Develop Reference

Android Studio: autoSize of EditText doesn't work

in my current project there's an EditText with fixed layout_width and layout_height, called exercise that is expanded downwards programmatically: One line of text (String) + "\n" is added to the EditText.
Sometimes the line added to the EditText, let's call it element, is too long to fit inside the full width of the object so it's splitted into a new line.
The thing is I would either like the lines' text size in exercise to be resized to fit the EditText's width or have a clear visible distance between each line (element), but just not inside the newline due to not fitting inside the exercise's width.
Therefore I googled as much as I could and tried out every possible solution I could find today.
What I tried:
Using either EditText as the object and android:autoSizeTextType="uniform" & android:inputType="textMultiLine|textCapSentences"as attributes or androidx.appcompat.widget.AppCompatEditText, accompanied by the attributes app:autoSizeMaxTextSize="28sp", app:autoSizeMinTextSize="8sp"and app:autoSizeStepGranularity="1sp"
(with a device that supports just exactly API 26)
using other types of text objects
using lineSpacingExtra to insert some spacing. This unfortunately also inserted the spacing between the wrapped/ splitted line so the original element's line that got splitted by wrapping inside the EditText had the spacing aswell.
That's where I am now. I can't get the text size be reduced automatically when the line would be too wide for the EditText's width.
I could supply the full XML, if needed.
I'm grateful for any hint that could help here. Thanks in advance!

