RECYCLERVIEW - Android Fundamentals

[@ohmegatech666]

OK I didn't understand your explanation of what RecyclerView does but after looking it up now I understand. When a view (the container for one of the rows) goes off screen, instead of just being off screen and taking up resources for no reason, or just being deleted and replaced with a new one, Android keeps it but replaces all the content (the actual image and words you see) with new content. This way the system doesn't need to store all the hundreds of views (which would eat up all the memory), and it doesn't have to constantly delete view objects only to replace them with new ones (which would use up CPU power). Instead it only creates the minimum number of view objects (however many fit on the screen) and just replaces the content in them with whatever needs to be displayed.

[@Domo22xD]

Okay so I see a lot of people have problem with this tutorial. Problem 17:36 So in your build.gradle file add this code inside of android {} and make sure you press sync. BUILD.GRADLE buildFeatures { viewBinding true } And this is how your code should look like. CODE: class ToDoAdapter(var todos: List): RecyclerView.Adapter() { inner class ToDoViewHolder(val binding: ItemTodoBinding) : RecyclerView.ViewHolder(binding.root) override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ToDoViewHolder { val layoutInflater = LayoutInflater.from(parent.context) val binding = ItemTodoBinding.inflate(layoutInflater, parent, false) return ToDoViewHolder(binding) } override fun onBindViewHolder(holder: ToDoViewHolder, position: Int) { holder.binding.apply { // tvTitle this now works } } override fun getItemCount(): Int { return todos.size } } This is not bad tutorial but for beginners it's hard. Also Philipp should update with pined comment or something about this problem. And how to solve it. Enjoy

[@renatovg6337]

Thank you, it works!!! Yes, and update or at least a pinned comment is definitely needed.

[@Domo22xD]

@@renatovg6337 Croatia? I ask because of VG in username?

[@chairulfajri9030]

He used buildgradle:app plugin add id 'kotlin-android-extensions'

[@AB-sq1sy]

King

[@ViperVGP]

Thanks a lot!

[@ARIZONAMUSIC]

the best explanation ever I'm learning android programming in Kotlin and for 1 week I've been trying to understand RV setting. Thanks you lot, Phillip!

[@PhilippLackner]

Glad it was helpful!

[@mrodriguezalas]

A really easy improvement for anyone reading is to add etTodo.text.clear() to remove the text for the item that was just added. btnAddTodo.setOnClickListener { val title = etTodo.text.toString() val todo = Todo(title, false) todoList.add(todo) //update recycler view adapter.notifyItemInserted(todoList.size - 1) // Clear text etTodo.text.clear() } Nice tutorial, thanks!

[@abrammedrano991]

I was stuck on a problem for a whole day until I saw this video! Thank you!

[@guy1407]

Thanks for the great demo On minute 18:50 , I used an inner apply : todos[position].apply { txtTitle.text = title chkDone.isChecked = isChecked }

[@terrencejackson4451]

I havent seen the video yet but.... CAN WE TALK ABOUT HOW COOL THAT INTRO TRANSITION WAS???!!! xD

[@tiagocastro9039]

I think this video is very clear. I'd just add the mention that as an option to LinearLayoutManager you can have LinearLayout.Horizontal in case you want to have it scrollable horizontally.

[@megumin4625]

Anybody wondering why your viewbinding isn't working? Here's how to fix it -->>> 1. Set it in gradle -> (NOTE: this belongs under -> android { } , section) buildFeatures { viewBinding true } 2. Use LayoutNameBinding as the class to inflate from in onCreateViewHolder (as "LayoutName" suggests, you replace this with the name of your xml layout) val layoutInflater = LayoutInflater.from(parent.context) val binding = LayoutNameBinding.inflate(layoutInflater, parent, false) return MyViewHolder(binding) 3. Send the binding to the ViewHolder (update the viewholder to hold a reference to LayoutNameBinding type) inner class MyViewHolder(val binding: LayoutNameBinding) : RecyclerView.ViewHolder(binding.root) 4. Enjoy viewbinding in onBindViewHolder() method! holder.binding.apply { tvtext.text = somedata message.text = mymessage date.text = date } (NOTE, you may need additional implement's or whatnot in gradle. You can google for those)

[@crateer]

Lifesaver! Thanks!

[@amalsunil4722]

Thanks a ton buddy, Have a great day my friend!

[@Prskati]

This should be pinned. Wasted a headache trying to understand what was wrong

[@abdulwehabmohammed5580]

Thank you very much.

[@KotlinBek]

thanks

[@vasiliv6872]

Thank you Philipp, for the great tutorials! I follow the ANDROID FUNDAMENTALS FOR BEGINNERS and the tutorials are perfect so far.

