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I try to create a notification overlay inside my application that can show notifications about certain application wise important events.
I decided to use a RecyclerView which will be drown directly on WindowManager.
This works fine for showing initial items, however the the items don't get updated.
Below is my implementation. So when I call start the not1 and not2 are shown, but when removeNotification function get called, the notification is actually being removed and a correct list is being submitted to the adapter, but the view on screen does not update.
However if I add windowManager.updateViewLayout(recyclerView, layoutParams) after submitList inside removeNotification, everything seems to work as expected, but this time I am loosing RV animations..
As this is the first time I work with WindowManager directly, I am quite confused. Can someone help me to figure out what's going on and how can I achieve what I want to, if only that's possible.
class NotificationOverlay(private val context: Context) {
private val windowManager: WindowManager =
context.getSystemService(Context.WINDOW_SERVICE) as WindowManager
private val layoutParams = WindowManager.LayoutParams().apply {
gravity = android.view.Gravity.TOP or android.view.Gravity.CENTER_HORIZONTAL
width = WindowManager.LayoutParams.MATCH_PARENT
height = WindowManager.LayoutParams.WRAP_CONTENT
format = PixelFormat.TRANSLUCENT
dimAmount = 0.5f
flags = WindowManager.LayoutParams.FLAG_DIM_BEHIND
type = WindowManager.LayoutParams.TYPE_APPLICATION_PANEL
}
private val notifications = mutableListOf<NotificationItem>().also {
it.addAll(listOf(
NotificationItem(title = "not 1", message = "first notification"),
NotificationItem(title = "not 2", message = "second notification")
))
}
private val notificationsAdapter = NotificationAdapter(::removeNotification)
private val recyclerView = RecyclerView(context).apply {
layoutManager = LinearLayoutManager(context, LinearLayoutManager.VERTICAL, false)
adapter = notificationsAdapter
}
private fun removeNotification(notification: NotificationItem){
notifications.remove(notification)
notificationsAdapter.submitList(notifications)
if(notificationsAdapter.currentList.isEmpty()){
windowManager.removeView(recyclerView)
}
}
fun show(){
windowManager.addView(recyclerView, layoutParams)
notificationsAdapter.submitList(notifications)
}
}
Edited
Well, I found out that the issue is not in WindowManager but rather in DiffUtils, but cannot understand what's wrong with it, as it is very simple one, and I implemented such DiffUtils a lot of times, anyways, I'll post the code here if you could have any idea on why this does not work:
class NotificationAdapter(private val onCloseClicked: (NotificationItem) -> Unit):
ListAdapter<NotificationItem, NotificationAdapter.NotificationViewHolder>(DiffCallback()) {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): NotificationViewHolder {
val binding = ItemNotificationOverlayBinding.inflate(LayoutInflater.from(parent.context), parent, false)
return NotificationViewHolder(binding, onCloseClicked)
}
override fun onBindViewHolder(holder: NotificationViewHolder, position: Int) {
holder.bind(currentList[position])
}
class NotificationViewHolder(private val itemBinding: ItemNotificationOverlayBinding, private val onCloseClicked: (NotificationItem) -> Unit): RecyclerView.ViewHolder(itemBinding.root) {
fun bind(item: NotificationItem) {
itemBinding.title.text = item.title
itemBinding.message.text = item.message
itemBinding.close.setOnClickListener {
onCloseClicked.invoke(item)
}
}
}
class DiffCallback : DiffUtil.ItemCallback<NotificationItem>() {
override fun areItemsTheSame(oldItem: NotificationItem, newItem: NotificationItem) =
oldItem.id == newItem.id
override fun areContentsTheSame(oldItem: NotificationItem, newItem: NotificationItem) =
oldItem == newItem
}
}
What can every be wrong in such a simple construction? I am going crazy already and want to throw away this DiffUtils and implement the old school notifyItemRemoved
Edited 2
So the answer offered by #IamFr0ssT fixed the issue. I dig a bit deeper to see why this happens and the reason is in androidx.recyclerview.widget.AsyncListDiffer class in main submitList function. It is doing the following check there:
if (newList == mList) {
// nothing to do (Note - still had to inc generation, since may have ongoing work)
if (commitCallback != null) {
commitCallback.run();
}
return;
}
so my diff was never being even tried to be calculated as I was submitting the same reference of the list.