Here's a really basic RecyclerView implementation (using view binding, let me know if you're not familiar with that - you can just findViewById all the things instead):
class MainFragment : Fragment(R.layout.fragment_main) {
lateinit var binding: FragmentMainBinding
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
binding = FragmentMainBinding.bind(view)
with(binding) {
val adapter = MyAdapter()
recyclerView.adapter = adapter
recyclerView.layoutManager = LinearLayoutManager(requireContext())
addButton.setOnClickListener {
val item = textEntry.text.toString()
if (item.isNotBlank()) {
adapter.addItem(item)
textEntry.text.clear()
}
}
}
}
}
class MyAdapter : RecyclerView.Adapter<MyAdapter.ViewHolder>() {
private var data: List<String> = emptyList()
fun addItem(item: String) {
data = data + item
notifyItemInserted(data.lastIndex)
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
val view = ItemViewBinding.inflate(LayoutInflater.from(parent.context), parent, false)
return ViewHolder(view)
}
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
holder.binding.textView.text = data[position]
}
override fun getItemCount(): Int = data.size
class ViewHolder(val binding: ItemViewBinding) : RecyclerView.ViewHolder(binding.root)
}
fragment_main.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:orientation="vertical"
android:gravity="center"
android:padding="10dp">
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/recyclerView"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_marginBottom="8dp"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintBottom_toTopOf="#id/textEntry"
/>
<EditText
android:id="#+id/textEntry"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:singleLine="true"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintEnd_toStartOf="#id/addButton"
/>
<Button
android:id="#+id/addButton"
android:text="ADD"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
/>
</androidx.constraintlayout.widget.ConstraintLayout>
item_view.xml
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:paddingHorizontal="16dp"
>
<TextView
android:id="#+id/textView"
app:autoSizeTextType="uniform"
android:layout_width="match_parent"
android:layout_height="48sp"
android:maxLines="1"
android:gravity="center_vertical"
/>
</FrameLayout>
It's pretty simple - you have a text entry field and a button to add the contents as a new line. The button passes the contents to addItem on the adapter, which appends it to the list of lines in data. The RecyclerView just displays all the items in data, using a ViewHolder layout that has an auto-sizing TextView to scale each item.
Ideally you'd want to persist data somehow (e.g. the Add button passes the new data to a ViewModel, stores it somehow, updates the current list which the adapter has observed so it updates whenever there's a change) - I just left it as a basic proof of concept. Also, it's easier to store separate items if they're kept separate - you can always serialise it by joining them into a single string if you really want! But generally you wouldn't want to do that
edit - since you're having trouble with the setTypeface thing, this is all it is:
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
with(holder.binding.textView) {
val styled = position % 2 == 0
text = data[position]
setTypeface(typeface, if (styled) Typeface.BOLD else Typeface.NORMAL)
setTextColor(if (styled) Color.RED else Color.BLACK)
}
}
The logic is just styling alternate items differently, but hopefully you get the idea. You decide how to style a given item depending on what it is, and then you apply that style by setting attributes as appropriate. It's always an "if this is true do A, otherwise do B" situation, so you're always setting the attribute one way or the other. You never only set it for one case, because then you're leaving old state displayed if it's not that case.
It's more complicated, but you also have the option of creating different ViewHolders (with their own XML layouts) for different kinds of item. So instead of having a single ViewHolder that has to work with everything, where you have to reconfigure things like all the styling in onBindViewHolder depending on which type of item is displayed, you can just have different ViewHolders with different styling, different layouts etc:
// creating a sealed class so we can say our adapter handles a MyViewHolder type,
// and we can have a specific set of possible subclasses of that
sealed class MyViewHolder(view: View) : RecyclerView.ViewHolder(view)
class HeaderViewHolder(val binding: HeaderItemBinding) : MyViewHolder(binding.root)
class ItemViewHolder(val binding: ItemViewBinding) : MyViewHolder(binding.root)
// the Adapter now uses the MyViewHolder type (which as above, covers a couple of different
// ViewHolder classes we're using)
class MyAdapter : RecyclerView.Adapter<MyViewHolder>() {
private var data: List<String> = emptyList()
fun addItem(item: String) {
data = data + item
notifyItemInserted(data.lastIndex)
}
// some identifiers for the different ViewHolder types we're using
private val HEADER_TYPE = 0
private val ITEM_TYPE = 1
override fun getItemViewType(position: Int): Int {
// Work out what kind of ViewHolder the item in this position should display in.
// This gets passed to onCreateViewHolder, where you create the appropriate type,
// and that type of ViewHolder is what gets passed into onBindViewHolder for this position
return if (data[position].startsWith("Section")) HEADER_TYPE else ITEM_TYPE
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyViewHolder {
val inflater = LayoutInflater.from(parent.context)
// creating the appropriate ViewHolder instance depending on the type requested
return when(viewType) {
HEADER_TYPE -> HeaderViewHolder(HeaderItemBinding.inflate(inflater, parent, false))
ITEM_TYPE -> ItemViewHolder(ItemViewBinding.inflate(inflater, parent, false))
else -> throw RuntimeException("Unhanded view type!")
}
}
override fun onBindViewHolder(holder: MyViewHolder, position: Int) {
// The type of MyViewHolder passed in here depends on what getItemViewType returns
// for this position - binding is a different type in each case,
// because it's been generated from different layouts
when(holder) {
is HeaderViewHolder -> holder.binding.textView.text = data[position]
is ItemViewHolder -> holder.binding.textView.text = data[position]
}
}
override fun getItemCount(): Int = data.size
}
(You could be a bit more clever than this, but just to illustrate the general idea!)
That's using the same item_view.xml as before, and a header_item.xml variation on that (but you could have literally anything, they're completely separate layouts, completely separate ViewHolders):
header_item.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:paddingHorizontal="16dp"
>
<TextView
android:id="#+id/textView"
app:autoSizeTextType="uniform"
android:layout_width="match_parent"
android:layout_height="48sp"
android:layout_weight="1"
android:textStyle="bold"
android:textColor="#DD1100"
android:maxLines="1"
android:gravity="center_vertical"
/>
</LinearLayout>
So instead of having to "redesign" one ViewHolder in code to go back and forth between different item types and their styling, You can just use two differently-styled layouts. It's a bit more work to set up, but it can be neater and much more flexible when you have completely independent things - especially if you want to give them different functionality. It depends whether it's worth it to you, or if you're happy to just have a single ViewHolder and restyle things in code, hide or show elements etc.

