KeyWindow add subView, did not shows in the front - ios

Question

I use keyWindow to add a subView, it add success but did not shows in the front of the screen hierarchy.
The deep gray view is my added view:
My code is:
#interface ViewController ()
{
LMLUpspringView *pop_v;
}
#end
#implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
pop_v = [[LMLUpspringView alloc] initWithFrame:CGRectMake(0, 0, self.view.bounds.size.width, self.view.bounds.size.height)];
UIWindow *keywindow = [[[UIApplication sharedApplication] delegate] window];
[keywindow addSubview:pop_v];
//[keywindow bringSubviewToFront:pop_v];
//[self.view addSubview:pop_v];
}
I have tried use [keywindow bringSubviewToFront:pop_v] to bring to front.But do not work.
And if I use [self.view addSubview:pop_v], it shows in the front.

Answer 1

You run into this issue, is caused by you do not know the difference between the viewDidLoad method and the viewDidAppear: method.
viewWillAppear:
Called before the view is added to the windows’ view hierarchy
viewDidAppear:
Called after the view is added to the view hierarchy
The controller's view add to the window's view hierarchy is betweenviewWillAppear: and viewDidAppear:, the viewDidLoad is in front of viewWillAppear:, so you can not do that. you should in viewDidAppear: add your view.

Answer 2

You can solve this problem using appdelegate's Windows :
AppDelegate *appDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
[appDelegate.window addSubview:pop_v]

Answer 3

Use this:
#interface ViewController ()
{
LMLUpspringView *pop_v;
}
#end
#implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
pop_v = [[LMLUpspringView alloc] initWithFrame:CGRectMake(0, 0, self.view.bounds.size.width, self.view.bounds.size.height)];
UIWindow *keywindow = [[UIApplication sharedApplication] keyWindow];
[keywindow addSubview:pop_v];
//[keywindow bringSubviewToFront:pop_v];
//[self.view addSubview:pop_v];
}