You don't need to down grade. You can run more than one version of Java on MacOS. You can set the version of your terminal with this command in MacOS.

# List Java versions installed
/usr/libexec/java_home -V

# Java 11
export JAVA_HOME=$(/usr/libexec/java_home -v 11)

# Java 1.8
export JAVA_HOME=$(/usr/libexec/java_home -v 1.8)

# Java 1.7
export JAVA_HOME=$(/usr/libexec/java_home -v 1.7)

# Java 1.6
export JAVA_HOME=$(/usr/libexec/java_home -v 1.6)

You can set the default value in the .bashrc, .profile, or .zprofile

Install another JDK

You can install multiple JDKs on your Mac. You can have a JDK for Java 11 as well as a JDK for Java 17. And perhaps you might want another JDK for the new Java 21 that arrived yesterday. These can all live together, side-by-side.

Each JDK is just a folder full of files. You can add JDKs, and delete JDKs, at will.

The environment variable JAVA_HOME is a hint various software as to which JDK you would like to use by default.

You might find a feature within Android Studio to install another JDK. (At least the sibling product, IntelliJ, offers such a feature.)

Configure project

Within your project in Android Studio, you need to set some settings to indicate which of your installed JDKs should be used for compiling, building, and executing your app. See the Android Studio documentation.

SDKMAN!

Personally, I find it easiest to install SDKMAN!, a bunch of shell scripts that manage installing/uninstalling JDKs (and other such kits). This works well on macOS.

SDKMAN! is designed to be utterly simple to use.

On a console such as Terminal.app, execute:

• sdk list java
  See a list of all JDK products from vendors who chose to submit their data to the SDKMAN! database. From this list you copy the exact name of the JDK product you want to install. The list of products indicates any you have currently installed.
• sdk install java product_name_goes_here
  Install the JDK product of your choosing. Takes a moment to download and install. At the end, SDKMAN! prompts you to specify whether you want to make this newly installed JDK the default.
• sdk uninstall java product_name_goes_here
  Removes that particular JDK product from your Mac.

Here is how I do it on my Linux (Ubuntu / Mint mate), I guess Mac can do it similarly.

Install & config

Steps:

• [Basic - part]
• Download jdk (the .tgz file) by hand.
• Uncompress & rename properly, at a proper location.
  e.g /mnt/star/program/java/jdk-1.8
• Make a soft link, which will be changed to switch java version later.
  e.g ln -s /mnt/star/program/java/jdk-1.8 /mnt/star/program/java/java
  Thus /mnt/star/program/java/java is the soft link.
• Set JAVA_HOME in a start script.
  Could use file like /etc/profile.d/eric.sh, or just use ~/.bashrc.
  e.g JAVA_HOME=/mnt/star/program/java/java
• Then open a new bash shell. java -version should print the java version.
• [More version - part]
• Download & install more Java version, as need, similar as above steps.
  e.g
  /mnt/star/program/java/jdk-11
• [Switch - part]
• In ~/.bashrc, define variable for various Java version.
  e.g
  _E_JAVA_HOME_11='/mnt/star/program/java/jdk-11'
_E_JAVA_HOME_8='/mnt/star/program/java/jdk-8'
# dir of default version,
_E_JAVA_HOME_D=$_E_JAVA_HOME_8
• In ~/.bashrc, define command to switch Java version.
  e.g
  ## switch java version,
alias jv11="rm $JAVA_HOME; ln -s $_E_JAVA_HOME_11 $JAVA_HOME"
alias jv8="rm $JAVA_HOME; ln -s $_E_JAVA_HOME_8 $JAVA_HOME"
# default java version,
alias jvd="rm $JAVA_HOME; ln -s $_E_JAVA_HOME_D $JAVA_HOME"
alias jv="java -version"
• In terminal, source ~/.bashrc to make the changes take effect.
• Then could switch using the defined commands.

Commands - from above config

Commands:

• jv11
  Switch to Java 11
• jv8
  Switch to Java 8
• jvd
  Switch to default Java version, which is denoted by _E_JAVA_HOME_D defined above.
• jv
  Show java version.

Example output:

eric@eric-pc:~$ jv
java version "1.8.0_191"
Java(TM) SE Runtime Environment (build 1.8.0_191-b12)
Java HotSpot(TM) 64-Bit Server VM (build 25.191-b12, mixed mode)

eric@eric-pc:~$ jv11
eric@eric-pc:~$ jv
java version "11.0.1" 2018-10-16 LTS
Java(TM) SE Runtime Environment 18.9 (build 11.0.1+13-LTS)
Java HotSpot(TM) 64-Bit Server VM 18.9 (build 11.0.1+13-LTS, mixed mode)

eric@eric-pc:~$ jvd
eric@eric-pc:~$ jv
java version "1.8.0_191"
Java(TM) SE Runtime Environment (build 1.8.0_191-b12)
Java HotSpot(TM) 64-Bit Server VM (build 25.191-b12, mixed mode)

eric@eric-pc:~$ 

Mechanism

• It switch by changing the soft link, which is used as JAVA_HOME.

Tips

• On my machine when install jdk by hand, I keep the minor version, then make a soft link with the major version but without the minor version.
  e.g
  // this is the actual dir,
  jdk1.8.0_191

  // this is a soft link to jdk1.8.0_191
jdk-8

  // this is a soft link to jdk-8 or jdk-11
java

• I define command alias in ~/.bashrc, but define variable in a separate file.
  I am using ~/.eric_var to define the variables, and ~/.bashrc will source it (e.g source $HOME/.eric_var).

That does not seem to be accurate any more.

I just managed to downgrade both JRE and compiler from Java 8 to 7 by looking into /Library/Java/JavaVirtualMachines, and moving away the directory with the highest version number, e.g.

sudo mv jdk1.8.0.jdk ~/Desktop/

Welcome to SO!

Even though you already solved it, using sdkman greatly reduces stress if you want to switch regularly between versions.

I had this same problem: I had Java 8 installed, but later installed 10. Then, I removed 10, and when I launched a jar from the terminal it would run in version 8, and when I checked the version with java -version in the terminal I would get back java version "1.8.0_181. However when I ran a .jar from the Finder, it would run in v.10, and also if I went to the Java preference pane the version was listed as version 10. This was undesirable: I was trying to remove v10 completely.

Then, I deleted JavaAppletPlugin with rm /Library/Internet\ Plug-Ins/JavaAppletPlugin.plugin and reinstalled Java SE JDK 8 from online, and lo! it works now. When I run .jar, they run in Java 8.

I realize you mentioned this in your first step, but I infer that you didn't do this step? If I'm wrong about that then you've got a different problem. But this solved mine.