问题
I'm quite new to iOS development. Right now i'm trying to hide my tabbar when I scroll down and when scrolling up the tabbar should appear. I would like to have this animated in the same way like the navigation bar. For the navigation bar I simply clicked the option in the Attributes Inspector. I saw some examples for the toolbar, but I cant adopt it the tabbar.
self.tabBarController?.tabBar.hidden = true just hides my tabbar, but its not animated like the navigation controller.
回答1:
This is code that i'm actually using in a production app.
It's in Swift and it also updates UITabBar.hidden var.
func scrollViewWillBeginDragging(scrollView: UIScrollView) {
if scrollView.panGestureRecognizer.translation(in: scrollView).y < 0{
changeTabBar(hidden: true, animated: true)
}
else{
changeTabBar(hidden: false, animated: true)
}
}
You can also use the other callback method:
func scrollViewDidScroll(scrollView: UIScrollView) {
...
}
but if you choose so, then you must handle multiple calls to the helper method that actually hides the tabBar.
And then you need to add this method that animates the hide/show of the tabBar.
func changeTabBar(hidden:Bool, animated: Bool){
var tabBar = self.tabBarController?.tabBar
if tabBar!.hidden == hidden{ return }
let frame = tabBar?.frame
let offset = (hidden ? (frame?.size.height)! : -(frame?.size.height)!)
let duration:NSTimeInterval = (animated ? 0.5 : 0.0)
tabBar?.hidden = false
if frame != nil
{
UIView.animateWithDuration(duration,
animations: {tabBar!.frame = CGRectOffset(frame!, 0, offset)},
completion: {
println($0)
if $0 {tabBar?.hidden = hidden}
})
}
}
Update Swift 4
func changeTabBar(hidden:Bool, animated: Bool){
guard let tabBar = self.tabBarController?.tabBar else { return; }
if tabBar.isHidden == hidden{ return }
let frame = tabBar.frame
let offset = hidden ? frame.size.height : -frame.size.height
let duration:TimeInterval = (animated ? 0.5 : 0.0)
tabBar.isHidden = false
UIView.animate(withDuration: duration, animations: {
tabBar.frame = frame.offsetBy(dx: 0, dy: offset)
}, completion: { (true) in
tabBar.isHidden = hidden
})
}
回答2:
Building on Ariel's answer, I have updated the code for Swift3. This worked great on my collection views.
override func scrollViewDidEndDragging(_ scrollView: UIScrollView, willDecelerate decelerate: Bool) {
if scrollView.panGestureRecognizer.translation(in: scrollView).y < 0 {
changeTabBar(hidden: true, animated: true)
}else{
changeTabBar(hidden: false, animated: true)
}
}
func changeTabBar(hidden:Bool, animated: Bool){
let tabBar = self.tabBarController?.tabBar
if tabBar!.isHidden == hidden{ return }
let frame = tabBar?.frame
let offset = (hidden ? (frame?.size.height)! : -(frame?.size.height)!)
let duration:TimeInterval = (animated ? 0.5 : 0.0)
tabBar?.isHidden = false
if frame != nil
{
UIView.animate(withDuration: duration,
animations: {tabBar!.frame = frame!.offsetBy(dx: 0, dy: offset)},
completion: {
print($0)
if $0 {tabBar?.isHidden = hidden}
})
}
}
回答3:
This answer is a slight modification to Ariel answer which adds animation while user scrolls.
extension ViewController:UIScrollViewDelegate{
func scrollViewDidScroll(_ scrollView: UIScrollView) {
if scrollView.panGestureRecognizer.translation(in: scrollView).y < 0{
//scrolling down
changeTabBar(hidden: true, animated: true)
}
else{
//scrolling up
changeTabBar(hidden: false, animated: true)
}
}
func changeTabBar(hidden:Bool, animated: Bool){
let tabBar = self.tabBarController?.tabBar
let offset = (hidden ? UIScreen.main.bounds.size.height : UIScreen.main.bounds.size.height - (tabBar?.frame.size.height)! )
if offset == tabBar?.frame.origin.y {return}
print("changing origin y position")
let duration:TimeInterval = (animated ? 0.5 : 0.0)
UIView.animate(withDuration: duration,
animations: {tabBar!.frame.origin.y = offset},
completion:nil)
}
}
回答4:
You can control UITabBar precisly by setting up your class as delegate for scrollView and implementing scrolling in scrollViewDidScroll: method.
Here is an example how I do it my application. You can probably easily modify that for your needs. Some helper function to get UITabBar included.
#define LIMIT(__VALUE__, __MIN__, __MAX__) MAX(__MIN__, MIN(__MAX__, __VALUE__))
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
CGFloat scrollOffset = scrollView.contentOffset.y;
CGFloat scrollDiff = scrollOffset - self.previousScrollViewYOffset;
CGFloat scrollHeight = scrollView.frame.size.height;
CGFloat scrollContentSizeHeight = scrollView.contentSize.height + scrollView.contentInset.bottom;
CGFloat scrollOffsetGlobal = scrollOffset + scrollView.contentInset.top;
[self updateUITabBarY:[self UITabBarView].frame.origin.y + scrollDiff];
self.previousScrollViewYOffset = scrollOffset;
}
- (UITabBar*) UITabBarView
{
for(UIView *view in self.tabBarController.view.subviews)
{
if([view isKindOfClass:[UITabBar class]])
{
return (UITabBar*) view;
}
}
return nil;
}
- (void) updateUITabBarY:(CGFloat) y
{
UITabBar* tabBar = [self UITabBarView];
if(tabBar)
{
CGRect frame = tabBar.frame;
frame.origin.y = LIMIT(y, [self UITabBarMiny], [self UITabBarMaxY]);
tabBar.frame = frame;
}
}
- (CGFloat) UITabBarMiny
{
return [UIScreen mainScreen].bounds.size.height - [self UITabBarView].frame.size.height - [[UIApplication sharedApplication] statusBarFrame].size.height + 20.0f;
}
- (CGFloat) UITabBarMaxY
{
return [UIScreen mainScreen].bounds.size.height;
}
回答5:
According to @Ariel Hernández Amador answer for black screen after hiding Tabbar just use this line of code in your ViewDidLoad(). Working Superbly...I have posted this here as I am unable to comment over there.
viewDidLoad()
{
if #available(iOS 11.0, *) {
self.myScroll.contentInsetAdjustmentBehavior = .never
}
}
Here myScroll is the Scrollview I am using in my VC. Just replace it with your VC.
来源：https://stackoverflow.com/questions/31928394/ios-swift-hide-show-uitabbarcontroller-when-scrolling-down-up