Points to be noted :- use older java ie jdk 8 not jdk 9 use ndk version not later than 13b simply follow the instructions for the betterment of you :-

• Make sure to have a copy of brltty, version 4.5 checked out. This can be checked out from subversion as follows (run from within the eyes-free directory as per above): $ svn checkout svn://mielke.cc//releases/brltty-4.5
  braille/service/jni/brlttywrapper/brltty

• Make sure to have a copy of liblouis, version 2.6.0 checked out. This can be checked out from Github as follows (run under directory braille/service/jni/liblouiswrapper/liblouis):

  $ git clone --branch v2.6.0 https://github.com/liblouis/liblouis.git

• Apply patches to the dependencies: $ (cd braille/service/jni/brlttywrapper && patch -p1 < brltty.patch) $ (cd braille/service/jni/liblouiswrapper && patch -p1 < liblouis.patch)

• Update the local ant property files: $ android update project -p libraries/utils -t android-18 $ android update project -p libraries/compatutils -t android-18 $ android update project -p braille/client -t android-18 $ android update project -p braille/service -t android-18 $ android update project -p braille/brailleback -t android-18

• Build the native libraries: $ (cd braille/service && ndk-build -j16)

• Build the BrailleBack apk: $ (cd braille/brailleback && ant debug)

• Alternatively, build and install on a connected device: $ (cd braille/brailleback && ant debug install)