Overlay an image when app is inactive - ios

Question

I'm using these code to
1) overlay an image when the app is inactive (double tap the home button twice).
2) Remove the image when the app is active (reopen the app)
In appdelegate.h file:
#property (nonatomic, strong) UIImageView *splashScreenImageView;
In appdelegate.m file:
- (void)applicationWillResignActive:(UIApplication *)application
{
UIImage *splashScreenImage = [UIImage imageNamed:#"BackgroundScreenCaching"];
_splashScreenImageView = [[UIImageView alloc] initWithImage:splashScreenImage];
[self.window addSubview:_splashScreenImageView];
}
- (void)applicationDidBecomeActive:(UIApplication *)application
{
if(_splashScreenImageView != nil) {
[_splashScreenImageView removeFromSuperview];
_splashScreenImageView = nil;
}
}
Problem:
However, SOMETIME when pressing the home button twice, the iOS still caches the app screen with sensitive information instead of the overlay image in iOS 11. Tested no issue in iOS10.
Updated
Issue still persist after changing to this:
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
BOOL result = [super application:application didFinishLaunchingWithOptions:launchOptions];
...
UIImage *splashScreenImage = [UIImage imageNamed:#"BackgroundScreenCaching"];
_splashScreenImageView = [[UIImageView alloc] initWithImage:splashScreenImage];
[_splashScreenImageView setFrame:self.window.bounds];
return result;
}
- (void)applicationDidBecomeActive:(UIApplication *)application
{
// Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
if(_splashScreenImageView != nil) {
[_splashScreenImageView removeFromSuperview];
}
}
- (void)applicationWillResignActive:(UIApplication *)application
{
// Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.
// Use this method to pause ongoing tasks, disable timers, and throttle down OpenGL ES frame rates. Games should use this method to pause the game.
[self.window addSubview:_splashScreenImageView];
}

Answer 1

I found a tricky way and it works with iOS 11 or iOS 10.
In Appdelegate.m file:
#implementation AppDelegate {
UIImageView *splashScreenImageView;
UIViewController *viewController;
}
Add this code in didFinishLaunchingWithOptions to set image and update frame
splashScreenImageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, [UIScreen mainScreen].bounds.size.width, [UIScreen mainScreen].bounds.size.height)];
splashScreenImageView.image = [UIImage imageNamed:#"BackgroundScreenCaching"];
Implement this method for getting topmost view controller
- (UIViewController *)topViewController{
return [self topViewController:[UIApplicationsharedApplication].keyWindow.rootViewController];
}
- (UIViewController *)topViewController:(UIViewController *)rootViewController
{
if (rootViewController.presentedViewController == nil) {
return rootViewController;
}
if ([rootViewController.presentedViewController isKindOfClass:[UINavigationController class]]) {
UINavigationController *navigationController = (UINavigationController *)rootViewController.presentedViewController;
UIViewController *lastViewController = [[navigationController viewControllers] lastObject];
return [self topViewController:lastViewController];
}
UIViewController *presentedViewController = (UIViewController *)rootViewController.presentedViewController;
return [self topViewController:presentedViewController];
}
Now in applicationWillResignActive method first get the top viewController and set splashScreenImageView on that view as subview
- (void)applicationWillResignActive:(UIApplication *)application {
viewController = [self topViewController];
[viewController.view addSubview:splashScreenImageView];
}
Finally in applicationDidBecomeActive when app open first remove the overlay image and open app
- (void)applicationDidBecomeActive:(UIApplication *)application {
[splashScreenImageView removeFromSuperview];
}
This tricks will work.

Answer 2

Your code should work fine ,
May be your app didn't get time to alloc your imageView on time when applicationWillResignActive called
and you are re-creating object every time . with [UIImageView alloc] initWithImage
So my suggestion is put this code in didFinishLaunching
UIImage *splashScreenImage = [UIImage imageNamed:#"BackgroundScreenCaching"];
_splashScreenImageView = [[UIImageView alloc] initWithImage:splashScreenImage];
and just add subview on UIWindow and remove it when applicationDidBecomeActive
Also bring _splashScreenImageView to front !!
Hope it may solve your problem
Good Luck
UPDATE
to add in main queue
dispatch_async(dispatch_get_main_queue(), ^{
[self.window addSubview:_splashScreenImageView];
[self.window bringSubviewToFront:_splashScreenImageView];
});
to remove in main queue
dispatch_async(dispatch_get_main_queue(), ^{
[_splashScreenImageView removeFromSuperview];
});
UPDATE 2
according to https://developer.apple.com/library/content/qa/qa1838/_index.html
and
https://developer.apple.com/library/content/documentation/iPhone/Conceptual/iPhoneOSProgrammingGuide/StrategiesforHandlingAppStateTransitions/StrategiesforHandlingAppStateTransitions.html
Prepare for the App Snapshot
Shortly after an app delegate’s applicationDidEnterBackground: method returns, the system takes a snapshot of the app’s windows. Similarly, when an app is woken up to perform background tasks, the system may take a new snapshot to reflect any relevant changes. For example, when an app is woken to process downloaded items, the system takes a new snapshot so that can reflect any changes caused by the incorporation of the items. The system uses these snapshot images in the multitasking UI to show the state of your app.
If you make changes to your views upon entering the background, you can call the snapshotViewAfterScreenUpdates: method of your main view to force those changes to be rendered. Calling the setNeedsDisplay method on a view is ineffective for snapshots because the snapshot is taken before the next drawing cycle, thus preventing any changes from being rendered. Calling the snapshotViewAfterScreenUpdates: method with a value of YES forces an immediate update to the underlying buffers that the snapshot machinery uses.
Try to present temp view controller applicationDidEnterBackground as done in demo of Apple

Answer 3

I fix your bug like this:
#import "AppDelegate.h"
#interface AppDelegate () {
UIImageView *test ;
}
#end
#implementation AppDelegate
- (void)applicationDidEnterBackground:(UIApplication *)application {
UIImage *splashScreenImage = [UIImage imageNamed:#"ic_target_black"];
test = [[UIImageView alloc] initWithImage:splashScreenImage];
[self.window addSubview:test];
}
- (void)applicationDidBecomeActive:(UIApplication *)application {
if (test) {
[test removeFromSuperview];
}
}
#end

Answer 4

Do this two simple steps to set your black image when double click the app and it is in recent apps list. And remove the black image when the application becomes active.
#interface AppDelegate (){
UIImageView *test ;
}
- (void)applicationWillResignActive:(UIApplication *)application {
UIImage *splashScreenImage = [UIImage imageNamed:#"ss.png"];
test = [[UIImageView alloc] initWithImage:splashScreenImage];
[self.window addSubview:test];
}
- (void)applicationDidBecomeActive:(UIApplication *)application {
if (test) {
[test removeFromSuperview];
}
}