Setting up Android SDK on Mac OS X 11 El Capitan

[Ben Rubinstein]

Having foolishly updated my machine to 10.11, I've doubled down by deciding to 
take another look at Android, for the first time in many years.

I installed the Android SDK 'shell', and then ran it to install the tools, and 
immediately said (three times)
	No Java runtime present, requesting install.

which caused a dialog to appear
	To use the "Java" command-line tool you need to install a JDK.
  	Click "More info..." to visit the Java Developer's Kit download
	website.

I went through that dance, and installed Java 8, confirmed it was running etc; 
this made no difference to the android tools.  Rebooted, same issue.

Googling locates a lot of people who have that dialog but are only looking to 
get rid of it, not to actually have Java working. (It also located an Apple 
page to install the "legacy" Java 6 for Mac.)

What is the cure for this? Do I need to install the legacy Java 6?  Do I need 
to "Disable Rootless System Integrity Protection", even though Java thinks 
it's already running fine?  Or is just not possible to install the Android SDK 
on El Capitan?

TIA,

Ben