what the additional toList() function suggested by #IamFr0ssT did, is created a new instance of the list thus making the differ to calculate my diff. If you go deeper inside toList() function, it eventually creates a new instance of an ArrayList based on provided list ...return ArrayList(this)
So well, this issue had nothing to do with WindowManager just the DiffUtil
You are passing the MutableList notifications to the adapter, and the adapter is not making a copy of the list, it is just using the same list.
When you edit the list in your removeNotification callback, you are editing the list that the adapter is using.
Because of that, when the diff is being calculated, it is comparing the list that it thinks is currently displayed, but is not, to itself. Thus no diff and no notifyItemRemoved or other events.
What you can do to fix it, I think, is just call .toList() on the mutable list when you call submitList():
class NotificationOverlay(private val context: Context) {
...
private fun removeNotification(notification: NotificationItem){
notifications.remove(notification)
notificationsAdapter.submitList(notifications.toList())
if(notificationsAdapter.currentList.isEmpty()){
windowManager.removeView(recyclerView)
}
}
fun show(){
windowManager.addView(recyclerView, layoutParams)
notificationsAdapter.submitList(notifications.toList())
}
}
Also, how do you get NotificationItem.id? It should be different for each entry.
Um.. I think you should try to manually notify your RecyclerView to redraw with notifyDataSetChanged()
If it doesn't work ListAdapter you are using as adapter does diff computation and dispatches the result to the RecyclerView. Maybe diff is not correct and the adapter does not see a difference between the old list and the new one - in this case it won't update UI. You may try to check diff behaviour and maybe comparing behavior of your data to change it.
I'm learning android programming and for practicing I'm trying to do a controller for some dc motors, then I did a customview for making a virtual joypad, which uses an interface and a callback for the ontouch listener.
The problem is, I'm working on my app using a single MainActivity as a navhost and then I'm navigating through different fragments, My customview just works when I override the interface method on my MainActivity but I can't make it works on my fragment, where I want to handle all the logic of the joypad.
I've a couple of days researching but most of the post that I've found are written on Java and I just can't make it work on Kotlin.
My custom view class
class KanJoypadView: SurfaceView, SurfaceHolder.Callback, View.OnTouchListener{
...kotlin
var joypadCallback: JoypadListener? = null
//the main constructor for the class
constructor(context: Context): super(context){
...
getHolder().addCallback(this)
setOnTouchListener(this)
...
}
//the interface for the main functionally of the view
interface JoypadListener {
fun onJoypadMove(x: Float, y: Float, src: Int){}
}
...
}
My MainActivity
class NavActivity : AppCompatActivity(), KanJoypadView.joypadListener {
...
//Overriding the Function from the interface,
//I just did this for debguging, but I dont want this override here
override fun onJoypadMove(x: Float, y: Float, src: Int) {
Log.d(src.toString(), y.toString()) //** I wanna do this in my Fragment, not in my activity **
}
}
My Fragment
class JoystickFragment : Fragment(), KanJoypadView.joypadListener {
...
var enginesArray = arrayOf(0.toFloat(), 0.toFloat(), 0.toFloat(), 0.toFloat())
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
...
val binding = DataBindingUtil.inflate(
inflater, R.layout.fragment_joystick, container, false
)
binding.leftJoypad.joypadCallback = (container?.context as KanJoypadView.JoypadListener?)
