Mark,
Great book. I recommend it to all.
I like the subscription model also. Very cool.
Bob
On Dec 10, 7:57 am, Justin (Google Employee) [EMAIL PROTECTED]
wrote:
I'm glad that you've found a solution that works for you. Yes,
unfortunately while we expect most Android devices to be pretty
powerful and have fairly large amounts of memory, they still aren't
desktop machines and more careful design and implementation will
sometimes be necessary.
Cheers,
Justin
Android Team @ Google
On Dec 9, 5:42 pm, mscwd01 [EMAIL PROTECTED] wrote: Hi Justin,
I too have spent a great deal of time debugging this - with little
luck.
Thanks for taking the time to explain your findings, it does help to
understand what was going on.
In the end I chose to redesign my application and use just the one
MapView - mainly due to the memory issues.
The reason I found myself in this problem was due to the fact I needed
a TabHost and a MapView in the same activity. However I found I
couldn't extend both a TabActivity and MapActivity in the same
Activity so I opted to create my own TabbedMapActivity, created
using the Android source code.
I explained it all here if you want to see how I achieved
this:http://groups.google.com/group/android-developers/browse_thread/threa...
Ultimately, I believe you are right, having multiple MapViews will
inevitable lead to memory issues regardless of how careful you are to
save map states and recycle resources; so I think using just the one
MapView is the only answer at this moment in time.
Thanks
On Dec 9, 11:49 pm, Justin (Google Employee) [EMAIL PROTECTED]
wrote:
Once upon a time I spent a lot of time debugging this issue, so here
is what I found.
***WARNING: This information was valid on an internal version of the
SDK between M5-RC15 and 0.9 beta, it may no longer be valid, test
thoroughly and proceed with caution.***
First, some information about MapView and MapActivity. Each Android
process may have multiple MapViews and MapActivitys, but they all
manipulate a single MapView backing object. This is because MapViews
take a *huge* amount of memory, roughly half of the 16MB allowed to
each application. This *also means* you need to be very careful about
your memory usage when using MapView. Make sure to use DDMS to analyze
memory usage to make sure you don't run out of space. Because a single
view backs all map views in an application, you also need to save and
restore the map state (including center position and zoom) when your
MapActivity subclass pauses/resumes.
For the purposes of discussion I will refer to two activities,
ActivityAlpha and ActivityBeta, each is a subclass of MapActivity and
has a MapView. ActivityAlpha starts ActivityBeta. The user will
eventually return to ActivityAlpha either via the 'back' button or
ActivityBeta finishing naturally.
When ActivityBeta finishes, there are two issues that I believe causes
the problem you see:
1) onCreate is not called on the launching ActivityAlpha, onResume is
2) a certain UI focal change doesn't occur
Certain initialization of the MapView and various helper entities are
done by MapActivity when onCreate is called. When ActivityBeta is
launched, onPause is called on ActivityAlpha and the helpers for the
MapView are stopped. onResume does some of the restarting, but clearly
not all that is necessary. This can be worked around by calling
super.onCreate(null) from your onResume or onActivityResult method of
your launching MapActivity subclass. ***WARNING***: This is
potentially very dangerous, MapActivity may not expect to be abused
this way, test thoroughly and proceed with caution.
The second issue results in the above hack not quite working. When
ActivityBeta finishes, and the above hack is applied, ActivityAlpha is
ready to load tiles, but it won't until the MapView is touched so that
the MapView checks to see if it needs tiles. So far, I don't have a
workaround for this, possibly a programmatic pan or zoom would cause
the MapView to load any missing tiles. Some of my previous testing
also indicated that any missing tiles would load when ActivityAlpha
resumes if you use startActivity() to start ActivityBeta instead of
startActivityForResult().
The bottom line is that maps were never designed to have multiple map
views in a single application, they're very heavy objects. Hopefully
this helps and is still valid information, let me know how it goes.
Cheers,
Justin
Android Team @ Google
On Dec 8, 5:39 pm, mscwd01 [EMAIL PROTECTED] wrote:
Having tried the test you suggested it seems I can go back and forth
between my Activity1 map and the inbuilt Google Maps app perfectly
fine - no memory worries. However my application, constantly throws up
OutOfMemory errors.
One thing I have noticed is after Activity1 calls
