In fading a view controller in from black, I am doing the following within viewDidLoad:
Creating a UIView with a black background;
Giving the UIView an alpha value of 1.0f;
Adding the UIView as a subview of [self view];
Fading the black UIView out via animateWithDuration by changing its alpha value to 0.0f; and
Removing the black UIView from [[self view] subviews]
More often than not, this works as planned. Occasionally, however, I see a glimpse of the view controller I want initially hidden, just before the black UIView is drawn.
Is there a way to avoid this? Is there a better method to place this code in than viewDidLoad?
Many thanks
Yes, add the view in the loadView method and do the actual animation in viewDidLoad or viewDidAppear. Or do as the above commentor said and simply use the view alpha.
I would create the UIView that I want hidden in UIViewController's nib file, then link that to via an IBOutlet
#interface SomeViewController: UIViewController
{
IBOutlet UIView *blackView;
}
then in UIViewController's -(void) viewDidLoad; method, I would do the following
- (void)viewDidLoad
{
[super viewDidLoad];
// Fade the opacity of blackView over 1 second,
// then remove it from the view controller.
[UIView animateWithDuration:1
delay:0
options:UIViewAnimationOptionCurveEaseOut
animations:^{
blackView.layer.opacity = 0;
}
completion:^(BOOL finished) {
// This line prevents the flash
blackView.layer.opacity = 0;
[blackView removeFromSuperview];
}];
}
Related
I’m trying to make an iOS Action app extension with minimal UI. Basically it would just show a progress indicator until the action completed. I just want to be able to animate the view so that it slides down from the top & then slides back up when the action has completed. If anyone is familiar with Instapaper’s Share extension, then that’s the kind of basic UI I’m looking for.
The problem is that when I try to duplicate this functionality - I just have a small UIView that animates down from the top - I get a black background behind my view. I can’t figure out how to make that background transparent so that the stuff behind my view is still visible. Does anyone know how to do this?
As a starting point I’m just using the default Action Extension template that’s created by Xcode...
Create a new iOS app project in Xcode.
Add a new target -> Action Extension.
In the ActionViewController.m file add a viewWillAppear method to animate the view (using a 1 second animation so that the black background is easily seen):
Code:
- (void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
CGRect currFrame = self.view.frame;
CGRect newFrame = currFrame;
newFrame.origin.y -= newFrame.size.height;
self.view.frame = newFrame;
[UIView animateWithDuration:1.0 animations:^{
self.view.frame = currFrame;
}];
}
When this is run the view is animated sliding down from the top. However rather than seeing the UI of the calling App all you see is a black background.
I’ve tried a number of things - changing the modalPresentationStyle (doesn’t seem to do anything), setting the entire view to hidden (this just makes the whole screen black), etc.
For reference this is using iOS 9.3.2 and Xcode 7.3.1.
From what I understand from Apple docs
In iOS, an Action extension:
Helps users view the current document in a different way
Always appears in an action sheet or full-screen modal view
Receives selected content only if explicitly provided by the host app
The fact that the Action extension always appear in a full-screen view on an iPhone might mean that there's no way of having a transparent background.
I am certain that a Share extension can be animated (I've done it myself) how you want it and have a transparent background. That's why Instapaper's Share extension works nicely.
You are facing two problems:
1. When you present a view controller, the default behavior is the controller is full screen context. That is the reason you see a black screen.
2. You are trying to change self.view.frame when the controller is presented on full screen.
Yet there is a way to achieve this kind of behavior you are looking for, in one of three ways:
A. Specify "modalPresentationStyle" to "UIModalPresentationOverCurrentContext" and set the presenting controller to "definesPresentationContext".
That way, when you present the controller, the presenting controller will be behind the presented controller.
And insted of changing self.view.frame you will set self.view background color to clear, and add a subview and use it as a background view:
//Presenting view controller:
-(void) presentPopUpViewController {
self.definesPresentationContext = YES; //self is presenting view controller
self.presentedVC.modalPresentationStyle = UIModalPresentationOverCurrentContext;
[self presentViewController:self.presentedVC animated:NO completion:nil];
}
//Presented view controller:
-(void) viewDidLoad {
[super viewDidLoad];
CGRect currFrame = self.view.frame;
CGRect newFrame = currFrame;
newFrame.origin.y -= newFrame.size.height;
self.myBackroundView = [[UIView alloc] init];
self.myBackroundView.backgroundColor = [UIColor yellowColor];
self.myBackroundView.frame = newFrame;
[self.view addSubview:self.myBackroundView];
self.view.backgroundColor = [UIColor clearColor];
}
- (void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
[UIView animateWithDuration:5.0 animations:^{
self.myBackroundView.frame = self.view.frame;
}];
}
B. Add the presented view controller as a Child view controller. that way the life cycle stays the same, but you can add I'ts view as a subview, and change I'ts frame.
