This bash script compiles openalpr for android. You just need to provide the path to Android SDK and Android NDK in the first lines of this code and execute it. Tested on ubuntu 17.04 64bit

build_openalpr_android.sh

#!/bin/bash

# You should tweak this section to adapt the paths to your need
export ANDROID_HOME=/home/jeremy/Android/Sdk
export NDK_ROOT=/home/jeremy/Android/Sdk/ndk-bundle

ANDROID_PLATFORM="android-21"

# In my case, FindJNI.cmake does not find java, so i had to manually specify these
# You could try without it and remove the cmake variable specification at the bottom of this file
JAVA_HOME=/usr/lib/jvm/oracle-java8-jdk-amd64
JAVA_AWT_LIBRARY=$JAVA_HOME/jre/lib/amd64
JAVA_JVM_LIBRARY=$JAVA_HOME/jre/lib/amd64
JAVA_INCLUDE_PATH=$JAVA_HOME/include
JAVA_INCLUDE_PATH2=$JAVA_HOME/include/linux
JAVA_AWT_INCLUDE_PATH=$JAVA_HOME/include

SCRIPT=`realpath $0`
SCRIPTPATH=`dirname $SCRIPT`

####################################################################
# Prepare Tesseract and Leptonica, using rmtheis/tess-two repository
####################################################################

git clone --recursive https://github.com/rmtheis/tess-two.git tess2

cd tess2
echo "sdk.dir=$ANDROID_HOME
ndk.dir=$NDK_ROOT" > local.properties
./gradlew assemble
cd ..


####################################################################
# Download and extract OpenCV4Android
####################################################################

wget -O opencv-3.2.0-android-sdk.zip -- https://sourceforge.net/projects/opencvlibrary/files/opencv-android/3.2.0/opencv-3.2.0-android-sdk.zip/download 
unzip opencv-3.2.0-android-sdk.zip
rm opencv-3.2.0-android-sdk.zip

####################################################################
# Download and configure openalpr from jav974/openalpr forked repo
####################################################################

git clone https://github.com/jav974/openalpr.git openalpr
mkdir openalpr/android-build

TESSERACT_SRC_DIR=$SCRIPTPATH/tess2/tess-two/jni/com_googlecode_tesseract_android/src

rm -rf openalpr/src/openalpr/ocr/tesseract
mkdir openalpr/src/openalpr/ocr/tesseract
shopt -s globstar
cd $TESSERACT_SRC_DIR

cp **/*.h $SCRIPTPATH/openalpr/src/openalpr/ocr/tesseract

cd $SCRIPTPATH

declare -a ANDROID_ABIS=("armeabi"
			 "armeabi-v7a"
			 "armeabi-v7a with NEON"
			 "arm64-v8a"
			 "mips"
			 "mips64"
			 "x86"
			 "x86_64"
			)

cd openalpr/android-build

for i in "${ANDROID_ABIS[@]}"
do
    if [ "$i" == "armeabi-v7a with NEON" ]; then abi="armeabi-v7a"; else abi="$i"; fi
    TESSERACT_LIB_DIR=$SCRIPTPATH/tess2/tess-two/libs/$abi

    if [[ "$i" == armeabi* ]];
    then
	arch="arm"
	lib="lib"
    elif [[ "$i" == arm64-v8a ]];
    then
	arch="arm64"
	lib="lib"
    elif [[ "$i" == mips ]] || [[ "$i" == x86 ]];
    then
	arch="$i"
	lib="lib"
    elif [[ "$i" == mips64 ]] || [[ "$i" == x86_64 ]];
    then
	arch="$i"
	lib="lib64"
    fi
    
    echo "
######################################
Generating project for arch $i
######################################
"
    rm -rf "$i" && mkdir "$i"
    cd "$i"
    
    cmake \
	-DANDROID_TOOLCHAIN=clang \
	-DCMAKE_TOOLCHAIN_FILE=$NDK_ROOT/build/cmake/android.toolchain.cmake \
	-DANDROID_NDK=$NDK_ROOT \
	-DCMAKE_BUILD_TYPE=Release \
	-DANDROID_PLATFORM=$ANDROID_PLATFORM \
	-DANDROID_ABI="$i" \
	-DANDROID_STL=gnustl_static \
	-DANDROID_CPP_FEATURES="rtti exceptions" \
	-DTesseract_INCLUDE_BASEAPI_DIR=$TESSERACT_SRC_DIR/api \
	-DTesseract_INCLUDE_CCSTRUCT_DIR=$TESSERACT_SRC_DIR/ccstruct \
	-DTesseract_INCLUDE_CCMAIN_DIR=$TESSERACT_SRC_DIR/ccmain \
	-DTesseract_INCLUDE_CCUTIL_DIR=$TESSERACT_SRC_DIR/ccutil \
	-DTesseract_LIB=$TESSERACT_LIB_DIR/libtess.so \
	-DLeptonica_LIB=$TESSERACT_LIB_DIR/liblept.so \
	-DOpenCV_DIR=$SCRIPTPATH/OpenCV-android-sdk/sdk/native/jni \
	-DJAVA_AWT_LIBRARY=$JAVA_AWT_LIBRARY \
	-DJAVA_JVM_LIBRARY=$JAVA_JVM_LIBRARY \
	-DJAVA_INCLUDE_PATH=$JAVA_INCLUDE_PATH \
	-DJAVA_INCLUDE_PATH2=$JAVA_INCLUDE_PATH2 \
	-DJAVA_AWT_INCLUDE_PATH=$JAVA_AWT_INCLUDE_PATH \
	-DPngt_LIB=$TESSERACT_LIB_DIR/libpngt.so \
	-DJpgt_LIB=$TESSERACT_LIB_DIR/libjpgt.so \
	-DJnigraphics_LIB=$NDK_ROOT/platforms/$ANDROID_PLATFORM/arch-$arch/usr/$lib/libjnigraphics.so \
	-DANDROID_ARM_MODE=arm \
	../../src/

    cmake --build . -- -j 8
    
    cd ..
done

echo "
All done !!!"