Stop Thread in Kotlin

Question

First of all, I'm new in Kotlin, so please be nice :). It's also my first time posting on StackOverflow

I want to literally STOP the current thread that I created but nothing works.

I tried quit(), quitSafely(), interrupt() but nothing works.

I created a class (Data.kt), in which I create and initialize a Handler and HandlerThread as follows :

class Dispatch(private val label: String = "main") {

    var handler: Handler? = null
    var handlerThread: HandlerThread? = null

    init {
        if (label == "main") {
            handlerThread = null
            handler = Handler(Looper.getMainLooper())
        } else {
            handlerThread = HandlerThread(label)
            handlerThread!!.start()
            handler = Handler(handlerThread!!.looper)
        }
    }

    fun async(runnable: Runnable) = handler!!.post(runnable)

    fun async(block: () -> (Unit)) = handler!!.post(block)

    fun asyncAfter(milliseconds: Long, function: () -> (Unit)) {
        handler!!.postDelayed(function, milliseconds)
    }

    fun asyncAfter(milliseconds: Long, runnable: Runnable) {
        handler!!.postDelayed(runnable, milliseconds)
    }

    companion object {
        val main = Dispatch()
        private val global = Dispatch("global")
        //fun global() = global
    }
}

And now, in my DataManager, I use these to do asynchronous things :

fun getSomething(forceNetwork: Boolean ) {

    val queue1 = Dispatch("thread1") // Create a thread called "thread1"
    queue1.async {
        for (i in 0..2_000_000) {
             print("Hello World")
             // Do everything i want in the current thread
        }

        // And on the main thread I call my callback
        Dispatch.main.async {
            //callback?.invoke(.........)
        }
    }
}

Now, in my MainActivity, I made 2 buttons :

1. One for running the function getSomething()
2. The other one is used for switching to another Controller View :

val button = findViewById<Button>(R.id.button)
button.setOnClickListener {
    DataManager.getSomething(true)
}

val button2 = findViewById<Button>(R.id.button2)
button2.setOnClickListener {
    val intent = Intent(this, Test::class.java) // Switch to my Test Controller
    intent.setFlags(Intent.FLAG_ACTIVITY_NO_HISTORY)
    startActivity(intent)
    finish()
}

Is there a way to stop the thread, because when I switch to my second View, print("Hello World") is still triggered, unfortunately.

Thanks for helping me guys I hope that you understand !

Answer 1

A thread needs to periodically check a (global) flag and when it becomes true then the thread will break out from the loop. Java threads cannot be safely stopped without its consent.

Refer to page 252 here http://www.rjspm.com/PDF/JavaTheCompleteReference.pdf that describes the true story behind the legend.

I think that a truly interruptible thread is only possible through the support of the operating system kernel. The actual true lock is held deep down by the CPU hardware microprocessor.