I am trying to use ViewModel with Jetpack Compose,
By doing a number increment.
But it's not working. Maybe I'm not using the view model in right way.
Heres my Main Activity code
class MainActivity : ComponentActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContent {
Greeting()
}
}
}
@Composable
fun Greeting(
helloViewModel: ViewModel = viewModel()
) {
Column(
verticalArrangement = Arrangement.Center,
horizontalAlignment = Alignment.CenterHorizontally,
modifier = Modifier.fillMaxSize()
) {
Text(
text = helloViewModel.number.toString(),
fontSize = 60.sp,
fontWeight = FontWeight.Bold
)
Button(onClick = { helloViewModel.addNumber() }) {
Text(text = "Increment Number ${helloViewModel.number}")
}
}
}
@Preview(showBackground = true)
@Composable
fun DefaultPreview() {
JetpackcomposepracticeTheme {
Greeting()
}
}
And here is my Viewmodel class.
It works fine with xml.
How do i create the object of view model:
class ViewModel: ViewModel() {
var number : Int = 0
fun addNumber(){
number++
}
}
Compose can recompose when some with mutable state value container changes. You can create it manually with mutableStateOf(), mutableStateListOf(), etc, or by wrapping Flow/LiveData.
class ViewModel: ViewModel() {
var number : Int by mutableStateOf(0)
private set
fun addNumber(){
number++
}
}
I suggest you start with state in compose documentation, including this youtube video which explains the basic principles.