I hope that you all know about it, iOS takes screenshot before your application goes to background.
I got it from official document.
Remove sensitive information from views before moving to the background: When an app transitions to the background, the system takes a snapshot of the app’s main window, which it then presents briefly when transitioning your app back to the foreground. Before returning from your applicationDidEnterBackground: method, you should hide or obscure passwords and other sensitive personal information that might be captured as part of the snapshot.
So, Here We can hide our "sensitive personal information" and the system takes a snapshot of the app’s main window, so we can not change its feature.
But I want to know..
1) If in my application I'm at 4th View, and my app goes to background then system takes screen shot of which view/page? first one (start up view of apps?) or 4th view/page of the app ?? (here is little confusion for me).
2) Can we fire any action when system is taking screenshot or any notification is available that will inform us of system taking screenshot ??
3) I just want to know, is it possible to take screen shot (programmatically) before my application launch ?? If YES then give me suggestion for how to do it. And if NO then where/when I'm able to take screenshot (I mean at which minimum stage of application we'll be able to take screenshot ?) ?
It will take a screen short of the top most view, actually it is taking a screen shot of the window which is displaying your app.
No there is no notification that the screen shot is going to or being taken. You should just handle the handle it in the applicationDidEnterBackground; method. Just a stated in the documentation
No this is not possible, how do you want to execute any code before you app is running? The OS will make the screen shot, just be sure to have everything hidden in the applicationDidEnterBackground;. The minimum state is that your app is up and running.
What I've done is on of my apps is as soon as my app gets pushed to the background place an extra view on my UIWindow. Thus when the screen shot is made this view is captured.
1) There is just one screen. The screenshot is taken of that screen. In your model case that should be the 4th view controller's view. However, it is quite possible that your 4th controller's view does not cover all of the screen or has transparent elements. In that case parts of the 3rd or even 2nd and 1st view controller's view are part of the screen.
It is a screenshot not a view controller shot or anything.
2) You understood the documentation all right. The screenshot is taken after you returned from applicationDidEnterBackground. There will be no further dokumentation.
3) No, you cannot execute any code before your app is invoked. However, I have the feeling that you are looking for something different than you asked literally.
For some other reason I have executed a small program in the simulator by implementing the main function only even without calling UIApplicatoinMain. This is the first point in time where code from your app may be executed, although that would not be exactly "out of the book". If I remember right, the screen was blank/black at that point in time. So if you are asking for a way of creating screenshots of other apps, this is not the way to go forward.
It is not taking a screenshot quite like a user pressing buttons.
This functionality is related to state restoration. When the application goes to the background it flattens the view hierarchy for each screen into a screenshot used for the task manager. If you are opted into state restoration it will also persist the state of the user interface. This means that a person can bring the application back from the background state and potentially see sensitive information that way as well, which may be something you need to handle.
Preventing information from being included in the state screenshot is covered in Tech QA 1838.
1) I'm pretty sure the system will take the snapshot of the current visible view, so the last one on the stack, not the first one
2) Also, there will probably be a Notification to let us know that the system is going to take a screenshot (otherwise how can we hide sensible information? :) ), but I'm afraid we're currently under NDA I guess?
3) What do you mean "take screenshot before my application launch"? Your code starts executing when your application launches, so this question almost makes no sense :-/
You can anywhere in your application take a snapshot of the screen, however, and there are many stackoverflow posts for that
Related
I would like to know when the screen is being drawn on iOS. In particular, I'd like to know if there are any visible changes being drawn on screen. This can be handy to know how long a page took to render, for example (assuming that the user is not interacting with the page). I would like to be able to capture this information in a regular production build, not in a developer build. And I'd like this to be a general solution applicable to most any page in my app, not just a specific page.
For example, I have a page that 1) asynchronously queries an API for data, 2) displays that data in a UITableView where some of the entries may be offscreen, and then 3) asynchronously downloads the images for each of the visible items on the screen. I want to get callbacks when the UITableView is rendered and when all of the images are rendered. The total time to render the page can be determined by looking at the timestamp of the last call to the callback (again, assuming no user interaction).
On Android, this is fairly simple. You can use ViewTreeObserver.addPreDrawListener to get a callback whenever the screen is being drawn. If there's no visible change to the screen, the callback is not called.
On iOS, it looks like CADisplayLink might potentially serve a similar purpose. However, when I hook up my CADisplayLink, it appears to be called over-and-over forever, whether or not there are visible changes on the screen.
Is there a way to know when there are visible changes to the screen being drawn in iOS?
