I know there are lots of questions similiar to this one, but i couldn't find a solution for my problem in any of those. Besides, I'll provide details for my specific case.

I coded an Ionic project in Ubuntu 16.04 LTS, and now I have to build it for release. So I run the command:

cordova build --release android

And I'm shown the following error:

Error: Could not find gradle wrapper within Android SDK. Might need to update your Android SDK.
Looked here: /home/user/Android/Sdk/tools/templates/gradle/wrapper

• I don't have this templates/gradle/wrapper directory.
• My Android Studio is 2.3, the latest version for now
• Android SDK Platform-Tools 25.0.3
• Android SDK Tools 25.3.1
• All Android versions from 2.1 (Eclair) to 7.1.1 (Nougat)

After extensive research, I put all the Android Studio-related environment variables in the file /etc/environment. So now it looks like this:

PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/game:/home/<user>/Android/Sdk:/home/<user>/Android/Sdk/tools:/home/<user>/Android/Sdk/platform-tools"

ANDROID_HOME=/home/<user>/Android/Sdk
export ANDROID_HOME

JAVA_HOME=/usr/lib/jvm/java-8-oracle
export JAVA_HOME

GRADLE_HOME=/opt/android-studio/gradle/gradle-3.2
export GRADLE_HOME

Now, for the sake of testing the environment variables, I run the following commands:

source /etc/environment
echo $PATH
echo $ANDROID_HOME
echo $JAVA_HOME
echo $GRADLE_HOME

And all the path variables are correctly displayed.

So, it looks like the environment variables are like they should be according to the various similar questions and in tutorials i've searched. Does anyone know what am I doing wrong? Why do I still get the Gradle Wrapper error?