When is ios auto screen capture taken?

Question

I am trying to change the screen shot that is automatically captured by iOS when the app enters the background.

However I am not entirely sure exactly when this screenshot is taken.

For example:

If you pull down the notification bar while in the app the following method is called:

- (void) applicationWillResignActive:(UIApplication *) application {
}

Also if you double tap the home button while in the app the same method is called. In addition if an alert view is show 'applicationWillResignActive' is called.

But in both of these cases

- (void) applicationDidEnterBackground:(UIApplication *) application {
}

is not called.

So my question is, is there a screenshot captured after the call to applicationWillResignActive even if the application does not enter the background? Or does iOS only capture a screenshot after applicationDidEnterBackground?

Answer 1

Look at official doc - "Preventing Sensitive Information From Appearing In The Task Switcher".

It says applicationDidEnterBackground: should be used for the said purpose.

Answer 2

you can look over here, in summary, change the view before return from applicationDidEnterBackground:

Answer 3

Yes.

- (void) applicationWillResignActive:(UIApplication *) application { }

is called when you pull down the notification bar or even when you double click the home button. You have to do something here to prevent your sensitive information to be captured by the OS. One workaround might be:

1. Set a blurry screen overlay before the app goes in the background
2. Once the app becomes active remove this overlay

Something like this:

-(void)applicationWillResignActive:(UIApplication *)application
{
    imageView = [[UIImageView alloc]initWithFrame:[self.window frame]];
    [imageView setImage:[UIImage imageNamed:@"blurryImage.png"]];
    [self.window addSubview:imageView];
}

And then remove this overlay before the application enters foreground:

- (void)applicationDidBecomeActive:(UIApplication *)application
{
    if(imageView != nil) {
        [imageView removeFromSuperview];
        imageView = nil;
    }
}