Gesture handling in Android Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to detect a tap gesture on a View.

Android Kotlin

val gestureDetector = GestureDetector(this, object : GestureDetector.SimpleOnGestureListener() {
    override fun onSingleTapUp(e: MotionEvent?): Boolean {
        Toast.makeText(this@MainActivity, "Tapped!", Toast.LENGTH_SHORT).show()
        return [1]
    }
})

Drag options to blanks, or click blank then click option'

AUnit

Bfalse

Cnull

Dtrue

Attempts:

3 left

💡 Hint

Common Mistakes

Returning false causes the tap event to be ignored.

Returning null or Unit causes a compile error.

Returning true means the tap event was handled successfully.

2fill in blank

medium

Complete the code to set a touch listener that passes events to the gesture detector.

Android Kotlin

myView.setOnTouchListener { v, event ->
    [1].onTouchEvent(event)
}

Drag options to blanks, or click blank then click option'

AgestureDetector

Bthis

Cv

Devent

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'this' instead of gestureDetector causes errors.

Using 'v' or 'event' does not call the gesture detector.

The gestureDetector handles the touch events to detect gestures.

3fill in blank

hard

Fix the error in the gesture listener to detect a long press gesture.

Android Kotlin

val gestureListener = object : GestureDetector.SimpleOnGestureListener() {
    override fun onLongPress(e: MotionEvent?) {
        super.[1](e)
        Toast.makeText(context, "Long pressed", Toast.LENGTH_SHORT).show()
    }
}

Drag options to blanks, or click blank then click option'

AonSingleTapUp

BonLongPress

ConDoubleTap

DonScroll

Attempts:

3 left

💡 Hint

Common Mistakes

Calling super.onSingleTapUp causes the long press not to work.

Omitting the super call can cause unexpected behavior.

Calling super.onLongPress ensures the base class handles the long press event properly.

4fill in blank

hard

Fill both blanks to detect a fling gesture with velocity check.

Android Kotlin

override fun onFling(e1: MotionEvent?, e2: MotionEvent?, velocityX: Float, velocityY: Float): Boolean {
    if (velocityX > [1] && velocityY > [2]) {
        Toast.makeText(context, "Fling detected", Toast.LENGTH_SHORT).show()
        return true
    }
    return false
}

Drag options to blanks, or click blank then click option'

A1000f

B500f

C1500f

D200f

Attempts:

3 left

💡 Hint

Common Mistakes

Using too low velocity values causes false positives.

Using integers instead of floats causes type errors.

Velocity thresholds like 1000f and 500f help detect a fast enough fling gesture.

5fill in blank

hard

Fill all three blanks to create a gesture detector that recognizes double taps and single taps.

Android Kotlin

val gestureDetector = GestureDetector(this, object : GestureDetector.SimpleOnGestureListener() {
    override fun onDoubleTap(e: MotionEvent?): Boolean {
        Toast.makeText(context, "Double tap", Toast.LENGTH_SHORT).show()
        return [1]
    }

    override fun onSingleTapConfirmed(e: MotionEvent?): Boolean {
        Toast.makeText(context, "Single tap", Toast.LENGTH_SHORT).show()
        return [2]
    }

    override fun onDown(e: MotionEvent?): Boolean {
        return [3]
    }
})

Drag options to blanks, or click blank then click option'

Atrue

Bfalse

Csuper.onDown(e)

DUnit

Attempts:

3 left

💡 Hint

Common Mistakes

Returning false in tap handlers causes gestures to be ignored.

Returning Unit causes compile errors.

Not calling super.onDown causes gesture detection issues.

Return true in onDoubleTap and onSingleTapConfirmed to indicate event handled; onDown should call super.onDown.