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DevPicon/FlowExample.kt

Created January 9, 2021 19:36
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StateFlow and Sharedflow... the end of LiveData?
Raw
FlowExample.kt
package sharedflow.macao.flow
import flow.others.log
import kotlinx.coroutines.delay
import kotlinx.coroutines.flow.collect
import kotlinx.coroutines.flow.filter
import kotlinx.coroutines.flow.flow
import kotlinx.coroutines.launch
import kotlinx.coroutines.runBlocking
import kotlin.random.Random
fun main() {
runBlocking {
delay(1000)
emitRandomNumbers()
.filter { value -> value % 2 == 0 }
.collect { value ->
log("Collector A: collected value $value")
}
}
}
fun emitRandomNumbers() = flow<Int> {
for (value in 0..100) {
delay(500)
log("Emitted value: $value")
emit(value)
}
}
Raw
FoodDetailViewModel.kt
import androidx.lifecycle.LiveData
import androidx.lifecycle.MutableLiveData
import androidx.lifecycle.ViewModel
import androidx.lifecycle.viewModelScope
import kotlinx.coroutines.launch
import pe.devpicon.android.compose.chukyeats.repository.FoodRepository
class FoodDetailViewModel : ViewModel() {
private val _detail: MutableLiveData<ScreenState> = MutableLiveData(ScreenState.Loading)
val detail: LiveData<ScreenState> = _detail
fun load(id: String) {
viewModelScope.launch {
try {
_detail.postValue(
ScreenState.Ready(FoodRepository.getFoodDetail(id))
)
} catch (e: Exception) {
_detail.postValue(ScreenState.Error(e.message ?: "This an unhandled error"))
}
}
//...
}
}
Raw
FoodDetailViewModelStateFlow.kt
import androidx.lifecycle.ViewModel
import androidx.lifecycle.viewModelScope
import kotlinx.coroutines.flow.MutableStateFlow
import kotlinx.coroutines.flow.StateFlow
import kotlinx.coroutines.launch
import pe.devpicon.android.compose.chukyeats.repository.FoodRepository
class FoodDetailViewModelStateFlow : ViewModel() {
private val _detailB: MutableStateFlow<ScreenState> = MutableStateFlow(ScreenState.Loading)
val detailB: StateFlow<ScreenState> = _detailB
fun load(id: String) {
viewModelScope.launch {
try {
_detailB.value = ScreenState.Ready(FoodRepository.getFoodDetail(id))
} catch (e: Exception) {
_detailB.value = ScreenState.Error(e.message ?: "This an unhandled error")
}
}
//...
}
}
Raw
SharedFlowExample.kt
package sharedflow.macao
import flow.others.log
import kotlinx.coroutines.channels.BufferOverflow
import kotlinx.coroutines.delay
import kotlinx.coroutines.flow.MutableSharedFlow
import kotlinx.coroutines.flow.asSharedFlow
import kotlinx.coroutines.flow.collect
import kotlinx.coroutines.flow.flow
import kotlinx.coroutines.launch
import kotlinx.coroutines.runBlocking
import kotlin.random.Random
fun main() {
val broadcastChannel = MyBroadcastChannel()
runBlocking {
launch {
emitterRandomIntegers().collect { value ->
broadcastChannel.postNewInteger(value)
}
}
launch {
delay(3000)
broadcastChannel.integers.collect { collectedValue ->
log("Collector A collected $collectedValue")
}
}
launch {
delay(5000)
broadcastChannel.integers.collect { collectedValue ->
log("Collector B collected $collectedValue")
}
}
}
}
class MyBroadcastChannel {
private val _integers = MutableSharedFlow<Int>(
extraBufferCapacity = 3,
onBufferOverflow = BufferOverflow.DROP_LATEST,
replay = 3
)
val integers = _integers.asSharedFlow()
suspend fun postNewInteger(newValue: Int) {
_integers.emit(newValue)
}
}
fun emitterRandomIntegers() = flow<Int> {
while (true) {
delay(1000)
val random = Random.nextInt(0, 200)
log("Emitter - emitted value $random")
emit(random)
}
}
Raw
StateFlowExample.kt
package sharedflow.macao
import flow.others.log
import kotlinx.coroutines.delay
import kotlinx.coroutines.flow.MutableStateFlow
import kotlinx.coroutines.flow.asStateFlow
import kotlinx.coroutines.flow.collect
import kotlinx.coroutines.flow.flow
import kotlinx.coroutines.launch
import kotlinx.coroutines.runBlocking
class StateModel {
private val _state = MutableStateFlow(0)
val state = _state.asStateFlow() // read-only public view
fun update(newValue: Int) {
_state.value = newValue // NOT suspending
}
}
fun main() {
val stateModel = StateModel()
runBlocking {
launch {
flow<Int> {
for (x in 1..6) {
log("emitting value $x")
emit(x)
}
}.collect { emmitedValue -> stateModel.update(emmitedValue) }
}
launch {
delay(2000)
stateModel.state.collect { value -> log("observed? value. $value") }
}
}
}
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