//Presenting view controller:
-(void) presentChildViewController {
[self addChildViewController:self.presentedVC];
[self.view addSubview:self.presentedVC.view];
[self.presentedVC didMoveToParentViewController:self];
}
//Presented view controller:
- (void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
CGRect currFrame = self.view.frame;
CGRect newFrame = currFrame;
newFrame.origin.y -= newFrame.size.height;
self.view.frame = newFrame;
[UIView animateWithDuration:1.0 animations:^{
self.view.frame = currFrame;
}];
}
C. Don't use UIViewController, use UIView. Use a "Decorator" object, that you pass it the ViewController you would like the view to disaply on, and the "Decorator" will add the view as subview, and deal with the animation. No need for an example for this scenario.
It is wrong to start animations when your view hasn't yet appeared. Can you, please, try the same code in viewDidAppear.
Also animating main view controller's view will make underlying layers visible, so you've got to use another view on top of view controller's main view, like this:
UIView *progressView = [[UIView alloc] init];
progressView.frame = self.view.bounds;
progressView.backgroundColor = [UIColor redColor];
[self.view addSubView:progressView];
I'm creating a custom selected-animation for my UITableView.
What I've got is a standard UIViewController that displays a UITableView, which upon didSelectRow:AtIndexPath: instantiates another VC from storyboard, prepares it and displays it modally using UIModalPresentationOverCurrentContext.
Then the second VC updates a constraint from the top layout guide to a UIImageView, hence placing it exactly where the cell was located on screen. This coordinate is passed from the first VC.
Next, this UIImageView slides up, creating the illusion that the cell slides up. However, this produces a flicker for a split second just before sliding the image quite often (not always, like 3/4 times).
What's a better way to position the UIImageView initially, before it's animated?
Here's my code doing this:
-(void)viewWillAppear:(BOOL)animated {
[super viewWillAppear:YES];
self.imageViewTopConstraint.constant = self.cellFrame.origin.y;
[self.view layoutIfNeeded];
self.imageView.image = self.image;
}
-(void)viewDidAppear:(BOOL)animated {
[super viewDidAppear:YES];
/* animate the opening */
[UIView animateWithDuration:0.45 delay:0 usingSpringWithDamping:1.0f initialSpringVelocity:1.2f options:UIViewAnimationOptionTransitionNone animations:^{
/* slide image */
self.imageViewTopConstraint.constant = 0.0f;
[self.view layoutIfNeeded];
}completion:^(BOOL finished) {
}];
}
When I change my UIBarButtonItems they change abruptly, unlike the default which gives a nice but speedy fade animation. You can see this when segueing between view controllers, for instance, the back button will fade in and out. How can I simulate the same effect?
Update - Based on this answer - https://stackoverflow.com/a/10939684/2649021
It looks like you would have to do something like this to make the button itself fade out.
[self.navigationItem setRightBarButtonItem:nil animated:YES];
And do something like this to make it fade in
[self.navigationItem setRightBarButtonItem:myButton animated:YES];
Otherwise if you want more control over animation properties you would have to create a custom view I believe.
EDIT: I just confirmed that you can fade a UIBarButtonItem custom view using this.
As a test I created a simple project and dropped a UIBarButtonItem onto the navigation bar. I created an outlet to the view controller. In viewDidLoad on the view controller I setup a custom view
-(void)viewDidLoad{
[super viewDidLoad];
UILabel *lbl = [[UILabel alloc]initWithFrame:CGRectMake(0,0,40,40)];
lbl.text = #"test";
UIView *customView = [[UIView alloc]initWithFrame:CGRectMake(0,0,40,40)];
[customView addSubview:lbl];
self.barButtonItem.customView = customView;
}
As a test in viewDidAppear I animated it
-(void)viewDidAppear:(BOOL)animated
{
[UIView animateWithDuration:3.0
delay:3.0
options:UIViewAnimationOptionCurveEaseOut
animations:^{
self.barButtonItem.customView.alpha = 0;
}
completion:^(BOOL finished) {
NSLog(#"animation complete");
}];
EDIT: Here's a link to Apples Documentation for a full explanation of UIView animations.
https://developer.apple.com/library/ios/documentation/windowsviews/conceptual/viewpg_iphoneos/animatingviews/animatingviews.html
You might have to create a custom bar button item using a view or an image, and then animate the properties of the view as digitalHound shows.
