Swipe to dismiss in Android Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a simple swipe-to-dismiss behavior using ItemTouchHelper.

Android Kotlin

val itemTouchHelper = ItemTouchHelper(object : ItemTouchHelper.SimpleCallback(0, [1]) {
    override fun onMove(recyclerView: RecyclerView, viewHolder: RecyclerView.ViewHolder, target: RecyclerView.ViewHolder): Boolean {
        return false
    }

    override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int) {
        // Handle item dismissal here
    }
})

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

AItemTouchHelper.DOWN

BItemTouchHelper.LEFT

CItemTouchHelper.RIGHT

DItemTouchHelper.UP

Attempts:

3 left

💡 Hint

Common Mistakes

Using UP or DOWN instead of LEFT or RIGHT for swipe direction.

Confusing swipe directions with move directions.

The swipe direction for dismissing an item to the left is ItemTouchHelper.LEFT.

2fill in blank

medium

Complete the code to attach the ItemTouchHelper to the RecyclerView.

Android Kotlin

itemTouchHelper.[1](recyclerView)

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

AconnectRecyclerView

BbindRecyclerView

CattachToRecyclerView

DsetRecyclerView

Attempts:

3 left

💡 Hint

Common Mistakes

Using non-existent methods like bindRecyclerView or setRecyclerView.

Forgetting to attach the helper to the RecyclerView.

The correct method to attach ItemTouchHelper to RecyclerView is attachToRecyclerView().

3fill in blank

hard

Fix the error in the onSwiped method to remove the dismissed item from the adapter's data list named 'items'.

Android Kotlin

override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int) {
    val position = viewHolder.adapterPosition
    items.[1](position)
    adapter.notifyItemRemoved(position)
}

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

AremoveAt

Bdelete

Cremove

Ddiscard

Attempts:

3 left

💡 Hint

Common Mistakes

Using remove() which expects an object, not an index.

Using non-existent methods like delete or discard.

The correct Kotlin List method to remove an item by index is removeAt().

4fill in blank

hard

Fill both blanks to enable swipe to dismiss only in the right direction and disable drag.

Android Kotlin

val itemTouchHelper = ItemTouchHelper(object : ItemTouchHelper.SimpleCallback([1], [2]) {
    override fun onMove(recyclerView: RecyclerView, viewHolder: RecyclerView.ViewHolder, target: RecyclerView.ViewHolder): Boolean {
        return false
    }

    override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int) {
        // Handle swipe
    }
})

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

A0

BItemTouchHelper.RIGHT

CItemTouchHelper.LEFT

DItemTouchHelper.UP

Attempts:

3 left

💡 Hint

Common Mistakes

Setting dragDirs to non-zero values enabling drag.

Using wrong swipe direction constants.

Drag directions are set to 0 to disable drag. Swipe direction is set to ItemTouchHelper.RIGHT to allow swipe right only.

5fill in blank

hard

Complete the code to create a swipe-to-dismiss that removes the item and shows a Toast with the dismissed item's name.

Android Kotlin

override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int) {
    val position = viewHolder.adapterPosition
    val item = items[position]
    items.removeAt(position)
    adapter.notifyItemRemoved(position)
    Toast.makeText(context, "Dismissed: " + item[1], Toast.LENGTH_SHORT).show()
}

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

A[

BremoveAt

C.name

D]

Attempts:

3 left

💡 Hint

Common Mistakes

Using parentheses instead of brackets to access list item.

Forgetting to remove the item from the list.

Not accessing the item's name property correctly.

Use [position] to get the item, removeAt(position) to remove it, and .name to get the item's name for the Toast.

Practice

1.

What is the main purpose of implementing onSwiped in ItemTouchHelper.SimpleCallback when using swipe to dismiss?

easy

A. To change the background color of the list item

B. To add a new item to the list

C. To disable swipe gestures on the list

D. To remove the swiped item from the data and update the UI

Solution

1. Step 1: Understand the role of onSwiped

   This method is called when a user swipes an item. It is used to handle what happens after the swipe gesture.

2. Step 2: Identify the correct action after swipe

   The typical action is to remove the swiped item from the data source and notify the adapter to update the UI.

3. Final Answer:

   To remove the swiped item from the data and update the UI -> Option D

4. Quick Check:

   onSwiped removes item [OK]

Hint: Remember: swipe means remove item and refresh list [OK]

Common Mistakes:

• Trying to add items in onSwiped
• Ignoring data update after swipe
• Using onSwiped to change colors only

2.

