Prevent homescreen/desktop from showing before my start-up app? I have this bootup app that listens to the system boot up event and will launch on system start up (pardon the verbosity).

Problem is, the system will stubbornly show the homescreen (or a static wallpaper,  I'm not so sure, basically it's a colorful, mostly blue geometry pattern, see the picture below) first before switching to my app, which is quite annoying.

I assume I need to delete files under /data/data or /system/priv-app to eliminate that?

Can someone please help me?

I'm running a customized (with heavy samsung influnece, I'm not the system level guy) build of android 5.1.
I can see nobody is answering this so I'll give you a long way of achieving this.   

You need to build a Launcher application, the launcher application will be blank, it simply starts the activity of your app, or preferably it just does nothing at all.  

After the blank launcher loads, the onBoot event will trigger your app to start.   

A long work around... 

To begin with,
Have a look on Stack Overflow, I found this question that fits perfectly in my opinion... 
Make my app the home screen launcher....?

This could be a good workaround as well, probably better than my original idea haha :) hope it helps.