I have an UIPanGestureRecognize which I use to change the frame of a view. Is there a way to simulate the deceleration of the UIScrollView or UITableView when the gesture's state is UIGestureRecognizerStateEnded? Here is my current code:
if (panGesture.state == UIGestureRecognizerStateEnded)
{
[UIView animateWithDuration:0.25 delay:0 options:UIViewAnimationOptionBeginFromCurrentState animations:^{
self.view.frame = CGRectMake(182, 0, self.view.frame.size.width, self.view.frame.size.height);
}
completion:^(BOOL finished) {
if (finished) {
//Do something
}
}];
}
but this is not a smooth scroll. I would like something that decelerates until it stops to the point I've set. Thanks
Session 223 at WWDC 2012, "Enhancing User Experience With Scroll Views", covered a method to use a scrollview's behavior and "feel" to animate the position of a different view (without the scrollview ever actually being visible to the user).
The benefit of the method shown in the session is that your deceleration would always match UIScrollView's, now and forever.
https://developer.apple.com/videos/wwdc/2012/?id=223
You would have to come up with an algorithm of some sort to calculate where you want the view to stop at depending on the velocity of the gesture, which can be obtained like this:
CGPoint velocity = [panGesture velocityInView:panGesture.view];
From there it should just be a matter of animating your view into its calculated resting place and adding an animation to get it there. I believe UIViewAnimationOptionCurveEaseOut would be appropriate here.
Related
I have a simple animation that im performing in my scroll view delegate method scrollViewDidEndDragging.
It looks like this:
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate {
NSLog(#"finger was lifted");
[UIView animateWithDuration:1.0
animations:^{
self.homeLabel.frame = self.view.frame;
}];
}
Using this animation after lifting the finger the my homeLabel is coming from top, and i want to add it a bounce animation to the label, so when it comes from top, instead of landing smoothly it will have a nice bounce...how can i DO THAT? thanksss
You can use the usingSpringWithDamping animation function.
[UIView animateWithDuration:1.0 delay:0 usingSpringWithDamping:0.2 initialSpringVelocity:5.0 options:UIViewAnimationOptionCurveLinear animations:^{
self.homeLabel.frame = self.view.frame;
} completion:^(BOOL finished) {
}];
Adjusting the Spring Damping and Initial Spring Velocity can give you the effect you want.
One good solution is to create a custom layer for your view that overrides the addAnimation:forKey: method to include a custom timing function.
This answer goes into the specifics of how to do that.
Another option is to take a look at key frame animation. This question and answer covers that approach very well.
I want a scroll view to automatically scroll when the user first loads the screen... so I'm using this code:
[UIView animateWithDuration:(float)1.25f
animations:^{
myScrollView.contentOffset = CGPointMake(2000, 800);
}
completion:nil];
So the code works great and the UIScrollView simulates a "scroll" (animation) to the CGPoint I want, but while it's scrolling if the user wants to manually put their finger on it and start scrolling or just stop it, the user can't over-ride this animation until after it's completed.
Anyone have any ideas of a better method to animate it with over-ride capabilities, and when to call said over-ride capabilities (I'm assuming this will involve touchesBegan on scrollView's view)
Simply add UIViewAnimationOptionAllowUserInteraction to your animation options:
[UIView animateWithDuration:1.25f delay:0.0f options:(UIViewAnimationOptionAllowUserInteraction) animations:^{
_scrollView.contentOffset = CGPointMake(0, 800);
}
completion:nil];
And cancel the animation on the UIScrollView scrollViewWillBeginDragging: delegate method
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
{
//Storing current offset
CALayer *currentLayer = _scrollView.layer.presentationLayer;
CGPoint scrollBoundsOrigin = currentLayer.bounds.origin;
//Cancelling animations
[_scrollView.layer removeAllAnimations];
//Restore offset
_scrollView.contentOffset = scrollBoundsOrigin;
}
I have UIScrollView subclass. Its content is reusable - about 4 or 5 views are used to display hundreds of elements (while scrolling hidden objects reused and jumps to another position when its needed to see them)
What i need: ability to automatically scroll my scroll view to any position. For example my scroll view displays 4th, 5th and 6th element and when I tap some button it needs to scroll to 30th element. In other words I need standard behaviour of UIScrollView.
