问题
I'd like to present modally, at first startup, a tutorial wizard to the user.
Is there a way to present a modal UIViewController on application startup, without seeing, at least for a millisecond, the rootViewController behind it?
Now I'm doing something like this (omitting first-launch checks for clarity):
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
// ...
UIStoryboard *storyboard = self.window.rootViewController.storyboard;
TutorialViewController* tutorialViewController = [storyboard instantiateViewControllerWithIdentifier:@"tutorial"];
tutorialViewController.modalTransitionStyle = UIModalTransitionStyleCrossDissolve;
[self.window makeKeyAndVisible];
[self.window.rootViewController presentViewController:tutorialViewController animated:NO completion:NULL];
}
with no luck. I've tried to move [self.window makeKeyAndVisible]; to before the [... presentViewController:tutorialViewController ...] statement, but then the modal doesn't even appear.
回答1:
All presentViewController methods require the presenting view controller to have appeared first. In order to hide the root VC an overlay must be presented. The Launch Screen can continued to be presented on the window until the presentation has completed and then fadeout the overlay.
UIView* overlayView = [[[UINib nibWithNibName:@"LaunchScreen" bundle:nil] instantiateWithOwner:nil options:nil] firstObject];
overlayView.frame = self.window.rootViewController.view.bounds;
overlayView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
UIStoryboard *storyboard = self.window.rootViewController.storyboard;
TutorialViewController* tutorialViewController = [storyboard instantiateViewControllerWithIdentifier:@"tutorial"];
tutorialViewController.modalTransitionStyle = UIModalTransitionStyleCrossDissolve;
[self.window makeKeyAndVisible];
[self.window addSubview:overlayView];
[self.window.rootViewController presentViewController:tutorialViewController animated:NO completion:^{
NSLog(@"displaying");
[UIView animateWithDuration:0.5 animations:^{
overlayView.alpha = 0;
} completion:^(BOOL finished) {
[overlayView removeFromSuperview];
}];
}];
回答2:
Bruce's upvoted answer in Swift 3:
if let vc = window?.rootViewController?.storyboard?.instantiateViewController(withIdentifier: "LOGIN")
{
let launch = UIStoryboard(name: "LaunchScreen", bundle: nil).instantiateInitialViewController()!
launch.view.frame = vc.view.bounds
launch.view.autoresizingMask = [UIViewAutoresizing.flexibleWidth, UIViewAutoresizing.flexibleHeight]
window?.makeKeyAndVisible()
window?.addSubview(launch.view)
//Using DispatchQueue to prevent "Unbalanced calls to begin/end appearance transitions"
DispatchQueue.global().async {
// Bounce back to the main thread to update the UI
DispatchQueue.main.async {
self.window?.rootViewController?.present(vc, animated: false, completion: {
UIView.animate(withDuration: 0.5, animations: {
launch.view.alpha = 0
}, completion: { (_) in
launch.view.removeFromSuperview()
})
})
}
}
}
回答3:
may be your can use the "childViewController"
UIStoryboard *storyboard = self.window.rootViewController.storyboard;
TutorialViewController* tutorialViewController = [storyboard instantiateViewControllerWithIdentifier:@"tutorial"];
[self.window addSubview: tutorialViewController.view];
[self.window.rootViewController addChildViewController: tutorialViewController];
[self.window makeKeyAndVisible];
When you need to dismiss your tutor, you can remove its view from the superview. Also you can add some animation on the view by setting the alpha property.Hope helpful:)
回答4:
This problem still exists in iOS 10. My fix was:
- in
viewWillAppearadd the modal VC as a childVC to the rootVC - in the
viewDidAppear:- Remove the modalVC as a child of the rootVC
- Modally present the childVC without animation
Code:
extension UIViewController {
func embed(childViewController: UIViewController) {
childViewController.willMove(toParentViewController: self)
view.addSubview(childViewController.view)
childViewController.view.frame = view.bounds
childViewController.view.autoresizingMask = [.flexibleHeight, .flexibleWidth]
addChildViewController(childViewController)
}
func unembed(childViewController: UIViewController) {
assert(childViewController.parent == self)
childViewController.willMove(toParentViewController: nil)
childViewController.view.removeFromSuperview()
childViewController.removeFromParentViewController()
}
}
class ViewController: UIViewController {
let modalViewController = UIViewController()
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
//BUG FIX: We have to embed the VC rather than modally presenting it because:
// - Modal presentation within viewWillAppear(animated: false) is not allowed
// - Modal presentation within viewDidAppear(animated: false) is not visually glitchy
//The VC is presented modally in viewDidAppear:
if self.shouldPresentModalVC {
embed(childViewController: modalViewController)
}
//...
}
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
//BUG FIX: Move the embedded VC to be a modal VC as is expected. See viewWillAppear
if modalViewController.parent == self {
unembed(childViewController: modalViewController)
present(modalViewController, animated: false, completion: nil)
}
//....
