background task not executing on iOS about capacitor-background-runner

[theproducer]

Hello! Have you tried executing your runner from the foreground by calling dispatchEvent("myCustomEvent")?
You can see an example here:

capacitor-background-runner/apps/example-app/src/pages/Tab1.tsx

Line 43 in c829507

const response = await BackgroundRunner.dispatchEvent({

If there is any problem, it should throw an error.

[patrick-tresp]

Hey, thanks for the response,

I implemented a dispatchEvent("myCustomEvent") in code and don't get an error, but interesting response:

{"__zone_symbol__state":null,"__zone_symbol__value":[]}

and not expected log from listener

console.warn('do something to update the system here');

i also copied exactly your examples from background.js which lead to same result…

[theproducer]

Sorry, and by "response", I mean did you see the console statement appear in Xcode's output console?

[patrick-tresp]

Yes :)

const response= BackgroundRunner.dispatchEvent({ /****/ })
console.log("response", response )

i will keep trying…

[theproducer]

No, if you are calling dispatchEvent('myCustomEvent'), and the handler for myCustomEvent is:

addEventListener('myCustomEvent', (resolve, reject, args) => {
    console.warn('do something to update the system here');
    resolve();
});

There should be no response except undefined really, and you should see the message 'do something to update the system here' in the Xcode console.

Do you see that message in the Xcode console?

[patrick-tresp]

I can see this message, when I dispatch the Event manually yes. It should be triggered by going into background mode when task is registered right?
But maybe we can narrow it down by finding out where the file "background-task.js" needs to be after compiling and cap-sync in App Folder.

working directory:
capacitor/background-task.js

dist folder:
dist/capacitor/background-task.js

after cap-sync:
ios/App/App/public/capacitor/background-task.js

i assume there is something misconfigured, that the file can not be found in runtime.

I also checked again Capacitor Object in scope and it does have BackgroundRunner in Plugins section

"Plugins": {
    "WebView": {},
    "Console": {},
    "CapacitorHttp": {},
    "CapacitorCookies": {},
    "PushNotifications": {},
    "BackgroundRunner": {}
  },

and all Methods are registered

{
      "name": "BackgroundRunner",
      "methods": [
        {
          "name": "addListener"
        },
        {
          "name": "removeListener"
        },
        {
          "name": "removeAllListeners",
          "rtype": "promise"
        },
        {
          "name": "checkPermissions",
          "rtype": "promise"
        },
        {
          "name": "requestPermissions",
          "rtype": "promise"
        },
        {
          "name": "dispatchEvent",
          "rtype": "promise"
        },
        {
          "name": "registerBackgroundTask",
          "rtype": "promise"
        },
        {
          "name": "checkPermissions",
          "rtype": "promise"
        },
        {
          "name": "requestPermissions",
          "rtype": "promise"
        }
      ]
    }

Can you share with me where your background-task.js is stored after cap-sync ?

[patrick-tresp]

After checking implementation again I guess it was meant to be used like this?

Or am I thinking wrong here? :)

if( runningInCapacitor ){
    App.addListener('appStateChange', (state) => {
        if (state.isActive) {
            console.log('App is active (foreground)');
        } else {
            console.log('App is in background');

            const response = BackgroundRunner.dispatchEvent({
                label: "de.domain.app.background.task",
                event: "myCustomEvent",
                details: {},
            });

            console.log("response ", response)
        }
    });
}

[theproducer]

If you see the message in the console, then its able to find your JS file (otherwise it would print an error).

After checking implementation again I guess it was meant to be used like this?

No, part of what Background Runner does is set up the native code configuration and registration settings for you. You do not need to do anything with App.addListener - read this comment here: #20 (comment)

In short, the plugin when configured properly will call your specified event handler based on the settings in the plugin config, during times when your app is the background.

For example, your config:

BackgroundRunner: {
          label: 'de.domain.app.background.task',
          src: 'capacitor/background-task.js',
          event: 'myCustomEvent',
          repeat: true,
          interval: 5,
          autoStart: true, \\\ <-- this should be true if you want it to register your background task automatically.
      },

will automatically register your task with iOS and Android, which will execute your myCustomEvent event handler approximately every 5 minutes (15 minutes on Android - be sure you read this) while your app is in the background.

Im currently working on some more practical examples that show real world examples of this plugin in use, in the meanwhile feel free to ask for more help in our discord: https://discord.com/invite/UPYYRhtyzp