iOS prevent rotations until after animation completes - ios

I'm creating an iOS app and in one method I have a for loop that does a series of animations that last around 2 seconds.
My problem is that if the user rotates the device while the animations are still in progress, it messes up the formatting for the new orientation (everything works just the way it should if the rotation happens after the animation is complete).
So I was wondering if there is a way to delay rotations

You could have a BOOL instance variable that you update based on whether your animation is complete or not. Then override the shouldAutorotate method and return that BOOL. Might look something like this:
#implementation YourViewController {
BOOL _shouldAutoRotate;
}
-(BOOL)shouldAutorotate {
[super shouldAutorotate];
return _shouldAutoRotate;
}
-(void)yourAnimationMethod {
_shouldAutoRotate = NO;
[UIView animateWithDuration:2.0f animations:^{
//your animations
} completion:^(BOOL finished) {
if(finished) {
_shouldAutoRotate = YES;
}
}];
}

Related

Why are completion handlers of [UIView animate] called in a wrong order?

In my project there's a ViewController which contains a few subviews(e.g. buttons).
It shows/hides those buttons, always with animation.
It has an interface like this:
#interface MyViewController: UIViewController
- (void)setMyButtonsVisible:(BOOL)visible;
#end
And an implementation looks like this:
- (void)setMyButtonsVisible:(BOOL)visible
{
if( visible )
{
// "show"
_btn1.hidden = NO;
_btn2.hidden = NO;
[UIView animateWithDuration:0.2 animations:^{
_btn1.alpha = 1.0;
_btn2.alpha = 1.0;
}];
}
else
{
// "hide"
[UIView animateWithDuration:0.2 animations:^{
_btn1.alpha = 0.0;
_btn2.alpha = 0.0;
} completion:^(BOOL finished) {
_btn1.hidden = YES;
_btn2.hidden = YES;
}];
}
}
When [_myVC setMyButtonsVisible:NO] is called, and then after some time ( > 0.2s) [_myVC setMyButtonsVisible:YES] is called, everything is OK.
However, it setMyButtonsVisible:YES is called immediately after ( < 0.2s) setMyButtonsVisible:NO, the animations overlap and setMyButtonsVisible:NO callback is called the last.
I've tried to change "hide" duration to 0.1, it doesn't help - after "hide(0.1)"+"show(0.2)" calls, "hide" callback is called after the "show" callback and my buttons are not visible.
I've added a quick-fix by caching the visible param and checking in "hide" completion handler if the state should be !visible.
My questions are:
Why the first animation completion handler is called the last if animations overlap?
What are better approahes to discard a previous "overlapping" animation?
Check the finished flag on completion:
if (finished) {
_btn1.hidden = YES;
_btn2.hidden = YES;
}

How to know if view is being animated?

Is there a way to know if my custom implementation of setFrame: (or an other setter of an animatable property) is being called from an animation block i.e. it will be animated or just set directly?
Example:
- (void)setFrame:(CGRect)newFrame {
[super setFrame:newFrame];
BOOL willBeAnimated = ?????
if (willBeAnimated) {
// do something
} else {
// do something else
}
}
In the above setter willBeAnimated should be YES it is called like this:
- (void)someMethod {
[UIView animateWithDuration:0.2
animations:^{view.frame = someRect;}
completion:nil];
}
and NO in this case:
- (void)someMethod {
view.frame = someRect;
}
someMethod here is a private method inside UIKit that I can't access or change, so I have to somehow determine this from the "outside".
You should be able to check the animationKeys of the layer of your UIView subclass right after changing the frame to see if it is being animated.
- (void)setFrame:(CGRect)newFrame {
[super setFrame:newFrame];
BOOL willBeAnimated = [super.layer animationForKey:#"position"] ? YES : NO;
if (willBeAnimated) {
// do something
} else {
// do something else
}
}
You can also to check if there are any animations by using animationsKeys which in this case would just return position.
In addition, if you want to force a change to not be animated you can use performWithoutAnimation:
[UIView performWithoutAnimation:^{
[super setFrame:newFrame];
}];
EDIT
Another tidbit I found by testing is that you can actually stop the animation if it is already in progress and instead making the change instantly by removing the animation from the layer and then using the above method instead.
- (void)setFrame:(CGRect)newFrame {
[super setFrame:newFrame];
BOOL willBeAnimated = [super.layer animationForKey:#"position"] ? YES : NO;
BOOL shouldBeAnimated = // decide if you want to cancel the animation
if (willBeAnimated && !shouldBeAnimated) {
[super removeAnimationForKey:#"position"];
[UIView performWithoutAnimation:^{
[super setFrame:newFrame];
}];
} else {
// do something else
}
}

