editor editor = value.edit();     textview percentage_display;      @override     protected void oncreate(bundle savedinstancestate) {         requestwindowfeature(window.feature_no_title);         super.oncreate(savedinstancestate);         setcontentview(r.layout.activity_post_4);         percentage_display = (textview)findviewbyid(r.id.textview1);         store();     }      @override     public boolean oncreateoptionsmenu(menu menu) {         getmenuinflater().inflate(r.menu.post_4, menu);         return true;     }      private void store(){         computation=value.getfloat("value_quotient", quotient_float)-quotient_float/value.getfloat("value_quotient", quotient_float);         if(value.getfloat("value_quotient", quotient_float)==0.0f || quotient_float < value.getfloat("value_quotient", quotient_float))         {             editor.putfloat("value_quotient", quotient_float);             editor.commit();             if(value.getfloat("value_quotient", quotient_float)==0.0f)                 percentage_display.settext("system cannot make comparison on first use.");              else                 percentage_display.settext("positive "+math.round(computation*100)+"%.");          }         else             percentage_display.settext("negative "+math.round(computation*100)+"%.");          } } 

error log:

08-29 01:42:59.390: e/androidruntime(29985): fatal exception: main 08-29 01:42:59.390: e/androidruntime(29985): java.lang.runtimeexception: unable instantiate activity componentinfo{com.example.mobile_app/com.example.mobile_app.post_4}: java.lang.nullpointerexception 08-29 01:42:59.390: e/androidruntime(29985):    @ android.app.activitythread.performlaunchactivity(activitythread.java:1991) 08-29 01:42:59.390: e/androidruntime(29985):    @ android.app.activitythread.handlelaunchactivity(activitythread.java:2092) 08-29 01:42:59.390: e/androidruntime(29985):    @ android.app.activitythread.access$600(activitythread.java:133) 08-29 01:42:59.390: e/androidruntime(29985):    @ android.app.activitythread$h.handlemessage(activitythread.java:1203) 08-29 01:42:59.390: e/androidruntime(29985):    @ android.os.handler.dispatchmessage(handler.java:99) 08-29 01:42:59.390: e/androidruntime(29985):    @ android.os.looper.loop(looper.java:137) 08-29 01:42:59.390: e/androidruntime(29985):    @ android.app.activitythread.main(activitythread.java:4797) 08-29 01:42:59.390: e/androidruntime(29985):    @ java.lang.reflect.method.invokenative(native method) 08-29 01:42:59.390: e/androidruntime(29985):    @ java.lang.reflect.method.invoke(method.java:511) 08-29 01:42:59.390: e/androidruntime(29985):    @ com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:789) 08-29 01:42:59.390: e/androidruntime(29985):    @ com.android.internal.os.zygoteinit.main(zygoteinit.java:556) 08-29 01:42:59.390: e/androidruntime(29985):    @ dalvik.system.nativestart.main(native method) 08-29 01:42:59.390: e/androidruntime(29985): caused by: java.lang.nullpointerexception 08-29 01:42:59.390: e/androidruntime(29985):    @ android.content.contextwrapper.getapplicationcontext(contextwrapper.java:101) 08-29 01:42:59.390: e/androidruntime(29985):    @ com.example.mobile_app.post_4.<init>(post_4.java:16) 08-29 01:42:59.390: e/androidruntime(29985):    @ java.lang.class.newinstanceimpl(native method) 08-29 01:42:59.390: e/androidruntime(29985):    @ java.lang.class.newinstance(class.java:1319) 08-29 01:42:59.390: e/androidruntime(29985):    @ android.app.instrumentation.newactivity(instrumentation.java:1053) 08-29 01:42:59.390: e/androidruntime(29985):    @ android.app.activitythread.performlaunchactivity(activitythread.java:1982) 08-29 01:42:59.390: e/androidruntime(29985):    ... 11 more 

sharedpreferences value = getapplicationcontext().getsharedpreferences("values", mode_private); sharedpreferences.editor editor = value.edit(); 

move 2 lines function store. in case when class created try access context of application using getapplicationcontext function time context wont created wait oncreate happen , save these 2 values. hope help.

it clear crash log context not created. see line

caused by: java.lang.nullpointerexception 08-29 01:42:59.390: e/androidruntime(29985):    @ android.content.contextwrapper.getapplicationcontext(contextwrapper.java:101) 

do thing instead.

sharedpreferences value; sharedpreferences.editor editor;  @override protected void oncreate(bundle savedinstancestate) {     requestwindowfeature(window.feature_no_title);     super.oncreate(savedinstancestate);     setcontentview(r.layout.activity_post_4);     percentage_display = (textview)findviewbyid(r.id.textview1);     value = getapplicationcontext().getsharedpreferences("values",  mode_private);     editor = value.edit();     store(); }