App freezing after several restarts - codenameone

Question

I built this app that takes pictures, displays them for acceptance and uploads them to a webserver via post.
It is very simple in concept and execution. But then the app is freezing in the Android handset (I have an Xperia Z3+ which i has a fairly good amount of resources, also tried in a Moto X).
To try and reproduce this I take a picture (it will automatically tried the upload)... push the power button for the screen to shutdown... then when I light up the screen it takes a while for the app to start working again (I can see because I have a background animation). After some retries of these... the app will freeze and I'll have to close it to retry.
Any suggestions on how to troubleshoot this problem?
My thinking is that I can aliviate the problem a little by removing the animation elements from the screen... at least the perceived performance will be far better is the app does not appear frozen on any app switch... therefore I want to be able to use the onPause, onStop from the activity lifecycle events to clear the animations. I guess those objects are serialized, so I will save serialization and deserialization time and also the perceived performance will improve as no freezed app will be seen while the onResume, onRestart events.
Is this posible?
Thank you very much
Chuck

Answer 1

This isn't caused by the animation, it may be caused by an uncaught Exception or poor app performance.
To review your app performance, move any long process that requires feedback to the UI (AsyncTask) to postShow() method of your forms and not beforeShow(). If it doesn't require feedback to UI in real time (IntentService), consider using Display.getInstance().scheduleBackgroundTask() which runs your task on a low priority thread while serializing it and this can be done in the beforeShow() method. If your forms are handcoded (Not GUI), do heavy long process in addShowListener().
Also cut down the amount of images you use in your app as this could also hinder your app performance when loading heavy images.
Avoid unnecessary use of revalidate(), usually by not calling it in a loop, it's a bit expensive, use repaint() instead.
You can also use Android ddms to check if your app is running into some errors.
Locking your screen or minimizing shouldn't affect your app in anyway other than when the app is starting up and the splash screen is shown (This usually freezes the app if you minimize your app when splash is shown). I believe this is a known issue though.
Another option could be the "suspend-resume" behavior. When an app is suspended (power button, incoming phone call etc.) the stop() method is invoked followed by a call to the start() method when it returns.
If you have a progress indicator during the stop() method then the restore call will reshow the progress indicator with the previous form as its "before form". That way when the progress indicator is dismissed it shows the "previous form". You can test this behavior in the simulator using the "suspend/resume" menu.
To workaround it just dispose the progress indicator in the stop() method as such:
public void stop() {
current = Display.getInstance().getCurrent();
if(current instanceof Dialog) {
((Dialog)current).dispose();
current = Display.getInstance().getCurrent();
}
}