RecyclerView Sample in 2022 (for my memo)

(:app)build.gradle

plugins {
    id 'com.android.application'
    id 'org.jetbrains.kotlin.android'
    id 'kotlin-kapt'
    id 'dagger.hilt.android.plugin'
}

android {
    compileSdk 32

    defaultConfig {
        applicationId "com.example.recyclerviewsample"
        minSdk 21
        targetSdk 32
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
    kotlinOptions {
        jvmTarget = '1.8'
    }
}

dependencies {
    implementation 'androidx.core:core-ktx:1.7.0'
    implementation "androidx.fragment:fragment-ktx:1.4.1"

    implementation 'androidx.appcompat:appcompat:1.4.1'
    implementation 'com.google.android.material:material:1.6.0'
    implementation 'androidx.constraintlayout:constraintlayout:2.1.3'

    implementation "androidx.recyclerview:recyclerview:1.2.1"
    // For control over item selection of both touch and mouse driven selection
//    implementation "androidx.recyclerview:recyclerview-selection:1.1.0"

    implementation "org.jetbrains.kotlinx:kotlinx-coroutines-android:1.6.0"

    implementation "androidx.lifecycle:lifecycle-viewmodel-ktx:$rootProject.ext.versions.lifecycle"
    implementation "androidx.lifecycle:lifecycle-livedata-ktx:$rootProject.ext.versions.lifecycle"
    implementation "androidx.lifecycle:lifecycle-runtime-ktx:$rootProject.ext.versions.lifecycle"
    implementation "androidx.lifecycle:lifecycle-common-java8:$rootProject.ext.versions.lifecycle"

    // DI
    implementation "com.google.dagger:hilt-android:$rootProject.ext.versions.hilt"
    kapt "com.google.dagger:hilt-android-compiler:$rootProject.ext.versions.hilt"
//    implementation "androidx.hilt:hilt-lifecycle-viewmodel:1.0.0-alpha03"
    kapt 'androidx.hilt:hilt-compiler:1.0.0'

    testImplementation 'junit:junit:4.13.2'
    androidTestImplementation 'androidx.test.ext:junit:1.1.3'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
}

build.gradle

// Top-level build file where you can add configuration options common to all sub-projects/modules.
plugins {
    id 'com.android.application' version '7.1.3' apply false
    id 'com.android.library' version '7.1.3' apply false
    id 'org.jetbrains.kotlin.android' version '1.6.0' apply false
    id 'com.google.dagger.hilt.android' version '2.41' apply false
}

ext {
    versions = [
            "lifecycle"     : "2.4.1",
            "hilt"          : "2.41",
    ]
}

task clean(type: Delete) {
    delete rootProject.buildDir
}

MainActivity.kt

package com.example.recyclerviewsample.ui

import android.os.Bundle
import android.view.View
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import androidx.fragment.app.Fragment
import androidx.fragment.app.viewModels
import androidx.lifecycle.Lifecycle
import androidx.lifecycle.lifecycleScope
import androidx.lifecycle.repeatOnLifecycle
import androidx.recyclerview.widget.RecyclerView
import com.example.recyclerviewsample.R
import dagger.hilt.android.AndroidEntryPoint
import kotlinx.coroutines.launch

@AndroidEntryPoint
class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
    }
}

@AndroidEntryPoint
class MainFragment : Fragment(R.layout.fragment_main) {
    private val viewModel: MainViewModel by viewModels()
    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        val listView = view.findViewById<RecyclerView>(R.id.listView).apply {
            adapter = MyAdapter()
        }
        viewLifecycleOwner.lifecycleScope.launch {
            viewLifecycleOwner.repeatOnLifecycle(Lifecycle.State.STARTED) {
                viewModel.uiState.collect { uiState ->
                    listView.submitList(uiState.data)
                    uiState.userMessages.firstOrNull()?.let { userMessage ->
                        showToast(userMessage.message)
                        viewModel.userMessageShown(userMessage.id)
                    }
                }
            }
        }
    }

    private fun showToast(message: String) =
        Toast.makeText(requireContext(), message, Toast.LENGTH_SHORT).show()

    private fun RecyclerView.submitList(itemDataList: List<ItemDataItemUiState>) =
        (this.adapter as MyAdapter).submitList(itemDataList)
}

