Neste tutorial, você aprenderá passo a passo como criar um recyclerview aninhado. É assim que você está colocando uma visualização de reciclagem dentro de outra visualização de reciclagem. Cada recyclerview precisa ter seu adaptador independente para vincular seus dados. Cada um também tem que lidar com a rolagem apropriadamente.
Confira os exemplos abaixo.
Exemplo 1: Kotlin Android Nested RecyclerView
Aqui está a demonstração deste projeto:
Etapa 1: criar projeto
Comece criando um projeto Android Studio vazio.
Etapa 2: dependências
Instale o GravitySnapHelper adicionando a seguinte declaração de implementação em seu arquivo app/build.gradle:
implementation 'com.github.rubensousa:gravitysnaphelper:2.1.0'Etapa 3: Layouts de design
Existem três layouts para este projeto:
aninhado_adaptador_item.xml
Este é o layout para o item de visualização de reciclagem interna:
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="@dimen/item_width"
android:layout_height="@dimen/item_height"
android:layout_margin="4dp"
android:background="@android:color/black"
tools:context=".MainActivity">
<TextView
android:id="@+id/textView"
style="@style/TextAppearance.AppCompat.Title"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:gravity="center"
android:textColor="@android:color/white"
android:textSize="@dimen/item_text_size"
tools:text="0" />
</FrameLayout>(b). aninhado_adaptador_lista
O layout para o recyclerview interno. Adicionar OrientationAwareRecyclerView:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
tools:context=".MainActivity">
<TextView
android:id="@+id/nestedTitleTextView"
style="@style/TextAppearance.AppCompat.Title"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="16dp"
android:layout_marginTop="16dp" />
<com.github.rubensousa.gravitysnaphelper.OrientationAwareRecyclerView
android:id="@+id/nestedRecyclerView"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
</LinearLayout>(c). aninhado_adaptador_item.xml
O layout para a visualização externa do reciclador. Mais uma vez, adicione o OrientationAwareRecyclerView:
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<com.github.rubensousa.gravitysnaphelper.OrientationAwareRecyclerView
android:id="@+id/recyclerView"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</androidx.constraintlayout.widget.ConstraintLayout>Etapa 4: criar classe de dados
Esta classe de dados será nossa classe de modelo:
(uma). TiledList.kt
data class TitledList(
val title: String,
val texts: MutableList<String>
)Etapa 5: criar o detentor do estado de rolagem
Crie uma classe para manter o estado de rolagem:
ScrollStateHolder.kt
import android.os.Bundle
import android.os.Parcelable
import androidx.recyclerview.widget.RecyclerView
/**
* Persists scroll state for nested RecyclerViews.
*
* 1. Call [saveScrollState] in [RecyclerView.Adapter.onViewRecycled]
* to save the scroll position.
*
* 2. Call [restoreScrollState] in [RecyclerView.Adapter.onBindViewHolder]
* after changing the adapter's contents to restore the scroll position
*/
class ScrollStateHolder(savedInstanceState: Bundle? = null) {
companion object {
const val STATE_BUNDLE = "scroll_state_bundle"
}
/**
* Provides a key that uniquely identifies a RecyclerView
*/
interface ScrollStateKeyProvider {
fun getScrollStateKey(): String?
}
/**
* Persists the [RecyclerView.LayoutManager] states
*/
private val scrollStates = hashMapOf<String, Parcelable>()
/**
* Keeps track of the keys that point to RecyclerViews
* that have new scroll states that should be saved
*/
private val scrolledKeys = mutableSetOf<String>()
init {
savedInstanceState?.getBundle(STATE_BUNDLE)?.let { bundle ->
bundle.keySet().forEach { key ->
bundle.getParcelable<Parcelable>(key)?.let {
scrollStates[key] = it
}
}
}
}
fun setupRecyclerView(recyclerView: RecyclerView, scrollKeyProvider: ScrollStateKeyProvider) {
recyclerView.addOnScrollListener(object : RecyclerView.OnScrollListener() {
override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
super.onScrollStateChanged(recyclerView, newState)
if (newState == RecyclerView.SCROLL_STATE_IDLE) {
saveScrollState(recyclerView, scrollKeyProvider)
}
}
override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
super.onScrolled(recyclerView, dx, dy)
val key = scrollKeyProvider.getScrollStateKey()
if (key != null && dx != 0) {
scrolledKeys.add(key)
}
}
})
}
fun onSaveInstanceState(outState: Bundle) {
val stateBundle = Bundle()
scrollStates.entries.forEach {
stateBundle.putParcelable(it.key, it.value)
}
outState.putBundle(STATE_BUNDLE, stateBundle)
}
fun clearScrollState() {
scrollStates.clear()
scrolledKeys.clear()
}
/**
* Saves this RecyclerView layout state for a given key
*/
fun saveScrollState(
recyclerView: RecyclerView,
scrollKeyProvider: ScrollStateKeyProvider
) {
val key = scrollKeyProvider.getScrollStateKey() ?: return
// Check if we scrolled the RecyclerView for this key
if (scrolledKeys.contains(key)) {
val layoutManager = recyclerView.layoutManager ?: return
layoutManager.onSaveInstanceState()?.let { scrollStates[key] = it }
scrolledKeys.remove(key)
}
}
/**
* Restores this RecyclerView layout state for a given key
*/
fun restoreScrollState(
recyclerView: RecyclerView,
scrollKeyProvider: ScrollStateKeyProvider
) {
val key = scrollKeyProvider.getScrollStateKey() ?: return
val layoutManager = recyclerView.layoutManager ?: return
