How to prevent a UIWindow to be a key window? - ios

Question

When I show an alert with UIAlertController, the alert itself presented in a new window. (for now at least) And when the alert window dismisses, system seems to set a random window key-window.
I am presenting a new "banner" window to render some banners over status-bar (AppStore compatibility is out of topic here), and usually, this "banner" window becomes next key window, and causes many problems on user input and first responder management.
So, I want to prevent this "banner" window to become a key window, but I cannot figure out how. For now, as a workaround, I am just re-setting my main window to be a key window again as soon as that "banner" window becomes key window. But it doesn't feel really good.
How can I prevent a window to become a key window?

Answer 1

As a workaround, we can set main window key again as soon as the "banner" window becomes a key like this.
class BannerWindow: UIWindow {
weak var mainWindow: UIWindow?
override func becomeKeyWindow() {
super.becomeKeyWindow()
mainWindow?.makeKeyWindow()
}
}

Answer 2

Faced with this too. It seems that it's enough to just make:
class BannerWindow: UIWindow {
override func makeKey() {
// Do nothing
}
}
This way you don't need to keep a reference to a previous keyWindow, which is especially cool if it might get changed.
For Objective-C it's:
#implementation BannerWindow
- (void)makeKeyWindow {
// Do nothing
}
#end

Answer 3

I've been trying to solve this problem for years. I finally reported a Radar for it: http://www.openradar.me/30064691
My workaround looks something like this:
// a UIWindow subclass that I use for my overlay windows
#implementation GFStatusLevelWindow
...
#pragma mark - Never become key
// http://www.openradar.me/30064691
// these don't actually help
- (BOOL)canBecomeFirstResponder
{
return NO;
}
- (BOOL)becomeFirstResponder
{
return NO;
}
- (void)becomeKeyWindow
{
LookbackStatusWindowBecameKey(self, #"become key window");
[[self class] findAndSetSuitableKeyWindow];
}
- (void)makeKeyWindow
{
LookbackStatusWindowBecameKey(self, #"make key window");
}
- (void)makeKeyAndVisible
{
LookbackStatusWindowBecameKey(self, #"make key and visible window");
}
#pragma mark - Private API overrides for status bar appearance
// http://www.openradar.me/15573442
- (BOOL)_canAffectStatusBarAppearance
{
return NO;
}
#pragma mark - Finding better key windows
static BOOL IsAllowedKeyWindow(UIWindow *window)
{
NSString *className = [[window class] description];
if([className isEqual:#"_GFRecordingIndicatorWindow"])
return NO;
if([className isEqual:#"UIRemoteKeyboardWindow"])
return NO;
if([window isKindOfClass:[GFStatusLevelWindow class]])
return NO;
return YES;
}
void LookbackStatusWindowBecameKey(GFStatusLevelWindow *self, NSString *where)
{
GFLog(GFError, #"This window should never be key window!! %# when in %#", self, where);
GFLog(GFError, #"To developer of %#: This is likely a bug in UIKit. If you can get a stack trace at this point (by setting a breakpoint at LookbackStatusWindowBecameKey) and sending that stack trace to nevyn#lookback.io or support#lookback.io, I will report it to Apple, and there will be rainbows, unicorns and a happier world for all :) thanks!", [[NSBundle mainBundle] gf_displayName]);
}
+ (UIWindow*)suitableWindowToMakeKeyExcluding:(UIWindow*)notThis
{
NSArray *windows = [UIApplication sharedApplication].windows;
NSInteger index = windows.count-1;
UIWindow *nextWindow = [windows objectAtIndex:index];
while((!IsAllowedKeyWindow(nextWindow) || nextWindow == notThis) && index >= 0) {
nextWindow = windows[--index];
}
return nextWindow;
}
+ (UIWindow*)findAndSetSuitableKeyWindow
{
UIWindow *nextWindow = [[self class] suitableWindowToMakeKeyExcluding:nil];
GFLog(GFError, #"Choosing this as key window instead: %#", nextWindow);
[nextWindow makeKeyWindow];
return nextWindow;
}