I have a UIViewController that, depending on the frequency set by user, displays images in a animateWithDuration fade-in/fade-out every X seconds (say, 5 or 10). To manage the regularly timed calls to fade-in/out the images, I have a NSTimer that is set every time viewWillAppear is called.
Some function that does the animation, let's call it "showImageNow":
// on...
[UIView animateWithDuration:someInterval
delay:0
options:UIViewAnimationCurveEaseInOut
animations:
^{
// UI alpha = ... code here
}
// off...
completion:^(BOOL finished){
[UIView animateWithDuration:someOtherInterval
delay:yetAnotherValue
options:UIViewAnimationCurveEaseInOut
animations:
^{
// UI alpha = ... code here
}
completion:nil
];
}
];
In viewWillAppear:
if(myTimer != nil)
{
[myTimer invalidate]; // in case user changed the frequency in settings view
}
myTimer = [NSTimer scheduledTimerWithTimeInterval: [[NSUserDefaults standardUserDefaults] doubleForKey:#"userFrequency"]
target:self
selector: #selector(showImageNow:)
userInfo: nil
repeats: YES];
In viewDidAppear:
if(myTimer) { [myTimer fire]; }
While everything works as expected most of the time, the fade-out part of the first animation is cut off/stutters every time the UIViewController is re-appeared (from say, app went to background or app was in another view). The fade-in part of the animation works always, oddly enough. This is observed on a real device, not the simulator. So the fade-in/out works for every animation except the first one (the fade-out part doesn't work).
Notes:
Yes, I've tried [myTimer fire] in the viewWillAppear (instead of viewDidAppear) as well, but this causes other issues like the UIViewController's elements show up rather abruptly when user switches to that view from other views or from background mode.
The frequency is much longer than the animateWithDuration's animation values, so there shouldn't be any frame overlaps or whatever UI overlaps there may be.
I put debug code before every animateWithDuration call in the UIVIewController, so I know for certain that no other animateWithDuration is interrupting the very first image animateWithDuration call.
So this is perplexing. I've tried using CADisplayLink but apparently that's not the right way to do it. Any ideas how to resolve this issue?
I'd try enabling the UIViewAnimationOptionBeginFromCurrentState option in your animation code and see if that helps
I'm new to programming Xcode/objectiveC and this questions seems like it should be painfully obvious but I cannot find an answer; how do i move to a different view controller after an animation completes (without a button or other user interaction). in other words go back to the "home" screen automatically after it finishes. right now the image that is animated just stops moving and stays there after the animation finishes and i'm stuck in that viewController.
i'm guessing the coding should have something to do with the selector but i'm not sure
[UIView setAnimationDidStopSelector:#selector ???];
thanks!
UIView's animateWithDuration has a completion block in which you can put code that is executed when the animation is completed.
[UIView animateWithDuration:duration
animations:^{
animations
}
completion:^(BOOL success) {
[self performSegueWithIdentifier:#"YOUR_SEGUE"];
}];
I have an odd problem in one of my chain animations. I have block object for each of the blocks on my screen (26 of them), and when the user presses them I perform a flip. It works great, but I'm adding a scale animation before I do these to make them about 50% bigger on the screen. So, my sequence is:
enlarge
delay (let user see the large image)
spin-out 90% (removes block from view) - using transform.rotation.y
change image & spin-in
shrink.
I have setup the window view controller to be a delegate of these blocks, such that it can pass a counter to the blocks so I can position the right sublayer on the top (using setZposition).
It all works great, except when I have 2 blocks on positioned above/below each other on the screen, such that the enlarge will cause them to overlap, and then when the spin-out animation starts, it immediately has the right side of the block pop behind the block below it. I've tried changing the animation to transform.rotation.x and get the same behavior when the blocks are side-to-side.
I'm not sure if it's an iOS bug of if I'm just not doing something correct. Any suggestions are greatly appreciated. Here is the spin-out method:
- (void)spinOut:(id)sender
{
NSTimeInterval animationTime=0.85;
[UIView animateWithDuration:animationTime
delay:0
options: UIViewAnimationOptionCurveLinear
animations:^{
// setup the animation to spin the current view out
[CATransaction begin];
[CATransaction setDisableActions:YES];
CABasicAnimation *spinOut = [CABasicAnimation animationWithKeyPath:#"transform.rotation.y"];
[spinOut setDelegate:self];
[spinOut setDuration:animationTime];
CAMediaTimingFunction *tf = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseIn];
[spinOut setTimingFunction:tf];
[spinOut setFromValue:[NSNumber numberWithFloat:M_PI * 0.0]];
[spinOut setToValue:[NSNumber numberWithFloat:M_PI * 0.5]];
[spinOut setRemovedOnCompletion:NO];
[spinOut setFillMode:kCAFillModeForwards];
// setup variables used to roll in the next view on animation completion.