you can try something like this
if(et.getText().length()>10) {
et.setTextSize(newValue)

Custom View with canvas in RecyclerView

I have a custom view in which you can draw with your fingers, I fill out a recyclerview with this view, made an adapter, and for example a list with size = 10 is obtained, where each item is a custom view, and if the user draws for example in item with position 5 then when scrolling the same picture appears in another item where he did not draw.
here is my adapter:
class CustomViewListAdapter : RecyclerView.Adapter<CustomViewListAdapter.ViewHolder>() {
private var listSchedule = ArrayList<Int>()
class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
var calendarView: CustomView= itemView.calendar!!
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
return ViewHolder(
LayoutInflater.from(parent.context).inflate(
R.layout.schedule_item,
parent,
false
)
)
}
override fun getItemCount(): Int = listSchedule.size
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
holder.calendarView.setValue(listSchedule[position] )
}
fun setSchedules(listSchedule: ArrayList<Int>) {
this.listSchedule = listSchedule
notifyDataSetChanged()
}
}

Are you aware of how RecyclerView works? Lets assume you have 1000 items in your list. A simple approach would be to create 1000 views from your schedule_item layout bind them and show them in e.g. a scrollview. However, doing that would cost a lot of time and memory. So the clever Android developers came up with the following idea:
Since of the 1000 items only e.g. 10 are visible at the same time, lets just create 10 views and only change the content of the views depending on the actual item they show. So the 10 views are reused or recycled.
For this to work, the onBindViewHolder implementation must make sure that it updates the provided viewholder in a way that it shows the content of the item at the given position.
Now in your code, all you do in onBindViewHolder is, to set a single integer. There is no sign of setting any custom drawing etc. So I assume the drawing is just stored inside the CustomView. And since there are only those 10 or so CustomViews (as explained above), when they are reused to show a different item, they contain the original drawings because you didn't change that in onBindViewHolder.

Nested Recyclerviews with Complex Room LiveData

I have a collection of parent objects each having a collection of child objects. Call these ParentModels and ChildModels.
On screen I want to display a RecyclerView of rendered ParentModels, each containing inter alia a RecyclerView of rendered ChildModels.
Wishing to avoid having a god LiveData that redraws everything just because one property of one ChildModel changes, I intend to separate these.
I can't figure out how to structure this with Recyclerview Adapters and Holders plus whatever Fragments and ViewModels I need. Right now I have
class MyFragment: Fragment() {
private lateinit val mViewModel: FragmentViewModel
// ...
fun onViewCreated(/*...*/) {
val parentAdapter = ParentAdapter()
view.findViewById<RecyclerView>(/*...*/).apply {
adapter = parentAdapter
//...
}
viewModel.getParents().observe(this, Observer {
parentAdapter.setParents(it)
}
}
}
class FragmentViewModel #Inject constructor(repository: RoomRepo): ViewModel() {
mParents: LiveData<List<ParentModel>> = repository.getParents()
fun getParents() = mParents
//...
}
class ParentAdapter: RecyclerView.Adapter<ParentHolder>() {
private lateinit var mParents: List<ParentModel>
fun setParents(list: List<ParentModel>) {
mParents = list
notifyDataSetChanged()
}
override fun onCreateViewHolder(parent: ViewGroup, /*...*/) {
return ParentHolder(LayoutInflater.from(parent.context).inflate(R.layout.parent, parent, false))
}
override fun onBindViewHolder(holder: ParentHolder, position: Int) {
holder.bind(/*UNKNOWN*/)
}
// ...
inner class ParentHolder(private val mView: View): RecyclerView.ViewHolder(mView) {
fun bind(/*UNKNOWN*/) {
// WHAT TO DO HERE???
}
}
}
Plus my R.layout.parent (I've omitted other irrelevant stuff like a View that just draws a horizontal line, but that's why I have my RecyclerView nested inside a LinearLayout):
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
android:orientation="vertical"
android:layout_height="wrap_content"
android:layout_width="match_parent"
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools">
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/recycler_view"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
</LinearLayout>
I have written a ChildAdapter, ChildHolder, and a few other things unthinkingly because I thought this would be trivial to implement, but at this point something's gunked up my brain and I'm likely not seeing the obvious thing.
I've got the first RecyclerView loading correctly based on underlying data. But this parent recyclerview also needs to:
fetch children based on a single parent.id
create a child recyclerview for a single parent recyclerview item that displays the children
Room returns a LiveData> from function repository.getChildrenByParentId(id: Long). That's the data I'm working from.
But where do I fetch this, how do I hook it into the relevant child recyclerview that belongs to the parent recyclerview?
I don't want to have a God fragment that does
viewModel.getParents().observe(...) { parentAdapter.update(it) } and also have to do some kind of viewModel.getChildren().observe(...) { parentAdapter.updateChildren(it) }
because that destroys separation of concerns. Seems to me each item in the parent recyclerview should have a viewmodel that fetches the children that would belong to it, then creates a recyclerview and uses a ChildAdapter to display these children, but I can't seem to figure out where to plug in the ChildFragment and ChildViewModel (with repository.getChildrenByParentId in it) to get this all working.
All examples I find online don't seem to help as they use contrived examples with no LiveData and a God fragment/activity that puts everything inside a single adapter.

