I have one class name as myClassCalculate have the following method
- (void) accelerometer:(UIAccelerometer *)accelerometer didAccelerate:(UIAcceleration *)acceleration {
NSLog(#"Accelerometer is called");
}
I am making object in
- (void)applicationDidFinishLaunching:(UIApplication *)application {
// Override point for customization after app launch
myObject = [[myClassCalculate alloc] init];
now when app will go in background, I want this
- (void) accelerometer:(UIAccelerometer *)accelerometer didAccelerate:(UIAcceleration *)acceleration {
What can I do, so that this method will get called in app background
Thanks
You can't, only VOIP, audio and navigation apps are allowed to run in background.
Thus if your app does not fall in one of these it gets suspended and wil not receive any events.
More about backgrounding: App States and Multitasking
Declaring Your App’s Supported Background Tasks
Support for some types of background execution must be declared in
advance by the app that uses them. An app declares support for a
service using its Info.plist file. Add the UIBackgroundModes key to
your Info.plist file and set its value to an array containing one or
more of the following strings:
audio — The app plays audible content to the user while in the background. (This content includes streaming audio or video content using AirPlay.)
location — The app keeps users informed of their location, even while it is running in the background.
voip — The app provides the ability for the user to make phone calls using an Internet connection.
newsstand-content — The app is a Newsstand app that downloads and processes magazine or newspaper content in the background.
external-accessory — The app works with a hardware accessory that needs to deliver updates on a regular schedule.
At WWDC this year they said that accelerometer updates could be observed in the background but I'm not sure how to do it. I think it would be iOS 5 only.
To do background tasks you need to add them to your info.plist in the UIBackgroundModes key.
Here is what's available right now.
audio
The application plays audible content in the background.
location
The application provides location-based information to the user and requires the use of the standard location services (as opposed to the significant change location service) to implement this feature.
voip
The application provides Voice-over-IP services. Applications with this key are automatically launched after system boot so that the application can reestablish VoIP services. Applications with this key are also allowed to play background audio.
newsstand-content
The application processes content that was recently downloaded in the background using the Newsstand Kit framework, so that the content is ready when the user wants it.
This value is supported in iOS 5.0 and later.
external-accessory
The application communicates with an accessory that delivers data at regular intervals.
Try putting location in the plist or using [UIApplication beginBackgroundTaskWithHandler:]
This value is supported in iOS 5.0 and later.
When app goes in backgroound this method is called onUserLeaveHint()
Related
Our app would like to access accelerometer data in background. A possible way to achieve is to use Core Motion for accelerometer readings -
with
CLLocationManager* locationManager;
CMMotionManager* motionManager;
...
[motionManager startAccelerometerUpdatesToQueue: ... withHandler: ...]
which works fine on the foreground, but the only way I've found to receive the updates in background is to set the app to allow using Location in background, and call
[locationManager startUpdatingLocation]
in -applicationWillResignActive:
The problem is, when I call startUpdatingLocation that a window pops up with text Turn On Location Services to Allow "app" to Determine Your Location.
But of course, I receive accelerometer readings regardless of whether Location Services are enabled, but the popup is annoying and will probably confuse users.
Is getting accelerometer data in the background somewhat tied to attempting to receive location updates?
You can use startAccelerometerUpdatesToQueue in background, the only thing you need to meet — use any background mode to make you app running in the background (location updates (your case), playback, VoIP or BT4 central).
I'm building an app that is location-aware and triggers text to speech whenever the user gets near a certain point. I have singleton classes GPSManager (for getting location updates) and RouteDetails (for defining the points that should trigger the text-to-speech). I also have a view controller that shows a map updating the user's location from GPSManager and showing a route from RouteDetails.
What I want to do is keep the functionality of the view controller running when the app is suspended, i.e. be notified when the location is updated, compare it to the locations in RouteDetails, and then play the text-to-speech. However I can't seem to find a good example of this being done - how do I made sure RouteDetails and GPSManager stay in memory? And where should I put the text-to-speech module where it can access the details in RouteDetails and also be in memory so that it can play when the app is suspended and the phone is locked? I'm assuming the view controller can't receive notifications when the app is suspended.
Also, I've added the location and audio options to the UIBackgroundModes key in the Info.plist file. And I don't need the app to bring itself back into the foreground when it gets a location update/plays a sound, it just needs to play a sound and update a variable in RouteDetails.
I'm working on a radio alarm clock, and i have some issues.
I am using local notifications for the alarms, so it has a gentle fallback if the app is not running.
I am well aware of the limitations of the device, and i know what i can and cannot do when the device has gone into background.
But my question is this:
I have seen other apps starting an audio streamer when i've locked the device. How is this possible? May this be inside an execution-timeframe?
How is the best way to implement this? Is it any way i can activate a streaming session when the device is locked?