[pageView.layer addAnimation:spinOut forKey:kMyVeryOwnABCsSpinOutKey];
[CATransaction commit];
}
completion:^(BOOL finished){
[self setFlipOutAnimationTimer:[NSTimer scheduledTimerWithTimeInterval:animationTime target:self selector:#selector(spinIn:) userInfo:nil repeats:NO]];
}];
}
OK - this is an old question, but I kindof figured out this problem. Since I was flipping these images around the Y axis, I was able to change the animated image's Zposition. In my startAnimation method, I added:
float pageLevelLayerPosition;
// logic to set the zposition variable 100 more than anything nearby
_originalImageViewZPosition = bigImageView.layer.zPosition;
[bigImageView.layer setZPosition:pageLevelLayerPosition];
and then when in the animationDidStop, I added the relevant line of code to reset it back to 0 where I was removing the animation. I had some code to manage the variable so that I was assured that the number was greater than anything nearby.
I guess if I ever get into 3-D animation, then I'll need to control this much more closely, but that is what was causing my problem.
I have a problem when putting my iPhone app to background by pushing the exit button, and then relaunching by tapping the launch icon on the home screen: the app's view does return to its initial state like I want it to, but before that it flashes the earlier, wrong view state onscreen briefly.
Background
My main view consists basically of a sequence of interlinked UIAnimateWithDuration calls. The behavior I want whenever any interruption occurs, is to reset the animation to its initial state (unless the animations have all finished and the app has entered the static final phase), and start over from there whenever the app returns to active and visible state.
After studying the subject I learned I need two types of interruption handling code to provide good ux: "instant" and "smooth". I have the method resetAnimation that resets the view properties to the initial state instantly, and the method pauseAnimation that animates quickly to the same state, with an additional label stating "paused" fading in on the top of the view.
Double clicking exit button
The reason for this is the "double clicking exit button" use case, that actually does not hide your view or put you in the background state, it just scrolls up a bit to show the multitasking menu at the bottom. So, resetting the view state instantly in this case just looked very ugly. The animated transition and telling the user you're paused seemed like a better idea.
This case works nice and smootly by implementing the applicationWillResignActive delegate method in my App Delegate and calling pauseAnimation from there. I handle returning from that multitasking menu by implementing the applicationDidBecomeActive delegate method and calling from there my resumeAnimation method, that fades out the "paused" label if its there, and starts my animation sequence from the initial state.
This all works fine, no flickering anywhere.
Visiting flipside
My app's built over the Xcode "utility" template, so it has a flipside view to show info/settings. I handle visiting the flipside and returning back to the main view by implementing these two delegate methods in my main view controller:
(void)viewDidDisappear:(BOOL)animated
(void)viewDidAppear:(BOOL)animated
I call my resetAnimation in the viewDidDisappear method and resumeAnimation in viewDidAppear. This all works fine, the main view is its initial state from the very beginning of the transition to visible state - no unexpected flashing of wrong animation states of anything. But:
Pushing exit button and relaunching from my app icon (the buggy part!)
This is where the trouble starts. When I push exit button once and my app begins its transition to background, two things happen. First, applicationWillResignActive gets called here too, so my pauseAnimation method launches also. It wouldn't need to, since the transition doesn't need to be smooth here – the view just goes static, and "zooms out" to reveal the home screen – but what can you do? Well, it wouldn't do any harm either if I just could call resetAnimation before the exact moment that the system takes the snapshot of the view.
Anyways, secondly, applicationDidEnterBackground in the App Delegate gets called. I tried to call resetAnimation from there so that the view would be in the right state when the app returns, but this doesn't seem to work. It seems the "snapshot" has been taken already and so, when I tap my app launch icon and relauch, the wrong view state does flash briefly on the screen before the correct, initial state shows. After that, it works fine, the animations go about like they're supposed to, but that ugly flicker at that relaunch moment won't go away, no matter what I try.
Fundamentally, what I'm after is, what exact moment does the system take this snapshot? And consequently, what would be the correct delegate method or notification handler to prepare my view for taking the "souvenir photo"?
