How to detect swipe direction between left/right and up/down in Android using Kotlin?

This example demonstrates how to detect swipe direction between left/right and up/down in Android using Kotlin.

Step 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project.

Step 2 − Add the following code to res/layout/activity_main.xml.

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
   android:id="@+id/relativeLayout"
   android:layout_width="match_parent"
   android:layout_height="match_parent">
   <TextView
      android:id="@+id/textView"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_centerHorizontal="true"
      android:layout_marginTop="70dp"
      android:background="#008080"
      android:padding="5dp"
      android:text="TutorialsPoint"
      android:textColor="#fff"
      android:textSize="24sp"
      android:textStyle="bold" />
   <TextView
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:layout_centerInParent="true"
      android:text="Swipe to Detect swipe Event"
      android:textAlignment="center"
      android:textColor="@android:color/holo_purple"
      android:textSize="24sp"
      android:textStyle="bold" />
</RelativeLayout>

Step 3 − Add the following code to src/MainActivity.kt

import android.content.Context
import android.os.Bundle
import android.view.GestureDetector
import android.view.MotionEvent
import android.view.View
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import kotlin.math.abs
class MainActivity : AppCompatActivity() {
   var onSwipeTouchListener: OnSwipeTouchListener? = null
   override fun onCreate(savedInstanceState: Bundle?) {
      super.onCreate(savedInstanceState)
      setContentView(R.layout.activity_main)
      title = "KotlinApp"
      onSwipeTouchListener = OnSwipeTouchListener(this, findViewById(R.id.relativeLayout))
   }
   class OnSwipeTouchListener internal constructor(ctx:Context, mainView: View):View.OnTouchListener{
      private val gestureDetector: GestureDetector
      private var context: Context
      private lateinit var onSwipe:OnSwipeListener
      init{
         gestureDetector = GestureDetector(ctx, GestureListener())
         mainView.setOnTouchListener(this)
         context = ctx
      }
      override fun onTouch(v:View, event: MotionEvent):Boolean {
         return gestureDetector.onTouchEvent(event)
      }
      private companion object {
         private const val swipeThreshold = 100
         private const val swipeVelocityThreshold = 100
      }
      inner class GestureListener:GestureDetector.SimpleOnGestureListener() {
         override fun onDown(e:MotionEvent):Boolean {
            return true
         }
         override fun onFling(e1:MotionEvent, e2:MotionEvent, velocityX:Float, velocityY:Float):Boolean {
            var result = false
            try{
               val diffY = e2.y - e1.y
               val diffX = e2.x - e1.x
               if (abs(diffX) > abs(diffY)){
                  if (abs(diffX) > swipeThreshold && abs(velocityX) > swipeVelocityThreshold){
                     if (diffX > 0){
                        onSwipeRight()
                     }
                     else{
                        onSwipeLeft()
                     }
                     result = true
                  }
               }
               else if (abs(diffY) > swipeThreshold && abs(velocityY) > swipeVelocityThreshold){
                  if (diffY > 0){
                     onSwipeBottom()
                  }
                  else{
                     onSwipeTop()
                  }
                  result = true
               }
            }
            catch (exception:Exception) {
               exception.printStackTrace()
            }
            return result
         }
      }
      internal fun onSwipeRight() {
         Toast.makeText(context, "Swiped Right", Toast.LENGTH_SHORT).show()
         this.onSwipe.swipeRight()
      }
      internal fun onSwipeLeft() {
         Toast.makeText(context, "Swiped Left", Toast.LENGTH_SHORT).show()
         this.onSwipe.swipeLeft()
      }
      internal fun onSwipeTop() {
         Toast.makeText(context, "Swiped Up", Toast.LENGTH_SHORT).show()
         this.onSwipe.swipeTop()
      }
      internal fun onSwipeBottom() {
         Toast.makeText(context, "Swiped Down", Toast.LENGTH_SHORT).show()
         this.onSwipe.swipeBottom()
      }
      internal interface OnSwipeListener {
         fun swipeRight()
         fun swipeTop()
         fun swipeBottom()
         fun swipeLeft()
      }
   }
}

Step 4 − Add the following code to androidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://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>

Let's try to run your application. I assume you have connected your actual Android Mobile device with your computer. To run the app from android studio, open one of your project's activity files and click the Run  icon from the toolbar. Select your mobile device as an option and then check your mobile device which will display your default screen