Android Revisited.

Sun 18 June 2017
By Bram

Every year or so, I come back to Android development. And often, quite a bit has changed. On top of that, I will have forgotten gotchas, and fall in the same trap twice. Hence, I need to document my process better. So here's another Android report.

I managed to hold out on IDEs altogether. I never used Eclipse, and always did ndk-build and ant on the command line. This time around, I have been forced to use Android Studio, as the google play game services are only updated for Android Studio builds. Android Studio is built on top of the Gradle build system. Gradle is a Java-only thing. For C++ it depends on either ndk-build (couldn't make it work with Android Studio) or CMake. So CMake it is now. You have to write a lot of CMakeLists.txt files for your game, and its dependencies. It is a hassle.

You can only add a single CMakeLists.txt to your Android project. So dependencies need to be included from a top level file. To do this, use: add_subdirectory( srcdir builddir )

Settings in your Gradle files are used to overwrite settings in your AndroidManifest.xml file.

Google Play Games is a mess as always. The latest version will crash on launch for me, so I had to downgrade it in my app's Gradle file.

The 'DEX' gets too large, so you need to selectively use Google Play Games dependencies like this:

dependencies {
    compile 'com.google.android.gms:play-services-auth:10.0.1'
    compile 'com.google.android.gms:play-services-nearby:10.0.1'
    compile 'com.google.android.gms:play-services-games:10.0.1'
}

If you target SDK level 21 then the Android Soft Keys will be hiding your app's content. For proper sizing, switch to targetSdk 19 instead.

After changing dependencies in your app's Gradle file, you need to do a clean, otherwise conflicts can arise, like duplicate definitions.

To link against a pre-built library, e.g. the Google provided gpg-cpp-sdk library, use the following CMake syntax:

add_library( gpg
             STATIC
             IMPORTED
)
set_target_properties( gpg
  PROPERTIES IMPORTED_LOCATION
  $ENV{HOME}/src/gpg-cpp-sdk/android/lib/gnustl/${ANDROID_ABI}/libgpg.a )

There is something wrong with the arm64-v8a build of Google Play Games gpg.a static library.

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