I need to be able to differentiate between application didFinishLaunching and application entering background and being loaded back into the foreground. I noticed that if I register for the UIApplicationDidBecomeActiveNotification, it is called in both instances. How do I distinguish between the two?
Use the didFinishLaunchingWithOptions vs applicationWillEnterForeground to distinguish if app is starting cold or returning from background.
I tried listening to the UINotification's in one of my apps, but the notification was being delivered too late, so I resorted to listening to these method calls directly.
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
// only call when app is freshly launched
}
- (void)applicationWillEnterForeground:(UIApplication *)application
{
// Only called when app is returning from background
}
I need to be able to differentiate between application
didFinishLaunching
UIApplicationDidFinishLaunchingNotification
application entering background
UIApplicationDidEnterBackgroundNotification
being loaded back into the foreground
UIApplicationWillEnterForegroundNotification
Related
I have built a simple apps that connect to a sqlite database, and the app uses storyboards for UI. On first time, it will throw up a login view. If my authenticate was successful, I change my status in the sqlite database to 1. By default, it is 0. After login, I can use the app.
For example if I kill the app, how can I know my app has been killed? I need to change the status become default again. so whenever I click on the app again, I have to sign in again.
Any idea how to do this? thanks.
Your application delegate implements several methods which handle state changes in your application. From the UIApplication.h header.
- (void)applicationDidFinishLaunching:(UIApplication *)application;
- (BOOL)application:(UIApplication *)application willFinishLaunchingWithOptions:(NSDictionary *)launchOptions NS_AVAILABLE_IOS(6_0);
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions NS_AVAILABLE_IOS(3_0);
- (void)applicationDidBecomeActive:(UIApplication *)application;
- (void)applicationWillResignActive:(UIApplication *)application;
- (void)applicationWillTerminate:(UIApplication *)application;
You can implement whichever methods are relevant, in this case the applicationWillTerminate method to change state. Alternatively, always throw up a login view in applicationDidBecomeActive. (This doesn't, however solve the issue updating the database. If the database is local, there's no problem, simply change the database before resigning or terminating. The challenge here would be if your database lives on a server. Although it might bot be an issue, I could see connection timeouts affecting the integrity of the remote values.)
These methods are added to your project automatically in your application delegate, which can be found in the AppDelegate.h & AppDelegate.m files.
For a complete explanation, have a look at the UIApplication Delegate protocol reference.
You can perform close down actions in,
- (void)applicationWillTerminate:(UIApplication *)application
{
// Log out?
}
You can also do the same if your app isn't killed but just gets suspended, such as during an incoming call,
- (void)applicationWillResignActive:(UIApplication *)application
{
// Log out?
}
or,
- (void)applicationDidEnterBackground:(UIApplication *)application
{
// Log out?
}
Alternatively, on resume,
- (void)applicationDidBecomeActive:(UIApplication *)application
{
// Log in?
}
or,
- (void)applicationWillEnterForeground:(UIApplication *)application
{
// Log in?
}
You can't detect if you app was killed, since the process of you app gets killed by the system and no code is called to inform your app that it has been killed.
What you want is to set te some kins of boolean in :
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
Since this is called if you restart the app after it has been killed.
For the other states seen the answer by Moshe
EDIT
use the delegate methods
such as:
applicationWillResignActive
I have an application where there are 3 tabs to calculate distance and all. When I first launch the app, on clicking 3 rd tab some network call is happening. Now I put the application to background.
When the application comes to foreground, it should call viewwillappear to go for the network call again. but it is not happening. it is not calling viewwillappear.
How can I check when application comes to foreground, it should check for 3rd tab and call network method
Please help me
When application comes to foreground,
- (void)applicationWillEnterForeground:(UIApplication *)application;
of the app delegate is called.
You can restart all your paused tasks in:
- (void)applicationDidBecomeActive:(UIApplication *)application;
- (void)applicationDidEnterBackground:(UIApplication *)application
{
//save in NSUserDefaults (or wherever) which tab is currently active
}
- (void)applicationWillEnterForeground:(UIApplication *)application
{
// read from NSUserDefaults which tab was active before,
// and use an IF statement to control the further behavior
}
- (void)applicationDidEnterBackground:(UIApplication *)application {
if(tab3){
[viewController3 netWorkCallFromHere];
}
}
in this approach you will have to declare BOOL tab3 in Appdelegate.
set it true in third viewController and set it false in another viewController .
when it returns from the background then it will check the flag and it will work accordingly.
