滚动到顶部时显示导航栏。 IOS

Question

目前我有一个UICollection，当您向下滚动40px时，我会隐藏UINavigation顶栏。当您向上滚动到顶部时，UINavigation顶栏会再次出现。

但是我希望能够在用户滚动40px时显示/隐藏UINavigation顶栏，而不仅仅是当您从顶部滚动时。

例如，当您从顶部开始滚动时，栏会隐藏，您可以滚动到UICollectionView的中间位置，然后当您通过滚动回到顶部时，UINavigation顶栏会再次显示。

有什么想法吗？

#pragma mark - UIScrollViewDelegate Methods
-(void)scrollViewDidScrollToTop:(UIScrollView *)scrollView
{
if([[[UIDevice currentDevice] systemVersion] floatValue] < 7.0f){
    return;
}

CGRect frame = self.navigationController.navigationBar.frame;
frame.origin.y = 20;
}

-(void)scrollViewDidScroll:(UIScrollView *)scrollView
{
if([[[UIDevice currentDevice] systemVersion] floatValue] < 7.0f){
    return;
}

CGFloat offsetY = scrollView.contentOffset.y;
CGFloat contentHeight = scrollView.contentSize.height - 300;
if (offsetY > contentHeight - scrollView.frame.size.height)
{
    [self.homePaginator fetchNextPage];
}

CGRect frame = self.navigationController.navigationBar.frame;
CGFloat size = frame.size.height - 25;

if([scrollView.panGestureRecognizer translationInView:self.view].y < 0)
{
    frame.origin.y = -size;

    if(self.navigationController.navigationBar.items.count > 0){

        [UIView animateWithDuration:0.25 delay:0 options:UIViewAnimationOptionCurveEaseInOut | UIViewAnimationOptionAllowUserInteraction
                         animations:^{

                             CGFloat navBarHeight = 25.0f;
                             CGRect frame = CGRectMake(0.0f, 0.0f, 320.0f, navBarHeight);
                             [self.navigationController.navigationBar setFrame:frame];
                         }
                         completion:^(BOOL finished) {

                             self.navigationItem.titleView.alpha = 0;
                             self.piccingTitleIcon.alpha = 0;
                             self.navigationItem.rightBarButtonItem = nil;

                         }];
    }
}
else if([scrollView.panGestureRecognizer translationInView:self.view].y > 0)
{

    [UIView animateWithDuration:0.5 delay:0 options:UIViewAnimationOptionCurveEaseInOut | UIViewAnimationOptionAllowUserInteraction
                     animations:^{
                         CGFloat navBarHeight = 64.0f;
                         CGRect frame = CGRectMake(0.0f, 0.0f, 320.0f, navBarHeight);
                         [self.navigationController.navigationBar setFrame:frame];
                         self.navigationItem.titleView.alpha = 1;
                         self.piccingTitleIcon.alpha = 1;
                         self.btnSearch = [[UIBarButtonItem alloc] initWithCustomView:self.searchIconButton];
                         [self.navigationItem setRightBarButtonItem:self.btnSearch];
                     }
                     completion:^(BOOL finished) {

                         [self performSelector:@selector(addIconsToNavBar) withObject:nil afterDelay:-1.0];
                     }];
}
}

Answer 1

试试这个！

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
    CGPoint scrollOffset = scrollView.contentOffset;
    if (scrollOffset.y >= 40) {
        if (![self.navigationController isNavigationBarHidden]) {
            [self.navigationController setNavigationBarHidden:YES animated:YES];
        }
    } else {
        if ([self.navigationController isNavigationBarHidden]) {
            [self.navigationController setNavigationBarHidden:NO animated:YES];
        }
    }
}

Answer 2

在用户滚动之前获取起始内容偏移量。

– scrollViewWillBeginDragging:(UIScrollView *)scrollView {
  currentOffset = scrollView.contentOffset.y;
}

-(void)scrollViewDidScroll:(UIScrollView *)scrollView
{

CGFloat scrollPos = scrollView.contentOffset.y - currentOffset;

if(scrollPos >= 40 || scrollPos <= -40 /* or whatever the height of your toolbar is */){
    //Fully hide your toolbar
   [UIView animateWithDuration:2.25 animations:^{
    [self.navigationController setNavigationBarHidden:YES animated:YES];

}];
} else {
   //Slide it up incrementally, etc.
 [self.navigationController setNavigationBarHidden:NO animated:YES];
}
}

Answer 3

任何想要了解简单方法的人都可以使用以下代码。

有一些库可以很容易地做到这一点，但我发现我必须用他们的自定义类UINavgationController重写应用程序的导航如果你有一个现有的项目，你可以更容易地做到这一点...... / p>

#pragma mark - UIScrollViewDelegate Methods
-(void)scrollViewDidScrollToTop:(UIScrollView *)scrollView
{
if([[[UIDevice currentDevice] systemVersion] floatValue] < 7.0f){
    return;
}

CGRect frame = self.navigationController.navigationBar.frame;
frame.origin.y = 20;
}

-(void)scrollViewDidScroll:(UIScrollView *)scrollView
{
if([[[UIDevice currentDevice] systemVersion] floatValue] < 7.0f){
    return;
}

CGFloat offsetY = scrollView.contentOffset.y;
CGFloat contentHeight = scrollView.contentSize.height - 300;
if (offsetY > contentHeight - scrollView.frame.size.height)
{
    [self.homePaginator fetchNextPage];
}

CGRect frame = self.navigationController.navigationBar.frame;
CGFloat size = frame.size.height - 25;

if([scrollView.panGestureRecognizer translationInView:self.view].y < 0)
{
    frame.origin.y = -size;

    if(self.navigationController.navigationBar.items.count > 0){

        [UIView animateWithDuration:0.25 delay:0 options:UIViewAnimationOptionCurveEaseInOut | UIViewAnimationOptionAllowUserInteraction
                         animations:^{

                             CGFloat navBarHeight = 25.0f;
                             CGRect frame = CGRectMake(0.0f, 0.0f, 320.0f, navBarHeight);
                             [self.navigationController.navigationBar setFrame:frame];
                         }
                         completion:^(BOOL finished) {

                             self.navigationItem.titleView.alpha = 0;
                             self.piccingTitleIcon.alpha = 0;
                             self.navigationItem.rightBarButtonItem = nil;

                         }];
    }
}
else if([scrollView.panGestureRecognizer translationInView:self.view].y > 0)
{

    [UIView animateWithDuration:0.5 delay:0 options:UIViewAnimationOptionCurveEaseInOut | UIViewAnimationOptionAllowUserInteraction
                     animations:^{
                         CGFloat navBarHeight = 64.0f;
                         CGRect frame = CGRectMake(0.0f, 0.0f, 320.0f, navBarHeight);
                         [self.navigationController.navigationBar setFrame:frame];
                         self.navigationItem.titleView.alpha = 1;
                         self.piccingTitleIcon.alpha = 1;
                         self.btnSearch = [[UIBarButtonItem alloc] initWithCustomView:self.searchIconButton];
                         [self.navigationItem setRightBarButtonItem:self.btnSearch];
                     }
                     completion:^(BOOL finished) {

                         [self performSelector:@selector(addIconsToNavBar) withObject:nil afterDelay:-1.0];
                     }];
}
}