Based on luaj, with enhanced interoperability with kotlin.
Assuming you are already familiar with the basic API of luaj.
- Add the JitPack repository to your build file
allprojects {
repositories {
...
maven { url 'https://jitpack.io' }
}
}- Add dependency with luaj
dependencies {
implementation 'com.github.only52607.luakt:luakt:$luakt_version'
}or without luaj
dependencies {
implementation 'com.github.only52607.luakt:luakt-core:$luakt_version'
implementation 'com.github.only52607.luakt:luakt-extension:$luakt_version'
}
luaktcontains the following three modules
luakt-core: The core module of luakt, including features such as type coercion.
luakt-extension: The extension module of luakt provides some useful utility functions.
luakt-luaj: The luaj library, if your project already includes this library, you don’t need to add it repeatedly.
main.kt
val globals = JsePlatform.standardGlobals()
globals.load(LuaKotlinLib())
globals.loadfile("main.lua").invoke()main.lua
-- launch a thread
Thread = luakotlin.bindClass("java.lang.Thread")
Thread(function()
print("print from new thread: " .. tostring(Thread:currentThread()))
end):start()If you are going to interact with kotlin in luaj, you can use Luajava library, but LuaKotlin library is a better choice, it provides similar api to Luajava library, but it interacts with kotlin much simpler.
- bind class
Thread = luakotlin.bindClass("java.lang.Thread")- new instance
-- bindClass and new
Random = luakotlin.bindClass("java.util.Random")
local r = luakotlin.new(Random, 10) -- use 10 as rand seed
-- newInstance
local r = luakotlin.newInstance("java.util.Random", 10)
-- with invoke sugar
Random = luakotlin.bindClass("java.util.Random")
local r = Random(10)- create proxy
Thread = luakotlin.bindClass("java.lang.Thread")
local runnable = luakotlin.createProxy("java.lang.Runnable", {
run = function ()
print("print from new thread: " .. tostring(Thread:currentThread()))
end
})
Thread(runnable):start()If a variable is a previously bound interface class, it can be called directly, which will return a proxy.
Thread = luakotlin.bindClass("java.lang.Thread")
Runnable = luakotlin.bindClass("java.lang.Runnable")
local runnable = Runnable {
run = function ()
print("print from new thread: " .. tostring(Thread:currentThread()))
end
}
Thread(runnable):start()- Single abstract method(SAM) interface coercion
If the interface is a SAM interface, then the proxy can be created like below without specifying the method name.
Thread = luakotlin.bindClass("java.lang.Thread")
Runnable = luakotlin.bindClass("java.lang.Runnable")
-- use function to create proxy ofsingle method interface
local runnable = Runnable(function ()
print("print from new thread: " .. tostring(Thread:currentThread()))
end)
Thread(runnable):start()If the type of a parameter is a SAM interface, you can pass in a Lua function as follows, and the proxy will be created automatically.
Thread = luakotlin.bindClass("java.lang.Thread")
Thread(function ()
print("print from new thread: " .. tostring(Thread:currentThread()))
end):start()- getter and setter
class Cat {
var color: String = "white"
set(value) {
field = value
println("color changed to $value")
}
}Cat = luakotlin.bindClass("Cat")
local c = Cat()
print(c.color) -- white
c.color = "pink" -- print "color changed to pink"
print(c.colot) -- pink- call suspend function blocking
class Cat {
suspend fun sleep(duration: Long) {
println("start sleep")
delay(duration)
println("wake up")
}
}Cat = luakotlin.bindClass("Cat")
local c = Cat()
c.sleep(1000) -- will block here- Interact with singleton objects
object TomCat {
fun run() {
prinln("TomCat is runnning")
}
}TomCat = luakotlin.bindClass("TomCat")
TomCat:run()- Interact with companion object
class Cat private constructor(val name: String) {
companion object {
fun create(name: String) {
println("Cat $name is created")
return Cat(name)
}
}
}Cat = luakotlin.bindClass("Cat")
Cat:create("tom")LuaKotlinExlib provides more utility functions based on the LuaKotlinLib.
globals.load(LuaKotlinlib()) // Make sure the LuaKotlinlib is preloaded
globals.load(LuaKotlinExlib())- import class
import "java.util.Random" -- Shorthand for `Random = luakotlin.bindClass("java.util.Random")`
Random(10).nextInt()
-- with alias
import("java.util.Random", MyRandom) -- Equivalent to `MyRandom = luakotlin.bindClass("java.util.Random")`
MyRandom(10).nextInt()- convert kotlin Collection or Map as lua table
The Array will be automatically converted to a lua table, but the Collection interface and Map interface will not be automatically converted. If you want to convert, you can use the totable function, which receives a userdata that implements the Collection or Map interface. And return the corresponding table.
object C {
fun getMap(): Map<String, String> = mapOf(Pair("k1", "v1"))
fun getList(): List<String> = listOf("v1", "v2")
}local map = C:getMap()
for k, v in pairs(totable(map)) do
print(k, v) -- k1 v1
end
local map = C:getList()
for i, v in ipairs(totable(map)) do
print(i, v)
-- v1
-- v2
end - convert lua table as kotlin Collection or Map
tolist({"v1", "v2"}) -- listOf("v1", "v2")
toset({"v1", "v2"}) -- setOf("v1", "v2")
tomap({ k1 = "v1", k2 = "v2" }) -- mapOf(Pair("k1", "v1"), Pair("k2", "v2"))luakt also provides some useful extension functions in kotlin
- create LuaFunction
val add = VarArgFunction { varargs ->
return LuaValue.valueOf(varargs.checkint(1) + varargs.checkint(2))
}- deconstruct varargs
val v = LuaValue.varargsOf(LuaValue.valueOf(1), LuaValue.valueOf(2))
val (a, b) = v // deconstruct
print(a, b) // 1 2
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