UIView绑定了广播监听，绑定的位置和移除绑定的位置应该放在什么地方。
- (void)willMoveToWindow:(UIWindow *)newWindow{
[super willMoveToWindow:newWindow];
if (self.window != nil) {
[[NSNotificationCenter defaultCenter]removeObserver:self];
}
}
- (void)didMoveToWindow {
if (self.window != nil) {
//添加键盘显示与消失通知
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyBoWillAppear:) name:UIKeyboardWillShowNotification object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyBoWillDismiss:) name:UIKeyboardWillHideNotification object:nil];
}
}
