Android constructors

Question

So after a while of programming android apps(1 uploaded on market, have 3k+ active installs with a 4,7 rating), I started to wonder, how can I make my app even more awesome. I realized, that I couldnt really add any really new, and world changing features, so I started to inspect the performance, and how to optimize just about everything, how to find the best cpu/memory usage ratio, and so on.

Anyway, I found out that onCreate will run in the case of rotating the screen, which is quite logic, but there are some(big) calculations, that I surely dont need to redo after every rotate. One of this is iterating through a csv with 6500 rows, having 4 columns, 2 of it always contains some data, 2 of it not always. The 2 column with datas will be used for autocomplete adapter, the another 2 is optional for a feature, but it still need to be initialized. Currently, this is running in an asynctask, triggered at the end of the onCreate, and takes about 3 seconds on my HTC Desire S, which has a quite good CPU, so lower budget devices will have a longer initialize time after every rotate which is surely not I want... It wont crash the UI, but there won't be any autocomplete until thoose seconds are over.

SO: my question is, can I do this in some separate method, for example a constructor(like in standard java), or is it a bad practise, because the special lifecycle of activities? I mean, I instantiate my activity the way the "constructor" will run, and just after that, my onCreate will run. In case of rotating, my "constructor" won't run again, but the onCreate will. Stability will still be my nr1 goal. Or, is there any good way to do this? Something that is created for exactly like this, which im unaware of? I really want to improve a lot in this matter, and I would really appreciate some help in this, preferrably from ones with experience in this, but any help is welcome! :)

For example, if I want to make a new activity this way, I would do it something like this:

new MyActivity(some parameters);

so the constructor runs, which ends something like this:

startActivity(new Intent(context, MyActivity.class));

So this way, the constructor runs, my variables will be initalized(not connecting to any view etc), and after that, my activity can run its onCreate variable anytime it has to.

Pardon me if Im wrong the syntax, I just fasttyped it :)

Answer 1

You should decouple this logic from your activity. There are many ways to do this, but the end goal is to have your csv parsing done in a different class, and this class should expose information about whether or not the data has already been parsed. So, in onCreate, you call your class to get the data. If it already exists, you get your cached data immediately. If this is the first time the method is called or for some reason your cache has been cleaned up, you parse your csv file and do whatever calculations you need.

Answer 2

you could take a look at onRetainNonConfigurationInstance which can return an object which you can access after your activity has been recreated.. so you would simply return an object containing all your processed results of onCreate and the next time around you check if there is a getLastNonConfigurationInstance() - and don't recalculate everything