Edit
To clarify: I know how i make audio play in the background. But the issue is triggering the audio-playback when an local notification or some other event fires.
One app that seems to do this, is Radio Alarm Clock. I haven't tried it for long period of times yet. But it seems to do this. A video demo of the app: http://www.youtube.com/watch?v=KJQiFOcdBWk
Have you already declared your background task?
Support for some types of background execution must be declared in advance by the app that uses them. An app declares support for a service using its Info.plist file. Add the UIBackgroundModes key to your Info.plist file and set its value to an array containing one or more of the following strings:
audio — The app plays audible content to the user while in the background. (This content includes streaming audio or video content using AirPlay.)
iOS App Programming Guide - Implementing Long Running Background Tasks
You can add this by clicking on your main project icon, then under the Info tab you can add "Required Background Modes" to the "Custom iOS Target Properties" section. "App Plays Audio" will be one of the three default values.
Big Edit With New Answer:
If everything else is already in order, you can keep your app running in the background using the UIApplication method
- (UIBackgroundTaskIdentifier)beginBackgroundTaskWithExpirationHandler:(void (^)(void))handler
detailed here: UIApplication Class Reference
with an example here: Hour 21: Building Background-Aware Applications
This allows you to run an instance of NSTimer which triggers your music player. The difference between this approach and UILocalNotifications is that this method never lets the app fully enter the background mode, the music player exists the entire time which subverts the need to create it from the background, which looks to be impossible.
There may be limitations to how long of a timer you can set, I haven't tested this past 14 minutes out.
Hello I am planning to develop a simple iPhone game. I would like to be able to distinguish between a genuine crash, and the user killing the app ( by double tapping home screen and long-clicking it to kill it) .
Can someone please shed some light on what exactly happens when the user kill the app through the multitasking bar.
If your app is in the background and suspended when the user kills it, it will receive no notification. This accounts for the majority of cases.
If your app is currently running in the background (there are only very specific categories of apps that can do that), then it receives applicationWillTerminate.
Indeed, Apple is very clear as to the fact that you should save any relevant data before entering the background. Have a look at this (chapter "Responding to Application Termination"):
Even if you develop your application using iOS SDK 4 and later, you must still be prepared for your application to be killed without any notification. The user can kill applications explicitly using the multitasking UI. In addition, if memory becomes constrained, the system might remove applications from memory to make more room. If your application is currently suspended, the system kills your application and removes it from memory without any notice. However, if your application is currently running in the background state (in other words, not suspended), the system calls the applicationWillTerminate: method of your application delegate. Your application cannot request additional background execution time from this method.
EDIT:
about the "saying sorry" thing...
you can certainly do that on the next launch. simply store a key in NSUserDefaults and remove it when the app enters the background (I hope all this sounds familiar to you, otherwise look into the UIApplicationDelegate protocol).
when the app starts up, you check the key; if it is there, then the app was not closed by the user; if the app is not there, then the user at least moved the app to the background and did not experience any sudden termination...
For iOS6 and later there is a way to do this. A side effect of State Restoration is that it will delete the state when there is either a crash during restore or a user manually kills the app. You can use this to your advantage to detect a user manually killing the app.
From the documentation:
Be aware that the system automatically deletes an app’s preserved state when the user force quits the app. Deleting the preserved state information when the app is killed is a safety precaution. (The system also deletes preserved state if the app crashes at launch time as a similar safety precaution.) If you want to test your app’s ability to restore its state, you should not use the multitasking bar to kill the app during debugging. Instead, use Xcode to kill the app or kill the app programmatically by installing a temporary command or gesture to call exit on demand.
The following code assumes that you already have a BOOL for crash detection called _didCrashInLastSession. There are different approaches for getting this value such as this 3rd party library. In your code call the method [self getLaunchType] to see which type of launch you are dealing with and act on that accordingly. Put the following in your AppDelegate.m:
typedef NS_ENUM(NSInteger, LaunchType) {
LaunchTypeUnknown,
LaunchTypeNewInstall,
LaunchTypeNormalLaunch,
LaunchTypeCrashedLastSession,
LaunchTypeUserManualQuit,
};
static BOOL hadStateToRestore = NO;
static NSString * const kAppHasEverRunKey = #"appHasEverRun";
- (BOOL)application:(UIApplication *)application shouldSaveApplicationState:(NSCoder *)coder
{
// Called when going into the background
[[NSUserDefaults standardUserDefaults] setBool:YES forKey:kAppHasEverRunKey];
[[NSUserDefaults standardUserDefaults] synchronize];
return YES;
}
- (BOOL)application:(UIApplication *)application shouldRestoreApplicationState:(NSCoder *)coder
{
// Called on start up
hadStateToRestore = YES;
return YES;
}
- (LaunchType)getLaunchType
{
if (_didCrashInLastSession) {
return LaunchTypeCrashedLastSession;
}
if (![[NSUserDefaults standardUserDefaults] boolForKey:kAppHasEverRunKey]) {
return LaunchTypeNewInstall;
}
if (!hadStateToRestore) {
return LaunchTypeUserManualQuit;
}
return LaunchTypeNormalLaunch;
}
Update: At least one 3rd party SDK breaks this technique: Urban Airship.
