This question already has answers here:
What is the AppDelegate for and how do I know when to use it?
(4 answers)
Closed 8 years ago.
I have an android background . I want to learn XCode . Now i want to understand what does the Appdelegate.h and Appdelegate.m do? As in Android Manifest.xml is the mainFile which launches other Activities . permissions, feature ,broadcast service etc are written in it.
Now can some one explain me the importance of AppDelegate file and explain its component and benefits ?
And where to include permission or Service or BroadCast in app.
I have created an app in Android . Now i am creating it in IPhone which requires permission and services...
Thanks in Advance..
Edit..
According to my study and knowledge. AppDelegate is a controller, it doesn't visually present data (a view) nor does it represent the actual data (a model) but it does determine what view controllers to show etc and manage other views (status bar etc) at the start of the application .it is the launcher class where the first class launches . it consist of some predefined function didFinishLauching and other functions. Is there any detail explanation.
From:
https://developer.apple.com/library/ios/documentation/iphone/conceptual/iphoneosprogrammingguide/AppArchitecture/AppArchitecture.html
The app delegate is a custom object created at app launch time,
usually by the UIApplicationMain function. The primary job of this
object is to handle state transitions within the app. For example,
this object is responsible for launch-time initialization and handling
transitions to and from the background. For information about how you
use the app delegate to manage state transitions, see “Managing App
State Changes.”
In iOS 5 and later, you can use the app delegate to handle other
app-related events. The Xcode project templates declare the app
delegate as a subclass of UIResponder. If the UIApplication object
does not handle an event, it dispatches the event to your app delegate
for processing. For more information about the types of events you can
handle, see UIResponder Class Reference.
Related
I tested:
UIControl().sendAction(#selector(URLSessionTask.suspend), to: UIApplication.shared, for: nil)
which is for putting app on background and it works.
How do I put app back on foreground?
I tried:
UIControl().sendAction(#selector(URLSessionTask.resume), to: UIApplication.shared, for: nil)
But eventually it crashes...
Thank you
Update:
Since you've indicated that you're looking for any technical solution, even those not compatible with the App Store or Apple's terms, this should be possible using the Private API LSApplicationWorkspace: openApplicationWithBundleID. Try something like this:
Create a .h file and set up an interface to the LSApplicationWorkspace class and list the required method. You will need to #import "PrivateHeaders.h" in your bridging header.
//
// PrivateHeaders.h
//
#ifndef PrivateHeaders_h
#define PrivateHeaders_h
#interface LSApplicationWorkspace : NSObject
- (bool)openApplicationWithBundleID:(id)arg1;
#end
#endif /* PrivateHeaders_h */
You should then be able to call this function and pass in the Bundle Identifier of your app as an string.
//
// SomeClass.swift
//
import MobileCoreServices
let workspace = LSApplicationWorkspace()
/**
Launch an App given its bundle identifier
- parameter bundleIdentifier: The bundle identifier of the app to launch
- returns: True if app is launched, otherwise false
*/
func openApp(withBundleIdentifier bundleIdentifier: String) -> Bool {
// Call the Private API LSApplicationWorkspace method
return workspace.openApplication(withBundleID: bundleIdentifier)
}
Original:
What you are doing is likely a violation of the iOS Human Interface Guidelines (although the "Don’t Quit Programmatically" is no longer specifically defined), so as the comments have said, it is not suited to the App Store. Regardless, once your app is suspended in this way, I don't expect that there is a way to resume it programmatically, unless you can hook into a Background Operation to run URLSessionTask.resume, but I have not tested it and am unsure whether it can work.
Apps can be launched (and hence brought into the foreground) programmatically from another app or today extension by using a Custom URL Scheme, or via a Push Notification. It isn't possible to launch the app from the Background Operation via a URL Scheme, since it is part of the UIKit framework, which must be run in the main thread.
In summary, I think your best option is to try to use a Notification. This just means that the user will need to click on the notification to bring your app back into the foreground.
Closing/opening the app should be done explicitly by the user. Any other way of closing or opening the app is not supported by Apple and will be rejected when uploaded to app store. iOS Human Interface Guideline states:
Don’t Quit Programmatically
Never quit an iOS application
programmatically because people tend to interpret this as a crash.
However, if external circumstances prevent your application from
functioning as intended, you need to tell your users about the
situation and explain what they can do about it. Depending on how
severe the application malfunction is, you have two choices.