Coordinating two UIView animations on UIButton down/up

I'm trying to build an animation around a UIButton. The UIButton has a UIImageView that contains an image that I'd like to shrink when the UIButton is held down and then when the UIButton is let go, I'd like to play a separate animation that does a bounce.
The issue I'm experiencing right now is that the 2nd part of the animation doesn't seem to play if I press down and then up very quickly. If I press and hold (wait for the first animation to finish), then let go, it seems to work fine.
Here's the relevant code:
-(void)pressedDown
{
[UIView animateWithDuration:0.2 delay:0 options:UIViewAnimationOptionCurveEaseOut animations:^{
self.heartPart.layer.transform = CATransform3DMakeScale(0.8, 0.8, 1);
} completion:nil];
}
-(void)pressedUp
{
[UIView animateWithDuration:0.8
delay:0.0
usingSpringWithDamping:20
initialSpringVelocity:200
options:UIViewAnimationOptionBeginFromCurrentState
animations:^{
self.heartPart.layer.transform = CATransform3DIdentity;
}
completion:nil];
}];
}
In my ViewDidLoad I add the following:
[self.heartButton addTarget:self
action:#selector(pressedUp)
forControlEvents:UIControlEventTouchUpInside];
[self.heartButton addTarget:self
action:#selector(PressedDown)
forControlEvents:UIControlEventTouchDown];
Any idea how I can get the two animations to sequence and not interrupt each other even on a quick press?
Here's a potential plan of action. Keep two global variables, BOOL buttonPressed and NSDate *buttonPressDate. When the button is pressed, you should set buttonPressed to true and set buttonPressDate to the current date. Now in the touch up method, you would set buttonPressed to false and check whether the time interval between buttonPressDate and the current date is greater than the duration of the animation. If it is, then run the touch up animation; if not, return. In the completion block of the touch down method, you would check if the button was still pressed. If it is, then do nothing; if it's not pressed anymore, then run the touch up animation.
The effect you'll get using this approach should be the following: if you tap the button quickly, it will run the full 0.2-second shrink animation and then run the enlarge animation in sequence.
Now, if you don't want the touch down animation to run in the case of a quick touch, you should probably delay the first animation and check if the button is still pressed when you start it. If it was a quick touch, you would run a modified animation that covered both the touch down and touch up phases.
You could try out the following :-
//Set only one target with TouchUpInside.
[self.heartButton addTarget:self
action:#selector(pressedUp)
forControlEvents:UIControlEventTouchUpInside];
-(void)pressedDown
{
[UIView animateWithDuration:0.2 delay:0 options:UIViewAnimationOptionCurveEaseOut animations:^{
self.heartPart.layer.transform = CATransform3DMakeScale(0.8, 0.8, 1);
}
completion:
[self pressedUp];
//Or
[self performSelector:#selector(pressedUp) withObject:self afterDelay:0.5];
];
}
-(void)pressedUp
{
[UIView animateWithDuration:0.8
delay:0.0
usingSpringWithDamping:20
initialSpringVelocity:200
options:UIViewAnimationOptionBeginFromCurrentState
animations:^{
self.heartPart.layer.transform = CATransform3DIdentity;
}
completion:nil];
}];
}
This way as first animation is completed then next animation will start But my concern is that it won't look appropriate and it would be a bit long animation to show to a user. Rest it's upto your app design and what all it is going to achieve with it.
I assume you are familiar with the concept of operations. If not then NSOperations allow you to keep your code modular and enable you to set the order of execution.
You could create a custom subclass of NSOperation and run animation within its execution block, then add operations with animations on queue each time user interacts with the button.
Apart from documentation from Apple, there is a great example of how to subclass NSOperation available on Github:
https://github.com/robertmryan/AFHTTPSessionOperation/blob/master/Source/AsynchronousOperation.m
Based on that "blueprint" for your custom operations, it's very trivial to achieve what you want, i.e.:
#interface PressDownAnimationOperation : AsynchronousOperation
- (instancetype)initWithView:(UIView *)view;
#end
#implementation PressDownAnimationOperation {
UIView *_view;
}
- (instancetype)initWithView:(UIView *)view {
self = [super init];
if(self) {
_view = view;
}
return self;
}
- (void)main {
// dispatch UIKit related stuff on main thread
dispatch_async(dispatch_get_main_queue(), ^{
// animate
[UIView animateWithDuration:0.2 delay:0 options:UIViewAnimationOptionCurveEaseOut animations:^{
_view.layer.transform = CATransform3DMakeScale(0.8, 0.8, 1);
} completion:^(BOOL finished){
// mark operation as finished
[self completeOperation];
}];
});
}
#end
Now in order to run animations you need to create NSOperationQueue. You can keep it within your view controller, i.e.:
#implementation ViewController {
NSOperationQueue *_animationQueue;
}
- (void)viewDidLoad {
[super viewDidLoad];
_animationQueue = [[NSOperationQueue alloc] init];
// limit queue to run single operation at a time
_animationQueue.maxOperationCount = 1;
}
#end
Now when you want to chain animations, you simply create new operation, add it to queue and that's it, i.e.:
- (void)pressedDown {
NSOperation *animationOperation = [[PressDownAnimationOperation alloc] init];
[_animationQueue addOperation:animationOperation];
}
If user taps too fast and you notice that your operation queue is clogged with animations, you can simply cancel all animations before adding new one, i.e.:
[_animationQueue cancelAllOperations];