PS. Then there's the default.png, which doesn't seem to only show at first launch, but also whenever the processor's having a hard time or returning to the app is delayed briefly for some other reason. It's a bit ugly, especially if you're returning to your flipside view that looks totally different from your default view. But this is such a core iOS feature, I'm guessing I shouldn't even try to figure out or control that one :)
Edit: since people were asking for actual code, and my app has already been released after asking this question, I'll post some here. ( The app's called Sweetest Kid, and if you want to see how it actually works, it's here: http://itunes.apple.com/app/sweetest-kid/id476637106?mt=8 )
Here's my pauseAnimation method – resetAnimation is almost identical, except its animation call has zero duration and delay, and it doesn't show the 'Paused' label. One reason I'm using UIAnimation to reset the values instead of just assigning the new values is that for some reason, the animations just didn't stop if I didn't use UIAnimation. Anyway, here's the pauseAnimation method:
- (void)pauseAnimation {
if (currentAnimationPhase < 6 || currentAnimationPhase == 255) {
// 6 means finished, 255 is a short initial animation only showing at first launch
self.paused = YES;
[UIView animateWithDuration:0.3
delay:0
options:UIViewAnimationOptionAllowUserInteraction |
UIViewAnimationOptionBeginFromCurrentState |
UIViewAnimationOptionCurveEaseInOut |
UIViewAnimationOptionOverrideInheritedCurve |
UIViewAnimationOptionOverrideInheritedDuration
animations:^{
pausedView.alpha = 1.0;
cameraImageView.alpha = 0;
mirrorGlowView.alpha = 0;
infoButton.alpha = 1.0;
chantView.alpha = 0;
verseOneLabel.alpha = 1.0;
verseTwoLabel.alpha = 0;
verseThreeLabel.alpha = 0;
shine1View.alpha = stars1View.alpha = stars2View.alpha = 0;
shine1View.transform = CGAffineTransformIdentity;
stars1View.transform = CGAffineTransformIdentity;
stars2View.transform = CGAffineTransformIdentity;
finishedMenuView.alpha = 0;
preparingMagicView.alpha = 0;}
completion:^(BOOL finished){
pausedView.alpha = 1.0;
cameraImageView.alpha = 0;
mirrorGlowView.alpha = 0;
infoButton.alpha = 1.0;
chantView.alpha = 0;
verseOneLabel.alpha = 1.0;
verseTwoLabel.alpha = 0;
verseThreeLabel.alpha = 0;
shine1View.alpha = stars1View.alpha = stars2View.alpha = 0;
shine1View.transform = CGAffineTransformIdentity;
stars1View.transform = CGAffineTransformIdentity;
stars2View.transform = CGAffineTransformIdentity;
finishedMenuView.alpha = 0;
preparingMagicView.alpha = 0;
}];
askTheMirrorButton.enabled = YES;
againButton.enabled = NO;
shareOnFacebookButton.enabled = NO;
emailButton.enabled = NO;
saveButton.enabled = NO;
currentAnimationPhase = 0;
[[cameraImageView subviews] makeObjectsPerformSelector:#selector(removeFromSuperview)]; // To remove the video preview layer
}
}
The screenshot is taken immediately after this method returns. I guess your -resetAnimation method completes in the next runloop cycle and not immediately.
I've not tried this, but you could try to let the runloop run and then return a little bit later:
- (void) applicationDidEnterBackground:(UIApplication *)application {
// YOUR CODE HERE
// Let the runloop run for a brief moment
[[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate dateWithTimeIntervalSinceNow:0.01]];
}
I hope this helps,
Fabian
Update: -pauseAnimation and -resetAnimation distinction
Approach: Delay the animation happening in -applicationWillResignActive: and cancel the delayed animation in -applicationDidEnterBackground:
- (void) applicationWillResignActive:(UIApplication *)application {
// Measure the time between -applicationWillResignActive: and -applicationDidEnterBackground first!
[self performSelector:#selector(pauseAnimation) withObject:nil afterDelay:0.1];
// OTHER CODE HERE
}
- (void) applicationDidEnterBackground:(UIApplication *)application {
[NSObject cancelPreviousPerformRequestsWithTarget:self selector:#selector(pauseAnimation) object:nil];
// OTHER CODE HERE
}
I've now run some tests, and eliminated the problem, thanks to #Fabian Kreiser.