You can do it through your device also.
Connect your device to your machine.
Run xcode and go to organizer.
There select your device and device logs.
There you can also see crash logs of your app or game.
first of all, I know there is only support for voip, audio and location apps to run in background and that they will run just while the audio is been played or while using location services, etc.
What I want to know is if there is a way to keep my app running on background fully operational, doesn't matter the impact on battery's life.
That way the user of my app can select from settings to keep alive the app whenever he wants and just for the amount of time he wish. e.g if he is waiting for something that requires the app to be running, after receiving the messages he can turn off the keep alive functionality.
I don't know if this is possible but I had read some post that say so but unfortunately they didn't say how to =(
UPDATE: In this tutorial, I found that Acrobits has two apps on the Apple Store that "can force the application to stay alive and awake in the background". So there is a way to do this?
From ioS 7 onwards, there are newer ways for apps to run in background. Apple now recognizes that apps have to constantly download and process data constantly.
Here is the new list of all the apps which can run in background.
Apps that play audible content to the user while in the background, such as a music player app
Apps that record audio content while in the background.
Apps that keep users informed of their location at all times, such as a navigation app
Apps that support Voice over Internet Protocol (VoIP)
Apps that need to download and process new content regularly
Apps that receive regular updates from external accessories
You can declare app's supported background tasks in Info.plist using X Code 5+. For eg. adding UIBackgroundModes key to your app’s Info.plist file and adding a value of 'fetch' to the array allows your app to regularly download and processes small amounts of content from the network. You can do the same in the 'capabilities' tab of Application properties in XCode 5 (attaching a snapshot)
You can find more about this in Apple documentation
You can perform tasks for a limited time after your application is directed to go to the background, but only for the duration provided. Running for longer than this will cause your application to be terminated. See the "Completing a Long-Running Task in the Background" section of the iOS Application Programming Guide for how to go about this.
Others have piggybacked on playing audio in the background as a means of staying alive as a background process, but Apple will only accept such an application if the audio playback is a legitimate function. Item 2.16 on Apple's published review guidelines states:
Multitasking apps may only use
background services for their intended
purposes: VoIP, audio playback,
location, task completion, local
notifications, etc
If any background task runs more than 10 minutes,then the task will be suspended and code block specified with beginBackgroundTaskWithExpirationHandler is called to clean up the task. background remaining time can be checked with [[UIApplication sharedApplication] backgroundTimeRemaining].
Initially when the App is in foreground backgroundTimeRemaining is set to bigger value. When the app goes to background, you can see backgroundTimeRemaining value decreases from 599.XXX ( 1o minutes). once the backgroundTimeRemaining becomes ZERO, the background task will be suspended.
//1)Creating iOS Background Task
__block UIBackgroundTaskIdentifier background_task;
background_task = [application beginBackgroundTaskWithExpirationHandler:^ {
//This code block is execute when the application’s
//remaining background time reaches ZERO.
}];
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
//### background task starts
//#### background task ends
});
//2)Making background task Asynchronous
if([[UIDevice currentDevice] respondsToSelector:#selector(isMultitaskingSupported)])
{
NSLog(#"Multitasking Supported");
__block UIBackgroundTaskIdentifier background_task;
background_task = [application beginBackgroundTaskWithExpirationHandler:^ {
//Clean up code. Tell the system that we are done.
[application endBackgroundTask: background_task];
background_task = UIBackgroundTaskInvalid;
}];
**//Putting All together**
//To make the code block asynchronous
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
//### background task starts
NSLog(#"Running in the background\n");
while(TRUE)
{
NSLog(#"Background time Remaining: %f",[[UIApplication sharedApplication] backgroundTimeRemaining]);
[NSThread sleepForTimeInterval:1]; //wait for 1 sec
}
//#### background task ends
//Clean up code. Tell the system that we are done.
[application endBackgroundTask: background_task];
background_task = UIBackgroundTaskInvalid;
});
}
else
{
NSLog(#"Multitasking Not Supported");
}
For running on stock iOS devices, make your app an audio player/recorder or a VOIP app, a legitimate one for submitting to the App store, or a fake one if only for your own use.
Even this won't make an app "fully operational" whatever that is, but restricted to limited APIs.
Depends what it does. If your app takes up too much memory, or makes calls to functions/classes it shouldn't, SpringBoard may terminate it. However, it will most likely be rejected by Apple, as it does not follow their 7 background uses.
May be the link will Help bcz u might have to implement the code in Appdelegate in app run in background method ..
Also consult the developer.apple.com site for application class
Here is link for runing app in background