Receta de LocalLifecycleOwner

En esta receta, se muestra cómo usar LifecycleResumeEffect en las entradas de Navigation 3 para pausar y reanudar el trabajo según el estado del ciclo de vida de la entrada.

Cómo funciona

En Navigation 3, de forma predeterminada, cada NavEntry recibe su propio LifecycleOwner a través de LocalLifecycleOwner.current. Esto significa que cualquier componente que tenga en cuenta el ciclo de vida dentro de la entrada se limita automáticamente al NavEntry.

LifecycleResumeEffect con escenas de diálogo

  1. RouteA (pantalla):

    • Usa LifecycleResumeEffect(Unit) con alcance en el LocalLifecycleOwner.current de NavEntry para avanzar el LinearProgressIndicator mientras está en el estado RESUMED.
    • Restablece automáticamente progressValue a 0f cada vez que alcanza 1f.

  2. RouteB (diálogo):

    • Se configura como un diálogo con DialogSceneStrategy.dialog().
    • Cuando el usuario abre el diálogo RouteB, RouteA permanece visible detrás del diálogo en el estado STARTED (dejando RESUMED).
    • LifecycleResumeEffect llama a onPauseOrDispose y pausa el indicador de progreso.
    • Cuando se descarta el diálogo, RouteA vuelve a RESUMED y LifecycleResumeEffect reanuda el indicador de progreso automáticamente.
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package com.example.nav3recipes.lifecycleowner

import android.os.Bundle
import android.util.Log
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.compose.animation.core.LinearEasing
import androidx.compose.animation.core.animateFloatAsState
import androidx.compose.animation.core.snap
import androidx.compose.animation.core.tween
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.Spacer
import androidx.compose.foundation.layout.height
import androidx.compose.foundation.layout.padding
import androidx.compose.material3.AlertDialog
import androidx.compose.material3.Button
import androidx.compose.material3.LinearProgressIndicator
import androidx.compose.material3.Text
import androidx.compose.runtime.Composable
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableFloatStateOf
import androidx.compose.runtime.remember
import androidx.compose.runtime.rememberCoroutineScope
import androidx.compose.runtime.setValue
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.unit.dp
import androidx.lifecycle.Lifecycle
import androidx.lifecycle.compose.LifecycleEventEffect
import androidx.lifecycle.compose.LifecycleResumeEffect
import androidx.lifecycle.compose.dropUnlessResumed
import androidx.navigation3.runtime.NavKey
import androidx.navigation3.runtime.entryProvider
import androidx.navigation3.runtime.rememberNavBackStack
import androidx.navigation3.scene.DialogSceneStrategy
import androidx.navigation3.ui.NavDisplay
import com.example.nav3recipes.content.ContentGreen
import com.example.nav3recipes.ui.setEdgeToEdgeConfig
import kotlinx.coroutines.delay
import kotlinx.coroutines.launch
import kotlinx.serialization.Serializable
import kotlin.time.Duration.Companion.milliseconds

@Serializable
private data object RouteA : NavKey

@Serializable
private data object RouteB : NavKey

class LifecycleOwnerActivity : ComponentActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        setEdgeToEdgeConfig()
        super.onCreate(savedInstanceState)
        setContent {
            val backStack = rememberNavBackStack(RouteA)
            val dialogStrategy = remember { DialogSceneStrategy<NavKey>() }

            NavDisplay(
                backStack = backStack,
                onBack = backStack::removeLastOrNull,
                sceneStrategies = listOf(dialogStrategy),
                entryProvider = entryProvider {
                    entry<RouteA> {
                        LogLifecycleEffect("ScreenA")
                        ContentGreen("Screen A") {
                            var progressValue by remember { mutableFloatStateOf(0f) }
                            val coroutineScope = rememberCoroutineScope()

                            val animatedProgress by animateFloatAsState(
                                targetValue = progressValue,
                                animationSpec = if (progressValue == 0f) snap() else tween(durationMillis = 100, easing = LinearEasing),
                                label = "ProgressAnimation"
                            )

                            // LifecycleResumeEffect runs only while ScreenA is in the RESUMED state.
                            // When the dialog opens, ScreenA transitions to PAUSED, which calls onPauseOrDispose.
                            LifecycleResumeEffect(Unit) {
                                val job = coroutineScope.launch {
                                    while (true) {
                                        delay(100.milliseconds)
                                        progressValue += 0.01f
                                        if (progressValue >= 1f) {
                                            progressValue = 0f
                                        }
                                    }
                                }
                                onPauseOrDispose {
                                    job.cancel()
                                }
                            }

                            Column(
                                horizontalAlignment = Alignment.CenterHorizontally,
                                modifier = Modifier.padding(16.dp)
                            ) {
                                LinearProgressIndicator(progress = { animatedProgress })
                                Spacer(modifier = Modifier.height(16.dp))
                                Button(onClick = dropUnlessResumed { backStack.add(RouteB) }) {
                                    Text("Open Dialog")
                                }
                            }
                        }
                    }
                    entry<RouteB>(metadata = DialogSceneStrategy.dialog()) {
                        LogLifecycleEffect("Dialog")
                        AlertDialog(
                            onDismissRequest = backStack::removeLastOrNull,
                            title = { Text("Dialog") },
                            text = {
                                Text("Screen A is no longer in resumed state, pausing the progress indicator.")
                            },
                            confirmButton = {
                                Button(onClick = dropUnlessResumed { backStack.removeLastOrNull() }) {
                                    Text("Dismiss Dialog")
                                }
                            }
                        )
                    }
                }
            )
        }
    }
}

@Composable
private fun LogLifecycleEffect(screenName: String) {
    LifecycleEventEffect(Lifecycle.Event.ON_CREATE) {
        Log.d("LifecycleOwner", "$screenName: ON_CREATE")
    }
    LifecycleEventEffect(Lifecycle.Event.ON_START) {
        Log.d("LifecycleOwner", "$screenName: ON_START")
    }
    LifecycleEventEffect(Lifecycle.Event.ON_RESUME) {
        Log.d("LifecycleOwner", "$screenName: ON_RESUME")
    }
    LifecycleEventEffect(Lifecycle.Event.ON_PAUSE) {
        Log.d("LifecycleOwner", "$screenName: ON_PAUSE")
    }
    LifecycleEventEffect(Lifecycle.Event.ON_STOP) {
        Log.d("LifecycleOwner", "$screenName: ON_STOP")
    }
    // Note that ON_DESTROY event is not observable from composables.
}