After changing the constraints on some of my view components, I'm calling layoutIfNeeded to perform the changes. The problem is that sometimes there's a very evident delay between the method call and the actual visual change. What am I doing wrong?
[self.view layoutIfNeeded];
I just realised you're supposed to call layoutIfNeeded while on the main queue:
dispatch_async(dispatch_get_main_queue(), ^{
self.loginFormConstraintX.constant = -1024;
[self.view layoutIfNeeded];
});
Related
I have a view controller and have a few objects that I have some simply animations hooked up to.
[UIView animateWithDuration:0.25
delay: 10.1
options: UIViewAnimationOptionCurveEaseIn
animations:^{
addNameViewConstraint.constant = 10;
addNameView.alpha = 1.0;
[self.view layoutIfNeeded]; // move
}
completion:nil];
[UIView animateWithDuration:0.25
delay: 0.15
options: UIViewAnimationOptionCurveEaseIn
animations:^{
addEmailViewConstraint.constant = 10;
addEmailView.alpha = 1.0;
[self.view layoutIfNeeded]; // move
}
completion:nil];
When I was using the push segue the animation works fine. But when I switched to using a modal segue the animation stopped working. I increased the delay in the first one to 10.2 seconds thinking that maybe it was animating before I got to see it. I am calling this animation in the viewWillAppear method. Again works if I'm doing a push segue.. but not for modal. Any ideas?
I am calling this animation in the viewWillAppear method
This is a common mistake. viewWillAppear: is too soon to start the animation. The view has not yet appeared so there is nothing to animate. Move the animateWithDuration:... code to viewDidAppear: and all will be well.
This is, however, as you say in your comment, insufficiently satisfying. What you are after is that the modal transition should be happening and your extra animations within the new view should already be happening as the modal view is in the process of appearing. Instead, with viewDidAppear:, the modal view finishes appearing, it settles into place, and then your other animations start, which is not as cool.
One solution might be to move the animations again, this time to viewWillLayoutSubviews. This is trickier because this method gets called a lot. You will need to use a BOOL instance variable as a flag to ensure that your animations run only once. Thus, this should work (I tried it and it seemed fine):
-(void)viewWillLayoutSubviews {
if (!self->didLayout) {
self->didLayout = YES;
[UIView animateWithDuration:0.25 animations:^{
// mess with constraint constants here
[self.subv layoutIfNeeded];
}];
}
}
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 tried to use setNeedsDisplay, but that is very much up to the mercy of the system whether to refresh right the way. Currently I remove and add the subview every time, so the latest content is forced to show. The code works, however it lacks gracefulness.
[myView removeFromSuperview];
[myView release];
myView = [[MyView alloc] initWithFrame:CGRectMake(0.0, MY_VIEW_Y, 320.0, MY_VIEW_H)];
[self.view addSubview:myView];
//[self.myView setNeedsDisplay];
[self.view bringSubviewToFront: myView];
Your view should be getting redrawn at the next drawing cycle. Is this not happening or is this too slow for you? ... i.e.: how fast do you need it to redraw and what latency are you seeing between calling setNeedsDisplay and drawRect being called?
If you need more precise control of the drawing, you may need to use a view backed by CAEAGLLayer, in which case it runs from openGL and setNeedsDisplay has no effect.
I'm looking for a way to implement consecutive animations using nested animation blocks.
Somewhat complicated by happening inside a UIScrollView, the size of three UIImageViews (there are many images, and as I scroll through them I constantly swapping out the images in the UIImageViews).
When a scroll is finished, I want to switch out the image in the (visible) middle UIImageView, three times, then back to the original view. I'm trying it thus:
- (void) doAnimation {
// get the animation frames, along with the current image
NSString *swap1 = #"first.png";
NSString *swap2 = #"second.png";
UIImage *original = currentPage.image;
UIViewAnimationOptions myOptions = UIViewAnimationOptionBeginFromCurrentState | UIViewAnimationOptionAllowUserInteraction;
[UIView animateWithDuration:2.0 delay:2.0 options:myOptions
animations:^{ [currentPage setImage:[UIImage imageNamed:swap1]]; }
completion:^(BOOL finished) {
[UIView animateWithDuration:2.0 delay:2.0 options:myOptions
animations:^{ [currentPage setImage:[UIImage imageNamed:swap2]]; }
completion:^(BOOL finished) {
[UIView animateWithDuration:2.0 delay:2.0 options:myOptions
animations:^{ [currentPage setImage:[UIImage imageNamed:swap1]]; }
completion:^(BOOL finished) {
[currentPage setImage:original]; }]; }]; }];
}
When I run this, there is no duration, no delay, it all happens at once, almost too fast for the eye to see. Could this be because "currentPage" is a UIImageView? (Similar to this question?)
There's no delay because UIImageView.image isn't an animateable property. As such, the UIView animation machinery will have no animations to set up and will just call your completion block immediately.
What sort of animation did you expect? You can attach a CATransition object to the underlying layer to get a simple cross-fade, Just use [imageView.layer addAnimation:[CATransition animation] forKey:nil] to get the crossfade with the default values (you can customize the timing by modifying properties of the CATransition before attaching it to the layer). To achieve the subsequent animations, you can either use the delegate property of CAAnimation (CATransition's superclass) to learn when it's done and fire your second one, or you could just use -performSelector:withObject:afterDelay: to start your next animation step after a user-defined delay. The delegate method is going to be more accurate with regards to timing, but the performSelector method is a bit easier to write. Sadly, CAAnimation doesn't support a completion block.
Another approach for you to transition from one image view to another is by using the block animation function transitionFromView:toView:duration:options:completion as discussed in "Creating Animated Transitions Between Views". You would do this instead of animateWithDuration to change images.
This is probably a simple question but I can't seem to figure out how to do it. Basically all I want to do is fade a window before closing it:
[[window animator] setAlphaValue:0.0];
[window close];
This works fine without the [window close], but when that is included the window seems to close it before the animation finishes (which is obviously not what I want); the same seems to happen for orderOut:, performClose:, etc. Is there any way to avoid this?
[[window animator] setAlphaValue:0.0];
[window performSelector:#selector(performClose:) withObject:self afterDelay:[[NSAnimationContext currentContext] duration]];
This is an old (but still popular) question with obsolete answer.
The right way to wait for animator finished is using special NSAnimationContext's class method with completionHanler like this:
[NSAnimationContext runAnimationGroup:^(NSAnimationContext *context){
// Start some animations here.
[[window animator] setAlphaValue:0.0];
} completionHandler:^{
// This block will be invoked when all of the animations started above have completed or been cancelled.
NSLog(#"All done!");
}];
Implicit animations triggered through the animator proxy run on wall time. Get the duration from the current NSAnimationContext and perform delay your cleanup/post-animation operations using that interval.