lJoypad = binding.leftJoypad.id
}
/*what I really want to do, but it is not happening as it is just happenning the
override from the NavActivity, which I dont need, and not from here which I need*/
override fun onJoypadMove(x: Float, y: Float, src: Int) {
if (src == lJoypad) {
if (y >= 0) {
enginesArray[0] = 1.toFloat()
enginesArray[1] = y
} else if (y < 0) {
enginesArray[0] = 0.toFloat()
enginesArray[1] = y
}
if (src == rJoypad) {
if (y >= 0) {
enginesArray[0] = 1.toFloat()
enginesArray[1] = y
} else if (yAxis < 0) {
enginesArray[0] = 0.toFloat()
enginesArray[1] = y
}
Log.d("Engines array", enginesArray.toString())
}
}
}
}
Also I've tried to make a function in the fragment, and then call that function from the onMoveJoypad method from the Activity, but also I couldn't made it work. I'll appreciate any help or advice on how to implement this, thanks in advance !
This:
if (context is joypadListener){
is a very hacky and error prone way to get a listener reference. It’s also very limiting because it makes it impossible for the listener to be anything but the Activity that created the view. Don’t do this!
You already have a joypad listener property. Just remove the private keyword so any class can set any listener it wants from the outside. Remove that whole try/catch block. When it’s time to call the listener’s function, use a null-safe ?. call to do it so it gracefully does nothing if a callback hasn’t been set yet.
Side note: all class and interface names should start with a capital letter by convention. Your code becomes very hard to read and interpret if you fail to follow this convention.
Also, I advise you to avoid using the pattern of making a class implement an interface to serve as a callback for one of the objects it is manipulating or for its own internal functions. You’re doing this twice in your code above. Your custom view does it for its own touch listener, and your Activity does it to serve as the joypad listener.
The reason is that it publicly exposes the class’s inner functionality and reduces modularity. It can make unit testing more difficult. It needlessly exposes ways to misuse the class you’ve designed. It’s not as big deal for Activities to do this because you rarely if ever work with Activity instances from the outside anyway. But it’s ugly for a view class to do it.
The alternative is to implement the interface as an anonymous object or lambda so the functionality of the callback is hidden from outside classes.
Edit: How to do this in your fragment
If you want to follow my advice above, don't implement callback interfaces in your classes. Use lambdas or anonymous classes instead.
class JoystickFragment : Fragment() {
//...
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
//...
adapter.joypadCallback = joypadListener
//...
}
private val joypadListener = KanJoypadView.JoypadListener { x, y, src ->
if (src == lJoypad) {
if (y >= 0) {
enginesArray[0] = 1.toFloat()
enginesArray[1] = y
} else if (y < 0) {
enginesArray[0] = 0.toFloat()
enginesArray[1] = y
}
if (src == rJoypad) {
if (y >= 0) {
enginesArray[0] = 1.toFloat()
enginesArray[1] = y
} else if (yAxis < 0) {
enginesArray[0] = 0.toFloat()
enginesArray[1] = y
}
Log.d("Engines array", enginesArray.toString())
}
}
}
}
Currently, I have a RecyclerView implementing the new ListAdapter, using submitList to differ elements and proceed to update the UI automatically.
Lately i had to implement drag & drop to the list using the well known ItemTouchHelper. Here is my implementation, pretty straight forward:
class DraggableItemTouchHelper(private val adapter: DestinationsAdapter) : ItemTouchHelper.Callback() {
private val dragFlags = ItemTouchHelper.UP or ItemTouchHelper.DOWN
private val swipeFlags = 0
override fun isLongPressDragEnabled() = false
override fun isItemViewSwipeEnabled() = false
override fun getMovementFlags(recyclerView: RecyclerView, viewHolder: RecyclerView.ViewHolder): Int {
return makeMovementFlags(dragFlags, swipeFlags)
}
override fun onMove(
recyclerView: RecyclerView,
viewHolder: RecyclerView.ViewHolder,
target: RecyclerView.ViewHolder
): Boolean {
val oldPos = viewHolder.adapterPosition
val newPos = target.adapterPosition
adapter.swap(oldPos, newPos)
return true
}
override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int) {
}
}
this is my swap function inside the adapter:
fun swap(from: Int, to: Int) {
submitList(ArrayList(currentList).also {
it[from] = currentList[to]
it[to] = currentList[from]
})
}
Everything works well EXCEPT when moving the FIRST item of the list. Sometimes it behaves OK, but most of the time (like 90%), it snaps several positions even when moving it slightly above the second item (to move 1st item on 2nd position for example). The new position seems random and i couldn't figure out the issue.
