Set ANDROID_HOME environment variable in mac

To make it permanent on your system and the variable keep working after close the terminal, ou after a restart use:

nano ~/.bash_profile 

Add lines:

export ANDROID_HOME=/Users/<username>/Library/Android/sdk
export PATH=$PATH:$ANDROID_HOME/platform-tools
export PATH=$PATH:$ANDROID_HOME/tools
export PATH=$PATH:$ANDROID_HOME/tools/bin
export PATH=$PATH:$ANDROID_HOME/emulator

Reopen terminal and check if it worked:

source ~/.bash_profile
echo $ANDROID_HOME

The above answer is correct. Works really well. There is also quick way to do this.

1. Open command prompt
   

2. Type - echo export "ANDROID_HOME=/Users/yourName/Library/Android/sdk" >> ~/.bash_profile
   

   Thats's it.
   

3. Close your terminal.
   

4. Open it again.
   

5. Type - echo $ANDROID_HOME to check if the home is set.

Open the terminal and type :

export ANDROID_HOME=/Applications/ADT/sdk

Add this to the PATH environment variable

export PATH=$PATH:$ANDROID_HOME/platform-tools

If the terminal doesn't locate the added path(s) from the .zshrc, please run this command

source ~/.zshrc

Hope it works to you!