- (void)applicationDidEnterBackground:(UIApplication *)application
{
// Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later.
// If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits.
}
- (void)applicationWillEnterForeground:(UIApplication *)application
{
NSLog(#"%d",tabBar.selectedIndex);
if (tabBar.selectedIndex == 2) {
NSLog(#"Your work");
}
}
I'm making an app that keeps track of some reminders that repeats with an user defined interval.
I've made it so when the alert displays, the action title says "Renew". When you click this, the app opens, and here I want to create the next reminder, but the problem is that I don't know if the app opens because the notification button was tapped or if the notification fired while the app was running.
Anyone got any ideas?
The 'correct' way to do this is to examine your NSApplication's applicationState property in the application:didReceiveRemoteNotification: method of your delegate.
From the documentation for handling local notifications:
iOS Note: In iOS, you can determine whether an application is launched
as a result of the user tapping the action button or whether the
notification was delivered to the already-running application by
examining the application state. In the delegate’s implementation of
the application:didReceiveRemoteNotification: or
application:didReceiveLocalNotification: method, get the value of the
applicationState property and evaluate it. If the value is
UIApplicationStateInactive, the user tapped the action button; if the
value is UIApplicationStateActive, the application was frontmost when
it received the notification.
This is similar to your solution using flags set in applicationWillEnterForeground and applicationDidBecomeActive but with system support.
I don't know if my question was unclear but it seems that I got 4 different answers that all misinterpreted my question :P
However, I discovered that the didReceiveLocalNotivication happens between willEnterForeground and didBecomeActive, so I did this to determine if the app was already open or not:
-(void)application:(UIApplication *)application didReceiveLocalNotification:(UILocalNotification *)notification
{
NSLog(#"Opened from notification? %#", wasInactive ? #"yes!" : #"no!");
}
- (void)applicationWillEnterForeground:(UIApplication *)application
{
wasInactive = YES;
}
- (void)applicationDidBecomeActive:(UIApplication *)application
{
wasInactive = NO;
}
Look up the documentation for UIApplication launch option keys. The last parameter to your application:didFinishLaunchingWithOptions: delegate method contains the information you need.
Also, look at application:didReceiveLocalNotification.
You're looking for
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
or
- (void)application:(UIApplication *)application didReceiveLocalNotification:(UILocalNotification *)notification
Documentation
If your application is already running you'll get this delegate message on the app delegate
application:didReceiveLocalNotification:
If it wasn't running you'll have to use
application:didFinishLaunchingWithOptions:
You need to respond appropriately in both methods to cover all cases
UPDATED
To detect if the user activated the action button requires a little more complexity. We can tell that application:didFinishLaunchingWithOptions: will have the local notification as a launch option, but it's more difficult with the application:didReceiveLocalNotification:.
Since the application becomes active after the user taps the button, we have to defer until we see that message (or not). Set an NSTimer in application:didReceiveLocalNotification and cancel it in didBecomeActive. That means the user pressed the action button. If the timer isn't cancelled the user was inside the app when it fired.
In your app delegate in this method:
- (BOOL) application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
You have to examine the launchOptions looking at this key:
UIApplicationLaunchOptionsLocalNotificationKey
When you are already active this will be called:
- (void) application:(UIApplication *)application didReceiveLocalNotification:(UILocalNotification *)notification
I'm planning to implement multi-task in my app.
I can see many methods here to do that in the AppDelegate like applicationWillResignActive, applicationDidEnterBackground, applicationWillEnterForeground, ...
But.... I don't see the way they should be used, nor why they are not in the ViewControllers... Nor what they are here for.
I mean : when the app enter in background, i don't know on which view my user is.
And back, when the app comes into foreground, how would I know what to do and what I may call, to update the view for example ?
I would have understood if those methods where in each view controller, but here, I don't see what they can be used for in a concrete way...
Can you help me to understand the way to implement things into those methods ?