MainViewModel.kt

package com.example.recyclerviewsample.ui

import androidx.lifecycle.ViewModel
import androidx.lifecycle.viewModelScope
import com.example.recyclerviewsample.data.ItemDataRepository
import com.example.recyclerviewsample.model.ItemData
import dagger.hilt.android.lifecycle.HiltViewModel
import kotlinx.coroutines.flow.MutableStateFlow
import kotlinx.coroutines.flow.StateFlow
import kotlinx.coroutines.flow.asStateFlow
import kotlinx.coroutines.flow.update
import kotlinx.coroutines.launch
import java.util.*
import javax.inject.Inject

data class UserMessage(
    val id: Long,
    val message: String
)

data class ItemDataItemUiState(
    val id: String,
    val title: String,
    val onItemLongClick: () -> Unit,
    val onItemClick: () -> Unit,
)

data class MainUiState(
    val data: List<ItemDataItemUiState> = emptyList(),
    val userMessages: List<UserMessage> = emptyList()
) {
    fun updateData(newData: List<ItemDataItemUiState>) =
        this.copy(data = newData)

    fun addMessage(id: Long = UUID.randomUUID().mostSignificantBits, message: String) =
        this.copy(userMessages = userMessages + UserMessage(id, message))

    fun removeMessage(id: Long) =
        this.copy(userMessages = userMessages.filterNot { it.id == id })
}

@HiltViewModel
class MainViewModel @Inject constructor(
    private val itemDataRepository: ItemDataRepository,
) : ViewModel() {

    private val _uiState = MutableStateFlow(MainUiState())
    val uiState: StateFlow<MainUiState> = _uiState.asStateFlow()

    init {
        viewModelScope.launch {
            val data = itemDataRepository.getAll()
            _uiState.update { currentUiState ->
                currentUiState.updateData(data.map { it.toItemUiState() })
            }
        }
    }

    private fun remove(itemData: ItemData) {
        viewModelScope.launch {
            itemDataRepository.remove(itemData)
            val data = itemDataRepository.getAll()
            _uiState.update { currentUiState ->
                currentUiState.updateData(data.map { it.toItemUiState() })
            }
        }
    }

    private fun showItemDataInfo(itemData: ItemData) {
        _uiState.update { currentUiState ->
            currentUiState.addMessage(message = "clicked item: $itemData")
        }
    }

    fun userMessageShown(messageId: Long) {
        _uiState.update { currentUiState ->
            currentUiState.removeMessage(messageId)
        }
    }

    private fun ItemData.toItemUiState(): ItemDataItemUiState {
        return ItemDataItemUiState(
            id = id,
            title = name,
            onItemLongClick = { [email protected](this) },
            onItemClick = { [email protected](this) }
        )
    }
}

Module.kt

package com.example.recyclerviewsample

import com.example.recyclerviewsample.data.ItemDataRepository
import dagger.Module
import dagger.Provides
import dagger.hilt.InstallIn
import dagger.hilt.components.SingletonComponent
import kotlinx.coroutines.CoroutineDispatcher
import kotlinx.coroutines.Dispatchers
import javax.inject.Qualifier
import javax.inject.Singleton

@Retention(AnnotationRetention.RUNTIME)
@Qualifier
annotation class IoDispatcher

@Module
@InstallIn(SingletonComponent::class)
class RepositoryModule {
    @Singleton
    @Provides
    fun provideItemDataRepository(
        @IoDispatcher coroutineDispatcher: CoroutineDispatcher,
    ): ItemDataRepository = ItemDataRepository(coroutineDispatcher)
}

@Module
@InstallIn(SingletonComponent::class)
class CoroutineDispatcherModule {
    @IoDispatcher
    @Provides
    fun provideIoDispatcher(): CoroutineDispatcher = Dispatchers.IO
}

MyAdapter.kt

package com.example.recyclerviewsample.ui

import android.view.LayoutInflater
import android.view.ViewGroup
import android.widget.TextView
import androidx.recyclerview.widget.DiffUtil
import androidx.recyclerview.widget.ListAdapter
import androidx.recyclerview.widget.RecyclerView
import com.example.recyclerviewsample.R

private typealias ItemUiState = ItemDataItemUiState

class MyAdapter : ListAdapter<ItemDataItemUiState, RecyclerView.ViewHolder>(DIFF_CALLBACK) {

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
        val view = LayoutInflater.from(parent.context)
            .inflate(R.layout.simple_text_item, parent, false)
        return object : RecyclerView.ViewHolder(view) {}
    }

    override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
        val itemUiState = getItem(position)
        val view = holder.itemView.apply {
            setOnClickListener { itemUiState.onItemClick() }
            setOnLongClickListener { itemUiState.onItemLongClick(); true }
        }
        val textView = view.findViewById<TextView>(R.id.textView)
        textView.text = itemUiState.title
    }
}

private val DIFF_CALLBACK = object : DiffUtil.ItemCallback<ItemUiState>() {
    override fun areItemsTheSame(old: ItemUiState, new: ItemUiState) =
        old.id == new.id

    override fun areContentsTheSame(old: ItemUiState, new: ItemUiState) =
        old == new
}

Warning: It's bad practice to pass the ViewModel into the RecyclerView adapter because that tightly couples the adapter with the ViewModel class.

https://developer.android.com/topic/architecture/ui-layer/events#recyclerview-events

RecyclerViewのAdapterにViewModelは渡さないこと。AdapterとViewModelが密結合してしまうバッドプラクティスです。