I would literally have 1 adapter that can render everything, using the DiffUtil (or its async version) class to ensure I don't (and I quote) "redraw everything just because one property of one ChildModel changes".
I would move this complex responsibility of constructing (and providing) the data, to your repository (or, if you prefer to have it closer, to your ViewModel acting as a coordinator between 1 or more (I don't know how your model looks, so I am only imagining) repositories providing data.
This would allow you to offer to the ui a much more curated immutable list of ParentsAndChildren together and your RecyclerView/Adapter's responsibility is suddenly much simpler, display this, and bind the correct view for each row. Your UI is suddenly faster, spends much less time doing things on the main thread and you can even unit test the logic to create this list, completely independent of your Activity/Fragment.
I imagine ParentsAndChildren to be something like:
class ParentChildren(parent: Parent?, children: Children?)
Your bind could then inflate one view when parent is not null and children is. When children is not null, you know it's a children (you could include the parent as well, depends on how you construct this data). Problem solved here, your adapter would look like
class YourAdapter : ListAdapter<ParentChildren, RecyclerView.ViewHolder>(DiffUtilCallback()) {
...
You'd need to implement your DiffUtilCallback():
internal class DiffUtilCallback : DiffUtil.ItemCallback<ParentChildren>() {
and its two methods (areContentsTheSame, areItemsTheSame).
And your adapter's two methods:
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
val inflater = LayoutInflater.from(parent.context)
return when (viewType) {
viewTypeParent -> YourParentViewHolder(inflater.inflate(R.layout.your_layout_for_parent), parent, false))
viewTypeChildren -> YourChildrenViewHolder(inflater.inflate(R.layout.your_layout_for_children), parent, false))
else -> throw IllegalArgumentException("You must supply a valid type for this adapter")
}
}
I would have an abstract base to simplify the adapter even further:
internal abstract class BaseViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
abstract fun bind(data: ParentChildren)
}
This allows you to have your
// I'm writing pseudo code here... keep it in mind
internal class ParentViewHolder(itemView: View) : BaseViewHolder(itemView) {
private val name: TextView = itemView.findViewById(R.id.item_text)
override fun bind(data: ParentChildren) {
name.text = parentChildren.parent?.name
}
}
internal class ChildrenViewHolder(itemView: View) : BaseViewHolder(itemView) {
private val name: TextView = itemView.findViewById(R.id.item_text)
override fun bind(data: ParentChildren) {
name.text = parentChildren.children?.name
}
}
You get the idea.
Now... ListAdapter<> has a method called submitList(T) where T is the Type of the adapter ParentChildren in the above pseudo-example.
This is as far as I go, and now you have to provide this Activity or Fragment hosting this adapter, the list via either LiveData or whatever is that you prefer for the architecture you have.
It can be a repository passing it to a MutableLiveData inside the viewModel and the ViewModel exposing a LiveData<List<ParentChildren> or similar to the UI.
The sky is the limit.
This shifts the complexity of putting this data together, closer to where the data is, and where the power of SQL/Room can leverage how you combine and process this, regardless of what the UI needs or wants to do with it.
This is my suggestion, but based upon the very limited knowledge I have about your project.
Good luck! :)