As a guide, i used the https://github.com/material-components/material-components-android example to implement Drag&Drop and for their (simple) list&layout works well. My list is a bit complex since it's inside a viewpager, using Navigation component and having many other views constrained together in that screen, but i don't think this should be related.
At this point i don't even know how to search on the web for this issue anymore.
The closest solution I found for this might be https://issuetracker.google.com/issues/37018279 but after implementing and having the same behaviour, I am thinking it's because I use ListAdapter which differs and updates the list asynchronously, when the solution uses RecyclerView.Adapter which uses notifyItemMoved and other similar methods.
Switching to RecyclerView.Adapter is not a solution.
This seems to be a bug in AsyncListDiffer, which is used under the hood by ListAdapter. My solution lets you manually diff changes when you need to. However, it's rather hacky, uses reflection, and may not work with future appcompat versions (The version I've tested it with is 1.3.0).
Since mDiffer is private in ListAdapter and you need to work directly with it, you'll have to create your own ListAdapter implementation(you can just copy the original source). And then add the following method:
fun setListWithoutDiffing(list: List<T>) {
setOf("mList", "mReadOnlyList").forEach { fieldName ->
val field = mDiffer::class.java.getDeclaredField(fieldName)
field.isAccessible = true
field.set(mDiffer, list)
}
}
This method silently changes the current list in the underlying AsyncListDiffer without triggering any diffing, as submitList() would.
The resulting file should look like this:
package com.example.yourapp
import androidx.recyclerview.widget.AdapterListUpdateCallback
import androidx.recyclerview.widget.AsyncDifferConfig
import androidx.recyclerview.widget.AsyncListDiffer
import androidx.recyclerview.widget.AsyncListDiffer.ListListener
import androidx.recyclerview.widget.DiffUtil
import androidx.recyclerview.widget.RecyclerView
abstract class ListAdapter<T, VH : RecyclerView.ViewHolder?> : RecyclerView.Adapter<VH> {
private val mDiffer: AsyncListDiffer<T>
private val mListener =
ListListener<T> { previousList, currentList -> onCurrentListChanged(previousList, currentList) }
protected constructor(diffCallback: DiffUtil.ItemCallback<T>) {
mDiffer = AsyncListDiffer(
AdapterListUpdateCallback(this),
AsyncDifferConfig.Builder(diffCallback).build()
).apply {
addListListener(mListener)
}
}
protected constructor(config: AsyncDifferConfig<T>) {
mDiffer = AsyncListDiffer(AdapterListUpdateCallback(this), config).apply {
addListListener(mListener)
}
}
fun setListWithoutDiffing(list: List<T>) {
setOf("mList", "mReadOnlyList").forEach { fieldName ->
val field = mDiffer::class.java.getDeclaredField(fieldName)
field.isAccessible = true
field.set(mDiffer, list)
}
}
open fun submitList(list: List<T>?) {
mDiffer.submitList(list)
}
fun submitList(list: List<T>?, commitCallback: Runnable?) {
mDiffer.submitList(list, commitCallback)
}
protected fun getItem(position: Int): T {
return mDiffer.currentList[position]
}
override fun getItemCount(): Int {
return mDiffer.currentList.size
}
val currentList: List<T>
get() = mDiffer.currentList
open fun onCurrentListChanged(previousList: List<T>, currentList: List<T>) {}
}
Now you need to change your adapter implementation to inherit from your custom ListAdapter rather than androidx.recyclerview.widget.ListAdapter.