In iOS 9 Apple made it impossible to get access to things drawn onto the screen outside of your app. Prior, it was possible to use an API called IOSurface to do it, but Apple closed it down in iOS 9. (To prevent apps from snooping on each other.)
So if you're talking about ANYTHING being drawn to the screen the answer is no. If you're looking for changes within your app there's probably a way to do it.
I'm making an app with a different screen for its first run. Once it has completed its first run, this screen is never shown again. The issue I have is that my launch image is built to look like the view that the user sees every other time they run the app, so at first run the loading screen looks weird. Is there any way to have one loading screen for first run and one loading screen for other runs? Thanks
You cannot have multiple or dynamic launch images. Even with the new storyboard/nib launch files, they are still quite static.
Make sure to open an enhancement report with Apple, requesting this feature.
In the meantime, consider a slight change of your flow to first display the initial view, and have an animation to display your first-launch view. This way, the transition will be smoother and more natural to your users.
As the application loads, I want to make an image load at the same time, for example, a line would elongate form either side as the application loads, and when it has finished, the line would have reached its maximum length. I have seen this in a few websites, like rime arodaky for example, but I want to this for an iOS application. I have searched on Google but couldn't find anything!
Does anyone know how to do this?
The launch process if we REALY simplify it to accommodate your question, can be split into two parts.
The first part you do not have any control over, and during which a launch image is shown.and it ends with a delegate call-back on the application delegate called
applicationDidFinishLaunchingWithOptions
The second part is you might have some application specific behaviour which requires no activity from the user but you app still isn't interactive.
You need to implement such a progress bar yourself. There is no built in support for this in any of the app templates in Xcode.
You can only do what you want during this second phase. But you have absolutely no control over the first phase, except for that static non-animated launch image.
I think you can just add a photo as a launch image, launch image is just an image.Then you can add the animation when your first view controller appears.You can fake it this way.
Basically, I want my app could change its splash screen by app settings. Settings are saved in plist file.
Actually it's about different language, I want enable my user to choose my app language, even if it's different with the system preferred language.
Is it possible? I searched some answer, suggesting to use another view controller to simulate as splash screen, but my splash screen itself will take some to to load my app, not by my pause. So should I display nothing in the real splash screen?
I wonder if there is a way to change the splash screen by some conditions.
Thanks a guys.
The splash screen will show only for as long as it takes for the appDidFinishLoading method to return YES. One possible solution is for you to have a really simple (not localizable) splash screen and to basically do nothing in this method and return YES straight away.
You can then use an actual view controller as your splash screen that is dynamically initialized and actually does any initialization your app may need in the viewDidAppear method. Once the initialization is done, you can then proceed and show what would normally be your root view controller.
EDIT:
You should also consider, however, that splash screens are not intended to provide any kind of content to the user, as pointed out in this answer.
Apple does not provide a way to do that, as that would involve either modifying the Info.plist or modifying the splash images, both of which would in turn spoil your code signature. It would also open a very ugly can of worms, so modifying Info.plist will probably never be allowed which in turn means you will not be able to change the splash screen dynamically unless Apple adds explicit support for that via some other means. But right now, you're out of luck, I'm afraid.
How important is it to add Launch Images to an iOS application? I assume that these are like a cached file to show on the screen while the application is getting setup, when there might otherwise be nothing to show until it is fully running. Is this right?
If so, what should a launch image be if your app might start in different states, or does this not effect return to foreground when multitasking? If it is only for the very first initial launch of the app, then the launch image should just be the same as whatever graphic normally appears when you first start the app, right?
Apple must not care too much about whether your app actually includes these, since mine never have.
Note: as Zev mentions below, the Apple HIG recommendation has changed since I originally answered this question. Apple now recommends that you take all of the static elements of your first screen and make that into your default or launch page. All dynamic elements are to be removed, to give the impression that your app is going through an initialization process -- which in some cases may mean that your default screen is simply a background from your app. Thanks to Zev Eisenberg for pointing that out, "splash" pages are not recommended.
The launch image will show while your app is initializing, it's a good idea to have one. If you don't have one the user is likely to stare at a blank screen while waiting for your app to load. I believe the recommendation is to use an image that looks like the first page of your app. Here is the reference:
http://developer.apple.com/library/ios/#documentation/UserExperience/Conceptual/MobileHIG/IconsImages/IconsImages.html#//apple_ref/doc/uid/TP40006556-CH14-SW5
how about if app is starting immediately and no time passed ?
what if you see (or cannot see) for a 0.1 sec launch image ?
would it be still useful to have two images in main bundle that will never be seen or used ?