Requirements

Note: Mac® OS X® 10.10 (Yosemite) or higher, up to 10.14 (macOS Mojave)

1. Download android-studio-ide-xxx-mac.dmg and run...
2. Install Android SDK CLI with Studio's SDK manager
3. Install platform-tools with Studio's SDK manager (you can keep up-to-date with Android Studio)

By default the Android SDK location is stored at /Users/[USER]/Library/Android/sdk or at /Library/Android/sdk/

In my case it is /Users/zollak/Library/Android/sdk

1. android-sdk requires Java 8. You can install it with:

$ brew cask install homebrew/cask-versions/adoptopenjdk8

2. set the following global variables in your .bash_profile file:

# Set up for Android Studio
export ANDROID_HOME="/Users/zollak/Library/Android/sdk"
export PATH="${ANDROID_HOME}/tools/bin:${ANDROID_HOME}/platform-tools:${PATH}"
export ANDROID_SDK_ROOT="/Users/zollak/Library/Android/sdk"

Basically, the Android SDK is a bunch of packages necessary to develop for Android.

• tools: This package is mainly used to manage the other packages and to create AVD’s (e.g. avdmanager, sdkmanager)
• emulator: As the name suggest, this is the Android emulator
• platform-tools: Some tools to communicate with Android devices when you plug then in your computer (e.g. adb, sqlite3, etc.)

To use the emulator, the Android SDK must be installed on your system.

Emulator start script:

MacBook-Pro:~ zollak$ cat <<EOF > /Users/zollak/Mobile/Android/emulator
#!/bin/bash
# Description: emulator start script
# Usage: emulator <your_avd_name>
# Without any parameter the default AVD_NAME will start. 

ANDROID_HOME="/Users/zollak/Library/Android/sdk"
AVD_NAME="Nexus_5X_API29_Android10.0_x86_64"

if [ $# -gt 0 ]; then
        AVD_NAME=$1
        shift
fi

pushd ${ANDROID_HOME}/tools
./emulator -avd ${AVD_NAME} $* &
popd
EOF

Usage:

MacBook-Pro:~ zollak$ avdmanager list avd | grep Name:
    Name: Nexus4_API15_Android4.0.3_x86
    Name: Nexus4_API16_Android4.1_x86
    Name: Nexus5X_API24_Andoid7.0_x86_64
    Name: Nexus6_API26_Android8.0_x86_64
    Name: Nexus_5X_API29_Android10.0_x86_64
    Name: Samsung_API17_Android4.2_x86
    Name: Samsung_API18_Android4.3_x86
    Name: Pixel3a_API23_Android6.0_x86_64

MacBook-Pro:~ zollak$ emulator Samsung_API17_Android4.2_x86

It contains adb tool. Platform-tools can be directly downloaded from here. I prefer to install it from Android SDK manager in Android Studio.