Finally you'll need to change your adapter's swap() method implementation to use the setListWithoutDiffing() and notifyItemMoved() methods:
fun swap(from: Int, to: Int) {
setListWithoutDiffing(ArrayList(currentList).also {
it[from] = currentList[to]
it[to] = currentList[from]
})
notifyItemMoved(from, to)
}
An alternative solution would be to create a custom AsyncListDiffer version that lets you do the same without reflection, but this way seems easier. I will also file a feature request for supporting manual diffing out of the box and update the question with a Google Issue Tracker link.
I kept a copy of the items in my adapter, modified the copy, and used notifyItemMoved to update the UI as the user was dragging. I only save the updated items/order AFTER the user finishes dragging. This works for me because 1) I had a fixed length list of 9 items; 2) I was able to use clearView to know when the drag ended.
ListAdapter - kotlin:
var myItems: MutableList<MyItem> = mutableListOf()
fun onMove(fromPosition: Int, toPosition: Int): Boolean {
if (fromPosition < toPosition) {
for (i in fromPosition until toPosition) {
Collections.swap(myItems, i, i + 1)
}
} else {
for (i in fromPosition downTo toPosition + 1) {
Collections.swap(myItems, i, i - 1)
}
}
notifyItemMoved(fromPosition, toPosition)
return true
}
ItemTouchHelper.Callback() - kotlin:
// my items are only ever selected during drag, so when selection clears, drag has ended
override fun clearView(recyclerView: RecyclerView, viewHolder: RecyclerView.ViewHolder) {
super.clearView(recyclerView, viewHolder)
// clear drag style after item moved
viewHolder.itemView.requestLayout()
// trigger callback after item moved
val itemViewHolder = viewHolder as MyItemViewHolder
itemViewHolder.onItemMovedCallback(adapter.myItems)
}
MyItemViewHolder - kotlin
fun onItemMovedCallback(reorderedItems: List<MyItem>) {
// user has finished drag
// save new item order to database or submit list properly to adapter
}
I also had an itemOrder field on MyItem. I updated that field using the index of the re-ordered items when I saved it to the DB. I could probably update each items itemOrder field when I swap the items, but it seemed pointless (I just calculate the new order after the drag is finished).
I'm using LiveData from my database. I found the views "flickered" after the final database save because I changed the itemOrder on all the items and moved the items around in the adapter list. If this happens to you and you don't like it, just temporarily disable the recycler view item animator (I achieved this by setting it to null after the drag and restoring it after the list is updated in the RecyclerView/Adapter).
This worked for me and my specific case. Let me know if you need more details.
I am rendering a form based on JSON response that I fetch from the server.
My use case involves listening to a click from a radio button, toggling the visibility of certain text fields based on the radioButton selection, and refreshing the layout with the visible textView.
The expected output should be to update the same view with the textView now visible, but I'm now seeing the same form twice, first with default state, and second with updated state.
Have I somehow created an entirely new model_ class and passing it to the controller? I just want to change the boolean field of the existing model and update the view.
