MainActivity.kt
package com.cfsuman.composestate
import android.os.Bundle
import android.util.Log
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.compose.foundation.layout.*
import androidx.compose.material.*
import androidx.compose.runtime.*
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.unit.sp
import androidx.lifecycle.ViewModel
import androidx.lifecycle.viewmodel.compose.viewModel
import com.cfsuman.composestate.ui.theme.ComposeStateTheme
class MainActivity : ComponentActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContent {
ComposeStateTheme {
Scaffold(
topBar = { TopAppBar(
title = {
Text(text = "Compose - Count down flow")
}
)},
content = { MainContent() },
backgroundColor = Color(0xFFEDEAE0)
)
}
}
}
}
@Composable
fun MainContent() {
val viewModel = viewModel<MyViewModel>()
val counter = viewModel.countDownFlow
.collectAsState(initial = 20)
Box(
Modifier.fillMaxSize(),
contentAlignment = Alignment.Center
) {
Text(text = "${counter.value}", fontSize = 40.sp)
}
}
MyViewModel.kt
package com.cfsuman.composestate
import androidx.lifecycle.ViewModel
import kotlinx.coroutines.delay
import kotlinx.coroutines.flow.flow
class MyViewModel:ViewModel() {
val countDownFlow = flow<Int> {
val startingNumber = 20
var currentNumber = startingNumber
while (currentNumber > 0){
delay(1000)
currentNumber--
emit(currentNumber)
}
}
}
build.gradle [app]
dependencies {
implementation "androidx.lifecycle:lifecycle-viewmodel-ktx:2.5.0-alpha06"
implementation "androidx.lifecycle:lifecycle-viewmodel-compose:2.5.0-alpha06"
}
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