An Event Handler is a subroutine that executes code for a given event.
An Event Handler is a subroutine that executes code for a given event.
事件处理器为一个子程序，它可以为指定的事件执行相应代码。
An Event Handler is a subroutine that executes code for a given event.
事件处理器为一个子程序，它可以为指定的事件执行相应代码。