~/myApp$ sudo ionic build android

Running command: /home/hari/myApp/hooks/after_prepare/010_add_platform_class.js /home/hari/myApp
  add to body class: platform-android
  ERROR building one of the platforms: Failed to find 'ANDROID_HOME'  environment variable. Try setting setting it manually.
  Failed to find 'android' command in your 'PATH'. Try update your 'PATH' to include path to valid SDK directory.
You may not have the required environment or OS to build this project
Error: Failed to find 'ANDROID_HOME' environment variable. Try setting setting it manually.
Failed to find 'android' command in your 'PATH'. Try update your 'PATH' to include path to valid SDK directory.

echo $ANDROID_HOME
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/home/hari/Android/Sdk

echo $PATH
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/home/hari/Android/Sdk/tools:/home/hari/Android/Sdk/platform-tools:/usr/local/bin:/opt/gradle/bin

export ANDROID_HOME=/<installation location>/android-sdk-macosx
export PATH=${PATH}:$ANDROID_HOME/tools:$ANDROID_HOME/platform-tools

export ANDROID_HOME=/<installation location>/android-sdk-linux
export PATH=${PATH}:$ANDROID_HOME/tools:$ANDROID_HOME/platform-tools

set ANDROID_HOME=C:<installation location>android-sdk-windows
set PATH=%PATH%;%ANDROID_HOME%tools;%ANDROID_HOME%platform-tools

android

sudo gedit ~/.bashrc

export ANDROID_HOME=/opt/android-sdk-linux
export PATH=${PATH}:$ANDROID_HOME/tools:$ANDROID_HOME/platform-tools

source ~/.bashrc

ionic platform

Installed platforms:
  android 6.0.0
Available platforms:
  amazon-fireos ~3.6.3 (deprecated)
  blackberry10 ~3.8.0
  browser ~4.1.0
  firefoxos ~3.6.3
  ubuntu ~4.3.4
  webos ~3.7.0

ionic platform rm android
ionic platform add android

ionic platform add android

cd /home/ubuntu/
sudo rm -r .cordova

ionic platform add android

set PATH so it includes user's private bin directories
PATH="$HOME/bin:$HOME/.local/bin:$PATH"
export ANDROID_HOME='/home/<user_name>/Android/Sdk' <Path to android SDK>
export PATH=$PATH:$ANDROID_HOME/bin
export PATH=$PATH:$ANDROID_HOME/tools
export PATH=$PATH:$ANDROID_HOME/platform-tools

PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games"
JAVA_HOME="/usr/lib/jvm/java-8-oracle"
ANDROID_HOME="/home/<user_name>/Android/Sdk" <Path to android SDK>

JAVA_HOME=/usr/lib/jvm/java-8-oracle <Path where Java is installed>
JRE_HOME=$JAVA_HOME/jre
PATH=$PATH:$JAVA_HOME/bin:$JRE_HOME/bin
export JAVA_HOME
export JRE_HOME
export PATH

source ~/.profile
source /etc/environment
source /etc/profile

cd ..
    sudo chmod -R 777 helloWorld
    cd helloWorld
    ionic platform add android
    If you are still getting the error then remove ".cordova" folder from the home directory of your PC.

F:ADT_SDKsdkplatforms
F:ADT_SDKsdkplatform-tools

I had this issue before.
you need to add android to your environment path
"sdkstools" and "sdksbuild-tools"

Thanks