What is the best practice for coding addChangeHandler in Gwt?

in UiBinder

@UiField ListBox testListBox;  

in presenter, I have a method getData() that put data into the testListBox.

public void getData(){          getView().getTestListBox().clear();          getView().getTestListBox().addItem("itm 1");          getView().getTestListBox().addItem("itm 2");          getView().getTestListBox().addItem("itm 3");          getView().getTestListBox().addChangeHandler(new ChangeHandler(){                @Override              public void onChange(ChangeEvent event) {                  // TODO Auto-generated method stub                  int ind=getView().getTestListBox().getSelectedIndex();                  System.out.println(getView().getTestListBox().getValue(ind));              }            });  }  

Now, i also have a button to call getData(). If i click that button 1 time, then I select "itm 1" in thetestListBox everything is fine as it will print out:

itm 1  

However, if I click that button 2nd times, & select "itm 1" then it prints out twice "itm 1":

itm 1  itm 1  

If i click it 3rd time, it will print out triple "itm 1"....

But if i put the getView().getTestListBox().addChangeHandler outside getData() method before i add the item into the listbox (ie I do the addChangeHandler before there is actual item inside the listbox), then everything is fine as it print out only 1 time.

So What is the best practice for coding addChangeHandler in Gwt?

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