*Display
an attractive screen that describes the problem and suggests a
correction. A screen provides feedback that reassures usersthat
there’s nothing wrong with your application. It puts usersin control,
letting them decide whether they want to take corrective action and
continue using your application or press the Home button and open a
different application
*If only some of your application's features are
not working, display either a screen or an alert when people activate
the feature. Display the alert only when people try to accessthe
feature that isn’t functioning
Just as a follow up to Jordan's excellent answer I want to give an explanation for why your code works in the first place and why that alone will get your app rejected, even without any functionality to make it active again and bring it to the foreground.
As maddy pointed out in a comment, you're basically calling a method from UIApplication's private API. This works due to the Objective-C runtime's dynamic linking. You might wonder "But I am using Swift, what does that have to do with Objective-C?" The answer lies in #selector mechanism. A Selector is basically just a symbol that the Objective-C runtime looks up in a table to get a method it invokes (for you). This is why it's technically not correct to say you "call a method" when you do something like myObjectInstance.someMethod(). The correct way to phrase that would be to "send a message" to the object, because that's what is happening in the runtime. The target-action mechanism is build around that. The sendAction(_: Selector?, to: Any?) method does the same thing. So in effect your code does the following:
Get the symbol that corresponds to URLSessionTask's suspend() method.
Tell the shared instance of UIApplication to invoke the method that it has for that symbol.
Now usually that would result in a crash with the typical "unknown selector sent to instance..." error message. But here, by sure coincidence UIApplication also has a method for that instance (or rather, the runtime also has one of its methods listed in its table for that symbol). You kind of "found" a method that is not declared in its public header. You successfully circumvented a compile-time check for this and invoke a method that is part of a private API. This is explicitly forbidden in the Apple Developer Program License Agreement
Besides all that, I would strongly advise against trying to design an app that way in the first place. As maddy pointed out it's also likely considered to violate the HIGs. Even if you're not trying to do anything malicious and properly explain the feature in your app's description, that won't make Apple let it slide (I assume). Personally, as a user, I'd also find it annoying if the app did something the system already has a specific mechanic for in a different manner, at least in terms of app's coming to background and foreground.
I don't think it can be done without user interaction
The option is you can generate a push notification to tell the user to bring the application to foreground
When the operating system delivers push notification and the target application is not running in the foreground, it presents the notification.
If there is a notification alert and the user taps or clicks the action button (or moves the action slider), the application launches and calls a method to pass in the local-notification object or remote-notification payload.
I tested:
UIControl().sendAction(#selector(URLSessionTask.suspend), to: UIApplication.shared, for: nil)
which is for putting app on background and it works.
How do I put app back on foreground?
I tried:
UIControl().sendAction(#selector(URLSessionTask.resume), to: UIApplication.shared, for: nil)
But eventually it crashes...
Thank you
Update:
Since you've indicated that you're looking for any technical solution, even those not compatible with the App Store or Apple's terms, this should be possible using the Private API LSApplicationWorkspace: openApplicationWithBundleID. Try something like this:
Create a .h file and set up an interface to the LSApplicationWorkspace class and list the required method. You will need to #import "PrivateHeaders.h" in your bridging header.
//
// PrivateHeaders.h
//
#ifndef PrivateHeaders_h
#define PrivateHeaders_h
#interface LSApplicationWorkspace : NSObject
- (bool)openApplicationWithBundleID:(id)arg1;
#end
#endif /* PrivateHeaders_h */
You should then be able to call this function and pass in the Bundle Identifier of your app as an string.
//
// SomeClass.swift
//
import MobileCoreServices
let workspace = LSApplicationWorkspace()
/**
Launch an App given its bundle identifier
- parameter bundleIdentifier: The bundle identifier of the app to launch
- returns: True if app is launched, otherwise false
*/
func openApp(withBundleIdentifier bundleIdentifier: String) -> Bool {
// Call the Private API LSApplicationWorkspace method
return workspace.openApplication(withBundleID: bundleIdentifier)
}
Original:
What you are doing is likely a violation of the iOS Human Interface Guidelines (although the "Don’t Quit Programmatically" is no longer specifically defined), so as the comments have said, it is not suited to the App Store. Regardless, once your app is suspended in this way, I don't expect that there is a way to resume it programmatically, unless you can hook into a Background Operation to run URLSessionTask.resume, but I have not tested it and am unsure whether it can work.
