Is it possible to execute a listener when the App is not running?

Question

Is it possible to execute a listener when the App is not running?

Navigation

#1 by (3 votes)

1

The App would have to communicate to the user, that there was a change in a value on the server, but without using Push Notification. So I thought I'd add a listener on iOS, and that when I detected the change in value, it would trigger a local notification. And this should occur even though the App is not running.

Does anyone know where I can start?

listener swift ios background-services local-notification

asked by anonymous 28.05.2015 / 06:51

1 answer

Pure XML in PHP Variable map only receives null value

score 3 · Accepted Answer

You can launch the app in the background, check the server and then trigger the notification, using background fetch. The steps are as follows:

In the project settings under Capabilities , enable the Background Modes section and select Background fetch .

In the AppDelegate class, in the -(BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions you set the frequency at which the app will be called in the background, using the method: - (void)setMinimumBackgroundFetchInterval:(NSTimeInterval)minimumBackgroundFetchInterval

Example:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    //...
    [application setMinimumBackgroundFetchInterval:UIApplicationBackgroundFetchIntervalMinimum];
    return YES;
}

Now add in the AppDelete class the

- (void)application:(UIApplication *)application performFetchWithCompletionHandler:(void (^)(UIBackgroundFetchResult result))completionHandler;

This method will be called whenever the app is launched in the background. At the end of the execution of the operations it is always necessary to call the completionHandler , informing if the search for the data was successful. Example:

-(void)application:(UIApplication *)application performFetchWithCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler {

    /*
    ...
     */
    completionHandler(UIBackgroundFetchResultNewData);
}

To test, you set the target to launch the app in background mode. To do this, go to Product / Scheme / Manage Schemes . Now at Run / Option , select Launch due to a background fetch . When you build the app it will simulate the background release so you can test it without waiting for the system to do so.