To conclude: Kreiser had it right: iOS takes the screenshot immediately after the method applicationDidEnterBackground: returns -- immediately meaning, before the end of the current runloop.
What this means is, if you launch any scheduled tasks in the didEnterBackground method you want to finish before leaving, you will have to let the current runloop run for as long as the tasks might take to finish.
In my case, the scheduled task was an UIAnimateWithDuration method call -- I let myself be confused by the fact that both its delay and duration was 0 -- the call was nonetheless scheduled to run in another thread, and thus wasn't able to finish before the end of applicationDidEnterBackground method. Result: the screenshot was indeed taken before the display was updated to the state I wanted -- and, when relaunching, this screenshot flashed briefly onscreen, causing the unwanted flickering.
Furthermore, to provide the "smooth" vs. "instant" transition behavior explained in my question, Kreiser's suggestion to delay the "smooth" transition call in applicationWillResignActive: and cancel the call in applicationDidEnterBackground: works fine. I noticed the delay between the two delegate methods was around 0.005-0.019 seconds in my case, so I applied a generous margin and used a delay of 0.05 seconds.
My bounty, the correct answer tick, and my thanks go to Fabian. Hopefully this helps others in similar situation, too.
The runloop solution actually results in some problems with the app.
[[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate dateWithTimeIntervalSinceNow:0.01]];
If you go to the background and immediately open the app again, the app will turn into a black screen. When you reopen the app for the second time, everything is back to normal.
A better way is to use
[CATransaction flush]
This forces all current transactions to be immediately applied and does not have the problem resulting in a black screen.
Depending on how hardcore important it is to you to have this transition run smoothly, you could kill off multi-tasking for your app entirely w/ UIApplicationExitsOnSuspend. Then, you would be guaranteed your Default.png and a clean visual state.
Of course, you'd have to save/restore state on exit/startup, and without more info on the nature of your app, it's tough to say whether this would be worth the trouble.
In iOS 7, there is [[UIApplication sharedApplication] ignoreSnapshotOnNextApplicationLaunch] call that does exactly what you needed.
Is there a reason why animations do not work in a loop? I know you can do the command:
[UIView setAnimationRepeatCount: someNumber];
which was working fine until I put actual different pdfs to be loaded. So before, with just one pdf that would always get loaded, when I did the animation say 5 times to go to the last document, the animations would look correct. But now that I have 5 different pdfs, it will flip the page 5 times with the CurlUp but it will keep showing the 1st pdf in the list, and then at the end load the proper one. So I thought I could do it in a loop, keeping track of the location in the array, and load each pdf at each location as i flip through the pages so it gives the user the feeling of where they are in the stack of pdfs. But when I put the core animation code in a loop, it basically shows the animation once, but does get to the correct document.
From my understanding of what you're doing, it sounds like you're actually running all 5 animations at once. When you perform an animation block in a for-loop, the runloop doesn't iterate between each loop and only the last animation gets run.
What you'll need to use is use completion calls and "chain" them together. So you run the first animation, then on that completion call you run the second, then on that call the third, etc. Much more lengthy to code, but this will work.
Would be easier to use blocks in this scenario, then all your animation code will be in one place instead of having to spread it all across a bunch of methods for each animation. You would just nest the blocks, in the first animation's completion block you'd spawn the second, then the third, etc.
Here's an example using the blocks method. It's a little hard to read, but you'll get the idea. You might be able to create a single animation block and reuse it in each completion method, but I don't know all of the catches of doing that, and this is much easier to read when you're first trying to understand it.
Note that I haven't actually tried this or tested it, but I think it will do what you want.
[UIView animateWithDuration:1.0 animations:^(void) {
// Animation changes go here
// blah.alpha = 1.0
// blah.position = CGPointMake
// etc
} completion:^(BOOL finished) {
// Start next animation which will run with this one finishes
[UIView animateWithDuration:1.0 animations:^(void) {
// Animation changes go here
// blah.alpha = 1.0
// blah.position = CGPointMake
// etc
} completion:^(BOOL finished) {
// Start next animation which will run with this one finishes
[UIView animateWithDuration:1.0 animations:^(void) {
// Animation changes go here
// blah.alpha = 1.0
// blah.position = CGPointMake
// etc
} completion:^(BOOL finished) {
// Start next animation which will run with this one finishes
[UIView animateWithDuration:1.0 animations:^(void) {
// Animation changes go here
// blah.alpha = 1.0
// blah.position = CGPointMake
// etc
} completion:nil];
}];
}];
}];