Compiling Android project with gradle command line

Under the samples/android-21/folder in the Android SDK directory, either find a project if you compile directly on the command line

This error may be reported:
Gradle Buile.gradle

Failure:build failed with an exception.

If this is the case, first go back to the project directory and run

./gradlew

And then perform the compilation
./Gradlew Build
./Gradlew Tasks//View all quests for Android Gradle
./Gradlew Compilereleasesource//Generate Debug APK, under build/outpus/apk folder

or execute under Windows cmd:
Gradlew.bat Init Wrapper
Gradlew Build

Compiling Android project with gradle command line