java - Android NullPointerException on variable in instantiated class -

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i have activity calls expandablelistview. vanilla setup:

activity->creates expandablelistviewadapter->draw it.

when getchildview called , tries reference variable set via listadapter's constructor receives npe.

so activitya->data gets set, sent arbitrarylistadapter. when childview method referenced , tries use datafromactivitya nullpointerexception. i'm not sure why, when verify datafromactivitya in adapter class, verifies correctly. when try reference in getchildview method npe shows up.

to explain example:

class activitya extends activity {      private sparsearray<sparsearray<object>> data;     private arbitrarylistadapter adapter;      public void oncreate() {         this.data = arbitraryfunctiontopopulatedatavariable(); // populates         this.adapter = new arbitrarylistadapter(this, this.data);         // other stuff          this.adapter.notifydatasetchanged();     } // rest of activity here } /******************************/ class arbitrarylistadapter extends baseexpandablelistadapter {      private sparsearray<sparsearray<object>> datafromactivitya;      public arbitrarylistadapter(context context, sparsearray<sparsearray<object>> x) {         this.datafromactivitya = x; // @ point variable set     }      public view getchildview(int group, int child, boolean last, view convertview, viewgroup parent) {         // stuff         // npe arises!!!         for(int = 0;i< this.datafromactivitya.size();i++){             log.d(tag, "group: " + i);             for(int j = 0; j<this.datafromactivitya.get(i).size();j++) {                 log.d(tag, "child: " + this.datafromactivitya.get(j).tostring());             }             log.d(tag, "============================");         }     // other stuff     } // finish listadapter functions here }

sigh worlds worst developer. didn't see in onresume() of activity clearing list. how stupid i!?


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