Apps can be launched (and hence brought into the foreground) programmatically from another app or today extension by using a Custom URL Scheme, or via a Push Notification. It isn't possible to launch the app from the Background Operation via a URL Scheme, since it is part of the UIKit framework, which must be run in the main thread.
In summary, I think your best option is to try to use a Notification. This just means that the user will need to click on the notification to bring your app back into the foreground.
Closing/opening the app should be done explicitly by the user. Any other way of closing or opening the app is not supported by Apple and will be rejected when uploaded to app store. iOS Human Interface Guideline states:
Don’t Quit Programmatically
Never quit an iOS application
programmatically because people tend to interpret this as a crash.
However, if external circumstances prevent your application from
functioning as intended, you need to tell your users about the
situation and explain what they can do about it. Depending on how
severe the application malfunction is, you have two choices.
*Display
an attractive screen that describes the problem and suggests a
correction. A screen provides feedback that reassures usersthat
there’s nothing wrong with your application. It puts usersin control,
letting them decide whether they want to take corrective action and
continue using your application or press the Home button and open a
different application
*If only some of your application's features are
not working, display either a screen or an alert when people activate
the feature. Display the alert only when people try to accessthe
feature that isn’t functioning
Just as a follow up to Jordan's excellent answer I want to give an explanation for why your code works in the first place and why that alone will get your app rejected, even without any functionality to make it active again and bring it to the foreground.
As maddy pointed out in a comment, you're basically calling a method from UIApplication's private API. This works due to the Objective-C runtime's dynamic linking. You might wonder "But I am using Swift, what does that have to do with Objective-C?" The answer lies in #selector mechanism. A Selector is basically just a symbol that the Objective-C runtime looks up in a table to get a method it invokes (for you). This is why it's technically not correct to say you "call a method" when you do something like myObjectInstance.someMethod(). The correct way to phrase that would be to "send a message" to the object, because that's what is happening in the runtime. The target-action mechanism is build around that. The sendAction(_: Selector?, to: Any?) method does the same thing. So in effect your code does the following:
Get the symbol that corresponds to URLSessionTask's suspend() method.
Tell the shared instance of UIApplication to invoke the method that it has for that symbol.
Now usually that would result in a crash with the typical "unknown selector sent to instance..." error message. But here, by sure coincidence UIApplication also has a method for that instance (or rather, the runtime also has one of its methods listed in its table for that symbol). You kind of "found" a method that is not declared in its public header. You successfully circumvented a compile-time check for this and invoke a method that is part of a private API. This is explicitly forbidden in the Apple Developer Program License Agreement
Besides all that, I would strongly advise against trying to design an app that way in the first place. As maddy pointed out it's also likely considered to violate the HIGs. Even if you're not trying to do anything malicious and properly explain the feature in your app's description, that won't make Apple let it slide (I assume). Personally, as a user, I'd also find it annoying if the app did something the system already has a specific mechanic for in a different manner, at least in terms of app's coming to background and foreground.
I don't think it can be done without user interaction
The option is you can generate a push notification to tell the user to bring the application to foreground
When the operating system delivers push notification and the target application is not running in the foreground, it presents the notification.
If there is a notification alert and the user taps or clicks the action button (or moves the action slider), the application launches and calls a method to pass in the local-notification object or remote-notification payload.
I have been working on iOS framework (in Swift) which contains beacon functionality. I made it work except that I'm not sure how to handle scenario where I'm in foreground and I encounter multiple beacons in short duration.
If I want didReceive delegate method to show Alert for beacon while in foreground, and if I encounter many beacons it will not work nicely (alerts will display one over another). Is there some solution to queue notifications somehow?
Also I would like to know, if there is a way to make all that logic for receiving local notifications inside my framework?
I have to be able to support iOS-8.0 so I can't use Notification Center which is available from iOS-10.0
Can I create some class which would act like appdelegate (probably some class which would implement UIApplicationDelegate inside framework), is something like that possible?
I want to put as much code as I can inside framework itself so that it won't be too messy job for someone to include that framework with all functionality.
After some time I figured out a way to make this. I'm beginner in iOS with few months experience so I can't say if this solution is the best but it works for me.
I found a way to implement all push and local notification related delegate methods from framework. Basically if main application wants framework to take care of notifications without having to implement anything yourself, on runtime framework will dynamically implement certain UIApplicationDelegate methods for AppDelegate.swift class (or whatever is your AppDelegate class called).
I used object_getClass(UIApplication.shared.delegate!) to get the main class.
