Why You Shouldn’t Be Using a Task Killer with Android
I see this come up over and over again. People saying that a task is running in the background and they think it is killing their battery or hogging all of their memory. So their natural reaction is to download a program made to kill tasks. Here’s the thing… you are likely doing more harm than good by killing tasks that aren’t ready to end. I was the same way when I first got my CDMA Hero. There were tons of things running that I didn’t want so I just kept killing them. After a few weeks I realized that if I stopped using a task killer (and totally uninstalled it in fact) my phone actually began to run better! The applications would close themselves and things just seemed to be running better. I get that there may be short term benefits from clearing a task, but you should still take the time to read through this.
Here is some information directly from Android’s developer page. I have put the important parts in bold. This is quite a lengthy read but honestly I think it’s important. If you want the full read then you can check out the dev page here. If you just want the quick TL;DNR version then scroll to the bottom.
By default, every application runs in its own Linux process. Android starts the process when any of the application’s code needs to be executed, and shuts down the process when it’s no longer needed and system resources are required by other applications.
A content provider is active only while it’s responding to a request from a ContentResolver. And a broadcast receiver is active only while it’s responding to a broadcast message. So there’s no need to explicitly shut down these components.
Activities, on the other hand, provide the user interface. They’re in a long-running conversation with the user and may remain active, even when idle, as long as the conversation continues. Similarly, services may also remain running for a long time. So Android has methods to shut down activities and services in an orderly way:
An activity can be shut down by calling its finish() method. One activity can shut down another activity (one it started with startActivityForResult()) by calling finishActivity().
A service can be stopped by calling its stopSelf() method, or by calling Context.stopService().
Components might also be shut down by the system when they are no longer being used or when Android must reclaim memory for more active components.
If the user leaves a task for a long time, the system clears the task of all activities except the root activity. When the user returns to the task again, it’s as the user left it, except that only the initial activity is present. The idea is that, after a time, users will likely have abandoned what they were doing before and are returning to the task to begin something new.
Activity lifecycle
An activity has essentially three states:
It is active or running when it is in the foreground of the screen (at the top of the activity stack for the current task). This is the activity that is the focus for the user’s actions.
It is paused if it has lost focus but is still visible to the user. That is, another activity lies on top of it and that activity either is transparent or doesn’t cover the full screen, so some of the paused activity can show through. A paused activity is completely alive (it maintains all state and member information and remains attached to the window manager), but can be killed by the system in extreme low memory situations.
It is stopped if it is completely obscured by another activity. It still retains all state and member information. However, it is no longer visible to the user so its window is hidden and it will often be killed by the system when memory is needed elsewhere.
If an activity is paused or stopped, the system can drop it from memory either by asking it to finish (calling its finish() method), or simply killing its process. When it is displayed again to the user, it must be completely restarted and restored to its previous state.
The foreground lifetime of an activity happens between a call to onResume() until a corresponding call to onPause(). During this time, the activity is in front of all other activities on screen and is interacting with the user. An activity can frequently transition between the resumed and paused states — for example, onPause() is called when the device goes to sleep or when a new activity is started, onResume() is called when an activity result or a new intent is delivered. Therefore, the code in these two methods should be fairly lightweight.
http://geekfor.me/faq/you-shouldnt-b...-with-android/
