Android Connect to Running Thread

I am creating an app that has a UIThread and a background thread. The background thread is basically being used as a timer - every second it sends a message to the UIThread to update the UI. When the user exits the app by hitting the backbutton, the thread continues to run. I want this to happen since the user may want to open another app while the timer continues to count down.

My question is when the user comes back to my app. I want to connect to that background thread that is running to display the current state of the app - how much time is left, etc. My question is how to hook back in to the thread that is still running in the background. I have tried using Thread and AsyncTask, but the same issue occurs.

T开发者_JAVA技巧hanks for any help that you can provide.

Your thread is still turning by sheer chance - your application is in fact still running but it and the thread will be shut down when Android decides it needs the resources.

However what you want to do is well-provided for in Android - you need to implement a Service to have a process that runs in the background separately from your application. You can even have a Service start at boot and run whether or not your application is started.

This http://developer.android.com/reference/android/app/Service.html has most of what you need to know. To communicate between the Service and a foreground Activity you'll need to bind to a service interface, which is fortunately very easily done.

First thing that comes to mind is to change your timer thread to a Service and have apps interested in it bind to that service. Based on the Android documentation and suggested app design, you cannot depend on that thread to not be killed by the OS whenever it deems necessary.

http://developer.android.com/guide/topics/fundamentals/services.html

The android system provides a broadcast event every minute, it's call TIME_TICK.

You should:

• Create a service. This is the recommended way to have a part of the app running in the background
• Listen to the TIME_TICK event. This will consume less battery. (It won't wake the phone, though, so use an ALARM, too)
• Add an alarm (to wake the phone if necessary)
• Let the UI and the service interact. You need a callback via rpc (see the last callback example on the api page)

You should also ensure that the phone can sleep during the timeframe. You thus may want to compute the state as a delta between the starting point and now, instead of updating the state all the time.