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# Building Android Applications

Ren'Py contains tools that help you take a packaging-centric approach to Android game development. In this approach, you will use a PC to build an Android package and upload it to your device. You can then run the game like any Android application. When it works correctly, you can upload the package you make to Google Play and other app stores.

Building an Android application takes four or five steps:

1. Download and install RAPT, the Java Development Kit, and Android USB Drivers (scroll down for links).
2. Use the launcher to install the Android SDK and create keys.
3. Use the launcher to configure the Android build.
4. Use the launcher to build the Android application.

Once you've finished these steps, you'll have a runnable Android package. You'll only need to run step 3 when you decide to make changes to your game's configuration or when configuring a new game entirely; you'll run step 4 most often, whenever you need to make a new build of your game.

## Step 1: Installing the Dependencies

There are three things you may need to manually download and install before you can build packages:

Java Development Kit. The Java Development Kit (JDK) contains several tools that are used by RAPT, including the tools used to generate keys and sign packages. It can be downloaded from:

> http://www.oracle.com/technetwork/java/javase/downloads/index.html

Please note that the developer-focused JDK is different from the user-focused JRE, and you'll need the JDK to create Android packages.

Android Device Drivers. On Windows, you may want to install a device driver to access your device, although this is not necessary. Links to android device drivers can be found at:

> http://developer.android.com/sdk/oem-usb.html

On Linux or OS X, you won't need a device driver. If you can't access your device, you may need to read:

> http://developer.android.com/guide/developing/device.html#setting-up

However, modern versions of Linux and OS X should just work.

RAPT. The latest version of RAPT can be downloaded from:

> http://www.renpy.org/dl/android

Once RAPT has been downloaded, you should unpack it inside the Ren'Py directory. (The directory that contains renpy.exe, renpy.sh, and the Ren'Py app.) Then restart the launcher to ensure that it detects the presence of RAPT.

## Step 2: Set up the Android SDK and Development Environment

The next step is to set up the Android SDK and the rest of your development environment. This step will:

- Check that the JDK is installed properly.
- Install Apache Ant.
- Install the Android SDK.
- Use the Android SDK to install the appropriate development packages.
- Create a signing key that will be used to sign packages that are placed on the market (android.keystore: this will be generated in the RAPT directory).

This step requires Internet access.

To perform this step, choose "Install SDK & Create Keys" from the Android screen in the Ren'Py Launcher.

RAPT will report on what it's doing. It will also prompt you with warnings about licenses, and ask if you want it to generate a key.

Warning

The key generated by RAPT is created with a standard passphrase. You should really use keytool to generate your own signing keys.

> http://docs.oracle.com/javase/1.3/docs/tooldocs/win32/keytool.html

At the very least, you should keep the android.keyring file in a safe place. You should also back it up, because without the key, you won't be able to upload the generated applications.

## Step 3: Configure Your Game

Before building a package, you must give Ren'Py some information about the Android build of your game. To do this, choose "Configure" from the Android screen of the Ren'Py launcher.

If you need to change the information - for example, if you release a new version of your game - you can re-run the configure command. Your previous choices will be remembered.

## Step 4: Build and Install the Package

Finally, you can build and install the package. This is done with a by connecting your Android device to your computer, and choosing "Build & Install" from the Android screen of the Ren'Py launcher. (The first time you install, your Android device may ask you to authorize your computer to install applications.)

If you'd rather copy the game's apk file to your Android device manually, choose "Build Package" from the Android screen of the Ren'Py launcher. Then navigate to the 'bin' directory underneath the RAPT directory and copy the file mygame-release.apk into your Android Device. You will then need to find the .apk file in your Android device using a file manager application and open it to install the game.

## Viewing Debug Output

Debug output can be found by running the adb command manually from the terminal. After installing the SDK, the adb command can be found as rapt-dir/android-sdk/platform-tools/adb. (On Windows, use adb.exe.)

To view output from Ren'Py, consider a command line like:

> adb logcat -s python:*

## Google Play Expansion APKs

Ren'Py optionally supports the use of expansion APKs when used on a device supporting Google Play. Expansion APs allow Google Play to host games larger than 50MB in size. Please see:

> http://developer.android.com/google/play/expansion-files.html

For information about expansion APKs work. Right now, only the main expansion APK is supported, giving a 2GB limit. When an Expansion APK is created, all game files will be placed in the expansion APK. Ren'Py will transparently use these files.

To configure your game to use Expansion APKs, you'll need to set two variables:

`build.google_play_key` = "..."

  This is the Google Play license key associated with your application, which can be found on the "Services & APIs" tab associated with your application in the Google Play developer console. (Be sure to remove all spaces and newlines from the key.)

`build.google_play_salt` = ( ... )

  This should be a tuple of 20 bytes, where each byte is represented as an integer between -128 and 127. This is used to encrypt license information returned from Google Play.

  A valid (if insecure) value for this variable is:

      (0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)

RAPT will place the expansion APK on the device when installing the APK package on the device. The expansion APK will be an .obb file found inside the bin subdirectory of the RAPT directory.

In normal operation, Google Play will place the expansion APK on the device automatically when the user installs the application.

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