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To programming with the otherlanguages listed above, we can try the Scripting Layer for Android(SL4A) and Common Language Extension for Android(CLE), to get a quick start, please read thewiki pageof SL4A and an example about CLE.
Here, will not use the powerful SL4A and CLE (will talk about them in other articles), but instead, will expore some other ways to let a language work on Android, Let’suse the small Lua as our demo language.
“Lua is a powerful, fast, lightweight, embeddable scripting language.”
In this article, we will using LuaJIT, AndroLua on Android to do Lua programming.
- LuaJIT is a Just-In-Time Compiler (JIT) for the Lua programming language.
AndroLua is the Lua interpreter ported to the Android platform. Others have ported Lua to Android, but this project is special:
it includes LuaJava, so you can access (almost) everything the Android API provides because writing code on the soft keyboard can be hard, you can connect to it using TCP an upload code from your computer
Build LuaJIT withAndroid NDK
To share the common libraries provided by Android system, we can build LuaJIT with the ARM Cross Compiler from Android NDK :
$ wget -c http://luajit.org/download/LuaJIT-2.0.1.tar.gz $ tar zxf LuaJIT-2.0.1.tar.gz && cd LuaJIT-2.0.1 $ apt-get install gcc-multilib $ make HOST_CC="gcc -m32" CROSS=arm-linux-androideabi- TARGET_SYS=Linux $ adb push src/luajit /data/ 3177 KB/s (378280 bytes in 0.116s) $ adb shell root@android:/ # chmod 777 /data/luajit root@android:/ # /data/luajit LuaJIT 2.0.1 -- Copyright (C) 2005-2013 Mike Pall. http://luajit.org/ JIT: ON ARMv7 fold cse dce fwd dse narrow loop abc sink fuse > for i = 1,4 do print(i) end 1 2 3 4 >
The above LuaJIT is dynamically linked and its dynamic linker is: /system/bin/linker:
$ file src/luajit src/luajit: ELF 32-bit LSB executable, ARM, version 1 (SYSV), dynamically linked (uses shared libs), stripped $ arm-linux-androideabi-readelf -l src/luajit | grep interpreter [Requesting program interpreter: /system/bin/linker]
Build LuaJIT with Linaro ARM Cross Compiler
If no Andriod NDK installed, the Linaro ARM Cross Compiler can be used, for example, in Ubuntu system, it can be simply installed with:
$ sudo apt-get install gcc-arm-linux-gnueabi
Since this compiler use different dynamic linker and different libraries, to compile LuaJIT for Android, static linking may be better for it avoid the installation of the dynamic linker and the shared libraries:
The using is the same, let’s use the math operation as an example:
$ adb push src/luajit /data/ $ adb shell root@android:/ # /data/luajit LuaJIT 2.0.1 -- Copyright (C) 2005-2013 Mike Pall. http://luajit.org/ JIT: ON ARMv7 fold cse dce fwd dse narrow loop abc sink fuse > print(math.sin(2.3)) 0.74570521217672 >
Write a Lua script
$ cat > /tmp/test.lua #!/data/luajit print(math.sin(2.3)) $ adb push /tmp/test.lua /data/ $ adb shell chmod 777 /data/test.lua $ adb shell /data/test.lua 0.74570521217672
The above method allows us to build theLua programming environment easily but it lacks of some features provided by AndroLua:
- It integrates the official Lua 5.1, allows to execute generic Lua scripts, have no compatiblity issues
- It integrates the LuaJava,allows scripts written in Lua to manipulate components developed in Java
- It allows to write Lua programs on Android, excute it and check the status (Not mature enough)
- Because writing code on the soft keyboard can be hard, you can connect to it using TCP an upload code from your computer
Now, Let’s refer to the README, download, build, install and useAndrodLuaon Android.
AndrodLua is maintained under a git repository, just clone it:
$ git clone git://github.com/mkottman/AndroLua.git && cd AndroLua
To build AndroLua, we need to update the project with new Android version with the ‘android update’ command and then build a debug package with the ‘ant’ command. Here, we build it for Android 4.2.
$ android list Available Android targets: ---------- id: 1 or "android-16" Name: Android 4.1.2 Type: Platform API level: 16 Revision: 4 Skins: HVGA, WVGA800 (default), WXGA800, WVGA854, WQVGA400, WXGA800-7in, WQVGA432, QVGA, WSVGA, WXGA720 ABIs : no ABIs. ---------- id: 2 or "android-17" Name: Android 4.2 Type: Platform API level: 17 Revision: 1 Skins: HVGA, WVGA800 (default), WXGA800, WVGA854, WQVGA400, WXGA800-7in, WQVGA432, QVGA, WSVGA, WXGA720 ABIs : armeabi-v7a Available Android Virtual Devices: $ android update project -p ./ -t 2
Then, install ant, and build the AndroLua package:
$ sudo apt-get install ant $ ant debug
As a result, the package is compiled: bin/Main-debug.apk.
Now, let’s install it with ‘adb’:
$ adb install bin/Main-debug.apk
After installation, the AndrodLua icon will be listed in the desktop of your Android device, start it and it will looks like:
Write your Lua programs and execute them there.
As we can see, the AndroLua UI interface is very simple andwriting code in Android with the soft keyboard is hard, so, we can try the remote programming feature of AndrodLua, to use it, Let’s forward its remote service to local:
$ adb forward tcp:3333 tcp:3333
And then, start the local Lua intepreter with:
$ lua ./interp.lua loading init.lua > require 'import' > print(Math:sin(2.3)) > > 0.74570521217672
This is also very simple.
In this article, we have shown two methods to build the Lua programming environment for Android, accordingly, simple Lua scripts are written and executed on Android system with these environments.
As we can see, both of them are simple and only for newcomers:
- To build a full Lua programming environment, the SL4A and CLE, or the other commercial IDEs are required, we will discuss them in the other articles.
- But, both of themshow us the hidden details behind SL4A and CLE, based on these practical steps and the open source codes, we may be able tobuild the other native programming environments and develop similar IDEs ourselves.
For example, the book: Optimizing Embedded Systems using Busybox shows how to build native Bash and C programming environments for Android system.