Nested RecyclerView Example

This Android app demonstrates the use of nested RecyclerViews using Kotlin and XML. A parent RecyclerView contains child RecyclerViews, each displaying a list of items.

Project Structure

MainActivity.kt
ParentAdapter.kt
ChildAdapter.kt
ParentItem.kt
ChildItem.kt
activity_main.xml
item_parent.xml
item_child.xml

Files and Code

1. MainActivity.kt

package com.sksinha2410.ananotherreyclerview

import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.RecyclerView

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

        val parentRecyclerView = findViewById<RecyclerView>(R.id.parent_recyclerview)
        parentRecyclerView.layoutManager = LinearLayoutManager(this)
        parentRecyclerView.adapter = ParentAdapter(getParentData())
    }

    private fun getParentData(): List<ParentItem> {
        val childItems = List(5) { ChildItem("Child Item $it") }
        return List(10) { ParentItem("Parent Item $it", childItems) }
    }
}

2. ParentAdapter.kt

package com.sksinha2410.ananotherreyclerview

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

class ParentAdapter(private val parentList: List<ParentItem>) :
    RecyclerView.Adapter<ParentAdapter.ParentViewHolder>() {

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

    override fun onBindViewHolder(holder: ParentViewHolder, position: Int) {
        holder.bind(parentList[position])
    }

    override fun getItemCount(): Int = parentList.size

    class ParentViewHolder(private val view: View) : RecyclerView.ViewHolder(view) {
        private val childRecyclerView: RecyclerView = view.findViewById(R.id.child_recyclerview)

        fun bind(parentItem: ParentItem) {
            view.findViewById<TextView>(R.id.parent_title).text = parentItem.title
            childRecyclerView.layoutManager = LinearLayoutManager(view.context, LinearLayoutManager.HORIZONTAL, false)
            childRecyclerView.adapter = ChildAdapter(parentItem.childList)
        }
    }
}

3. ChildAdapter.kt

package com.sksinha2410.ananotherreyclerview

import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.TextView
import androidx.recyclerview.widget.RecyclerView

class ChildAdapter(private val childList: List<ChildItem>) :
    RecyclerView.Adapter<ChildAdapter.ChildViewHolder>() {

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

    override fun onBindViewHolder(holder: ChildViewHolder, position: Int) {
        holder.bind(childList[position])
    }

    override fun getItemCount(): Int = childList.size

    class ChildViewHolder(private val view: View) : RecyclerView.ViewHolder(view) {
        fun bind(childItem: ChildItem) {
            view.findViewById<TextView>(R.id.child_title).text = childItem.title
        }
    }
}

4. ParentItem.kt

package com.sksinha2410.ananotherreyclerview

data class ParentItem(
    val title: String,
    val childList: List<ChildItem>
)

5. ChildItem.kt

package com.example.nestedrecyclerview

data class ChildItem(
    val title: String
)

6. activity_main.xml

<?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="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/parent_recyclerview"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_margin="16dp" />
</LinearLayout>

7. item_parent.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical">

    <TextView
        android:id="@+id/parent_title"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Parent Title"
        android:textSize="18sp"
        android:layout_margin="8dp" />

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/child_recyclerview"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:layout_marginBottom="16dp" />
</LinearLayout>

8. item_child.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    android:layout_margin="8dp">

    <TextView
        android:id="@+id/child_title"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Child Title"
        android:textSize="16sp"
        android:layout_marginBottom="8dp" />
</LinearLayout>

Explanation

MainActivity.kt

Sets up the main RecyclerView (parentRecyclerView) with a ParentAdapter.
getParentData() creates a list of ParentItem objects, each containing a list of ChildItem objects.

ParentAdapter.kt

Binds each parent item to a view (item_parent.xml) that contains a title and another RecyclerView (childRecyclerView).
ParentViewHolder sets up the inner RecyclerView with a ChildAdapter.

ChildAdapter.kt

Binds each child item to a view (item_child.xml) that contains a simple title.

ParentItem.kt

A data class representing a parent item that includes a title and a list of child items.

ChildItem.kt

A data class representing a child item that includes a title.

activity_main.xml

Contains a single RecyclerView (parent_recyclerview) that fills the screen.

item_parent.xml

Defines the layout for each parent item, including a title and an inner RecyclerView.

item_child.xml

Defines the layout for each child item, with a simple title.

How it Works

MainActivity initializes the parent RecyclerView with a list of parent items.
ParentAdapter creates and binds view holders for each parent item, setting up a nested RecyclerView for each.
ChildAdapter binds view holders for each child item within the nested RecyclerView.
ParentItem and ChildItem are data classes used to hold the data for parent and child items respectively.

This setup allows each parent item to have its own horizontal list of child items, demonstrating the use of nested RecyclerViews in an Android app.

Conclusion

This example shows how to use nested RecyclerViews to create complex lists with different types of items. It is a common pattern in many apps, especially those displaying hierarchical data or lists within lists.

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