OnBindViewHolder does not apply after notifyitemmoved () in Android Recyclerview

The code above is the RecyclerViewAdapter, which changes color only when it is the first item, as shown below.
class TestAdapter : RecyclerView.Adapter<RecyclerView.ViewHolder>() {
private val textColor1 = Color.BLACK
private val textColor2 = Color.YELLOW
private val items = ArrayList<String>()
override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
val textColor = if(position==0) textColor1 else textColor2
holder.itemView.textView.setTextColor(textColor)
holder.itemView.textView.text = items[position]
}
fun move(from:Int,to:Int){
val item = items[from]
items.remove(item)
items.add(to,item)
notifyItemMoved(from,to)
}
}
In this state I would like to move Value 3 to the first position using the move function. The results I want are shown below.
But in fact, it shows the following results
When using notifyDataSetChanged, I can not see the animation transition effect,
Running the onBindViewHolder manually using findViewHolderForAdapterPosition results in what I wanted, but it is very unstable. (Causing other parts of the error that I did not fix)
fun move(from:Int,to:Int){
val item = items[from]
val originTopHolder = recyclerView.findViewHolderForAdapterPosition(0)
val afterTopHolder = recyclerView.findViewHolderForAdapterPosition(from)
items.remove(item)
items.add(to,item)
notifyItemMoved(from,to)
if(to==0){
onBindViewHolder(originTopHolder,1)
onBindViewHolder(afterTopHolder,0)
}
}
Is there any other way to solve this?

Using the various notifyItemFoo() methods, like moved/inserted/removed, doesn't re-bind views. This is by design. You could call
if (from == 0 || to == 0) {
notifyItemChanged(from, Boolean.FALSE);
notifyItemChanged(to, Boolean.FALSE);
}
in order to re-bind the views that moved.

notifyItemMoved will not update it. According to documentation:
https://developer.android.com/reference/android/support/v7/widget/RecyclerView.Adapter
This is a structural change event. Representations of other existing items in the data set are still considered up to date and will not be rebound, though their positions may be altered.
What you're seeing is expected.
Might want to look into using notifyItemChanged, or dig through the documentation and see what works best for you.

Why doesn't smooth scroll of RecyclerView work well with some Interpolator classes?

