CODEWITHSUNDEEP
androidkotlinkotlin-coroutinescoroutinecoroutinescope
Santanu Sur
Santanu Sur

Reputation: 11477

Suspend function 'callGetApi' should be called only from a coroutine or another suspend function

I am calling suspended function from onCreate(...)

override fun onCreate(savedInstanceState: Bundle?) {
    ...
    ...
    callGetApi()
}

and the suspended function is:-

suspend fun callGetApi() {....}

But the error shows up Suspend function 'callGetApi' should be called only from a coroutine or another suspend function

Upvotes: 79

Views: 99555

Answers (3)

Sergio
Sergio

Reputation: 30685

Suspend function should be called only from a coroutine.

That means to call a suspend function you need to use a coroutine builder, e.g. launch, async or runBlocking(recommended to use only in unit tests). For example:

class Activity : AppCompatActivity(), CoroutineScope {
    private var job: Job = Job()

    override val coroutineContext: CoroutineContext
        get() = Dispatchers.Main + job

    override fun onDestroy() {
        super.onDestroy()
        job.cancel()
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        launch {
            val result =  callGetApi()
            onResult(result) // onResult is called on the main thread
        }
    }

    suspend fun callGetApi(): String {...}

    fun onResult(result: String) {...}
}

To use Dispatchers.Main in Android add dependency to the app's build.gradle file:

implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-android:1.0.1'

The MOST RECENT APPROACH would be to use extension properties in ViewModel and Activity/Fragment:

It attached to the lifecycle of Activity/Fragment and cancels launched coroutines when they destroyed.

Upvotes: 84

Santanu Sur
Santanu Sur

Reputation: 11477

The above answer worked , but i solved it without inheriting CoroutineScope class by just using .... gradle.build

  dependencies {
      implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-core:1.3.3'
  }

Activity.kt

  import kotlinx.coroutines.GlobalScope
  import kotlinx.coroutines.Dispatchers

  GlobalScope.launch (Dispatchers.Main) { callGetApi() }

Dispatchers.Main is important cause you cannot update the UI in any other thread than main.

But its recommended to inherit CoroutineScope to maintain the lifecycle of the activity and onDestroy of the activity to kill the job

Upvotes: 15

Kipr
Kipr

Reputation: 1076

Looks like the most elegant way to do it as of July 2019, is the one described here:

import androidx.lifecycle.lifecycleScope
import kotlinx.coroutines.launch

class Activity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super...

        lifecycleScope.launch {
            val result =  callGetApi()
            onResult(result) 
        }
    }
}

Don't forget to add the correponding lib:

implementation "androidx.lifecycle:lifecycle-runtime-ktx:2.2.0-alpha02"

Upvotes: 46

Related Questions