#pragma mark 判断页面是否是向下滑动的
-(void)scrollViewWillBeginDragging:(UIScrollView *)scrollView {
CGPoint translation = [scrollView.panGestureRecognizer translationInView:scrollView.superview];
if (translation.y>0) {
[[NSNotificationCenterdefaultCenter]postNotificationName:@"downKeyWord"object:nil];
}
}