After spending considerable time looking at this issue, I strongly suggest
that you look into an Intent Service, for any long running task. Using
AsyncTasks is just fraught.
First of all, onDestroy is only called best effort. If you care about
getting it done, you can't do it in onDestroy. Further, as kris points
out, onDestroy is, often, called just as your *process* is about to be
destroyed. Worrying about allocation of memory in your process, just as it
is destroyed, is pretty pointless.
There are two issues you need to consider: making your program correct
according to Java ("If mutable state is referenced from more than one
thread, all references must take place holding a single lock" - B. Goetz,
paraphrased). You also have to be sure that the lifecycles of unmanaged
objects (e.g. AsyncTasks) don't interfere with the lifecycles of managed
objects (Activities).
Nulling out pointers and AsyncTasks that survive screen
reorientation (despite the fact that I proposed it myself, at one
point) are just Voodoo.
G. Blake Meike
Marakana
Programming Android 2ed is now in stores:
http://bit.ly/programmingandroid
On Monday, January 14, 2013 1:10:52 AM UTC-8, Greenhand wrote:
>
> Thank you.
> Another related question, in section "5. Implement a more intelligent
> AsyncTask dealing with screen orientation" of
> http://blog.doityourselfandroid.com/2010/11/14/handling-progress-dialogs-and-screen-orientation-changes/,
>
> it has private AsyncTaskComplex activity in ListFresher as a member
> variable. Shouldn't it be null out because it is not a static Activity
> references?
>
>
> Kristopher Micinski於 2013年1月14日星期一UTC+8下午4時24分53秒寫道：
>
>> Basically, as long as you aren't hanging static Activity references
>> you should be fine. The main activity will be thrown away upon its
>> destruction, at which point the Activity will be thrown away: along
>> with its contents. Of course, if you're holding onto Views elsewhere
>> that's bad (i.e., don't hold static refs).
>>
>> kris
>>
>> On Mon, Jan 14, 2013 at 1:42 AM, Greenhand <[email protected]> wrote:
>> > I read
>> >
>> http://android-developers.blogspot.tw/2009/01/avoiding-memory-leaks.html
>> > about avoiding memory leaks.
>> > I would like to know whether I should null out all member variables,
>> such as
>> > TextView and Button in onDestroy()? Or, unregistering listener,
>> unbinding
>> > service and etc.in onDestroy() are enough to prevent memory leak?
>> >
>> > --
>>
>>
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