How to Draw Border on Event of Click in Android with Kotlin?

Sometimes we want to display to the users that they have clicked an item by showing a border on the item. So, for this, we need to create two drawable resource files, one for the normal background of the item and another for the border. A sample video is given below to get an idea about what we are going to do in this article. Note that we are going to implement this project using the Kotlin language. 

Step by Step Implementation

Step 1: Create a New Project

To create a new project in Android Studio please refer to Create a new project in android studio in kotlin.

Step 2: Working with the activity_main.xml file

Navigate to the app > res > layout > activity_main.xml and add the below code to that file. Below is the code for the activity_main.xml file.

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"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/gfg"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="GeeksforGeeks"
        android:textSize="22sp"
        android:textColor="#189C1E"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.192" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="140dp"
        android:text="Option1"
        android:padding="3dp"
        android:textSize="18sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.501"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/gfg" />

    <TextView
        android:id="@+id/textView3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="18sp"
        android:text="Option2"
        android:padding="3dp"
        app:layout_constraintBottom_toTopOf="@+id/textView4"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView2" />

    <TextView
        android:id="@+id/textView4"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="240dp"
        android:text="Option3"
        android:textSize="18sp"
        android:padding="3dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.501"
        app:layout_constraintStart_toStartOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

Step 3: Creating drawable resource files

Refer to this article Create Drawable Resource XML File in Android Studio and create Drawable Resource XML File. Layout file for item_background.xml

XML

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">
    <solid android:color="#F3EDED" />
    <corners android:radius="4dp" />
    <stroke
        android:width="1dp"
        android:color="#EEE" />
</shape>

Layout for on_item_select.xml for the item is clicked.

XML

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">

<solid android:color="#FFF" />
<corners android:radius="6dp" />
<stroke
    android:width="2dp"
    android:color="#F40909" />
</shape>

Step 4: Working with the MainActivity.kt file

Go to the MainActivity.kt file and refer to the following code. Below is the code for the MainActivity.kt file. Comments are added inside the code to understand the code in more detail.

Kotlin

package com.ayush.gfgitemselect

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.Button
import android.widget.TextView

class MainActivity : AppCompatActivity() {

    // Initializing the views
    lateinit var option1: TextView
    lateinit var option2: TextView
    lateinit var option3: TextView
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        // Binding the views
        option1 = findViewById(R.id.textView2)
        option2 = findViewById(R.id.textView3)
        option3 = findViewById(R.id.textView4)

        // setting the normal background for the items
        option1.setBackgroundResource(R.drawable.item_background)
        option2.setBackgroundResource(R.drawable.item_background)
        option3.setBackgroundResource(R.drawable.item_background)

        // setting the background when item is clicked
        option1.setOnClickListener {
            option1.setBackgroundResource(R.drawable.on_item_select)
        }
        option2.setOnClickListener {
            option2.setBackgroundResource(R.drawable.on_item_select)
        }
        option3.setOnClickListener {
            option3.setBackgroundResource(R.drawable.on_item_select)
        }
    }
}

So, our app is ready.  And we can see the output.

Output: