android - AutoCompleteTextView with SimpleCursorAdapter return NullPointerException on filtering -

i have autocompletetextview have linked simplecursoradapter . working fine , when user input characters not in database , filtering method returns null cursor. cause non-fatal nullpointerexception. code is

madapter.setfilterqueryprovider(new filterqueryprovider() {         @override         public cursor runquery(charsequence constraint) {             string partial = null;             if(constraint!=null)                partial = constraint.tostring();             cursor result= dbhelper.readproductcategory(partial);             return result;         }     }); 

warning in logcat

 w/filter﹕ exception occured during performfiltering()! java.lang.nullpointerexception         @ com.orderoapp.ordero.data.productdatabasehelper.readproductcategory(productdatabasehelper.java:70)         @ com.orderoapp.ordero.ordersfragment$1.runquery(ordersfragment.java:87)         @ android.support.v4.widget.cursoradapter.runqueryonbackgroundthread(cursoradapter.java:397)         @ android.support.v4.widget.cursorfilter.performfiltering(cursorfilter.java:50)         @ android.widget.filter$requesthandler.handlemessage(filter.java:234)         @ android.os.handler.dispatchmessage(handler.java:102)         @ android.os.looper.loop(looper.java:136)         @ android.os.handlerthread.run(handlerthread.java:61) 

i don't know in case of null cursor. should return null ? best way handle this. when user delete text in autocompletetextview , got error

e/spannablestringbuilder﹕ span_exclusive_exclusive spans cannot have 0 length 

any ideas? gladly appreciate help. thanks.

the error due if statement in

  productdatabasehelper.readproductcategory  

method. if condition was

if ( con.length() > 0 ) {          result = getreadabledatabase().query(productentry.table_name, projection,                ....     } 

so when con null , gives nullpointerexception . solution simple . before checking if con.length() >0 , check if con not null.

if ( con!=null && con.length() > 0 ) { ...     }