[@nipponetzel]

at 17:14 in onBindViewHolder function I write holder.itemView and then . (dot) android studio doesnt find or recognize tvTitle or cbDone, I cant access those. Could anyone (or you Philipp Lackner) tell me what can be the problem? What am I missing? Please help!!!

[@glebshymko]

Hi, you need add Kotlin Android Extensions to your gradle file.

[@glebshymko]

put it in dependencies : apply plugin: 'com.android.application' apply plugin: 'kotlin-android' apply plugin: 'kotlin-android-extensions' But also Kotlin Android Extensions are now deprecate.

[@nipponetzel]

@@glebshymko I dont remember right now how I fixed this problem but I did not with extensions. Thank you for the answer and suggestion I preciate that...

[@MrSchloban]

@@glebshymko Thank you! Been staring at my code for 1h wondering what when wrong

[@megumin4625]

Anybody wondering why your viewbinding isn't working? Here's how to fix it -->>> 1. Set it in gradle -> (NOTE: this belongs under -> android { } , section) buildFeatures { viewBinding true } 2. Use LayoutNameBinding as the class to inflate from in onCreateViewHolder (as "LayoutName" suggests, you replace this with the name of your xml layout) val layoutInflater = LayoutInflater.from(parent.context) val binding = LayoutNameBinding.inflate(layoutInflater, parent, false) return MyViewHolder(binding) 3. Send the binding to the ViewHolder (update the viewholder to hold a reference to LayoutNameBinding type) inner class MyViewHolder(val binding: LayoutNameBinding) : RecyclerView.ViewHolder(binding.root) 4. Enjoy viewbinding in bind() method! (NOTE, you may need additional implement's or whatnot in gradle. You can google for those)

[@jacksonhall4322]

Great tutorial Phillip! The lesson is valuable and your narration is easy to understand. Thank you

[@PhilippLackner]

Thank you, you're welcome!

[@sdfewvdevvv]

Hello Phillip! Do you plan on creating a video about recyclerview in view binding?

[@natnaelsisay1424]

My understanding is alot better now, but am sure i will get back to it once more. Thanks mate

[@mateuszczuba9684]

Hi! Thanks for this tutorial! I have a question though (probably a noob question): how can you access e.g. the rvTodos and its properties directly inside the main class? Same question for e.g. the tvTitle inside the TodoAdapter class. To access these have to first declare a val and find the needed object by id (e.g. val tvTitle = findViewById(R.id.tvTitle)).

[@WisdomWhisper933]

In LayoutInflater function why attachToRoot parameter in need if its always going to be false??

[@harshmore6664]

Amazing , detailed and easy to understand , thank you so much

[@TheImaginativeSachin]

Wow this is really step by step love this.

[@thecoder9193]

I'm really thankful to you . This tutorial is very easy to understand and learn recycle view.

[@TefkrosAirliner]

Thank you Sir! Better than my lecturer's explanation

[@ZombeeStar]

if i had a delete button on the template then how would i attach a function to each one?

[@stephanvanellewee1653]

Wow, this is such an elegant tutorial! Thank you!

[@Domo22xD]

Also there is problem on 20:21. You need add RecyclerView, Button and TextView to use it. So in your MainActivity add code like this. CODE: override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_main) var todoList = mutableListOf( ToDo("Text",false) ) // This was added val rv = findViewById(R.id.rvTodos) as RecyclerView val btnAddTodo = findViewById(R.id.btnAddTodo) as Button val etTodo = findViewById(R.id.etTodo) as TextView val adapter = ToDoAdapter(todoList) rv.adapter = adapter rv.layoutManager = LinearLayoutManager(this) btnAddTodo.setOnClickListener{ val title = etTodo.text.toString() val todo = ToDo(title,false) todoList.add(todo) adapter.notifyItemInserted(todoList.size - 1) } } Enjoy

[@DanielTobi00]

Thanks man.

[@ronaldotiego]

When I run my app, I get Dublicate Classes error. What could be the problem please

[@shivamparimalbhaigohel6632]

Amazing Tutorial. Keep up the good work man!

[@Indently]

Really helpful tutorial! Could I ask you if you know any places online where I could really dive deep into recycler views?

[@PhilippLackner]

Thanks a lot! Take a look at codinginflow's channel, he has two new videos about recyclerview which I think are very detailed. I'm sure you can also find some good medium articles about recyclerviews

[@Zeresrail]

I wonder if you will answer my question - following your guide, for some reason the itemview does not show any of the views (like title etc) (in the apply part). As if it doesnt know them. Cant find a solution to this issue or why it is happening.

[@Madjber]

i have the same problem , any solution ??

[@Zeresrail]

@@Madjber I defined the fields in the holder inner class, finding them by Id, and accessed them that way.

[@fuadydheo3155]

good dude, fundamental is important, awesome!!

[@PhilippLackner]

Thank you!

[@simasbutavicius8485]

Thank you. The way you explain things, it's really easy to follow for newbies like me - very good job!

