When I clicked on the textfield,I want to open a panel. I think that I should use a delegate method to respond the clicked event. I found that the method - (void)textDidBeginEditingNSNotification *)aNotification not work , and then the method - (void)controlTextDidBeginEditingNSNotification *)aNotification worked ,but I found this method worked when I edited the textfield not to cliked it ,why? and that when I edited the textfield again ,This method not to work ,why?