android kotlin - RecyclerView StaggeredGridLayoutManager example

MainActivity.kt

package com.cfsuman.kotlintutorials

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


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

        // Get the widgets reference from XML layout
        val recyclerView = findViewById<RecyclerView>(R.id.recyclerView)


        // initialize a mutable list of color
        val colors = mutableListOf(
            "Aero blue", "African violet", "Air superiority blue",
            "Alice blue", "Alloy orange", "Amaranth pink",
            "Amaranth red", "Android green", "Antique brass",
            "Antique bronze", "Antique ruby", "Apple green",
            "Aquamarine", "Arctic lime", "Arylide yellow",
            "Asparagus", "Atomic tangerine"
        )

        // initialize staggered grid layout manager
        StaggeredGridLayoutManager(
            3, // span count
            StaggeredGridLayoutManager.VERTICAL // orientation
        ).apply {
            // specify the layout manager for recycler view
            recyclerView.layoutManager = this
        }

        // finally, data bind the recycler view with adapter
        recyclerView.adapter = RecyclerViewAdapter(colors)
    }
}

RecyclerViewAdapter.kt

package com.cfsuman.kotlintutorials

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


class RecyclerViewAdapter(private val colors: MutableList<String>)
    : RecyclerView.Adapter<RecyclerViewAdapter.ViewHolder>() {

    override fun onCreateViewHolder(
        parent: ViewGroup, viewType: Int): ViewHolder {
        // inflate the custom view from xml layout file
        val view: View = LayoutInflater.from(parent.context)
            .inflate(R.layout.custom_view,parent,false)

        // return the view holder
        return ViewHolder(view)
    }


    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        // display the current color
        holder.color.text = colors[position]
    }


    override fun getItemCount(): Int {
        // number of items in the data set held by the adapter
        return colors.size
    }


    class ViewHolder(itemView: View)
        : RecyclerView.ViewHolder(itemView){
        val color: TextView = itemView.findViewById(R.id.tvColor)
    }


    // this two methods useful for avoiding duplicate item
    override fun getItemId(position: Int): Long {
        return position.toLong()
    }


    override fun getItemViewType(position: Int): Int {
        return position
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/rootLayout"
    android:background="#DCDCDC">

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/recyclerView"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

custom_view.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.cardview.widget.CardView
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/cardView"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    app:cardBackgroundColor="#E5E4E2"
    app:cardCornerRadius="8dp"
    app:cardElevation="4dp"
    app:cardMaxElevation="6dp"
    app:contentPadding="24dp"
    android:layout_margin="4dp">

    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >
        <TextView
            android:id="@+id/tvColor"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:fontFamily="sans-serif"
            android:textSize="20sp"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent" />
    </androidx.constraintlayout.widget.ConstraintLayout>

</androidx.cardview.widget.CardView>