My Model Class
#EpoxyModelClass(layout = R.layout.layout_panel_input)
abstract class PanelInputModel(
#EpoxyAttribute var panelInput: PanelInput,
#EpoxyAttribute var isVisible: Boolean,
#EpoxyAttribute(EpoxyAttribute.Option.DoNotHash) var context: Context,
#EpoxyAttribute(EpoxyAttribute.Option.DoNotHash) var textChangedListener: InputTextChangedListener,
#EpoxyAttribute(EpoxyAttribute.Option.DoNotHash) var radioButtonSelectedListener: RadioButtonSelectedListener,
#EpoxyAttribute(EpoxyAttribute.Option.DoNotHash) var validationChangedListener: ValidationChangedListener
) : EpoxyModelWithHolder<PanelInputModel.PanelInputHolder>() {
#EpoxyAttribute var imageList = mutableListOf<ImageInput>()
override fun bind(holder: PanelInputHolder) {
val inflater = context.getSystemService(Context.LAYOUT_INFLATER_SERVICE) as LayoutInflater
generateViews(holder, inflater, panelInput.elements) // Generates textViews, radioButtons, etc, based on ElementType enum inside Panel input
}
fun generateRadioButtonView(element: Element) {
// Created a custom listener and calling its function
radioButtonSelectedListener.radioButtonSelected(chip.id, chip.text.toString())
}
fun generateTextView() {
// Show/hide textView based on isVisible value
}
My Controller Class
class FormInputController(
var context: Context,
var position: Int, // Fragment Position in PagerAdapter
var textChangedListener: InputTextChangedListener,
var radioButtonSelectedListener: RadioButtonSelectedListener,
var validationChangedListener: ValidationChangedListener
) : TypedEpoxyController<FormInput>() {
override fun buildModels(data: FormInput?) {
val panelInputModel = PanelInputModel_(
data as PanelInput,
data.isVisible,
context,
textChangedListener,
radioButtonSelectedListener,
validationChangedListener
)
panelInputModel.id(position)
panelInputModel.addTo(this)
}
}
My fragment implements the on radio button checked listener, modifies the formInput.isVisible = true and calls formInputController.setData(componentList)
Please help me out on this, thanks!
I don't think you are using Epoxy correctly, that's not how it's supposed to be.
First of all, let's start with the Holder: you should not inflate the view inside of bind/unbind, just set your views there. Also, the view is inflated for you from the layout file you are specifying at R.layout.layout_panel_input, so there is no need to inflate at all.
You should copy this into your project:
https://github.com/airbnb/epoxy/blob/master/kotlinsample/src/main/java/com/airbnb/epoxy/kotlinsample/helpers/KotlinEpoxyHolder.kt
And create your holder in this way:
class PanelInputHolder : KotlinHolder() {
val textView by bind<TextView>(R.id.your_text_view_id)
val button by bind<Button>(R.id.your_button_id)
}
Let's move to your model class: you should remove these variables from the constructor as they are going to be a reference for the annotation processor to create the actual class.
Also, don't set your layout res from the annotation as that will not be allowed in the future.
Like so:
#EpoxyModelClass
class PanelInputModel : EpoxyModelWithHolder<PanelInputHolder>() {
#EpoxyAttribute
lateinit var text: String
#EpoxyAttribute(DoNotHash)
lateinit var listener: View.OnClickListener
override fun getDefaultLayout(): Int {
return R.layout.layout_panel_input
}
override fun bind(holder: PanelInputHolder) {
// here set your views
holder.textView.text = text
holder.textView.setOnClickListener(listener)
}
override fun unbind(holder: PanelInputHolder) {
// here unset your views
holder.textView.text = null
holder.textView.setOnClickListener(null)
}
}
Loop your data inside the controller not inside the model:
class FormInputController : TypedEpoxyController<FormInput>() {
override fun buildModels(data: FormInput?) {
data?.let {
// do your layout as you want, with the models you specify
// for example a header
PanelInputModel_()
.id(it.id)
.text("Hello WOrld!")
.listener { // do something here }
.addTo(this)
// generate a model per item
it.images.forEach {
ImageModel_()
.id(it.imageId)
.image(it)
.addTo(this)
}
}
}
}
When choosing your id, keep in mind that Epoxy will keep track of those and update if the attrs change, so don't use a position, but a unique id that will not get duplicated.
My app has a RecyclerView which support drag items to change their order.
