So, time to kill my Monkey-X Android SDK.
I knew going in that this would be a chore, but blinkin' eck, that's an understatement!!

-=-=-

The Android NDK was installed a few days ago, but it whinged that it needed a more up to date Java SDK, and rather than break Monkey before compiling this week's game, I held off for a few days.

Java

Gradlew.bat (I don't know what that is, by the way!) seems to want Java SDK 1.8, but I have both 1.6 and 1.7 installed.
No clues were given to this fact.. The error message simply read "Unsupported major.minor version 52.0", and I had to google that to figure out what the heck it meant.

52 is Java SDK 1.8, apparently.
For future usage, 53 is 1.9!
So that was the first install.

A fresh version of 1.8

I sat watching the progress bar leap from 0% to 100% and back, about half a dozen times, over the course of about 10 minutes, before it then asked me where I wanted to install it..

!?! Then what was it doing for the last 10 minutes?!

*sigh*

Installed, I ran Gradlew.bat, only to be faced with the exact same error message.

I rebooted.. Because Windows!
Retrying Gradlew.bat, and the same error message appeared.
It turns out that simply installing Java doesn't actually change any Environmental Variables, so I had to tweak those myself.
(WinKey - Type "Variables" and the right Control Panel thing should pop up)

So I changed it to point to the new Java SDK, rebooted (because.. Windows) and finally I was able to get a teensy bit further with Gradlew.

Android SDK

So, I opened the SDK manager, and clicked "Install updates", whereupon it let me click an agreement.
I hope that's the right agreement, because it didn't pop up any other agreements!
It's now sitting there doing a boatload of downloads and installs, and I seriously hope that.. once finished.. Gradlew.bat finally does what it seems to want to do.

..And then I'll be able to figure out what gradlew actually is, and whether it's actually helpful at all!!

tl;dr;
It's been 3 hours since I started trying to get Android Compiling to work properly.
XCode -> iOS was infinitely easier than this!!