Display a view or splash screen before applicationDidEnterBackground (to avoid active view screenshot)

问题

I have confidential informations in my app, so I would like to hide them with a splash screen when the app is about to be moved to background.

I do run the app on iOS6 and further.

I tried to display the view in applicationWillResignActive but the problem is it display the splash screen even when user swipe control panel for example. I want it to show only when the app is moved to background.

I tried to displayed my splashScreen in applicationDidEnterBackground but it takes the screenShot before so informations are displayed at restoration during the animation.

Here the spirit of what I want :

- (void)applicationDidEnterBackground:(UIApplication *)application {
    [_window addSubview:__splashController.view];
}

回答1:

I think the problem is that you are testing in simulator. On device, it should work fine.

I tested this and it worked. Add an imageview with your splash image when app enters in background -

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

        UIImageView *imageView = [[UIImageView alloc] initWithFrame:self.window.bounds];

        imageView.tag = 101;    // Give some decent tagvalue or keep a reference of imageView in self
    //    imageView.backgroundColor = [UIColor redColor];
        [imageView setImage:[UIImage imageNamed:@"Default.png"]];   // assuming Default.png is your splash image's name

        [UIApplication.sharedApplication.keyWindow.subviews.lastObject addSubview:imageView];
}

And when app comes back in foreground -

- (void)applicationWillEnterForeground:(UIApplication *)application
{
    UIImageView *imageView = (UIImageView *)[UIApplication.sharedApplication.keyWindow.subviews.lastObject viewWithTag:101];   // search by the same tag value
    [imageView removeFromSuperview];

}

NOTE - On simulator (iOS 7.0), the added subview is not show when you check by pressing home button twice (Cmd + H), but on device it works as expected (like paypal, BofA apps)

EDIT: (Additional info)

In addition to obscuring/replacing sensitive information by adding subview / blur as explained above, iOS 7 provides you ability to ignore the screen snapshot via ignoreSnapshotOnNextApplicationLaunch of UIApplication inside applicationWillResignActive or applicationDidEnterBackground.

UIApplication.h

// Indicate the application should not use the snapshot on next launch, even if there is a valid state restoration archive.
// This should only be called from methods invoked from State Preservation, else it is ignored.
- (void)ignoreSnapshotOnNextApplicationLaunch NS_AVAILABLE_IOS(7_0);

Also, allowScreenShot flag can be explored in Restrictions Payload.

回答2:

Swift 3.0 Answer for those who are to lazy to translate.

func applicationDidEnterBackground(_ application: UIApplication) {

    let imageView = UIImageView(frame: self.window!.bounds)
    imageView.tag = 101
    imageView.image = ...

    UIApplication.shared.keyWindow?.subviews.last?.addSubview(imageView)
 }

func applicationWillEnterForeground(_ application: UIApplication) {

    if let imageView : UIImageView = UIApplication.shared.keyWindow?.subviews.last?.viewWithTag(101) as? UIImageView {
        imageView.removeFromSuperview()
    }

}

回答3:

Had the same issue, essentially I was using applicationDidEnterBackground to show a UIWindow on top of the content, but in iOS8 it didn't work as it did in iOS7.

The solution I found was to create the UIWindow in applicationWillResignActive but make it hidden securityWindow.hidden = YES; and then in applicationDidEnterBackground all I would do would be to change securityWindow.hidden = NO.

This seems to work exactly as iOS7 obscuring the content when multi tasking without affecting the view when using NotificationCenter or ControlPanel.

回答4:

Need to write the code as follows:

-(void)applicationWillResignActive:(UIApplication *)application
{
    imageView = [[UIImageView alloc]initWithFrame:[self.window frame]];
    [imageView setImage:[UIImage imageNamed:@"Portrait(768x1024).png"]];
    [self.window addSubview:imageView];
}

Here to remove the imageview:

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

It is working and properly tested.

回答5:

Don't know why, but none of the methods described here worked for me. I was simply trying to cover the screen for security reasons. So, what helped was a Technical Q&A from Apple: https://developer.apple.com/library/ios/qa/qa1838/_index.html

I guess the main difference is using a UIViewController? Anyways, the following code works perfectly for me on IOS 9.1:

- (void)applicationDidEnterBackground:(UIApplication *)application
{     
    UIViewController *blankViewController = [UIViewController new];
    blankViewController.view.backgroundColor = [UIColor blackColor];

    [self.window.rootViewController presentViewController:blankViewController animated:NO completion:NULL];
}

- (void)applicationWillEnterForeground:(UIApplication *)application
{
    [self.window.rootViewController dismissViewControllerAnimated:NO completion:NO];
}

回答6:

@interface MyAppDelegate ()
@property (strong, nonatomic) MySplashView *splashView;
@end
@implementation MyAppDelegate
- (void)applicationWillResignActive:(UIApplication *)application {
    // hide keyboard and show a splash view
    [self.window endEditing:YES];
    MySplashView *splashView = [[MySplashView alloc] initWithFrame:self.window.bounds];
    [self.window addSubview:splashView];
    self.splashView = splashView;
}
- (void)applicationDidBecomeActive:(UIApplication *)application {
    // remove the splash view
    if (self.splashView) {
        [self.splashView removeFromSuperview];
        self.splashView = nil;
    }
}
@end

回答7:

This fixed it for me, sorry this is for Xamarin.Forms but you should get the idea. You need to call UIView.SnapshotView(true) in xamarin or UIView snapshotViewAfterScreenUpdates on iOS. Works in DidEnterBackground on iOS7, and iOS8:

public override void DidEnterBackground(UIApplication uiApplication)
{
    App.Current.MainPage = new DefaultPage();
    **UIApplication.SharedApplication.KeyWindow.SnapshotView(true);**
    base.DidEnterBackground(uiApplication);
}

回答8:

I think this will help for Swift 3.0

func applicationWillResignActive(_ application: UIApplication) {

        let imageView = UIImageView(frame: self.window!.bounds)
        imageView.tag = 101
        imageView.backgroundColor = UIColor.white
        imageView.contentMode = .center
        imageView.image = #image#
        UIApplication.shared.keyWindow?.subviews.last?.addSubview(imageView)

    }

func applicationWillEnterForeground(_ application: UIApplication) {
        ReachabilityManager.shared.stopMonitoring()
        if let imageView : UIImageView = UIApplication.shared.keyWindow?.subviews.last?.viewWithTag(101) as? UIImageView {
            imageView.removeFromSuperview()
        }
    }

来源：https://stackoverflow.com/questions/19792850/display-a-view-or-splash-screen-before-applicationdidenterbackground-to-avoid-a