My app use ViewModel, Lifecycle, Room before adding paging library. And code to handle drag is easy.
override fun onMove(recyclerView: RecyclerView, viewHolder: RecyclerView.ViewHolder, target: RecyclerView.ViewHolder): Boolean {
val oPosition = viewHolder.adapterPosition
val tPosition = target.adapterPosition
Collections.swap(adapter?.data ,oPosition,tPosition)
adapter?.notifyItemMoved(oPosition,tPosition)
//save to db
return true
}
However, after I use paging library,
override fun onMove(recyclerView: RecyclerView, viewHolder: RecyclerView.ViewHolder, target: RecyclerView.ViewHolder): Boolean {
val oPosition = viewHolder.adapterPosition
val tPosition = target.adapterPosition
Collections.swap(adapter.currentList,oPosition,tPosition)
adapter.notifyItemMoved(oPosition,tPosition)
return true
}
my app crashed because PagedListAdapter.currentList do not support set.
java.lang.UnsupportedOperationException
at java.util.AbstractList.set(AbstractList.java:132)
at java.util.Collections.swap(Collections.java:539)
at gmail.zebulon988.tasklist.ui.TaskListFragment$MyItemTouchCallback.onMove(TaskListFragment.kt:119).
Then I change the code
override fun onMove(recyclerView: RecyclerView, viewHolder: RecyclerView.ViewHolder, target: RecyclerView.ViewHolder): Boolean {
val oPosition = viewHolder.adapterPosition
val tPosition = target.adapterPosition
Log.d("TAG","onMove:o=$oPosition,t=$tPosition")
val oTask = (viewHolder as VH).task
val tTask = (target as VH).task
if(oTask != null && tTask != null){
val tmp = oTask.order
oTask.order = tTask.order
tTask.order = tmp
tasklistViewModel.insertTask(oTask,tTask)
}
return true
}
This code change the task's order in db directly and the library update the display order by the db change. However, the animation is ugly.
Is there a way to use onMove and paging library together genteelly？
When you use a PagedList with Room you often tie it up so that the updates to the underlying data are reflected automatically via LiveData or Rx, and such an update happening in a background can always mess up your drag and drop. So IMHO you can't make it 100% bulletproof for all situations. Having said that, you can create (I almost said "hack together") a shim that will do what you want. This involves several pieces:
You need to hold the indexes of the items being swapped in your adapter
You need to override getItem() in the adapter and make it "swap" the items for you instead of swapping them using Collections.swap
You need to delay the actual item updating via Room until the item is dropped, at which point you also clear your "swapping in progress" state. Something along these lines:
fun swapItems(fromPosition: Int, toPosition: Int) {
swapInfo = SwapInfo(fromPosition, toPosition)
notifyItemMoved(fromPosition, toPosition)
}
override fun getItem(position: Int): T? {
return swapInfo?.let {
when (position) {
it.fromPosition -> super.getItem(it.toPosition)
it.toPosition -> super.getItem(it.fromPosition)
else -> super.getItem(position)
}
} ?: super.getItem(position)
}
fun clearSwapInfo() {
swapInfo = null
}
This way you will get a smooth dragging experience as long as there are no background updates for your list and you stay within already loaded list of items. It gets much more complicated if you need to be able to drag through a "refill".
You need to heck for moving items in PagedList.
Recyclerview's adapter needs to do two things perfectly if you want to drag items up and down for moving them. First is to swap two items in datalist, second is to notify cells re-render.
re-render is easy, you can use notifyItemMoved to update layout when moving, but PagedList is immutable, you cannot modify it.
And there is an animation bug when the cell ui has already changed but the datasource did not. You cannot override the render logic in inner of recyclerview, but you can heck the result of PagedStorageDiffHelper.computeDiff to fix the animation bug.
At last, dont forget to retrieve the most updated data after the drag and drop.
