iOS 如何从 Uiview 呈现 Modal ViewController

Question

i have subclass a UIView and now i need to show a view controller but UIView not have method to present view controller. this is my problem thank's

this is a piece of code inside my uiview subclass

-(void)tableView:(UITableView*)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath{

    if ([tabella isEqualToString:@"Articoli"]) {
        NSDictionary *itm=(NSDictionary*)[comanda objectAtIndex:indexPath.row];

        Articoli *aboutViewController = [[Articoli alloc] initWithNibName:@"Articoli" bundle:nil];

        aboutViewController.modalPresentationStyle = UIModalPresentationFormSheet;
        aboutViewController.modalTransitionStyle = UIModalTransitionStyleCoverVertical;
        aboutViewController.idarticolo=[itm objectForKey:@"idarticolo"];
        CGRect aboutSheetFrame = aboutViewController.view.frame;

        UIViewController *viewController = [UIViewController new];
        viewController.view = self;

        //here xcode give me a red error
        [self presentViewController:viewController animated:YES completion:nil] ;

        aboutSheetFrame =CGRectZero;
        aboutViewController.view.superview.bounds = aboutSheetFrame;

    }
}

Answer 1

When you need a communication between UIView instance and UIViewController , there are a few known iOS concepts, which you should adhere to. As you have figured out that UIView cannot really present a new controller (missing either presetViewController:animated:completion methods or navigationController property, which are both present in UIViewController ).

Views are supposed to be the most reusable parts of your code, so you must think of a way to design your views to be completely blind to where they are at. They usually only know about user interaction.

So first, what you must do is refactor your view.

1. If your UIView is supposed to be a UIControl (has some kind of target selectors), you need to use add target in your controller to get callback from view interaction.
2. You can use delegate pattern as used in UITableView or UICollectionView , which is designed as a protocol.
3. You can use gesture recognizers added to a view ( UITapGestureRecognizer for example), so the controller knows about user interaction.

You can even mix and match those architectural patterns.

But you should really look into iOS programming basics, to understand this better.

In addition the first error I see in your code is that you create a generic UIViewController , when you should really be creating custom subclasses of it, defined in Storyboard and separate subclass of UIViewController .

The second error I see is that your UIView responds do tableView:didSelectRowAtIndexPath: method, which should in fact never happen. All this code must be moved back to one UIViewController subclass.

Answer 2

You can do this without any view hierarchy issues using the below code.

ObjectiveC

UIViewController *currentTopVC = [self currentTopViewController];
currentTopVC.presentViewController......... 

- (UIViewController *)currentTopViewController
{
    UIViewController *topVC = [[[[UIApplication sharedApplication] delegate] window] rootViewController];
    while (topVC.presentedViewController)
    {
        topVC = topVC.presentedViewController;
    }
    return topVC;
}

Swift

var topVC = UIApplication.sharedApplication().keyWindow?.rootViewController
while((topVC!.presentedViewController) != nil){
     topVC = topVC!.presentedViewController
}
topVC?.presentViewController........

Answer 3

PresentViewController is method of UIViewController class not of UIView , you can do one thing, create UIViewController instance and set its view to the view you have and then present it. Something like below

YourCustomView *customView = [[YourCustomView alloc]initWithFrame:someFrame];

UIViewController *viewController = [UIViewController new];
viewController.view = customView;

//From currentViewController present this 
[self presentViewController:viewController animated:YES completion:nil] ;

Customize this code as per your requirement

But as you are in view you need to pass this event to viewController, so better implement delegate method and at place where you calling present viewController call delegate which is implemented in ViewController and in side that presentViewController with customView set to its view property

Answer 4

You can also present your viewcontroller from the navigation controller object

Create Global Navigation Object in App Delegate or anywhere, you can access navigationcontroller object from view

@property (strong, nonatomic) UINavigationController *gblNavigation;

//Present viewcontroller from NavigationController object

[gblNavigation presentViewController:YOUR_VC_Object animated:YES completion:nil];

Answer 5

You can't present a view controller from a view. You can only present a view controller from a view controller.

Apple wants views to be dumb. That is views should only know how to display content. View should not respond to user interaction: that should be passed to a view controller.

You may want to consider using a delegate pattern, target action, or something similar to allow a view controller to control the interaction.

Answer 6

iOS 15, compatible down to iOS 13

Based on Shamsudheen TK solution for anyone who comes across this question in the future.

let presentedWindow = UIApplication.shared.connectedScenes.flatMap { ($0 as? UIWindowScene)?.windows ?? [] }.first { $0.isKeyWindow }
guard let currentViewController = presentedWindow?.rootViewController else {
  return
}
currentViewController.present(UIViewController(nibName: nil, bundle: nil), animated: true)

Note that connectedScenes is available only since iOS 13. If you need to support earlier versions of iOS, you have to place this in an if #available(iOS 13, *) statement.