Kotlin का उपयोग करके Android RecyclerView में चयनित आइटम को सही तरीके से हाइलाइट कैसे करें?

परिचय

यह उदाहरण दर्शाता है कि Kotlin का उपयोग करके Android RecyclerView में चयनित आइटम को सही तरीके से कैसे हाइलाइट किया जाए। हम एक चरण-दर-चरण दृष्टिकोण का पालन करेंगे जिसमें लेआउट निर्माण, एडाप्टर कार्यान्वयन, और चयन स्थिति प्रबंधन शामिल है।

चरण 1: नया प्रोजेक्ट बनाएं

Android Studio खोलें, File → New Project पर जाएं और आवश्यक विवरण भरकर एक नया प्रोजेक्ट बनाएं।

चरण 2: activity_main.xml लेआउट जोड़ें

res/layout/activity_main.xml में निम्न कोड जोड़ें:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="https://schemas.android.com/apk/res/android"
    xmlns:tools="https://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="4dp"
    tools:context=".MainActivity">
    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/recyclerView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:paddingBottom="8dp" />
</RelativeLayout>

चरण 3: MainActivity.kt लागू करें

src/MainActivity.kt में निम्न कोड जोड़ें:

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)
        title = "KotlinApp"
        
        val recyclerView: RecyclerView = findViewById(R.id.recyclerView)
        recyclerView.addItemDecoration(SimpleItemDecoration(this))
        
        val layoutManager = LinearLayoutManager(this@MainActivity)
        recyclerView.layoutManager = layoutManager
        
        val posts = returnListItems()
        val adapter = RecyclerViewAdapter(this@MainActivity, posts)
        recyclerView.adapter = adapter
    }
    
    private fun returnListItems(): List<ItemObject>? {
        val items: MutableList<ItemObject> = ArrayList()
        items.add(ItemObject("Ballon'd'or", "2007", "Ricardo KaKa"))
        items.add(ItemObject("Ballon'd'or", "2008", "Cristiano Ronaldo"))
        items.add(ItemObject("Ballon'd'or", "2009 - 2012, 2015", "Lionel Messi"))
        items.add(ItemObject("Ballon'd'or", "2013, 2014, 2016, 2017", "Cristiano Ronaldo"))
        items.add(ItemObject("Ballon'd'or", "2018", "Luca Modric"))
        items.add(ItemObject("Ballon'd'or", "2019", "Lionel Messi"))
        return items
    }
}

चरण 4: आवश्यक Kotlin क्लास फाइलें बनाएं

ItemObject.kt

internal class ItemObject(
    val awardTitle: String,
    val awardYear: String,
    val player: String
)

RecyclerViewAdapter.kt

import android.view.LayoutInflater
import android.view.ViewGroup
import androidx.annotation.NonNull
import androidx.recyclerview.widget.RecyclerView

class RecyclerViewAdapter internal constructor(
    context: MainActivity,
    private val itemList: List<ItemObject>?
) : RecyclerView.Adapter<RecyclerViewHolders>() {
    
    @NonNull
    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerViewHolders {
        val layoutView = LayoutInflater.from(parent.context).inflate(R.layout.list_layout, null)
        return RecyclerViewHolders(layoutView)
    }
    
    override fun onBindViewHolder(holder: RecyclerViewHolders, position: Int) {
        holder.awardTitle.text = "Award Title: " + itemList!![position].awardTitle
        holder.awardYear.text = "Award Year: " + itemList[position].awardYear
        holder.player.text = "Player Name: " + itemList[position].player
    }
    
    override fun getItemCount(): Int {
        return this.itemList!!.size
    }
}

RecyclerViewHolders.kt

import android.util.SparseBooleanArray
import android.view.View
import android.widget.TextView
import androidx.recyclerview.widget.RecyclerView.ViewHolder

class RecyclerViewHolders(itemView: View) : ViewHolder(itemView), View.OnClickListener {
    var awardTitle: TextView
    var awardYear: TextView
    var player: TextView
    private val selectedItems = SparseBooleanArray()
    
    override fun onClick(view: View) {
        if (selectedItems[adapterPosition, false]) {
            selectedItems.delete(adapterPosition)
            view.isSelected = false
        } else {
            selectedItems.put(adapterPosition, true)
            view.isSelected = true
        }
    }
    
    init {
        itemView.setOnClickListener(this)
        awardTitle = itemView.findViewById(R.id.awardTitle)
        awardYear = itemView.findViewById(R.id.awardYear)
        player = itemView.findViewById(R.id.playerName)
    }
}

SimpleItemDecoration.kt

import android.content.Context
import android.graphics.Canvas
import android.graphics.drawable.Drawable
import androidx.annotation.NonNull
import androidx.core.content.ContextCompat
import androidx.recyclerview.widget.RecyclerView

internal class SimpleItemDecoration(context: Context) : RecyclerView.ItemDecoration() {
    private val drawable: Drawable = ContextCompat.getDrawable(context, R.drawable.line_divider)!!
    
    override fun onDrawOver(
        @NonNull canvas: Canvas,
        parent: RecyclerView,
        @NonNull state: RecyclerView.State
    ) {
        val left = parent.paddingLeft
        val right = parent.width - parent.paddingRight
        val childCount = parent.childCount
        
        for (i in 0 until childCount) {
            val child = parent.getChildAt(i)
            val params = child.layoutParams as RecyclerView.LayoutParams
            val top = child.bottom + params.bottomMargin
            val bottom = top + drawable.intrinsicHeight
            drawable.setBounds(left, top, right, bottom)
            drawable.draw(canvas)
        }
    }
}

चरण 5: ड्रॉएबल रिसोर्स फाइलें बनाएं

background_selector.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="https://schemas.android.com/apk/res/android">
    <item android:drawable="@android:color/holo_green_light" 
          android:state_pressed="false" android:state_selected="true" />
    <item android:drawable="@android:color/holo_purple" 
          android:state_selected="false" />
</selector>

line_divider.xml

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="https://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <size
        android:width="2dp"
        android:height="2dp" />
    <solid android:color="@color/colorPrimaryDark" />
</shape>

चरण 6: list_layout.xml लेआउट बनाएं

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="https://schemas.android.com/apk/res/android"
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@drawable/background_selector"
    android:padding="16dp">
    <TextView
        android:id="@+id/awardTitle"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="10dp"
        android:text="New Text"
        android:textColor="@android:color/background_dark"
        android:textSize="18sp"
        android:textStyle="bold" />
    <TextView
        android:id="@+id/awardYear"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/awardTitle"
        android:layout_alignStart="@+id/awardTitle"
        android:layout_marginTop="20dp"
        android:text="New Text"
        android:textColor="@android:color/background_dark" />
    <TextView
        android:layout_marginBottom="10dp"
        android:id="@+id/playerName"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentEnd="true"
        android:text="New Text"
        android:textColor="@android:color/background_dark" />
</RelativeLayout>

चरण 7: AndroidManifest.xml कॉन्फ़िगर करें

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="https://schemas.android.com/apk/res/android"
    package="com.example.q11">
    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>
</manifest>

एप्लिकेशन चलाएं

अपने Android डिवाइस को कंप्यूटर से कनेक्ट करें। Android Studio में प्रोजेक्ट की एक्टिविटी फाइल खोलें और टूलबार से Run आइकन पर क्लिक करें। अपना मोबाइल डिवाइस चुनें और डिफ़ॉल्ट स्क्रीन देखें।