This works fine:
[self setContentOffset:CGPointMake(index*elementWidth, 0) animated:YES];
but I need some customisation. For example, change animation duration, add some code to perform on end of animation.
Obvious decision:
[UIView animateWithDuration:3 delay:0 options:UIViewAnimationOptionBeginFromCurrentState animations:^{
[self setContentOffset:CGPointMake(index*elementWidth, 0)];
} completion:^(BOOL finished) {
//some code
}];
but I have some actions connected to scroll event, and so now all of them are in animation block and it causes all subview's frames to animate too (thanks to few reusable elements all of them animates not how i want)
The question is: How can I make custom animation (in fact I need custom duration, actions on end and BeginFromCurrentState option) for content offset WITHOUT animating all the code, connected to scrollViewDidScroll event?
UPD:
Thanks to Andrew's answer(first part) I solved issue with animation inside scrollViewDidScroll:
- (void)scrollViewDidScroll:(UIScrollView *)scrollView{
[UIView performWithoutAnimation:^{
[self refreshTiles];
}];
}
But scrollViewDidScroll must (for my purposes) executes every frame of animation like it was in case of
[self setContentOffset:CGPointMake(index*elementWidth, 0) animated:YES];
However, now it executes only once at start of animation.
How can I solve this?
Did you try the same approach, but with disabled animation in scrollViewDidScroll ?
On iOS 7, you could try wrapping your code in scrollViewDidScroll in
[UIView performWithoutAnimation:^{
//Your code here
}];
on previous iOS versions, you could try:
[CATransaction begin];
[CATransaction setDisableActions:YES];
//Your code here
[CATransaction commit];
Update:
Unfortunately that's where you hit the tough part of the whole thing. setContentOffset: calls the delegate just once, it's equivalent to setContentOffset:animated:NO, which again calls it just once.
setContentOffset:animated:YES calls the delegate as the animation changes the bounds of the scrollview and you want that, but you don't want the provided animation, so the only way around this that I can come up with is to gradually change the contentOffset of the scrollview, so that the animation system doesn't just jump to the final value, as is the case at the moment.
To do that you can look at keyframe animations, like so for iOS 7:
[UIView animateKeyframesWithDuration:duration delay:delay options:options animations:^{
[UIView addKeyframeWithRelativeStartTime:0.0 relativeDuration:0.5 animations:^{
[self setContentOffset:CGPointMake(floorf(index/2) * elementWidth, 0)];
}];
[UIView addKeyframeWithRelativeStartTime:0.5 relativeDuration:0.5 animations:^{
[self setContentOffset:CGPointMake(index*elementWidth, 0)];
}];
} completion:^(BOOL finished) {
//Completion Block
}];
This will get you two updates and of course you could use some math and a loop to add up a lot more of these with the appropriate timings.
On previous iOS versions, you'll have to drop to CoreAnimation for keyframe animations, but it's basically the same thing with a bit different syntax.
Method 2:
You can try polling the presentationLayer of the scrollview for any changes with a timer that you start at the beginning of the animation, since unfortunately the presentationLayer's properties aren't KVO observable. Or you can use needsDisplayForKey in a subclass of the layer to get notified when the bounds change, but that'll require some work to set up and it does cause redrawing, which might affect performance.
Method 3:
Would be to dissect exactly what happens to the scrollView when animated is YES try and intercept the animation that gets set on the scrollview and change its parameters, but since this would be the most hacky, breakable due to Apple's changes and trickiest method, I won't go into it.