Background
In an effort to make a nice&short overview of the items on a horizontal RecyclerView, we want to have a bounce-like animation , that starts from some position, and goes to the beginning of the RecyclerView (say, from item 3 to item 0) .
The problem
For some reason, all Interpolator classes I try (illustration available here) don't seem to allow items to go outside of the RecyclerView or bounce on it.
More specifically, I've tried OvershootInterpolator , BounceInterpolator and some other similar ones. I even tried AnticipateOvershootInterpolator. In most cases, it does a simple scrolling, without the special effect. on AnticipateOvershootInterpolator , it doesn't even scroll...
What I've tried
Here's the code of the POC I've made, to show the issue:
MainActivity.kt
class MainActivity : AppCompatActivity() {
val handler = Handler()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val itemSize = resources.getDimensionPixelSize(R.dimen.list_item_size)
val itemsCount = 6
recyclerView.adapter = object : RecyclerView.Adapter<RecyclerView.ViewHolder>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
val imageView = ImageView(this#MainActivity)
imageView.setImageResource(android.R.drawable.sym_def_app_icon)
imageView.layoutParams = RecyclerView.LayoutParams(itemSize, itemSize)
return object : RecyclerView.ViewHolder(imageView) {}
}
override fun getItemCount(): Int = itemsCount
override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
}
}
val itemToGoTo = Math.min(3, itemsCount - 1)
val scrollValue = itemSize * itemToGoTo
recyclerView.post {
recyclerView.scrollBy(scrollValue, 0)
handler.postDelayed({
recyclerView.smoothScrollBy(-scrollValue, 0, BounceInterpolator())
}, 500L)
}
}
}
activity_main.xml
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/recyclerView" xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto" android:layout_width="match_parent"
android:layout_height="#dimen/list_item_size" android:orientation="horizontal"
app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"/>
gradle file
apply plugin: 'com.android.application'
apply plugin: 'kotlin-android'
apply plugin: 'kotlin-android-extensions'
android {
compileSdkVersion 28
defaultConfig {
applicationId "com.example.myapplication"
minSdkVersion 15
targetSdkVersion 28
versionCode 1
versionName "1.0"
testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
}
}
}
dependencies {
implementation fileTree(dir: 'libs', include: ['*.jar'])
implementation"org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
implementation 'androidx.appcompat:appcompat:1.0.0-rc02'
implementation 'androidx.core:core-ktx:1.0.0-rc02'
implementation 'androidx.constraintlayout:constraintlayout:1.1.2'
implementation 'androidx.recyclerview:recyclerview:1.0.0-rc02'
}
And here's an animation of how it looks for BounceInterpolator , which as you can see doesn't bounce at all :
Sample POC project available here
The question
Why doesn't it work as expected, and how can I fix it?
Could RecyclerView work well with Interpolator for scrolling ?
EDIT: seems it's a bug, as I can't use any "interesting" interpolator for RecyclerView scrolling, so I've reported about it here .