//ItemTouchHelperAdapter
override fun onItemStartMove() {
//the most the most updated data; mimic pagedlist, but can be modified;
tempList = adapter.currentList?.toMutableList()
toUpdate = mutableListOf()
}
override fun onItemMove(fromPosition: Int, toPosition: Int): Boolean {
val itemFrom = tempList?.get(fromPosition) ?: return false
val itemTo = tempList?.get(toPosition) ?: return false
//change order property for data itself
val order = itemTo.order
itemTo.order = itemFrom.order
itemFrom.order = order
//save them for later update db in batch
toUpdate?.removeAll { it.id == itemFrom.id || it.id == itemTo.id }
toUpdate?.add(itemFrom)
toUpdate?.add(itemTo)
//mimic mutable pagedlist, for get next time get correct items for continuing drag
Collections.swap(tempList!!, fromPosition, toPosition)
//update ui
adapter.notifyItemMoved(fromPosition, toPosition)
return true
}
override fun onItemEndMove() {
tempList = null
if (!toUpdate.isNullOrEmpty()) {
mViewModel.viewModelScope.launch(Dispatchers.IO) {
//heck, fix animation bug because pagedList did not really change.
NoteListAdapter.disableAnimation = true
mViewModel.updateInDB(toUpdate!!)
toUpdate = null
}
}
}
//Fragment
mViewModel.data.observe(this.viewLifecycleOwner, Observer {
adapter.submitList(it)
//delay for fix PagedStorageDiffHelper.computeDiff running in background thread
if (NoteListAdapter.disableAnimation) {
mViewModel.viewModelScope.launch {
delay(500)
adapter.notifyDataSetChanged() //update viewholder's binding data
NoteListAdapter.disableAnimation = false
}
}
})
//PagedListAdapter
companion object {
//heck for drag and drop to move items in PagedList
var disableAnimation = false
private val DiffCallback = object : DiffUtil.ItemCallback<Note>() {
override fun areItemsTheSame(old: Note, aNew: Note): Boolean {
return disableAnimation || old.id == aNew.id
}
override fun areContentsTheSame(old: Note, aNew: Note): Boolean {
return disableAnimation || old == aNew
}
}
}
I had a slightly different problem and #dmapr's answer has finally led me to the solution after hours of debugging.
For me the issue was that the item I just moved suddenly jumped back to its previous position after the db was updated and the call to submitData was made. Basically the drag and drop action is sort of canceled, however the order with all the relevant data is correct in the database, and if I was to call notifyDataSetChanged() I'd see the real list where all items are where they should be. Here's what has worked for me:
class SomePagingAdapter(
private val onItemMoveUpdate: (fromPos: Int, toPos: Int) -> Unit,
) : PagingDataAdapter<Model, SomePagingAdapter.ViewHolder>(diffUtil), ItemMoveCallback {
companion object {
private val diffUtil = /* ... */
}
private var swapInfo: SwapInfo? = null
// viewHolder methods, etc.
// Called in touch helper's onMove
override fun onItemMove(fromPos: Int, toPos: Int) {
notifyItemMoved(fromPos, toPos)
}
// Called in touch helper's clearView() to save the result of this drag and drop
override fun onItemFinishedMove(fromPos: Int, toPos: Int) {
swapInfo = SwapInfo(fromPos, toPos)
onItemMoveUpdate(fromPos, toPos)
}
fun adjustRecentSwapPositions() {
// "Undo" the notifyItemMoved we did before that messed up positions
swapInfo?.let { swap ->
notifyItemMoved(swap.toPos, swap.fromPos)
}
swapInfo = null
}
}
interface ItemMoveCallback {
fun onItemMove(fromPos: Int, toPos: Int)
fun onItemFinishedMove(fromPos: Int, toPos: Int)
}
data class SwapInfo(val fromPos: Int, val toPos: int)
It's important that submitData is suspended and adjustRecentSwapPositions is called immediately after. Watch out for that if you use RxJava.
scope.launch {
flow.collectLatest { pagingData ->
adapter.submitData(pagingData)
adapter.adjustRecentSwapPositions()
}
}
It works great and recycler's animations are fine.