I want to convert a CGPoint from my UIView to UIWindow coordinates and have realized that UIApplication keyWindow is always nil; why is this?
I have tried the convertPoint:toView:
method from UIView.
Please see this sample code I tried in the view controller in a template of Xcode (View application):
- (void)viewDidLoad {
[super viewDidLoad];
UIView *test = [[UIView alloc] initWithFrame:CGRectMake(40,40,250,250)];
[test setBackgroundColor:[UIColor redColor]];
[self.view addSubview:test];
CGPoint p = CGPointMake(100, 100);
CGPoint np;
np = [test convertPoint:p toView:[[UIApplication sharedApplication] keyWindow]];
NSLog(@"p:%@ np:%@", NSStringFromCGPoint(p), NSStringFromCGPoint(np));
AppDelegate *appDel = (AppDelegate *)[UIApplication sharedApplication].delegate;
np = [test convertPoint:p toView:[appDel window]];
NSLog(@"p:%@ np:%@", NSStringFromCGPoint(p), NSStringFromCGPoint(np));
np = [test convertPoint:p toView:nil];
NSLog(@"p:%@ np:%@", NSStringFromCGPoint(p), NSStringFromCGPoint(np));
[test release];
if(![[UIApplication sharedApplication] keyWindow])
NSLog(@"window was nil");
}
and I get:
p:{100, 100} np:{100, 100}
p:{100, 100} np:{140, 160}
p:{100, 100} np:{100, 100}
window was nil
I can convert it but only when I access the window through the app delegate. And not UIApplication. According to the documentation, keyWindow should work here, but is nil. Why is this?
This code was executed before [window makeKeyAndVisible];
which is inside the app delegate.
So, no wonder why keyWindow
was nil
yet.