I am creating an app in GWT, and I just recently implemented code splitting there. I reduced the application size from 1.1MB to 570kB which is nice, so the startup time of the application is now faster (we are using special server where 500kB really matters... not important for my question though ...). After the application starts (in other words user can see login page, can login and use basic parts of the app), I would like to download the rest of the fragments.
I know the fragment will be downloaded when the code in the fragment is needed. But one of the fragments is about 300kB. So when I click in the menu of my app on an item, that causes this fragment to be downloaded, there is a very noticeable delay (1 - 2s), before the user gets a response.
Now I understand that this will most likely happen only once and then the fragment will be cached for like a year, so it will load faster next time. But for example when I try it again on another device, I will have to download fragment for the first time again.
I just need to be sure, that when user launches my app on a phone/tablet using wifi, then disconnects from the wifi or gets out of its range, he will still be able to launch the code in the fragments, even if he didn't launch the things that cause downloading them while he was still connected to the server.
Now he would have to open 3 menu items, to download all the fragments which is annoying.
So in short:
I want my initial download to stay 570kB, and download the rest of the app as soon as possible on the background (if possible).
EDIT: I found http://www.gwtproject.org/doc/latest/DevGuideCodeSplitting.html#sequence where you can setup initial loading sequence, so I guess it is what I am looking for. Not sure though if they are loaded asynchronously, because the login screen appears after the fragments are downloaded.
You can cause all fragments to be downloaded after the login panel is rendered. Simply call some method inside the rest of the code - it does not need to do something visible.
Also, if you plan to load all code this way, you only need to split one fragment - your entry point with the login panel. Each split point (a) slightly increases the overall size of the application, and (b) increases, sometimes significantly, the size of the leftover fragment which still needs to be loaded for the first fragment to show up. Thus, there is no point in having more than the initial fragment and the rest of the app, given your requirements.