Cordova - Implementing the Privacy Screen functionality with the ASWebAuthenticationSession usage - objective-c

Question

I'm adding the privacy screen functionality to the hybrid Cordova app via a plugin and following the approach adviced by apple.
Though it leads to unexpected issues when I open ASWebAuthenticationSession window I use for the OAuth authentication. What happens is, when system dialogue appears with a text "Your app wants to use xxx for Sign In", it makes the app to lose a focus and the privacy screen appears behind the overlay. After I choose "Yes", the app gains focus back and the code removing the privacy screen fires, the same code also closes the freshly opened ASWebAuthenticationSession window.
The code in PrivacyScreenPlugin.m:
UIViewController *blankViewController;
#interface PrivacyScreenPlugin ()
#end
#implementation PrivacyScreenPlugin
- (void)pluginInitialize
{
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(onAppDidBecomeActive:) name:UIApplicationDidBecomeActiveNotification object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(onPageDidLoad) name:CDVPageDidLoadNotification object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(onAppWillResignActive:) name:UIApplicationWillResignActiveNotification object:nil];
}
-(UIViewController *)createViewWithGradient {
UIViewController *viewController;
viewController = [UIViewController new];
viewController.modalPresentationStyle = UIModalPresentationOverFullScreen;
return viewController;
}
-(void) applyPrivacyScreen
{
if (blankViewController == NULL) {
blankViewController = [self createViewWithGradient];
}
blankViewController.view.window.hidden = NO;
[self.viewController.view.window.rootViewController presentViewController:blankViewController animated:NO completion:NULL];
}
#pragma mark - Explicit Commands
- (void) hidePrivacyScreen:(CDVInvokedUrlCommand*)command
{
[self removePrivacyScreen];
CDVPluginResult* pluginResult = [CDVPluginResult resultWithStatus:CDVCommandStatus_OK];
[self.commandDelegate sendPluginResult:pluginResult callbackId:command.callbackId];
}
- (void) showPrivacyScreen:(CDVInvokedUrlCommand*)command
{
[self applyPrivacyScreen];
CDVPluginResult* pluginResult = [CDVPluginResult resultWithStatus:CDVCommandStatus_OK];
[self.commandDelegate sendPluginResult:pluginResult callbackId:command.callbackId];
}
#pragma mark - Triggered functions
- (void) onPageDidLoad
{
[self removePrivacyScreen];
}
- (void)onAppDidBecomeActive:(UIApplication *)application
{
[self removePrivacyScreen];
}
- (void)onAppWillResignActive:(UIApplication *)application
{
[self applyPrivacyScreen];
}
#pragma mark - Helper functions
-(void) removePrivacyScreen
{
[self.viewController dismissViewControllerAnimated:NO completion:nil];
}
#end
So far I got that issue is related to the way view is dismissed, namely dismissViewControllerAnimated which dismisses the stack of modal windows:
[self.viewController dismissViewControllerAnimated:NO completion:nil];
Can it be helped or worked around? Maybe instead of removing a security screen, it can be hidden? Or is there a different way to draw the overlay which is free of the issue?
P.S. I tried to listen to UIApplicationDidEnterBackgroundNotification event, but it's not what I want. I'd like the app screen to be covered as soon as it's sent to the list of apps (via a double tap on the home button or long swipe).

Answer 1

To accomplish it, it's needed to render the privacy screen in a subview, instead of a modal view. It enables to hide/show a privacy screen view instead of adding/removing it:
-(void) removePrivacyScreen
{
blankViewController.view.hidden=YES;
}
-(void) applyPrivacyScreen
{
if (blankViewController == NULL) {
blankViewController = [self createViewWithGradient];
}
blankViewController.view.hidden = NO;
[self.viewController.view.window addSubview:blankViewController.view];
}