然后选择背景视图的Touch Down事件，连接 backgroundTap：即可。这样只要轻击一下虚拟键盘之外的区域，就能关闭虚拟键盘。这些方法都是使用resignFirstResponder方法来关闭虚拟键盘，还有其他的方法。
第五种方法，使用endEditing：方法 在所在的视图控制器类中，覆盖这个方法。
(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
[[self view] endEditing:YES];
}
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
[[self view] endEditing:YES];
}
This method looks at the current view and its subview hierarchy for the text field that is currently the first responder. If it finds one, it asks that text field to resign as first responder. If the force parameter is set to YES, the text field is never even asked; it is forced to resign.
但是，如果这个屏幕很复杂，虚拟键盘之外的区域中有很多按钮。轻击这些区域时可能会轻击到这些按钮，这样虚拟键盘就不能关闭。
要是找到一个没有按钮的空白区域都不容易且还有隐藏的视图对象时，通过轻击虚拟键盘之外的区域关闭虚拟键盘的方法实现起来就难了。
第六种方法，覆盖hitTest:withEvent:方法关闭虚拟键盘
在stackoverflow.com上，有人这样总结。说使用hitTest:withEvent:方法是最好的，也是最容易的解决方法。
I think the easiest (and best) way to do this is to subclass your global view and use hitTest:withEvent method to listen to any touch. Touches on keyboard aren't registered, so hitTest:withEvent is only called when you touch/scroll/swipe/pinch... somewhere else, then call [self endEditing:YES]. This is better than using touchesBegan because touchesBegan are not called if you click on a button on top of the view. It is better than UITapGestureRecognizer which can't recognize a scrolling gesture for example. It is also better than using a dim screen because in a complexe and dynamic user interface, you can't put dim screen every where. Moreover, it doesn't block other actions, you don't need to tap twice to select a button outside (like in the case of a UIPopover). Also, it's better than calling [textField resignFirstResponder], because you may have many text fields on screen, so this works for all of them.
