Part 4 – Click Handler

RecyclerView & CardView dependencies:

developer.android.com/jetpack/androidx/releases/recyclerview

developer.android.com/jetpack/androidx/releases/cardview

package com.codinginflow.recyclerviewexample

import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.ImageView
import android.widget.TextView
import androidx.recyclerview.widget.RecyclerView
import kotlinx.android.synthetic.main.example_item.view.*

class ExampleAdapter(
    private val exampleList: List<ExampleItem>,
    private val listener: OnItemClickListener
) :
    RecyclerView.Adapter<ExampleAdapter.ExampleViewHolder>() {

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ExampleViewHolder {
        val itemView = LayoutInflater.from(parent.context).inflate(R.layout.example_item,
            parent, false)

        return ExampleViewHolder(itemView)
    }

    override fun onBindViewHolder(holder: ExampleViewHolder, position: Int) {
        val currentItem = exampleList[position]

        holder.imageView.setImageResource(currentItem.imageResource)
        holder.textView1.text = currentItem.text1
        holder.textView2.text = currentItem.text2
    }

    override fun getItemCount() = exampleList.size

    inner class ExampleViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView),
        View.OnClickListener {
        val imageView: ImageView = itemView.image_view
        val textView1: TextView = itemView.text_view_1
        val textView2: TextView = itemView.text_view_2

        init {
            itemView.setOnClickListener(this)
        }

        override fun onClick(v: View?) {
            val position = adapterPosition
            if (position != RecyclerView.NO_POSITION) {
                listener.onItemClick(position)
            }
        }
    }

    interface OnItemClickListener {
        fun onItemClick(position: Int)
    }
}

package com.codinginflow.recyclerviewexample

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.view.View
import android.widget.Toast
import androidx.recyclerview.widget.LinearLayoutManager
import kotlinx.android.synthetic.main.activity_main.*
import kotlin.random.Random

class MainActivity : AppCompatActivity(), ExampleAdapter.OnItemClickListener {
    private val exampleList = generateDummyList(500)
    private val adapter = ExampleAdapter(exampleList, this)

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

        recycler_view.adapter = adapter
        recycler_view.layoutManager = LinearLayoutManager(this)
        recycler_view.setHasFixedSize(true)
    }

    fun insertItem(view: View) {
        val index = Random.nextInt(8)

        val newItem = ExampleItem(
            R.drawable.ic_android,
            "New item at position $index",
            "Line 2"
        )

        exampleList.add(index, newItem)
        adapter.notifyItemInserted(index)
    }

    fun removeItem(view: View) {
        val index = Random.nextInt(8)

        exampleList.removeAt(index)
        adapter.notifyItemRemoved(index)
    }

    override fun onItemClick(position: Int) {
        Toast.makeText(this, "Item $position clicked", Toast.LENGTH_SHORT).show()
        val clickedItem = exampleList[position]
        clickedItem.text1 = "Clicked"
        adapter.notifyItemChanged(position)
    }

    private fun generateDummyList(size: Int): ArrayList<ExampleItem> {

        val list = ArrayList<ExampleItem>()

        for (i in 0 until size) {
            val drawable = when (i % 3) {
                0 -> R.drawable.ic_android
                1 -> R.drawable.ic_audio
                else -> R.drawable.ic_sun
            }

            val item = ExampleItem(drawable, "Item $i", "Line 2")
            list += item
        }

        return list
    }
}

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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"
    tools:context=".MainActivity">

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/recycler_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_above="@id/buttons"
        android:clipToPadding="false"
        android:padding="4dp"
        tools:listitem="@layout/example_item" />

    <LinearLayout
        android:id="@+id/buttons"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:clipToPadding="true"
        android:padding="4dp">

        <Button
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:onClick="insertItem"
            android:text="Insert item" />

        <Button
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:onClick="removeItem"
            android:text="Remove item" />

    </LinearLayout>

</RelativeLayout>

<?xml version="1.0" encoding="utf-8"?>
<androidx.cardview.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_margin="4dp">

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:padding="8dp">

        <ImageView
            android:id="@+id/image_view"
            android:layout_width="50dp"
            android:layout_height="50dp"
            android:layout_marginEnd="8dp"
            android:src="@drawable/ic_android" />

        <TextView
            android:id="@+id/text_view_1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_toEndOf="@id/image_view"
            android:text="Line 1"
            android:textColor="@android:color/black"
            android:textSize="18sp"
            android:textStyle="bold" />

        <TextView
            android:id="@+id/text_view_2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_below="@id/text_view_1"
            android:layout_toEndOf="@id/image_view"
            android:text="Line 2" />

    </RelativeLayout>

</androidx.cardview.widget.CardView>

package com.codinginflow.recyclerviewexample

data class ExampleItem(val imageResource: Int, var text1: String, var text2: String)