How to set default file opening application on Android 5? I have Aldiko Premium ebook reader application and it's a nice app for reading epub ebooks.

I can't set it to be the default application for reading epub ebooks stored as files on my micro SD card.

Every time I open a epub from File Commander, I am asked which app to choose to open the epub. I also have Moon Reader, so that's in the list as well as Google Book and an option to Install UB Reader.

When I go into settings for the Aldiko app, there is no button to Set Defaults.

So how can I not be prompted to choose the app each time I open and epub.

Android 5.0.2, Sony Compact Z1.
I'm using Android 5.0.2 as well and installed File Commander to know how it provides options to choose a default app. It uses Android's default way. I don't have an E-book reader but the solution should work for your issue.

When you tap a file having multiple apps registered to open it and none set as default, you possibly would be shown options like:

(Click an image to enlarge it)





You would've noticed that there are two options with low visibility viz.  "Just Once", "Always". Tap on your app entry once and choose "Always" to set as default option.

If you somehow cannot make it work like the way I mentioned, then you may consider ES File Explorer which would give you the option to choose default in the following way: