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Fixed bug 2839 - No way to create pre-built libraries for Android

Mark Callow

README-android says to copy or link the SDL source tree to the jni folder in your Android project. It is not desirable to have to compile SDL with every application; furthermore the Android NDK has support for prebuilt libraries.

Attached is script (to be put in build-scripts) that builds the Android version of the libraries. The script builds both the existing SDL2 module and a new SDL2_main module. This is a static library containing the code from src/main/android/SDL_android_main.c. Also attached is a patch for Android.mk adding this module.

Note that when building an application's native .so using this prebuilt libSDL2main, you must use a link option, such as --whole-archive, that forces inclusion of the code in the .so because the functions in SDL_android_main are called only from Java.
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slouken committed Aug 14, 2017
1 parent c87e1d5 commit e977225937645764cfa5f26f4bab53af446d1cab
Showing with 94 additions and 0 deletions.
  1. +20 −0 Android.mk
  2. +74 −0 build-scripts/androidbuildlibs.sh
@@ -67,3 +67,23 @@ LOCAL_LDLIBS :=
LOCAL_EXPORT_LDLIBS := -Wl,--undefined=Java_org_libsdl_app_SDLActivity_nativeInit -ldl -lGLESv1_CM -lGLESv2 -llog -landroid

include $(BUILD_STATIC_LIBRARY)

###########################
#
# SDL main static library
#
###########################

include $(CLEAR_VARS)

LOCAL_C_INCLUDES := $(LOCAL_PATH)/include

LOCAL_MODULE := SDL2_main

LOCAL_MODULE_FILENAME := libSDL2main

LOCAL_SRC_FILES := $(LOCAL_PATH)/src/main/android/SDL_android_main.c

include $(BUILD_STATIC_LIBRARY)


@@ -0,0 +1,74 @@
#!/bin/sh
#
# Build the Android libraries without needing a project
# (AndroidManifest.xml, jni/{Application,Android}.mk, etc.)
#
# Usage: androidbuildlibs.sh [arg for ndk-build ...]"
#
# Useful NDK arguments:
#
# NDK_DEBUG=1 - build debug version
# NDK_LIBS_OUT=<dest> - specify alternate destination for installable
# modules.
#
# Note that SDLmain is not an installable module (.so) so libSDLmain.a
# can be found in $obj/local/<abi> along with the unstripped libSDL.so.
#


# Android.mk is in srcdir
srcdir=`dirname $0`/..
srcdir=`cd $srcdir && pwd`
cd $srcdir


#
# Create the build directories
#

build=build
buildandroid=$build/android
obj=
lib=
ndk_args=

# Allow an external caller to specify locations.
for arg in $*
do
if [ "${arg:0:8}" == "NDK_OUT=" ]; then
obj=${arg#NDK_OUT=}
elif [ "${arg:0:13}" == "NDK_LIBS_OUT=" ]; then
lib=${arg#NDK_LIBS_OUT=}
else
ndk_args="$ndk_args $arg"
fi
done

if [ -z $obj ]; then
obj=$buildandroid/obj
fi
if [ -z $lib ]; then
lib=$buildandroid/lib
fi

for dir in $build $buildandroid $obj $lib; do
if test -d $dir; then
:
else
mkdir $dir || exit 1
fi
done


# APP_* variables set in the environment here will not be seen by the
# ndk-build makefile segments that use them, e.g., default-application.mk.
# For consistency, pass all values on the command line.
ndk-build \
NDK_PROJECT_PATH=null \
NDK_OUT=$obj \
NDK_LIBS_OUT=$lib \
APP_BUILD_SCRIPT=Android.mk \
APP_ABI="all" \
APP_PLATFORM=android-12 \
APP_MODULES="SDL2 SDL2_main" \
$ndk_args

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