java - Start a new Activity with an extra class (android) -

i've found examples, didn't me out. i'm creating app mobile phone ran problem. problem want start new activity in new class doesn't work.

this class below want start new activity called "phonestatus"

package com.example.phone;  import android.content.intent; import android.view.view; import android.widget.button;  public class controller {     button ps;     phonestatus c_ps;      public controller(button ps) {         this.ps = ps;         c_ps = new phonestatus();         createphone_status();     }      private boolean createphone_status() {         ps.setonclicklistener(new view.onclicklistener() {             public void onclick(view v) {                 intent = new intent("com.example.phone.phonestatus");                 c_ps.startactivity(it);             }         });         return true;     } } 

can 1 me start new activity? because gave me error , crashed app. activity1 (so mainactivity) working fine.

the error: 07-22 15:38:35.946: e/androidruntime(30784): java.lang.nullpointerexception: attempt invoke virtual method 'android.app.activitythread$applicationthread android.app.activitythread.getapplicationthread()' on null object reference

phonestatus activity. should never instantiating android application components (like activities) yourself. responsibility of os this, because os needs setup attaching base context activity. because instantiated new phonestatus(), setup has not happened , call startactivity() results in error occurring somewhere in call stack. earliest should try use activity in oncreate() callback.

i think easiest solution this:

ps.setonclicklistener(new view.onclicklistener() {     public void onclick(view v) {         intent = new intent("com.example.phone.phonestatus");         ps.getcontext().startactivity(it);     } });