I have UIViewController, there is some animation in these UIViewController. UIView that animates on this UIViewController has different start and end position. I also have segue, that will push new UIViewController to the scene. All works okay, but if I return to my first UIViewController, position of my UIVIew changes to start position.
How can I fix this?
- (void)viewDidLoad
{
[super viewDidLoad];
[UIView animateWithDuration:0.3 animations:^{
self.myView.center = CGPointMake(self.myView.center.x,self.ahotherView.center.y);
}completion:^(BOOL complete){
}];
}
- (void)viewWillLayoutSubviews {
[super viewWillLayoutSubviews];
self.myView.center = CGPointMake(self.myView.center.x, self.ahotherView.center.y);
}
Autolayout is causing it to return to the beginning position. You can either turn it off or write a bit of code to override the constraints.
You'll have to first add constraints in Storyboard, which is an entirely different question in itself. I recommend doing some research. Once you've added the proper constraints and created IBOutlets for them, you'll be changing the values of the constraint constants, then calling [self.myView layoutIfNeeded] inside your animation block. Instead of changing the center property. Might look something like this:
//update constraint values
self.topConstraint.constant = 70;
self.bottomConstraint.constant = 20;
//animate
[UIView animateWithDuration:0.5f animations:^{
[self.myView layoutIfNeeded];
} completion:^(BOOL finished) {
}];
I want to use Storyboards to design content for a slider, and it seems like an easy way to design offscreen content is to use a childViewController. So I've done this
myViewController = [[UIStoryboard storyboardWithName:#"ipad" bundle:NULL] instantiateViewControllerWithIdentifier:#"keyPadOffScreen"];
[self addChildViewController:myViewController];
[myViewController didMoveToParentViewController:self];
newView = myViewController.view;
[self.view addSubview:newView];
And that adds the entire view controller over top of my root view. The problem is, I only want one of the subviews to show up, not the whole view. I can handle the animation, as long as I know how to add the root view. I tried this to just add the subview (sliderView is the name of the subview I want) instead of the whole view, but that did nothing
newView = myViewController.sliderView;
[self.view addSubview:newView];
Should I be using a different strategy?
EDIT: this DOES work, but it seems silly - setting the views size to just be the size of the subview.
newView.frame = CGRectMake(newView.frame.origin.x, newView.frame.origin.y, newView.frame.size.width, **myViewController.sliderView.frame.size.height**);
It does seem a bit overkill for just a view. Once you start doing a lot of custom view/animation/transition stuff it's often easier to implement in code, or at least it is for me since I've been doing it that way for a long time.
But maybe you want to stick with Storyboards. I respect that. And if you have a few developers working on this then it's important to keep some uniformity to how you set up your UI.
Instead of keeping it in a separate view controller and adding it when you need it to animate on-screen, simply add it to your existing view controller and either set it to hidden, or set it's alpha to 0.0 in IB. Then your animation can undo that and make it visible.
you can use custom segue here, for instance:
#implementation FRPresentEnteringPopupSegue
- (void)perform
{
FirstVC *toVC = self.destinationViewController;
SecondNavigationController *fromVC = self.sourceViewController;
toVC.view.frame = CGRectMake(0.0, 0.0, 300.0, 135.0);
toVC.view.center = CGPointMake(fromVC.view.bounds.size.width/2, fromVC.view.bounds.size.height + toVC.view.bounds.size.height/2);
[fromVC.view addSubview:toVC.view];
[toVC viewWillAppear:YES];
[UIView animateWithDuration:0.5
delay:0.0
usingSpringWithDamping:0.7
initialSpringVelocity:0.5
options:UIViewAnimationOptionBeginFromCurrentState
animations:^{
toVC.view.center = CGPointMake(fromVC.view.bounds.size.width/2, fromVC.view.bounds.size.height/2);
}completion:^(BOOL finished) {
[toVC viewDidAppear:YES];
}];
}
#end
make your UIStoryboardSegue subclass
override - (void)perform method with your custom view appearance code
use segue usual way