RecyclerView Basics

Question 1

What is the role of a RecyclerView Adapter?

Answer 1

1. Adapts a list so the RecyclerView can display its items

2. Produces ViewHolders

Question 2

What does a ViewHolder contain?

Answer 2

1. Views
2. Data
3. Meta information

Question 3

How does the RecyclerView know how many items to display?

Answer 3

getItemCount() in the Adapter

Question 4

Which two Adapter methods bind ViewHolders to data?

Answer 4

onCreateViewHolder()
and
onBindViewHolder()

Question 5

What 6 parts are required for a RecyclerView?

Answer 5

Data to be displayed
RecyclerView Instance in layout xml
Item layout xml
Layout Manager
ViewHolder
Adapter

Question 6

How are Views presented in the provided LinearLayoutManager?

Answer 6

A vertical list of full width rows

Question 7

Which 3 LayoutManagers are suggested by Android Studio?

Answer 7

LinearLayoutManager
GridLayoutManager
StaggeredGridLayoutManager

Question 8

What is the core task in implementing a RecyclerView?

Answer 8

Creating the Adapter

Question 9

Which 3 functions must be implemented in the Adapter?

Answer 9

onCreateViewHolder()
onBindViewHolder()
getItemCount()

Question 10

What will the functions in the Adapter be called by?

Answer 10

The RecyclerView

Question 11

What parameters are taken by onCreateViewHolder() ?

Answer 11

parent: ViewGroup (the RecyclerView)
viewType: int

Question 12

What is the role of the LayoutInflater?

Answer 12

It creates a View from a layout xml

Question 13

What is the syntax for creating a LayoutInflater?

Answer 13

val layoutInflater = LayoutInflater.from(parentView.context)

Question 14

Why is attachToRoot false when inflating a View?

Answer 14

Attaching the child View to its parent is not the responsibility of onCreateViewHolder()

Question 15

Which 3 parameters are passed to LayoutInflater.inflate() ?

Answer 15

1. The layout xml to be inflated into a View
2. The parent View to which this (return, child) View will be attached
3. attachToRoot: Boolean

Question 16

What is the role of onCreateViewHolder() ?

Answer 16

Converts layout xml to a View in a ViewHolder

Question 17

What is the role of onBindViewHolder() ?

Answer 17

Binds data from the list to the View in the ViewHolder

Question 18

Which function can the RecyclerView call to renew all its data?

Answer 18

notifyDataSetChanged()

Question 19

What parameters are taken in the constructor of an Adapter?

Answer 19

None - we don’t declare a constructor for an Adapter class

Question 20

How is an Adapter attached to a RecyclerView?

Answer 20

In Fragment.onCreateView()
using
val adapter = MyAdapter()
binding.recyclerViewXmlId.adapter = adapter

Question 21

Where is the data in Adapter instantiated / updated?

Answer 21

Fragment.onCreateView()
using
binding.list.observe(viewLifecycleOwner) {
  it?.let{
    adapter.data = it
    }

Question 22

What parameters are taken by onBindViewHolder() ?

Answer 22

1. holder: YourViewHolder

2. position: Int

Question 23

Why would a RecyclerView need to access ViewHolder.itemView? (3)

Answer 23

1. Binding an item to display on the screen
2. Drawing decorations around a view like a border
3. Implementing accessibility

Question 24

What does ViewHolder.itemView return?

Answer 24

The ViewHolder’s View (the one that was inflated in onCreateViewHolder)

Question 25

What is the usual class signature for a ViewHolder?

Answer 25

class MyViewHolder private constructor(itemView: View) : RecyclerView.ViewHolder(itemView)

Question 26

What is the class signature for a ViewHolder that is simply a wrapper for a TextView?

Answer 26

class MyViewHolder private constructor(textView: TextView) : RecyclerView.ViewHolder(textView)

Question 27

What is the class signature for an Adapter that uses a ViewHolder which is defined within the Adapter class itself?

Answer 27

class MyAdapter : RecyclerView.Adapter^MyAdapter.MyViewHolder^()