Question

I have been working on an Android app using Phonegap and now would like to make it so when the app is closed it can still execute the java/js code in the app. So I understand I need to create a service. If I create a service plugin on phonegap can I still execute the javascript code or only the java?

Has anyone does something like this? I found this discussion but did not seem to work: http://groups.google.com/group/phonegap/browse_thread/thread/722b0e796baa7fc6
So that is all I have right now.

Before I turn to developing it native if I can’t figure it out thought I would ask if anyone has done this before. I can’t seem to find any of the phonegap plugins that do something similar.

EDIT: I have got an app that executes Java code as a service. However when it calls sendjavascript it does not work. So is there a way to have the javascript code running in the background as well when an app is closed with phonegap?

Thanks

Answer 1

No, it is not possible to run Javascript code in the background (at least in my opinion) as a service. Phonegap on Android uses an special activity called Droidgap, which hosts a WebView. This browser control executes the JavaScript. This means that JS execution can only handled inside this activity, regardless if it is visible or not.

The code you linked from Google Groups tries to bind a service developed in Java to the DroidGap activity, so the service is NOT written in JS.

You can have some background activity within your JS code inside your child activity derived from the DroidGap activity. For example have a background thread in your activity, have a JS callback function and let the thread call this callback functionality.

If you really need a service you have to go native.

Update:
JS code can only be executed with the Droidgap activity. An activity can have 3 states (based on the Lifecycle of activites):

1. visible
2. invisible but still loaded
3. not loaded

I provided a sample in which I implemented a Phonegap plugin. The plugin allows the activity to register itself to SMS_RECEIVED. When the activies goes out of scope (event onbeforeunload), it deregisters, so only issue 1 is handled.

When you want all 3 issues handled, you have to forward the incoming SMS intent to the activity. When it is not loaded the system will automatically load and activate the activity. But this is not a background service anymore, your app would become visible whenever a SMS is received.

If you don’t want this (if you really want a background service), you have to provide a native implementation.