Android Kotlin Coroutine Scope for Activity, Fragment and ViewModel (Architecture Components)
October 10, 2019Dependencies
dependencies {
def lifecycle_extension_version = '2.2.0-beta01'
// activity, fragment
implementation "androidx.lifecycle:lifecycle-runtime-ktx:$lifecycle_extension_version"
// viewmodel
implementation "androidx.lifecycle:lifecycle-viewmodel-ktx:$lifecycle_extension_version"
// optional - livedata
implementation "androidx.lifecycle:lifecycle-livedata-ktx:$lifecycle_extension_version"
}
Activity and Fragment
class CardFragment : Fragment() { // CoroutineScope by MainScope() {
fun test() {
// launch in main/ui thread
// lifecylerOwner.lifecycleScope.launch { }
lifecycleScope.launch { // Dispatchers.Main
}
// launch in background thread
lifecycleScope.launch(Dispatchers.Default) {
}
}
}
Some new tricks is available
class CardFragment : Fragment() {
init {
lifecycleScope.launchWhenStarted {
}
lifecycleScope.launch {
whenStarted {
}
}
}
}
ViewModel
class CardViewModel : ViewModel() {
init {
// new trick to launch when ViewModel created
viewModelScope.launch {
}
}
fun test() {
viewModelScope.launch {
}
}
}
LiveData
Call suspend coroutines within LiveData source
val userLiveData: LiveData<User> = liveData {
val data = database.loadUser() // loadUser is a suspend function.
emit(data)
}
instead of
val userLiveData: LiveData<User> = MutableLiveData()
fun loadUser() {
launch {
val data = database.loadUser()
userLiveData.postValue(data)
}
}
NOTE: I have yet to explore more practical usage of LiveData coroutines
References:
- algo-trading
- algolia
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- android-studio
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