val savedState = scrollStates[key]
if (savedState != null) {
layoutManager.onRestoreInstanceState(savedState)
} else {
// If we don't have any state for this RecyclerView,
// make sure we reset the scroll position
layoutManager.scrollToPosition(0)
}
// Mark this key as not scrolled since we just restored the state
scrolledKeys.remove(key)
}
}Etapa 6: criar adaptadores
Existem dois adaptadores:
(uma). ChildAdapter.kt
Este é o adaptador para o recyclerview interno ou o recyclerview aninhado:
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.TextView
import androidx.recyclerview.widget.RecyclerView
class ChildAdapter : RecyclerView.Adapter<ChildAdapter.VH>() {
private var items = listOf<String>()
fun setItems(list: List<String>) {
this.items = list
notifyDataSetChanged()
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): VH {
return VH(
LayoutInflater.from(parent.context).inflate(
R.layout.nested_adapter_item,
parent,
false
)
)
}
override fun getItemCount(): Int = items.size
override fun onBindViewHolder(holder: VH, position: Int) {
holder.bind(items[position])
}
class VH(view: View) : RecyclerView.ViewHolder(view) {
private val textView: TextView = view.findViewById(R.id.textView)
init {
view.setOnClickListener {
it.isSelected = !it.isSelected
}
}
fun bind(item: String) {
textView.text = item
}
}
}(b). ParentAdapter.kt
Este é o adaptador para o recyclerview externo ou pai:
import android.view.Gravity
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.TextView
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.RecyclerView
import com.github.rubensousa.gravitysnaphelper.GravitySnapHelper
class ParentAdapter(private val scrollStateHolder: ScrollStateHolder) :
RecyclerView.Adapter<ParentAdapter.VH>() {
private var items = listOf<TitledList>()
fun setItems(list: List<TitledList>) {
this.items = list
notifyDataSetChanged()
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): VH {
val view = LayoutInflater.from(parent.context).inflate(
R.layout.nested_adapter_list,
parent, false
)
val vh = VH(view, scrollStateHolder)
vh.onCreated()
return vh
}
override fun getItemCount(): Int = items.size
override fun onBindViewHolder(holder: VH, position: Int) {
holder.onBound(items[position])
}
override fun onViewRecycled(holder: VH) {
super.onViewRecycled(holder)
holder.onRecycled()
}
override fun onViewDetachedFromWindow(holder: VH) {
super.onViewDetachedFromWindow(holder)
holder.onDetachedFromWindow()
}
class VH(view: View, private val scrollStateHolder: ScrollStateHolder) :
RecyclerView.ViewHolder(view), ScrollStateHolder.ScrollStateKeyProvider {
private val titleTextView: TextView = view.findViewById(R.id.nestedTitleTextView)
private val recyclerView: RecyclerView = view.findViewById(R.id.nestedRecyclerView)
private val layoutManager = LinearLayoutManager(
view.context,
RecyclerView.HORIZONTAL, false
)
private val adapter = ChildAdapter()
private val snapHelper = GravitySnapHelper(Gravity.START)
private var currentItem: TitledList? = null
override fun getScrollStateKey(): String? = currentItem?.title
fun onCreated() {
recyclerView.adapter = adapter
recyclerView.layoutManager = layoutManager
recyclerView.setHasFixedSize(true)
recyclerView.itemAnimator?.changeDuration = 0
snapHelper.attachToRecyclerView(recyclerView)
scrollStateHolder.setupRecyclerView(recyclerView, this)
}
fun onBound(item: TitledList) {
currentItem = item
titleTextView.text = item.title
adapter.setItems(item.texts)
scrollStateHolder.restoreScrollState(recyclerView, this)
}
fun onRecycled() {
scrollStateHolder.saveScrollState(recyclerView, this)
currentItem = null
}
/**
* If we fast scroll while this ViewHolder's RecyclerView is still settling the scroll,
* the view will be detached and won't be snapped correctly
*
* To fix that, we snap again without smooth scrolling.
*/
fun onDetachedFromWindow() {
if (recyclerView.scrollState != RecyclerView.SCROLL_STATE_IDLE) {
snapHelper.findSnapView(layoutManager)?.let {
val snapDistance = snapHelper.calculateDistanceToFinalSnap(layoutManager, it)
if (snapDistance!![0] != 0 || snapDistance[1] != 0) {
recyclerView.scrollBy(snapDistance[0], snapDistance[1])
}
}
}
}
}
}Etapa 7: Criar MainActivity
Aqui está o código para o MainActivity
MainActivity.kt
import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.RecyclerView
class MainActivity : AppCompatActivity() {
private lateinit var adapter: ParentAdapter
private lateinit var recyclerView: RecyclerView
private lateinit var scrollStateHolder: ScrollStateHolder
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
recyclerView = findViewById(R.id.recyclerView)
scrollStateHolder = ScrollStateHolder(savedInstanceState)
adapter = ParentAdapter(scrollStateHolder)
recyclerView.adapter = adapter
recyclerView.layoutManager = LinearLayoutManager(this)
loadItems()
}
override fun onSaveInstanceState(outState: Bundle) {
super.onSaveInstanceState(outState)
scrollStateHolder.onSaveInstanceState(outState)
}
private fun loadItems() {
val lists = arrayListOf<TitledList>()
repeat(20) { listIndex ->
val items = arrayListOf<String>()
repeat(30) { itemIndex -> items.add(itemIndex.toString()) }
lists.add(TitledList("List number $listIndex", items))
}
adapter.setItems(lists)
}
}Correr
Copie o código ou baixe-o no link abaixo, construa e execute.
Referência
Seguem os links de referência:
Download Exemplo
