当scrollView向下滚动时，按钮会向下移动消失，等scrollview向上滚动时，按钮则又会出现。
Simulator Screen Shot - iPhone X - 2018-08-09 at 09.45.03.png
//实现scrollView代理
- (void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset{
//竖直滑动时 判断是上滑还是下滑
// NSLog(@"----------%g", velocity.y);
if(velocity.y > 0){
//上滑
// NSLog(@"上滑");
[UIView animateWithDuration:0.25 animations:^{
CGRect frame = self.topicBtn.frame;
frame.origin.y = XJ_ScreenHeight;
self.topicBtn.frame = frame;
}];
}else if (velocity.y < -1){
//下滑
// NSLog(@"下滑");
[UIView animateWithDuration:0.25 animations:^{
CGRect frame = self.topicBtn.frame;
frame.origin.y = XJ_ScreenHeight - XJ_TabbarHeight - 35 - frame.size.height;
self.topicBtn.frame = frame;
}];
}
//
// //水平滑动时 判断是右滑还是左滑
// if(velocity.x>0){
// //右滑
// NSLog(@"右滑");
// }else{
// //左滑
// NSLog(@"左滑");
// }
}
//点击屏幕顶部触发的方法
- (void)scrollViewDidScrollToTop:(UIScrollView *)scrollView {
[UIView animateWithDuration:0.25 animations:^{
CGRect frame = self.topicBtn.frame;
frame.origin.y = XJ_ScreenHeight - XJ_TabbarHeight - 35 - frame.size.height;
self.topicBtn.frame = frame;
}];
}
