I was reading the Android "Application Fundamentals" page located at http://developer.android.com/guide/topics/fundamentals.html#actlife and found this interesting information in the "Multitasking" section:
"Note that when you write an activity, you can make it stop or continue running when it is moved to the background (see onStop() in Activity Lifecycle). For activities that download data from the network, it's recommended to let them continue downloading so the user can multi-task." As far as I was aware I had to create a service if I wanted to have a background activity such as a media player, internet download, or processing of data in files on the SD card continue when the activity was no longer in the foreground. I went and reread the onStop information on the "Activity Lifecycle" page, which was referred to. But I didn't find any mention of how an activity might continue to run in the background after onStop was called. The "Activity and Task Design Guidelines" page at http://developer.android.com/guide/practices/ui_guidelines/activity_task_design.html also mentions something similar when it says: "In addition, not all activities have the behavior that they are destroyed when BACK is pressed. When the user starts playing music in the Music application and then presses BACK, the application overrides the normal back behavior, preventing the player activity from being destroyed, and continues playing music, even though its activity is no longer visible — as a visual substitute, the Music application places a notification in the status bar so the user still has an easy way to get to the application to stop or control the music. Note that you can write an activity to stop when its screen is no longer visible, or to continue running in the background — the latter was chosen for the music player." Is the information on these pages accurate? Is there some mechanism that I have missed to keep an activity running while it is in the background? I have been re-reading all this documentation because I currently use services to perform these types of background functions, and I have a cooresponding activity screen from which the user started the background processing and where the user can see the progress and status of the background service activity. When the service has finished I need the user to be able to return to the activity where they started the background activity. I currently have the service use a notification with an intent to start the activity, but that requires that the notification intent for the activity have the FLAG_ACTIVITY_NEW_TASK flag and ends up creating another instance of the activity rather than returning to the one that is already waiting in the background. This has the additional problem that the new instance is on a new task and so the back button and/or calling Activity.finish() does not return back to the activity the user came from prior to starting the activity that initiated the background processing. If the user stays on my activity screen while the background service processing is running everything works fine. But if they press the home key and do some other tasks, getting back to the correct activity stack from the service notification icon is the area where I am not understanding how to bring that existing activity stack back to the foreground. As far as I can tell the only way to prevent the service notification intent from creating a new instance of the activity is to set the activity launchMode to singleInstance. However that requires the activity to be the root of a task and so prevents it from being part of an activity stack. In my case this activity can be reached from more than one activity, and I need the activity stack to function correctly so it will return back to the right place. Any help from those that better understand how to get back to an activity and its activity stack from a service would be greatly appreciated. -- You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