Custom iOS 7 Interactive Pop Animation goes blank after animating

I am recreating the UINavigationController Push animation using the new iOS 7 custom transitioning APIs.
I got the view pushing and popping fine using animationControllerForOperation
I added a edge gesture recogniser for the interactive pop gesture.
I used a UIPercentDrivenInteractiveTransition subclass and integrated code from WWDC 2013 218 - Custom Transitions Using View Controllers
It looks like it removes the fromViewController by mistake, but I don't know why.
The steps are:
Interactive pop starts
Finger is lifted after a short distance - red screenshot
The view animates back a short distance.
Red view is removed (I think) - black screenshot.
The full code is on GitHub, but here are 2 parts which I guess are important.
Gesture delegate
- (void)didSwipeBack:(UIScreenEdgePanGestureRecognizer *)edgePanGestureRecognizer {
if (state == UIGestureRecognizerStateBegan) {
self.isInteractive = YES;
[self.parentNavigationController popViewControllerAnimated:YES];
}
if (!self.isInteractive) return;
switch (state)
{
case UIGestureRecognizerStateChanged: {
// Calculate percentage ...
[self updateInteractiveTransition:percentagePanned];
break;
}
case UIGestureRecognizerStateCancelled:
case UIGestureRecognizerStateEnded: {
if (state != UIGestureRecognizerStateCancelled &&
isPannedMoreThanHalfWay) {
[self finishInteractiveTransition];
} else {
[self cancelInteractiveTransition];
}
self.isInteractive = NO;
break;
}
}
}
UIViewControllerAnimatedTransitioning protocol
- (void)animateTransition:(id <UIViewControllerContextTransitioning>)transitionContext
{
// Grab views ...
[[transitionContext containerView] addSubview:toViewController.view];
// Calculate initial and final frames
toViewController.view.frame = initalToViewControllerFrame;
fromViewController.view.frame = initialFromViewControllerFrame;
[UIView animateWithDuration:RSTransitionVendorAnimationDuration delay:0.0 options:UIViewAnimationOptionCurveLinear animations:^{
toViewController.view.frame = finalToViewControllerFrame;
fromViewController.view.frame = finalFromViewControllerFrame;
} completion:^(BOOL finished) {
[transitionContext completeTransition:YES];
}];
}
Anyone know why the screen is blank? Or Can anyone point me to some sample code. Apple don't appear have any sample code for interactive transitions using the percent driven interactions.
The first issue was a bug in the Apple sample code that I copied. The completeTransition method should have a more intelligent BOOL parameter like this:
[UIView animateWithDuration:RSTransitionVendorAnimationDuration delay:0.0 options:UIViewAnimationOptionCurveLinear animations:^{
toViewController.view.frame = finalToViewControllerFrame;
fromViewController.view.frame = finalFromViewControllerFrame;
} completion:^(BOOL finished) {
[transitionContext completeTransition:![transitionContext transitionWasCancelled]];
}];
Thanks to #rounak for pointing me to the objc.io post.
This then presented another issue relating to the animation. The animation would stop, present a blank view and them carry on. This was almost defiantly a UIKit bug. The fix was to set the completionSpeed to 0.99 instead of 1.0. The default value is 1.0 so I guess that setting it to this doesn't do some side effect in their custom setter.
// self is a UIPercentDrivenInteractiveTransition
self.completionSpeed = 0.99;
I don't think you need a UIPercentDrivenInteractiveTransition subclass. I just create a new UIPercentDrivenInteractiveTransition object, hold a strong reference to it and return it in interactionControllerForAnimationController method.
This link for interactive transitions is quite helpful.

iOS Add loading text with animating period character

Not sure how to describe this, but what would be the easiest way to have a UILabel display Loading, then Loading., then Loading.., then Loading..., and then repeat?
I have been looking into timers but it all seems a bit excessive. Anyone know of a cool and quick trick to pull something like that off? Thanks!
Not sure about your specific use case (more info please or code?) but have you tried animation blocks? Something like:
- (void)animate
{
__block UIView * blockSelf = self;
[UIView animateWithDuration:0.1f animations:^{
if ([blockSelf.label.text isEqualToString:#"Loading..."]) {
blockSelf.label.text = #"Loading";
} else {
blockSelf.label.text = [NSString stringWithFormat:#"%#.", blockSelf.label.text];
}
} completion:^(BOOL finished) {
if (blockSelf.processIsFinished) {
[self moveOn];
} else {
[blockSelf animate];
}
}];
}
Alternatively, something like MBProgressHUD might be useful depending on what type of process is "loading".

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