android - Calling a method from my MainActivity -

i've desperatly tried on internet able call thisisamethodjusttotryoutmybutton(view view), when user click delete button mainactivity, nothing works. button gives no reaction.

java.lang.nullpointerexception: attempt invoke virtual method 'android.content.res.resources android.content.context.getresources()' on null object reference 

adapter class

public class adapter extends baseadapter{  private arraylist<item> items= new arraylist<>();   public void additemtolistview(item item){     this.items.add(item); }  public void deleteitem(int position){     items.remove(position); }  @override public item getitem(int position) {     return items.get(position); }  @override public long getidofitem(int position) {     return position; }  @override public int getcount() {     return items.size(); }  class viewholder {     public textview title, content;      public viewholder(view view){         title= (textview) view.findviewbyid(r.id.title);         content= (textview) view.findviewbyid(r.id.content);     } }   @override public view getview(final int position, view convertview, viewgroup parent) {      viewholder viewholder;      if(null == convertview){         layoutinflater inflater = layoutinflater.from(parent.getcontext());         convertview = inflater.inflate(r.layout.custom_row, parent, false);         viewholder = new viewholder(convertview);         viewholder.header.settag(position);         convertview.settag(viewholder);      }     else{         viewholder = (viewholder) convertview.gettag();     }      item item= getitem(position);     viewholder.header.settext(item.title);     viewholder.bodytext.settext(item.content);     return convertview; } } 

mydialogfordeletingaitem class

 public class mydialogfordeletingaitem extends dialogfragment      implements view.onclicklistener {     button delete;      @nullable     @override     public view oncreateview(layoutinflater inflater, viewgroup container,      bundle savedinstancestate) {     view view = inflater.inflate(r.layout.deletedialog, null);     delete = (button) view.findviewbyid(r.id.delete);     delete.setonclicklistener(this);     return view; }  @override public void onclick(view view) { if (view.getid() == r.id.delete) { mainactivity main = new mainactivity();             main.thisisamethodjusttotryoutmybutton(view, //this problem is...  //i don't know pass in here); } 

mainactivity class

 public class mainactivity extends appcompatactivity implements            adapterview.onitemlongclicklistener, adapterview.onitemclicklistener {     adapter adapter;     listview listview;     @override     protected void oncreate(bundle savedinstancestate) {         super.oncreate(savedinstancestate);         setcontentview(r.layout.activity_main);         listview = (listview) findviewbyid(r.id.listview);         adapter= new adapter();         listview.setadapter(adapter);         listview.setonitemlongclicklistener(this);         listview.setonitemclicklistener(this);  public void longitemclick(view view) {     dialogfragment dialog = new mydialogfordeletingaitem();     dialog.show(this.getsupportfragmentmanager(), "mydialogfordeletingaitem");     thisisamethodjusttotryoutmybutton(view);  }   public void deleterow(int position){         adapter.delete(position);         adapter.notifydatasetchanged();      }      public void thisisamethodjusttotryoutmybutton(view view, int position){ deleterow(position);      toast.maketext(mainactivity.this,"" + position, toast.length_short).show(); }    <button         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:text="delete"         android:id="@+id/delete"          android:clickable="true"         android:layout_aligntop="@+id/edit"         android:layout_alignparentright="true"         android:layout_alignparentend="true"         android:layout_marginright="102dp"         android:layout_marginend="102dp" />   @ se.example.android.myapplication.mainactivity.thisisamethodjusttotryoutmybutton (mainactivity.java:100) @ se.example.android.myapplication.deleteandedit.onclick(deleteandedit.java:45) 

on onclick(view view) method creates new instance of mainactivity while need use loaded activity instance.

call

@override public void onclick(view view) { if (view.getid() == r.id.delete) {       ((mainactivity) getactivity()).thisisamethodjusttotryoutmybutton(view); } 

happy_coding;