KOTLIN : android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views

Question

I have this code:

    lifecycleScope.launch(Dispatchers.Default) {
        val specialMessage = URL("https://finepointmobile.com/api/inventory/v1/message").readText()
        d("Globby", "The message is: $specialMessage")
        lastSavedProduct.text = specialMessage                //line 41
    }

But when executing I get the following error:

ERROR : android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
        at com.example.MainActivity$onCreate$2.invokeSuspend(MainActivity.kt:41)

I tried changing lifecycleScope.launch(Dispatchers.IO) to lifecycleScope.launch(Dispatchers.Default) but it doesn't work.

tried it, got this : android.os.NetworkOnMainThreadException — Globby, Mar 12 '20 at 11:04

score 3 · Answer 1 · answered Mar 12 '20 at 12:09

If I remember coroutines correctly, then the following should work:

lifecycleScope.launch { // runs on Main by default
    val specialMessage = withContext(Dispatchers.IO) {
        URL("https://finepointmobile.com/api/inventory/v1/message").readText()
    } 
    lastSavedProduct.text = specialMessage
}

score 0 · Answer 2 · answered Mar 12 '20 at 17:18

0

Try this

// Make a CoroutineContext variable
val main: CoroutineContext by lazy { Dispatchers.Main }

then use it in your code

lifecycleScope.launch(main) {
    val specialMessage = URL("https://finepointmobile.com/api/inventory/v1/message").readText()
    d("Globby", "The message is: $specialMessage")
    lastSavedProduct.text = specialMessage //line 41
}

answered Mar 12 '20 at 17:18

Erwin Kurniawan A

958
2
9
17

Why do you need the lazy ref instead of just using Dispatchers.Main directly? – EpicPandaForce Mar 12 '20 at 18:59

KOTLIN : android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views

2 Answers2