For your convenience, every new Android project includes the Gradle Wrapper, so when you create a new project, you do not have to do anything at all to get the necessary files. It is, of course, possible to install Gradle manually on your computer and use it for your project, but the Gradle Wrapper can do the same things and guarantee that the correct version of Gradle is used. There is no good reason not to use the wrapper when working with Gradle outside of Android Studio.

You can check if the Gradle Wrapper is present in your project by navigating to the project folder and running ./gradlew –v from the terminal or gradlew.bat –v from Command Prompt. Running this command displays the version of Gradle and some extra information about your setup. If you are converting an Eclipse project, the wrapper will not be present by default. In this case, it is possible to generate it using Gradle, but you will need to install Gradle first to get the wrapper.

After you have downloaded and installed Gradle and added it to your PATH, create a build.gradle file containing these three lines:

task wrapper(type: Wrapper) {
    gradleVersion = '2.4'
}

After that, run gradle wrapper to generate the wrapper files.

In recent versions of Gradle, you can also run the wrapper task without modifying the build.gradle file, because it is included as a task by default. In that case, you can specify the version with the --gradle-version parameter, like this:

$ gradle wrapper --gradle-version 2.4

If you do not specify a version number, the wrapper is configured to use the Gradle version that the task is executed with.

These are all the files generated by the wrapper task:

myapp/
├── gradlew
├── gradlew.bat
└── gradle/wrapper/
    ├── gradle-wrapper.jar
    └── gradle-wrapper.properties

You can see here that the Gradle Wrapper has three parts:

The gradle-wrapper.properties file is the one that contains the configuration and determines what version of Gradle is used:

#Sat May 30 17:41:49 CEST 2015
distributionBase=GRADLE_USER_HOME
distributionPath=wrapper/dists
zipStoreBase=GRADLE_USER_HOME
zipStorePath=wrapper/dists
distributionUrl=https\://services.gradle.org/distributions/gradle-2.4-all.zip

You can change the distribution URL if you want to use a customized Gradle distribution internally. This also means that any app or library that you use could have a different URL for Gradle, so be sure to check whether you can trust the properties before you run the wrapper.

Android Studio is kind enough to display a notification when the Gradle version used in a project is not up to date and will suggest automatically updating it for you. Basically, Android Studio changes the configuration in the gradle-wrapper.properties file and triggers a build, so that the latest version gets downloaded.

In the terminal or command prompt, navigate to the project directory and run the Gradle Wrapper with the tasks command:

$ gradlew tasks

This will print out a list of all the available tasks. If you add the --all parameter, you will get a more detailed overview with the dependencies for every task.

To build the project while you are developing, run the assemble task with the debug configuration:

$ gradlew assembleDebug

This task will create an APK with the debug version of the app. By default, the Android plugin for Gradle saves the APK in the directory MyApp/app/build/outputs/apk.

Besides assemble, there are three other basic tasks:

We will discuss these tasks in detail in Chapter 2, Basic Build Customization.