I would take a look at Google's support animation package. Specifically https://developer.android.com/reference/android/support/animation/DynamicAnimation#SCROLL_X
It would look something like:
SpringAnimation(recyclerView, DynamicAnimation.SCROLL_X, 0f)
.setStartVelocity(1000)
.start()
UPDATE:
Looks like this doesn't work either. I looked at some of the source for RecyclerView and the reason that the bounce interpolator doesn't work is because RecyclerView isn't using the interpolator correctly. There's a call to computeScrollDuration the calls to the interpolator then get the raw animation time in seconds instead of the value as a % of the total animation time. This value is also not entirely predictable I tested a few values and saw anywhere from 100ms - 250ms. Anyway, from what I'm seeing you have two options (I've tested both)
User another library such as https://github.com/EverythingMe/overscroll-decor
Implement your own property and use the spring animation:
class ScrollXProperty : FloatPropertyCompat("scrollX") {
override fun setValue(obj: RecyclerView, value: Float) {
obj.scrollBy(value.roundToInt() - getValue(obj).roundToInt(), 0)
}
override fun getValue(obj: RecyclerView): Float =
obj.computeHorizontalScrollOffset().toFloat()
}
Then in your bounce, replace the call to smoothScrollBy with a variation of:
SpringAnimation(recyclerView, ScrollXProperty())
.setSpring(SpringForce()
.setFinalPosition(0f)
.setStiffness(SpringForce.STIFFNESS_LOW)
.setDampingRatio(SpringForce.DAMPING_RATIO_MEDIUM_BOUNCY))
.start()
UPDATE:
The second solution works out-of-box with no changes to your RecyclerView and is the one I wrote and tested fully.
More about interpolators, smoothScrollBy doesn't work well with interpolators (likely a bug). When using an interpolator you basically map a 0-1 value to another which is a multiplier for the animation. Example: t=0, interp(0)=0 means that at the start of the animation the value should be the same as it started, t=.5, interp(.5)=.25 means that the element would animate 1/4 of the way, etc. Bounce interpolators basically return values > 1 at some point and oscillate about 1 until finally settling at 1 when t=1.
What solution #2 is doing is using the spring animator but needing to update scroll. The reason SCROLL_X doesn't work is that RecyclerView doesn't actually scroll (that was my mistake). It calculates where the views should be based on a different calculation which is why you need the call to computeHorizontalScrollOffset. The ScrollXProperty allows you to change the horizontal scroll of a RecyclerView as though you were specifying the scrollX property in a ScrollView, it's basically an adapter. RecyclerViews don't support scrolling to a specific pixel offset, only in smooth scrolling, but the SpringAnimation already does it smoothly for you so we don't need that. Instead we want to scroll to a discrete position. See https://android.googlesource.com/platform/frameworks/support/+/247185b98675b09c5e98c87448dd24aef4dffc9d/v7/recyclerview/src/android/support/v7/widget/RecyclerView.java#387
UPDATE:
Here's the code I used to test https://github.com/yperess/StackOverflow/tree/52148251
UPDATE:
Got the same concept working with interpolators:
class ScrollXProperty : Property<RecyclerView, Int>(Int::class.java, "horozontalOffset") {
override fun get(`object`: RecyclerView): Int =
`object`.computeHorizontalScrollOffset()
override fun set(`object`: RecyclerView, value: Int) {
`object`.scrollBy(value - get(`object`), 0)
}
}
ObjectAnimator.ofInt(recycler_view, ScrollXProperty(), 0).apply {
interpolator = BounceInterpolator()
duration = 500L
}.start()
Demo project on GitHub was updated
I updated ScrollXProperty to include an optimization, it seems to work well on my Pixel but I haven't tested on older devices.
class ScrollXProperty(
private val enableOptimizations: Boolean
) : Property<RecyclerView, Int>(Int::class.java, "horizontalOffset") {
private var lastKnownValue: Int? = null
override fun get(`object`: RecyclerView): Int =
`object`.computeHorizontalScrollOffset().also {
if (enableOptimizations) {
lastKnownValue = it
}
}
override fun set(`object`: RecyclerView, value: Int) {
val currentValue = lastKnownValue?.takeIf { enableOptimizations } ?: get(`object`)
if (enableOptimizations) {
lastKnownValue = value
}
`object`.scrollBy(value - currentValue, 0)
}
}
The GitHub project now includes demo with the following interpolators:
<string-array name="interpolators">
<item>AccelerateDecelerate</item>
<item>Accelerate</item>
<item>Anticipate</item>
<item>AnticipateOvershoot</item>
<item>Bounce</item>
<item>Cycle</item>
<item>Decelerate</item>
<item>Linear</item>
<item>Overshoot</item>
</string-array>

Like I said, I wouldn't honestly expect a Release Candidate (recyclerview:1.0.0-rc02 in your case) would work properly without causing any issues since it's already under development.
Using third-party libraries might work but, I don't really think so since they have just introduced androidx dependencies and they're already under development and not stable enough to use by other developers.
Update The answer from Google Developers:
We have passed this to the development team and will update this issue
with more information as it becomes available.
So, better to wait for the new updates.

You need to enable overscroll bounce somehow.
The one of the possible solutions is to use
https://github.com/chthai64/overscroll-bouncy-android
Include it in your project
implementation 'com.chauthai.overscroll:overscroll-bouncy:0.1.1'
And then in your POV change RecyclerView in activity_main.xml to com.chauthai.overscroll.RecyclerViewBouncy
<?xml version="1.0" encoding="utf-8"?>
<com.chauthai.overscroll.RecyclerViewBouncy
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="#+id/recyclerView"
android:layout_width="match_parent"
android:layout_height="#dimen/list_item_size"
android:orientation="horizontal"
app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"/>
After this change you will see bounce in your app.