Each object receive a UIApplicationDidEnterBackgroundNotification notification when the app goes in background. So to run some code when the app goes in background, you just have to listen to that notification where you want :
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(appHasGoneInBackground:)
name:UIApplicationDidEnterBackgroundNotification
object:nil];
Don't forget to release the listener when you don't need to listen to it anymore :
[[NSNotificationCenter defaultCenter] removeObserver:self];
And best of the best, you can play the same way with the following notifications :
UIApplicationDidEnterBackgroundNotification
UIApplicationWillEnterForegroundNotification
UIApplicationWillResignActiveNotification
UIApplicationDidBecomeActiveNotification
They are not in any of your view controllers because iOS adopts a 'delegate' design pattern, where you can be assured that a method will fire upon a class (in this case, the App Delegate for your application) when required.
As a learning process, why don't you just put NSLog's in those methods to see when they're fired?
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
// Override point for customization after application launch.
NSLog(#"didFinishLaunchingWithOptions");
[self.window makeKeyAndVisible];
return YES;
}
- (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.
*/
NSLog(#"applicationWillResignActive");
}
- (void)applicationDidEnterBackground:(UIApplication *)application
{
/*
Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later.
If your application supports background execution, called instead of applicationWillTerminate: when the user quits.
*/
NSLog(#"applicationDidEnterBackground");
}
- (void)applicationWillEnterForeground:(UIApplication *)application
{
/*
Called as part of transition from the background to the active state: here you can undo many of the changes made on entering the background.
*/
NSLog(#"applicationWillEnterForeground");
}
- (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.
*/
NSLog(#"applicationDidBecomeActive");
}
- (void)applicationWillTerminate:(UIApplication *)application
{
/*
Called when the application is about to terminate.
See also applicationDidEnterBackground:.
*/
NSLog(#"applicationWillTerminate");
}
I am sending Push Notifications to my iPhone app, and I'd like a different set of instructions to execute depending on whether the app is already launched or not. I'm new to iPhone development, and while I suspect UIApplication or my project's AppDelegate class has the solution, I haven't found a good answer. Is there an easy way to check for this?
Here's the more appropriate way of handling active/inactive state of the app.
- (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo {
// check for the app state
UIApplicationState state = [application applicationState];
if (state == UIApplicationStateActive) {
//the app is in the foreground, so here you do your stuff since the OS does not do it for you
//navigate the "aps" dictionary looking for "loc-args" and "loc-key", for example, or your personal payload)
}
application.applicationIconBadgeNumber = 0;
}
didReceiveRemoteNotification: is called when the app is running, yes, but when it is suspended, the iOS takes care of putting up the badge, etc. If the app is in the foreground, the OS does nothing, and just calls your didReceiveRemoteNotification:.
Depending upon what you mean by "launched", you are either looking for:
Kevin's answer above (differentiates between launched or not launched)
or this (differentiates between suspended or active, but already launched):
Use a flag that is set true when the application becomes active, and false when the application is not active.
Flag (in header file [.h]):
BOOL applicationIsActive;
Code (in implementation file [.m]):
- (void)applicationDidBecomeActive:(UIApplication *)application {
applicationIsActive = YES;
}
- (void)applicationWillResignActive:(UIApplication *)application {
applicationIsActive = NO;
}
- (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo
{
if (applicationIsActive) {
// Handle notification in app active state here
}
else {
// Handle notification in app suspended state here
}
This works because when the application is suspended, the OS calls "applicationDidReceiveRemoteNotification" before it calls "applicationDidBecomeActive" during the "wake-up" process.
The "complete" answer is actually Kevin's answer plus this answer.
Hope this helps.
The UIApplication delegate has the method
- (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo
which you need to implement. This receives the notification when the app is running.
If your app is not currently running and a notification is received then your app can be launched with
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
with the notification details held in the launchOptions dictionary. if the dictionary is nil then the user tapped the application icon as normal.
If you are going to check applicationState on iOS less than 4, you'll need to check that applicationState is supported:
if ([application respondsToSelector:#selector(applicationState)] ){
// Safe to check applicationState
UIApplicationState state = [application applicationState];
}
The Apple documentation for push notifications explains this:
However, there are two situations where applicationDidFinishLaunching: is not a suitable implementation site:
The application is running when the notification arrives.
The notification payload contains custom data that the application can use.
In the first case, where the application is running when iPhone OS receives a remote notification, you should implement the application:didReceiveRemoteNotification: method of UIApplicationDelegate if you want to download the data immediately. After downloading, be sure to remove the badge from the application icon. (If your application frequently checks with its provider for new data, implementing this method might not be necessary.)
This means that if your application:didReceiveRemoteNotification: delegate method is called, your app is running.