Handling back press in Jetpack Compose

user_16564987 0
Viewed 9391

I have a Composable which has different views (see the code for better understanding)
When user clicks on the button it navigates to different view but when user press the back button it navigates to previous screen but I want to navigate to pervious view
Something like on Back press viewState changes it's value
Note: I don't found nice explanation than this

var viewState by remember { mutableStateOf(0) }
    Column {
        when (viewState) {
            0 -> { Button(onClick = { viewState = 1 }) { Text(text = "Goto 1") } }
            1 -> { Button(onClick = { viewState = 2 }) { Text(text = "Goto 2") } }
            2 -> { Button(onClick = { viewState = 3 }) { Text(text = "Goto 3") } }
            3 -> { Button(onClick = { viewState = 4 }) { Text(text = "Goto 0") } }
        }
    }
android-jetpack-compose kotlin android
1 Answers

I got the answer
I have not added for 0 because it will execute navController

var viewState by remember { mutableStateOf(0) }
    when(viewState){
        1 -> BackHandler(enabled = true) {
            viewState = 0
        }
        2 -> BackHandler(enabled = true) {
            viewState = 1
        }
        3 -> BackHandler(enabled = true) {
            viewState = 3
        }
    }
    Column {
        when (viewState) {
            0 -> { Button(onClick = { viewState = 1 }) { Text(text = "Goto 1") } }
            1 -> { Button(onClick = { viewState = 2 }) { Text(text = "Goto 2") } }
            2 -> { Button(onClick = { viewState = 3 }) { Text(text = "Goto 3") } }
            3 -> { Button(onClick = { viewState = 0 }) { Text(text = "Goto 0") } }
        }
    }

And the function

@Composable
public fun BackHandler(enabled: Boolean = true, onBack: () -> Unit) {
    // Safely update the current `onBack` lambda when a new one is provided
    val currentOnBack by rememberUpdatedState(onBack)
    // Remember in Composition a back callback that calls the `onBack` lambda
    val backCallback = remember {
        object : OnBackPressedCallback(enabled) {
            override fun handleOnBackPressed() {
                currentOnBack()
            }
        }
    }
    // On every successful composition, update the callback with the `enabled` value
    SideEffect {
        backCallback.isEnabled = enabled
    }
    val backDispatcher = checkNotNull(LocalOnBackPressedDispatcherOwner.current) {
        "No OnBackPressedDispatcherOwner was provided via LocalOnBackPressedDispatcherOwner"
    }.onBackPressedDispatcher
    val lifecycleOwner = LocalLifecycleOwner.current
    DisposableEffect(lifecycleOwner, backDispatcher) {
        // Add callback to the backDispatcher
        backDispatcher.addCallback(lifecycleOwner, backCallback)
        // When the effect leaves the Composition, remove the callback
        onDispose {
            backCallback.remove()
        }
    }
}
user_165649870
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