Android Gestures with Examples

import android.os.Bundle
import android.util.Log
import android.view.MotionEvent
import androidx.appcompat.app.AppCompatActivity
import kotlinx.android.synthetic.main.activity_main.*

// logs are added for better understanding. 
private const val TAG = "Gestures"

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

    override fun onTouchEvent(event: MotionEvent): Boolean {

        return when (event.action) {
            MotionEvent.ACTION_DOWN -> {
                // when we touch or tap on the screen
                Log.d(TAG, "Action was DOWN")
                gesture.text = "Action was DOWN"
                true
            }
            MotionEvent.ACTION_MOVE -> {
                // while pressing on the screen, 
                // we move our finger
                Log.d(TAG, "Action was MOVE")
                gesture.text = "Action was MOVE"

                true
            }
            MotionEvent.ACTION_UP -> {
                // Lifting up the finger after
                // pressing on the screen
                Log.d(TAG, "Action was UP")
                gesture.text = "Action was UP"

                true
            }
            MotionEvent.ACTION_CANCEL -> {
                Log.d(TAG, "Action was CANCEL")
                gesture.text = "Action was CANCEL"

                true
            }
            MotionEvent.ACTION_OUTSIDE -> {
                Log.d(TAG, "Movement occurred outside of screen element")
                gesture.text = "Movement occurred screen element"

                true
            }
            else -> super.onTouchEvent(event)
        }
    }
}

import android.os.Bundle
import android.util.Log
import android.view.GestureDetector
import android.view.MotionEvent
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import androidx.core.view.GestureDetectorCompat
import kotlinx.android.synthetic.main.activity_main.*

// logs are added for better understanding. 
private const val TAG = "Gestures"

// We have to implement the members as well
// because we are implementing the interfaces.
class MainActivity : AppCompatActivity(), GestureDetector.OnGestureListener, 
                                       GestureDetector.OnDoubleTapListener {

    private lateinit var detectorCompat: GestureDetectorCompat

    public override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        
        // Instantiate the gesture detector with the
        // application context and an implementation of
        // GestureDetector.OnGestureListener
        // since we have implemented these 
        // interfaces we can simply us the
        // this keyword to refer to the current activity
        detectorCompat = GestureDetectorCompat(this, this)
    }

    // this function connects touch events to gestures
    override fun onTouchEvent(event: MotionEvent): Boolean {
        return if (detectorCompat.onTouchEvent(event)) {
            true
        } else {
            super.onTouchEvent(event)
        }
    }

    override fun onDown(event: MotionEvent): Boolean {
        Log.d(TAG, "onDown: $event")
        return true
    }

    override fun onFling(
            event1: MotionEvent,
            event2: MotionEvent,
            velocityX: Float,
            velocityY: Float
    ): Boolean {
        Log.d(TAG, "onFling: $event1 $event2")
        return true
    }

    override fun onLongPress(event: MotionEvent) {
        Log.d(TAG, "onLongPress: $event")
        gesture.text = "Long Press"
    }

    override fun onScroll(
            event1: MotionEvent,
            event2: MotionEvent,
            distanceX: Float,
            distanceY: Float
    ): Boolean {
        Log.d(TAG, "onScroll: $event1 $event2")
        return true
    }

    override fun onShowPress(event: MotionEvent) {
        Log.d(TAG, "onShowPress: $event")
        gesture.text = "Press"
    }

    override fun onSingleTapUp(event: MotionEvent): Boolean {
        Log.d(TAG, "onSingleTapUp: $event")
        gesture.text = "Single Tap"

        return true
    }

    override fun onDoubleTap(event: MotionEvent): Boolean {
        Log.d(TAG, "onDoubleTap: $event")
        gesture.text = "DoubleTap"

        return true
    }

    override fun onDoubleTapEvent(event: MotionEvent): Boolean {
        Log.d(TAG, "onDoubleTapEvent: $event")
        
          // simple toast
        Toast.makeText(this, "Double Tap", Toast.LENGTH_SHORT).show() 
        return true
    }

    override fun onSingleTapConfirmed(event: MotionEvent): Boolean {
        Log.d(TAG, "onSingleTapConfirmed: $event")
        gesture.text = "Single Tap Confirmed"

        return true
    }
}