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Observe navController.previousBackStackEntry as a state #121

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Observe navController.previousBackStackEntry as a state #121

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10 changes: 9 additions & 1 deletion app/src/main/java/com/example/cupcake/CupcakeScreen.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,7 @@
*/
package com.example.cupcake

import android.annotation.SuppressLint
import android.content.Context
import android.content.Intent
import androidx.annotation.StringRes
Expand All @@ -40,6 +41,7 @@ import androidx.compose.ui.platform.LocalContext
import androidx.compose.ui.res.dimensionResource
import androidx.compose.ui.res.stringResource
import androidx.lifecycle.viewmodel.compose.viewModel
import androidx.navigation.NavGraph
import androidx.navigation.NavHostController
import androidx.navigation.compose.NavHost
import androidx.navigation.compose.composable
Expand Down Expand Up @@ -103,11 +105,17 @@ fun CupcakeApp(
backStackEntry?.destination?.route ?: CupcakeScreen.Start.name
)

@SuppressLint("RestrictedApi")
val backStack by navController.currentBackStack.collectAsState()
val previousBackStackEntry = backStack.asReversed().asSequence().drop(1).firstOrNull { entry ->
entry.destination !is NavGraph
}

Scaffold(
topBar = {
CupcakeAppBar(
currentScreen = currentScreen,
canNavigateBack = navController.previousBackStackEntry != null,
canNavigateBack = previousBackStackEntry != null,
navigateUp = { navController.navigateUp() }
)
}
Expand Down