Menampilkan Hasil (Berbasis Peristiwa)

Resep ini menunjukkan cara menampilkan hasil dari satu layar ke layar sebelumnya menggunakan pendekatan berbasis peristiwa.

Cara kerjanya

Contoh ini menggunakan ResultEventBus untuk memfasilitasi komunikasi antar-layar.

  1. ResultEventBusNavEntryDecorator: NavEntryDecorator yang menyediakan ResultEventBus melalui LocalResultEventBus.
  2. ResultEventBus: ResultEventBus dibuat dan disediakan untuk composable melalui LocalResultEventBus. EventBus ini mengirim dan menerima hasil.
  3. Mengirim hasil: Layar yang menghasilkan hasil memanggil resultBus.sendResult(person) untuk mengirim data kembali sebagai peristiwa satu kali.
  4. Menerima hasil: Layar yang memerlukan hasil menggunakan composable ResultEffect untuk memproses hasil dari jenis tertentu. Saat hasil diterima, lambda efek akan dipicu.

Pendekatan ini berguna untuk hasil yang bersifat sementara dan harus ditangani sebagai peristiwa satu kali.

/*
 * Copyright 2025 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.nav3recipes.results.common

import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.setValue
import androidx.lifecycle.ViewModel

class HomeViewModel : ViewModel() {
    var person by mutableStateOf<Person?>(null)
}
 
/*
 * Copyright 2025 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.nav3recipes.results.common

import androidx.navigation3.runtime.NavKey
import kotlinx.serialization.Serializable

@Serializable
data object Home : NavKey

@Serializable
class PersonDetailsForm : NavKey
 
/*
 * Copyright 2025 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.nav3recipes.results.common

import android.os.Parcelable
import kotlinx.parcelize.Parcelize

@Parcelize
data class Person(val name: String, val favoriteColor: String) : Parcelable
 
/*
 * Copyright 2025 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.nav3recipes.results.common

import androidx.compose.foundation.layout.Spacer
import androidx.compose.foundation.layout.height
import androidx.compose.foundation.text.input.rememberTextFieldState
import androidx.compose.material3.Button
import androidx.compose.material3.OutlinedTextField
import androidx.compose.material3.Text
import androidx.compose.runtime.Composable
import androidx.compose.ui.Modifier
import androidx.compose.ui.unit.dp
import androidx.lifecycle.compose.dropUnlessResumed
import com.example.nav3recipes.content.ContentBlue
import com.example.nav3recipes.content.ContentGreen

@Composable
fun HomeScreen(
    person: Person?,
    onNext: () -> Unit
) {
    ContentBlue("Hello ${person?.name ?: "unknown person"}") {

        if (person != null) {
            Text("Your favorite color is ${person.favoriteColor}")
        }

        Spacer(Modifier.height(16.dp))
        Button(onClick = dropUnlessResumed(block = onNext)) {
            Text("Tell us about yourself")
        }
    }
}

@Composable
fun PersonDetailsScreen(
    onSubmit: (Person) -> Unit
) {
    ContentGreen("About you") {

        val nameTextState = rememberTextFieldState()
        OutlinedTextField(
            state = nameTextState,
            label = { Text("Please enter your name") }
        )

        val favoriteColorTextState = rememberTextFieldState()
        OutlinedTextField(
            state = favoriteColorTextState,
            label = { Text("Please enter your favorite color") }
        )

        Button(
            onClick = dropUnlessResumed {
                val person = Person(
                    name = nameTextState.text.toString(),
                    favoriteColor = favoriteColorTextState.text.toString()
                )
                onSubmit(person)
            },
            enabled = nameTextState.text.isNotBlank() &&
                    favoriteColorTextState.text.isNotBlank()
        ) {
            Text("Submit")
        }
    }
}
 
/*
 * Copyright 2025 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.nav3recipes.results.event

import android.os.Bundle
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.compose.foundation.layout.padding
import androidx.compose.material3.Scaffold
import androidx.compose.runtime.remember
import androidx.compose.ui.Modifier
import androidx.lifecycle.viewmodel.compose.viewModel
import androidx.navigation3.runtime.entryProvider
import androidx.navigation3.runtime.rememberNavBackStack
import androidx.navigation3.runtime.result.LocalResultEventBus
import androidx.navigation3.runtime.result.ResultEffect
import androidx.navigation3.runtime.result.ResultEventBus
import androidx.navigation3.runtime.result.rememberResultEventBusNavEntryDecorator
import androidx.navigation3.ui.NavDisplay
import com.example.nav3recipes.results.common.Home
import com.example.nav3recipes.results.common.HomeScreen
import com.example.nav3recipes.results.common.HomeViewModel
import com.example.nav3recipes.results.common.Person
import com.example.nav3recipes.results.common.PersonDetailsForm
import com.example.nav3recipes.results.common.PersonDetailsScreen
import com.example.nav3recipes.ui.setEdgeToEdgeConfig

class ResultEventActivity : ComponentActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        setEdgeToEdgeConfig()
        super.onCreate(savedInstanceState)

        setContent {
            Scaffold { paddingValues ->

                val backStack = rememberNavBackStack(Home)

                NavDisplay(
                    backStack = backStack,
                    modifier = Modifier.padding(paddingValues),
                    onBack = { backStack.removeLastOrNull() },
                    entryDecorators = listOf(rememberResultEventBusNavEntryDecorator()),
                    entryProvider = entryProvider {
                        entry<Home> {
                            val viewModel = viewModel<HomeViewModel>(key = Home.toString())
                            ResultEffect<Person> { person ->
                                viewModel.person = person
                            }

                            val person = viewModel.person
                            HomeScreen(
                                person = person,
                                onNext = { backStack.add(PersonDetailsForm()) }
                            )
                        }
                        entry<PersonDetailsForm> {
                            val resultBus = LocalResultEventBus.current
                            PersonDetailsScreen(
                                onSubmit = { person ->
                                    resultBus.sendResult<Person>(result = person)
                                    backStack.removeLastOrNull()
                                }
                            )
                        }
                    }
                )
            }
        }
    }
}