Android development

Android devices allows you to freely run your own apps on them. It is very easy to build a version of your game and copy it onto an Android device. This manual explains the steps involved in bundling your game for Android. During development, running your game through the development app is often preferred since it allows you to hot reload content and code wirelessly directly to your device.

Android and Google Play signing process

Android requires that all APKs be digitally signed with a certificate before they are installed on a device or updated. If you use Android App Bundles, you need to sign only your app bundle before you upload it to the Play Console, and Play App Signing takes care of the rest. However, you can also manually sign your app for upload to Google Play, other app stores and for distribution outside of any store.

When you create an Android application bundle from the Defold editor or the command line tool you can provide a keystore (containing your certificate and key) and keystore password which will be used when signing your application. If you don’t, Defold generates a debug keystore and uses it when signing the application bundle.

You should never upload your application to Google Play if it was signed using a debug keystore. Always use a dedicated keystore which you have created yourself.

Creating a keystore

The Android signing process in Defold changed in version 1.2.173 from using a stand-alone key and certificate to a keystore.

You can create a keystore using Android Studio or from a terminal/command prompt:

keytool -genkey -v -noprompt -dname "CN=John Smith, OU=Area 51, O=US Air Force, L=Unknown, ST=Nevada, C=US" -keystore mykeystore.keystore -storepass 5Up3r_53cR3t -alias myAlias -keyalg RSA -validity 9125

This will create a keystore file named mykeystore.keystore containing a key and certificate. Access to key and certificate will be protected by the password 5Up3r_53cR3t. The key and certificate will be valid for 25 years (9125 days). The generated key and certificate will be identified by the alias myAlias.

Make sure to store the keystore and associated password somewhere safe. If you sign and upload your applications to Google Play yourself and the keystore or keystore password is lost there is no way for you to update the application on Google Play. You can avoid this by using Google Play App Signing and let Google sign your applications for you.

Creating an Android application bundle

The editor lets you easily create a stand alone application bundle for your game. Before bundling you can specify what icon(s) to use for the app, set version code etc in the “game.project” project settings file.

To bundle select Project ▸ Bundle... ▸ Android Application... from the menu.

If you want the editor to automatically create random debug certificates, leave the Keystore and Keystore password fields empty:

Signing Android bundle

If you want to sign your bundle with a particular keystore, specify the Keystore and Keystore password. The Kyestore is expected to have the .keystore file extension while the password is expected to be stored in a text file with the .txt extension:

Signing Android bundle

Defold supports the creation of both APK and AAB files. Select APK or AAB from the Bundle Format drop down.

Press Create Bundle when you have configured the application bundle settings. You will then be prompted to specify where on your computer the bundle will be created.

Android Application Package file

Installing an Android application bundle

Installing an APK

An .apk file can be copied to your device with the adb tool (see below), or to Google Play via the Google Play developer console.

$ adb install Defold\ examples.apk
4826 KB/s (18774344 bytes in 3.798s)
  pkg: /data/local/tmp/my_app.apk
Success

Installing an AAB

An .aab file can be uploaded to Google Play via the Google Play developer console. It is also possible to generate an .apk file from an .aab file to install it locally using the Android bundletool.

Permissions

The Defold engine requires a number of different permissions for all engine features to work. The permissions are defined in the AndroidManifest.xml, specified in the “game.project” project settings file. You can read more about Android permissions in the official docs. The following permissions are requested in the default manifest:

android.permission.INTERNET and android.permission.ACCESS_NETWORK_STATE (Protection level: normal)

Allows applications to open network sockets and access information about networks. These permission are needed for internet access. (Android official docs) and (Android official docs).

android.permission.WRITE_EXTERNAL_STORAGE (Protection level: dangerous)

Allows an application to write to external storage. Starting in API level 19, this permission is not required to read/write files in your application-specific directories returned by Context.getExternalFilesDir(String) and Context.getExternalCacheDir(). This permission is needed if you intend to save/load files from disk (using io.* or sys.save/load) outside of the folder provided by sys.get_save_file() and have android:minSdkVersion set to less than 19 in the Android manifest. (Android official docs).

android.permission.WAKE_LOCK (Protection level: normal)

Allows using PowerManager WakeLocks to keep processor from sleeping or screen from dimming. This permission is needed to temporarily prevent the device from sleeping while receiving a push notification. (Android official docs)

Android Debug Bridge

The adb command line tool is an easy to use and versatile program that is used to interact with Android devices. You can download and install adb as part of the Android SDK Platform-Tools, for Mac, Linux or Windows.

Download the Android SDK Platform-Tools from: https://developer.android.com/studio/releases/platform-tools. You find the adb tool in /platform-tools/. Alternatively, platform specific packages can be installed through respective package managers.

On Ubuntu Linux:

$ sudo apt-get install android-tools-adb

On Fedora 18/19:

$ sudo yum install android-tools

On Mac OS X (Homebrew)

$ brew cask install android-platform-tools

You can veryfy that adb works by connecting your Android device to your computer via USB and issue the following command:

$ adb devices
List of devices attached
31002535c90ef000    device

If your device does not show up, verify that you have enabled USB debugging on the Android device. Open the device Settings and look for Developer options (or Development).

Enable USB debugging

Debugging an application bundle

A bundle built with the debug mode version of the engine (i.e. “Debug” selected as variant during bundling) will send all its console output to the Android system log. Access the log with the adb tool and give the logcat command. You probably want to filter the output by a tag (-s [tagname]):

$ adb logcat -s "defold"
--------- beginning of /dev/log/system
--------- beginning of /dev/log/main
I/defold  ( 6210): INFO:DLIB: SSDP started (ssdp://192.168.0.97:58089, http://0.0.0.0:38637)
I/defold  ( 6210): INFO:ENGINE: Defold Engine 1.2.50 (8d1b912)
I/defold  ( 6210): INFO:ENGINE: Loading data from:
I/defold  ( 6210): INFO:ENGINE: Initialised sound device 'default'
I/defold  ( 6210):
D/defold  ( 6210): DEBUG:SCRIPT: Hello there, log!
...

FAQ

Q: Is it possible to hide the navigation and status bars on Android?

A: Yes, set the immersive_mode setting in the Android section of your game.project file. This lets your app take over the whole screen and capture all touch events on the screen.

Q: Why am I’m getting “Failure [INSTALL_PARSE_FAILED_INCONSISTENT_CERTIFICATES]” when installing a Defold game on device?

A: Android detects that you try to install the app with a new certificate. When bundling debug builds, each build will be signed with a temporary certificate. Uninstall the old app before installing the new version:

$ adb uninstall com.defold.examples
Success
$ adb install Defold\ examples.apk
4826 KB/s (18774344 bytes in 3.798s)
      pkg: /data/local/tmp/Defold examples.apk
Success

Did you spot an error or do you have a suggestion? Please let us know on GitHub!

GITHUB