在Kotlin中穿线的正确方法

Question

I have thread code block which basically displays progress bar for 2 seconds then shows a recycler view. I wonder if there is more proper way to write this for example coroutines or rxjava. I tried coroutines but I got crashes. Code :

 runOnUiThread {
            fabClose()
            isOpen = false
            rec_view.adapter=null
            progressBar.visibility = View.VISIBLE

        }
        val handler = Handler()
        val t = Timer()
        t.schedule(object: TimerTask() {
            override fun run() {
                handler.post {
                        runOnUiThread {
                            imageRecognition()
                            progressBar.visibility = View.GONE

                        }
                }
            }
        }, 2000)

Answer 1

While you could use coroutines, what you are trying to achieve seems pretty straightforward, it is only that you code looks a little bit more convoluted than necessary.

You could try using the postDelayed() method of a Handler invoked on the main looper (which is the looper that lives in the main thread):

// Code to show the loader here
Handler(Looper.getMainLooper()).postDelayed({
    // Code to show the recyclerview here 
}, 2000)

Answer 2

Yes, You can try your code snippet with Kotlin Coroutines like following:

GlobalScope.launch(Dispatchers.Main) { // We launch new coroutine with Main thread as dispatcher
    fabClose()
    isOpen = false
    rec_view.adapter=null
    progressBar.visibility = View.VISIBLE
    // Here delay is suspended function which stops further execution of thread without blocking it.
    delay(2000L) // We provide non-blocking delay for 2 second which suspends this coroutine execution
    imageRecognition()
    progressBar.visibility = View.GONE
}

Here, GlobalScope is used to create our lauch Coroutine with Main Thread CoroutineContext (One can also use async too, difference between both is return type they provide) & we put our asynchronous code in sequential manner where Coroutine handles it's execution asynchronously.