Which of the following is the correct way to create a SimpleCallback for swipe to dismiss only (no drag) in Kotlin?

val callback = object : ItemTouchHelper.SimpleCallback(?, ?) {}

easy

A. 0, ItemTouchHelper.LEFT or ItemTouchHelper.RIGHT

B. ItemTouchHelper.UP or ItemTouchHelper.DOWN, ItemTouchHelper.LEFT or ItemTouchHelper.RIGHT

C. ItemTouchHelper.LEFT or ItemTouchHelper.RIGHT, 0

D. ItemTouchHelper.UP or ItemTouchHelper.DOWN, 0

Solution

1. Step 1: Understand SimpleCallback constructor parameters

   The first parameter is for drag directions, the second for swipe directions.

2. Step 2: Set drag to 0 and swipe to left or right

   For swipe to dismiss only, drag should be 0 and swipe should allow left or right.

3. Final Answer:

   0, ItemTouchHelper.LEFT or ItemTouchHelper.RIGHT -> Option A

4. Quick Check:

   Drag=0, Swipe=LEFT|RIGHT [OK]

Hint: Drag=0 disables drag; swipe=LEFT|RIGHT enables swipe [OK]

Common Mistakes:

• Swapping drag and swipe parameters
• Using drag directions when only swipe needed
• Setting swipe to 0 disables swipe

3.

Given this code snippet inside onSwiped:

val position = viewHolder.adapterPosition
items.removeAt(position)
adapter.notifyItemRemoved(position)

What will happen when the user swipes an item?

medium

A. The item remains but the UI flashes

B. The item is removed from the list and the UI updates to reflect the change

C. The app crashes due to invalid position

D. Nothing happens because notifyItemRemoved is missing

Solution

1. Step 1: Remove item from data list

   The code removes the item at the swiped position from the data list.

2. Step 2: Notify adapter about removal

   Calling notifyItemRemoved updates the UI to remove the item visually.

3. Final Answer:

   The item is removed from the list and the UI updates to reflect the change -> Option B

4. Quick Check:

   Remove item + notify adapter = UI updates [OK]

Hint: Remove data then notify adapter to update UI [OK]

Common Mistakes:

• Not removing item from data list
• Forgetting to notify adapter
• Using wrong adapter position

4.

What is wrong with this onSwiped implementation?

override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int) {
    adapter.notifyItemRemoved(viewHolder.adapterPosition)
    items.removeAt(viewHolder.adapterPosition)
}

medium

A. The adapter position is not valid inside onSwiped

B. The method is missing a call to super.onSwiped

C. Calling notifyItemRemoved before removing item causes UI inconsistency

D. Nothing is wrong; this code works fine

Solution

1. Step 1: Check order of operations

   notifyItemRemoved should be called after removing the item from the data list.

2. Step 2: Understand impact of wrong order

   Calling notifyItemRemoved first causes the adapter to update UI before data changes, leading to inconsistency or crash.

3. Final Answer:

   Calling notifyItemRemoved before removing item causes UI inconsistency -> Option C

4. Quick Check:

   Remove data first, then notify adapter [OK]

Hint: Always update data before notifying adapter [OK]

Common Mistakes:

• Not removing item before notify
• Calling super.onSwiped unnecessarily
• Using wrong adapter position

5.

You want to implement swipe to dismiss in a RecyclerView but only allow swipe to the right. Which code snippet correctly sets up the SimpleCallback and handles the swipe?

val callback = object : ItemTouchHelper.SimpleCallback(0, ItemTouchHelper.RIGHT) {
    override fun onMove(...) = false
    override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int) {
        val pos = viewHolder.adapterPosition
        items.removeAt(pos)
        adapter.notifyItemRemoved(pos)
    }
}
ItemTouchHelper(callback).attachToRecyclerView(recyclerView)

hard

A. This code allows swipe only to the right and removes the item correctly

B. This code allows swipe both left and right

C. This code will crash because onMove is not implemented properly

D. This code does not remove the item from the list

Solution

1. Step 1: Check swipe directions in SimpleCallback

   Swipe is set to ItemTouchHelper.RIGHT only, so only right swipe is allowed.

2. Step 2: Verify onSwiped removes item and notifies adapter

   onSwiped removes the item at adapterPosition and calls notifyItemRemoved correctly.

3. Step 3: Confirm onMove returns false

   Returning false disables drag, which is intended here.

4. Final Answer:

   This code allows swipe only to the right and removes the item correctly -> Option A

5. Quick Check:

   Swipe=RIGHT only + remove item + notify adapter [OK]

Hint: Set swipe directions and remove item in onSwiped [OK]

Common Mistakes:

• Setting swipe to LEFT or both directions
• Not removing item from data list
• Returning true in onMove causing drag