Elementos compartidos con Navigation Compose

Para usar elementos compartidos con la dependencia de navigation-compose, puedes usar los mismos conceptos que se mostraron anteriormente: usa el Modifier.sharedElement() que toma un AnimatedVisibilityScope como parámetro. Puedes usar esto para decidir qué debe ser visible y cuándo.

El siguiente es un ejemplo del uso de navigation-compose con elementos compartidos:

@Preview
@Composable
fun SharedElement_PredictiveBack() {
    SharedTransitionLayout {
        val navController = rememberNavController()
        NavHost(
            navController = navController,
            startDestination = "home"
        ) {
            composable("home") {
                HomeScreen(
                    navController,
                    this@SharedTransitionLayout,
                    this@composable
                )
            }
            composable(
                "details/{item}",
                arguments = listOf(navArgument("item") { type = NavType.IntType })
            ) { backStackEntry ->
                val id = backStackEntry.arguments?.getInt("item")
                val snack = listSnacks[id!!]
                DetailsScreen(
                    navController,
                    id,
                    snack,
                    this@SharedTransitionLayout,
                    this@composable
                )
            }
        }
    }
}

@Composable
private fun DetailsScreen(
    navController: NavHostController,
    id: Int,
    snack: Snack,
    sharedTransitionScope: SharedTransitionScope,
    animatedContentScope: AnimatedContentScope
) {
    with(sharedTransitionScope) {
        Column(
            Modifier
                .fillMaxSize()
                .clickable {
                    navController.navigate("home")
                }
        ) {
            Image(
                painterResource(id = snack.image),
                contentDescription = snack.description,
                contentScale = ContentScale.Crop,
                modifier = Modifier
                    .sharedElement(
                        sharedTransitionScope.rememberSharedContentState(key = "image-$id"),
                        animatedVisibilityScope = animatedContentScope
                    )
                    .aspectRatio(1f)
                    .fillMaxWidth()
            )
            Text(
                snack.name, fontSize = 18.sp,
                modifier =
                Modifier
                    .sharedElement(
                        sharedTransitionScope.rememberSharedContentState(key = "text-$id"),
                        animatedVisibilityScope = animatedContentScope
                    )
                    .fillMaxWidth()
            )
        }
    }
}

@Composable
private fun HomeScreen(
    navController: NavHostController,
    sharedTransitionScope: SharedTransitionScope,
    animatedContentScope: AnimatedContentScope
) {
    LazyColumn(
        modifier = Modifier
            .fillMaxSize()
            .padding(8.dp),
        verticalArrangement = Arrangement.spacedBy(8.dp)
    ) {
        itemsIndexed(listSnacks) { index, item ->
            Row(
                Modifier.clickable {
                    navController.navigate("details/$index")
                }
            ) {
                Spacer(modifier = Modifier.width(8.dp))
                with(sharedTransitionScope) {
                    Image(
                        painterResource(id = item.image),
                        contentDescription = item.description,
                        contentScale = ContentScale.Crop,
                        modifier = Modifier
                            .sharedElement(
                                sharedTransitionScope.rememberSharedContentState(key = "image-$index"),
                                animatedVisibilityScope = animatedContentScope
                            )
                            .size(100.dp)
                    )
                    Spacer(modifier = Modifier.width(8.dp))
                    Text(
                        item.name, fontSize = 18.sp,
                        modifier = Modifier
                            .align(Alignment.CenterVertically)
                            .sharedElement(
                                sharedTransitionScope.rememberSharedContentState(key = "text-$index"),
                                animatedVisibilityScope = animatedContentScope,
                            )
                    )
                }
            }
        }
    }
}

data class Snack(
    val name: String,
    val description: String,
    @DrawableRes val image: Int
)
SharedElementsWithNavigationSnippets.kt

Gesto atrás predictivo con elementos compartidos

Si deseas usar el botón atrás predictivo con elementos compartidos, asegúrate de usar la dependencia navigation-compose más reciente con el fragmento de la sección anterior.

dependencies {
    def nav_version = "2.8.0-beta02"

    implementation "androidx.navigation:navigation-compose:$nav_version"
}

Agrega android:enableOnBackInvokedCallback="true" a tu archivo AndroidManifest.xml para habilitar el gesto atrás predictivo:

<manifest xmlns:android="http://schemas.android.com/apk/res/android">
   <uses-permission android:name="android.permission.INTERNET" />
   <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
   <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"
       android:maxSdkVersion="28" />

   <application
       android:allowBackup="true"
       android:icon="@mipmap/ic_launcher"
       android:label="@string/app_name"
       android:roundIcon="@mipmap/ic_launcher_round"
       android:supportsRtl="true"
       android:enableOnBackInvokedCallback="true"
       android:theme="@style/Theme.Snippets">