How to add UIView on the top of all views?

Question

I have such code:

@interface Alert : UIView 
{

}
/*
- (void) initWithTitle:(NSString*)title message:(NSString*)message cancelButtonTitle:(NSString*)cancelButtonTitle otherButtonTitles:(NSString*)buttonTitle,... delegate:(id)delegate;
*/
@end


@implementation Alert

- (void) drawRect:(CGRect)rect 
{
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextClearRect(context, rect); // Очистим context

    CGContextSetRGBFillColor(context, 255, 0, 0, 1);
    CGContextFillRect(context, CGRectMake(20, 20, 100, 100));
}

- (void) show
{
    self.center = [[[UIApplication sharedApplication] keyWindow] center];
    [[[UIApplication sharedApplication] keyWindow] addSubview:self];
    [[[UIApplication sharedApplication] keyWindow] bringSubviewToFront:self];
}

Then I'm use it so:

- (void)viewDidLoad
{
    [super viewDidLoad];
     Alert * alert = [[Alert alloc] initWithFrame:CGRectMake(0, 0, 100, 100)];
    [alert show];
    [alert release];
}

But it doesn't work(I want to see Alert above all other views). Could you help me?

Solution 1

The recommended solutions which handle device orientation properly are

• pod AGWindowView It will automatically deal with any rotation and framechanges so you won't have to worry about that.
• read and follow the official post https://developer.apple.com/library/content/qa/qa1688/_index.html

• Add your view to the first subview, instead of adding it to the window
  

  UIWindow* window = [UIApplication sharedApplication].keyWindow;
  if (!window) 
      window = [[UIApplication sharedApplication].windows objectAtIndex:0];
  [[[window subviews] objectAtIndex:0] addSubview:myView];
  

You can also add it to the window. It will not handle device orientation, though.

let window = UIApplication.sharedApplication().keyWindow!
let view = UIView(frame: CGRect(x: window.frame.origin.x, y: window.frame.origin.y, width: window.frame.width, height: window.frame.height))
window.addSubview(v);
view.backgroundColor = UIColor.blackColor()

Solution 2

There is also one other method

Add the following method in the view will appear to add every time push/pop view controller

-(void)viewWillAppear:(BOOL)animated
{
     [super viewWillAppear:animated];

     [[[UIApplication sharedApplication] keyWindow] addSubview:<yourViewObject>];
}

And for remove this view in next class add the following lines of code

-(void)viewWillDisappear:(BOOL)animated
{
    [super viewWillDisappear:animated];

    [<yourViewObject> removeFromSuperview];
 }

Solution 3

@MaciekWrocław answere swift version

Swift2

 var appDelegate = (UIApplication.sharedApplication().delegate! as! AppDelegate)
 var backgrView = UIView(frame: CGRectMake(0, 0, UIScreen.mainScreen().bounds.size.width, UIScreen.mainScreen().bounds.size.height))
 backgrView.backgroundColor = UIColor.redColor()
 backgrView.alpha = 0.6
 window?.addSubview(backgrView)

swift3

     var appDelegate: AppDelegate? = (UIApplication.shared.delegate as? AppDelegate)
     var backgrView = UIView(frame: CGRect(x: CGFloat(0), y: CGFloat(0), width: CGFloat(UIScreen.main.bounds.size.width), height: CGFloat(UIScreen.main.bounds.size.height)))
     backgrView.backgroundColor = UIColor.red
     backgrView.alpha = 0.6
     window?.addSubview(backgrView)

and i am doing for my application about net connection in the AppDelegate:

func checkReachabilityUpdateUI() -> Int {

    let remoteHostStatus = self.reachability?.currentReachabilityStatus()


    if remoteHostStatus?.rawValue == 0 {
        let backgrView = UIView(frame: CGRectMake(0, 60, UIScreen.mainScreen().bounds.size.width, 44))

        let statusMessage = UILabel(frame: CGRect(x: 0, y: 0, width: UIScreen.mainScreen().bounds.size.width, height: 44))

        statusMessage.text = "No internet Connection"
        statusMessage.textAlignment = .Center
        statusMessage.textColor =  UIColor.whiteColor()

        backgrView.backgroundColor = UIColor.redColor()

        backgrView.addSubview(statusMessage)

        backgrView.tag = 100

        window?.addSubview(backgrView)

        return (remoteHostStatus?.rawValue)!

    }
    else {

        if let viewWithTag = self.window!.viewWithTag(100) {
            print("Tag 100")
            viewWithTag.removeFromSuperview()
        }
        else {
            print("tag not found")
        }

       return (remoteHostStatus?.rawValue)!

    }

}