Then I used func class_addMethod(_ cls: AnyClass!, _ name: Selector!, _ imp: IMP!, _ types: UnsafePointer!) -> Bool
to implement delegate methods for push and local notifications from inside framework so now it comes down to write one or two lines to use framework entirely with working notifications and beacon location services instead of having to write a lots of code outside framework.
As for handling notifications in foreground mode I made that work by adding them to queue so that if more than one notification comes, and wants to be displayed in foreground regime, only one will be displayed by UIAlertController and the rest will be put in queue and sent again but with some small delay (I set fire date to be some value which I thought was appropriate in my case) after user makes an action regarding that first notification which was the only one presented.
These are just my ideas for the problems I had, if someone shows interest for these solutions I will write more details if needed. I will also gladly accept any criticism.
This question already has answers here:
How to detect first time app launch on an iPhone
(17 answers)
Closed 9 years ago.
I want to know how to use a condition saying
if(appHasNewlyLaunced)
{
// read a file
}
else
{
// read another file.
}
Is there any inbuilt class or property to check this. I am new to iOS so it could be a simple one , but I have no idea.
Thanks
i just want to know when the app. launches
There's a method in the app delegate that's called when the app launches. It's called -application:didFinishLaunchingWithOptions:. You need to implement that method in your app delegate, and you can add whatever code you want to execute when the app launches.
I am new to iOS
Take some time to learn what's expected of an iOS app before you dive in. If you invest some time up front, it'll pay for itself many times over. For example, you probably didn't know that applications are expected to provide an object to act as the application's delegate, else you would have looked at the UIApplicationDelegate protocol before asking your question.
Some background
I'm working on an iOS app where we want the state of the application to be preserved.
Before this app is out, iOS 7 is likely to have been released or is soon to be released and the majority seems to have moved away from iOS 5. We have therefore decided to develop for iOS 6 an onwards.
In iOS 6 there are some really nice functionality for preserving state. Just give all views in the storyboard unique IDs and implement these two functions in the "AppDelegate":
- (BOOL)application:(UIApplication*)application shouldSaveApplicationState:(NSCoder*)coder;
- (BOOL)application:(UIApplication*)application shouldRestoreApplicationState:(NSCoder*)coder;
iOS will then "automagically" preserve the navigation history of the app. The methods:
- (void)encodeRestorableStateWithCoder:(NSCoder*)coder;
- (void)decodeRestorableStateWithCoder:(NSCoder*)coder;
can then be used to store and retrieve data.
No problems there it works without issues. But, the methods that save the state are only triggered when the app entered the background.
Let's say we have one NavigationController with four ViewControllers: A, B, C and D. The user navigates from A to B, in B he switches over to Safari to google something. The application state is saved in B. The user then switches back to the app and navigates on to C and then to D. In D the app unfortunately encounters an exception and goes down. When the user restarts the app, iOS will try to restore the saved state. This state however, was saved in B. Which means that when the app launches, it doesn't start from the beginning, not where the user left it (D) and not even the previous view (C) but in B.
A possible solution
The above scenario could be avoided if the app saved its state at every new view. However there aren't (as far as I know) any public methods to trigger the state preservation process.
I have examined the call stack while debugging and found out that iOS calls the following method on the UIApplication object in iOS 6:
_saveApplicationPreservationState:
and the following method in iOS 7:
_saveApplicationPreservationState:viewController:sessionIdentifier:beginHandler:completionHandler:
There also seems to be another method that calls one of the above depending on the iOS version:
_saveApplicationPreservationStateIfSupported
By invoking this method like this:
if ([[UIApplication sharedApplication] respondsToSelector:#selector(_saveApplicationPreservationStateIfSupported)])
[[UIApplication sharedApplication] performSelector:#selector(_saveApplicationPreservationStateIfSupported)];
I can see that the expected methods are called.
The actual question
If I would go with the above solution could that get my app rejected from the App Store? I mean technically it's not a private method, it's just not exposed. By wrapping the call in "respondsToSelector" the app won't crash if the APIs are changed, it just won't save the state as often. But if it could get the app rejected it's not an option.
Or is there any other way to manually invoke the state preservation process other than the one described above? I would be nice to be able to use the built-in functionality rather than building a custom solution that saves the state to NSUserDefaults.
Event if the question is already 2 years old, i'll try my luck. Btw op, i guess, you'll have most likely solved it by now.
You're gonna for sure get rejected. They are scanning the sourcecode for methods you are calling. I had this several times, back when i was using the UDID methods. Hope it helped.