}
}
回答5:
May be a bad solution, but you could make a ViewController with 2 containers in it, where both of the containers are linked to a VC each. Then you can control which container should be visible in code, that's an idea
if (!firstRun) {
// Show normal page
normalContainer.hidden = NO;
firstRunContainer.hidden = YES;
} else if (firstRun) {
// Show first run page or something similar
normalContainer.hidden = YES;
firstRunContainer.hidden = NO;
}
回答6:
Bruce's answer pointed me in the right direction, but because my modal can appear more often than just on launch (it's a login screen, so it needs to appear if they log out), I didn't want to tie my overlay directly to the presentation of the view controller.
Here is the logic I came up with:
self.window.rootViewController = _tabBarController;
[self.window makeKeyAndVisible];
WSILaunchImageView *launchImage = [WSILaunchImageView new];
[self.window addSubview:launchImage];
[UIView animateWithDuration:0.1f
delay:0.5f
options:0
animations:^{
launchImage.alpha = 0.0f;
} completion:^(BOOL finished) {
[launchImage removeFromSuperview];
}];
In a different section I perform the logic of presenting my login VC in the typical self.window.rootViewController presentViewController:... format which I can use regardless if it's an app launch or otherwise.
If anyone cares, here is how I created my overlay view:
@implementation WSILaunchImageView
- (instancetype)init
{
self = [super initWithFrame:[UIScreen mainScreen].bounds];
if (self) {
self.image = WSILaunchImage();
}
return self;
}
And here's the logic for the launch image itself:
UIImage * WSILaunchImage()
{
static UIImage *launchImage = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
if (WSIEnvironmentDeviceHas480hScreen()) launchImage = [UIImage imageNamed:@"LaunchImage-700"];
else if (WSIEnvironmentDeviceHas568hScreen()) launchImage = [UIImage imageNamed:@"LaunchImage-700-568h"];
else if (WSIEnvironmentDeviceHas667hScreen()) launchImage = [UIImage imageNamed:@"LaunchImage-800-667h"];
else if (WSIEnvironmentDeviceHas736hScreen()) launchImage = [UIImage imageNamed:@"LaunchImage-800-Portrait-736h"];
});
return launchImage;
}
Aaaaand just for completion's sake, here is what those EnvironmentDevice methods look like:
static CGSize const kIPhone4Size = (CGSize){.width = 320.0f, .height = 480.0f};
BOOL WSIEnvironmentDeviceHas480hScreen(void)
{
static BOOL result = NO;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
result = CGSizeEqualToSize([UIScreen mainScreen].bounds.size, kIPhone4Size);
});
return result;
}
回答7:
let vc = UIViewController()
vc.modalPresentationStyle = .custom
vc.transitioningDelegate = noFlashTransitionDelegate
present(vc, animated: false, completion: nil)
class NoFlashTransitionDelegate: NSObject, UIViewControllerTransitioningDelegate {
public func presentationController(forPresented presented: UIViewController, presenting: UIViewController?, source: UIViewController) -> UIPresentationController? {
if source.view.window == nil,
let overlayViewController = UIStoryboard(name: "LaunchScreen", bundle: nil).instantiateInitialViewController(),
let overlay = overlayViewController.view {
source.view.addSubview(overlay)
UIView.animate(withDuration: 0, animations: {}) { (finished) in
overlay.removeFromSuperview()
}
}
return nil
}
}
回答8:
It can be late but in your AppDelegate you can do this :
//Set your rootViewController
self.window.rootViewController=myRootViewController;
//Hide the rootViewController to avoid the flash
self.window.rootViewController.view.hidden=YES;
//Display the window
[self.window makeKeyAndVisible];
if(shouldPresentModal){
//Present your modal controller
UIViewController *lc_viewController = [UIViewController new];
UINavigationController *lc_navigationController = [[UINavigationController alloc] initWithRootViewController:lc_viewController];
[self.window.rootViewController presentViewController:lc_navigationController animated:NO completion:^{
//Display the rootViewController to show your modal
self.window.rootViewController.view.hidden=NO;
}];
}
else{
//Otherwise display the rootViewController
self.window.rootViewController.view.hidden=NO;
}
回答9:
This is how I do it with storyboards and it works with multiple modals. This example has 3. Bottom, middle, and top.
Just be sure to have the storyboardID of each viewController set correctly in interface builder.
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
UIStoryboard * storyboard = [UIStoryboard storyboardWithName:@"Main" bundle:nil];
BottomViewController *bottomViewController = [storyboard instantiateViewControllerWithIdentifier:@"BottomViewController"];
UIWindow *window = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
[window setRootViewController:bottomViewController];
[window makeKeyAndVisible];
if (!_loggedIn) {
MiddleViewController *middleViewController = [storyboard instantiateViewControllerWithIdentifier:@"middleViewController"];
TopViewController *topViewController = [storyboard instantiateViewControllerWithIdentifier:@"topViewController"];
[bottomViewController presentViewController:middleViewController animated:NO completion:nil];
[middleViewController presentViewController:topViewController animated:NO completion:nil];
}
else {
// setup as you normally would.
}
self.window = window;
return YES;
}
来源：https://stackoverflow.com/questions/26355847/ios-present-modal-view-controller-on-startup-without-flash