A nice way to do this is with the AnimationEngine library. It's a very small library: six files, with three more if you want damped spring behavior.
Behind the scenes it uses a CADisplayLink to run your animation block once every frame. You get a clean block-based syntax that's easy to use, and a bunch of interpolation and easing functions that save you time.
To animate contentOffset:
startOffset = scrollView.contentOffset;
endOffset = ..
// Constant speed looks good...
const CGFloat kTimelineAnimationSpeed = 300;
CGFloat timelineAnimationDuration = fabs(deltaToDesiredX) / kTimelineAnimationSpeed;
[INTUAnimationEngine animateWithDuration:timelineAnimationDuration
delay:0
easing:INTULinear
animations:^(CGFloat progress) {
self.videoTimelineView.contentOffset =
INTUInterpolateCGPoint(startOffset, endOffset, progress);
}
completion:^(BOOL finished) {
autoscrollEnabled = YES;
}];
Try this:
UIView.animate(withDuration: 0.6, animations: {
self.view.collectionView.contentOffset = newOffset
self.view.layoutIfNeeded()
}, completion: nil)
I want something similar in purpose to Flipboard slight flipping animation on app start. Flipboard when launched has this slight flipping of up and down to show users unfamiliar with the interface that it is flippable.
I have a UIScrollView I want to animate a bit to show the user that it's scrollable. So I want to scroll to the right a little bit and back. UIScrollView has a setContentOffset:animated: message without a completion clause. I find that calling it twice results in seemingly no animation. What if I want an animation after animation in succession?
EDIT:
Thanks Levi for the answer.
And for the record, there is UIViewAnimationOptionAutoreverse and UIViewAnimationOptionRepeat that I can use. So this is what I ended up with that works.
CGPoint offset = self.scrollView.contentOffset;
CGPoint newOffset = CGPointMake(offset.x+100, offset.y);
[UIView animateWithDuration:0.5 delay:0 options:UIViewAnimationOptionCurveEaseIn | UIViewAnimationOptionAutoreverse |UIViewAnimationOptionRepeat animations:^{
[UIView setAnimationRepeatCount: 2];
[self.scrollView setContentOffset:newOffset animated: NO];
} completion:^(BOOL finished) {
[self.scrollView setContentOffset:offset animated:NO];
}];
For a scrollView, tableView or collectionView if you do something like this:
[self.collectionView setContentOffset:CGPointMake(self.collectionView.contentOffset.x+260.0,
self.collectionView.contentOffset.y)
animated:YES];
then you'll get back a:
-(void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView
when the scroll finishes.
You do NOT get this callback if the user moves the view.
Two options:
1) Use the -(void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView delegate callback
2) Try to put it into an animation block (with ... animated:NO];), which has the completion part.
During a sliding animation(down, pause, then up back to the original position) of a subview, the device is rotated, so the superview is rotated. I want to keep the subview's width the same as the superview, so I need to resize it during its sliding animation.
Here is the sliding animation code:
[UIView animateWithDuration:0.3 animations:^{
self.frame = finalFrame;
} completion:^(BOOL finished) {
[UIView animateWithDuration:0.3 delay:3 options:0 animations:^{
self.frame = initFrame;
} completion:^(BOOL finished) {
[self removeFromSuperview];
}];
}];
This is the method that is called when I detect rotation:
- (void)rotate:(NSNotification *)notif {
// What to do here to adjust the width but also keep the sliding animation going.
}
It seems there is no auto-resizing magic that can be used here. One must:
Record the progress of the animations.
On detection of rotations, cancel the old animations, adjust the view size, and add new animations starting from the current progress.
Here is a sample project for reference: http://d.pr/f/M4UW.
You can animate the bounds of the layer to change the width. Just make the height the same and apply an animation for the bounds.
If you want both animations to have the same duration, timing function etc. then you could add them both to an animation group and add that group to the layer you are animating.