[@TheImaginativeSachin]

Hey how can i remove the todo list after i check the checkbox?

[@marcw6875]

I'm having one problem with this tutorial. I don't know if anyone will reply in time to help me with this assignment, but I'll throw it out there in case anyone in the future has the same problem. In the adapter class, in the onBindViewHolder function, I tried using the same method to set the text in my recycler view, but I'm getting "unresolved references." For an example, I have a line of code "forecast_date.text = forecastList[position].date" where forecast_date is the ID for that particular TextView in my forecast_list_item.xml file. That is highlighted in red with the unresolved reference. I see that your program added that import kotlinx statement when started coding this part, but I don't seem to have that option. Any ideas why it's not seeing my forecast_list_item.xml file?...

[@xtd3000]

Thank you very much for this video, it was really easy to follow and understand. Your explanations are clear and concise :)

[@rolinejohnaguilar7819]

Thank you, this actually helped me to understand recycler view :D

[@PhilippLackner]

Congrats, you're welcome :D

[@abhirupamitra2895]

Hi, I am just starting out with the tutorials. I can see that the recycler view state/ items in the todo list are not save when I reopen the app. Is there a way to go about this?

[@MonishKrishnaS]

Glad I find this video at the first. The only thing is when you add the todo, the text on the keyboard is still there. How to get the EditText to empty itself after adding? Is there any systematic way?

[@brianryan4053]

I have mutableListOf in red. Does anybody know how to fix this issue?

[@prithvib8662]

Awesome tut. Only feedback is to use the GUI to add textviews/buttons/etc. instead of adding them manually via the XML editor as it is easier for viewers to follow along and see the app come together

[@illusion9423]

He said in a previous video he prefers to teach XML because it has way more options than what you see in the GUI

[@Defense89]

awesome video , simple exemple not to much in it , perfect to understand the basics of everything 5 star this!!!!!!!!!!! good job

[@apiuagou9601]

You are indeed the best teacher for this but I also noticed you didn't use the get function to get the individual items in your list item folder.Someone explain why

[@haxificality]

you're explanation was very detailed, but i found out this method was only possible in my case using a depreciated method of using 'kotlin-android-extensions' as plugin for gradle. i hope you can redo it in the new updated method as of 2023.

[@AdityaDey424]

I add the layout in onCreateViewHolder method. But I can't access the components of this layout in onBindViewHolder method . Anyone please help me .......

[@PiBou321]

Hi, first thank you for this tutorial ! Why do we put todos.size in the getItemCount function ? The number of items showed should be different from the total number of items of the list, no? I don’t understand where in the code the adapter takes into account the site of the user screen, can you help me to understand please?

[@derekdevs]

This is fantastic. Thank you so much!

[@arrayofsilicon]

Very Clean Explaination Thanks

[@rochmanramadhanichieftoira2695]

Awesome tutorial! Hello from Indonesia 😁

[@Beatboxerskills]

hey Phillip :) if you also had a Spinner with todo category how would you declare that in the data class?

[@youssefkhaled1189]

Thank you so much this was really simplified amazingly

[@kratom82]

do you have an idea how to build a recyclerview like the "contacts" in a standard phone? i have a large dataset via json and some items have a category lets say "bikes" and some have "cycles" .. item decoration seems the wrong choice :D

[@qasimmir336]

Hello mate. I have a question. I need to add RecyclerView to another activity do I need to create a new adapter and data class for the activity's RecyclerView or the same adapter can be used somehow? Waiting for your reply. Thank you.👍

[@calibur5518]

hi just create 1 adapter then from your mainActivity pass it to any new Activity you want

[@hasht7331]

Where is "rvTodoItems" coming from in the main activity????

[@SirDanMartin]

do you have a video showing how you can use a button from within each recycler view?

[@bigstrongrobot1330]

what is """tvTitle""" ? it's not working and we didn't declare it before !!!

[@durotimiemmanuel5840]

Thank you Philipp u are awesome all of the videos I have watched were top notch and easy to understand as well except for maybe this one. I didn't quite understand the whole thing about recycle view...can you please help me for am not so sure I can get a better place to learn than here? thanks in anticipation

[@SeemantAggarwal]

AMAZING, ABSOLUTELY AMAZING TUTORIAL, Can you please zoom in your code? I code it alongside and sometimes find it difficult, also DO CALL YOUR MOM, It is important hahaha

[@FelixEsUnDios]

I just died of cringe bro🥲

[@moisesgomez7820]

Hi Phillip, I hope you are well. I'm following your tutorial with my own example. I have two activities: MainAcitivity and CreateNoteActivity. I want to pass text from two EditTexts in CreateNoteActivity and display it in a RecyclerView in MainActivity. When I click in the Create Note button, the note is not display in the Main Activity. How I can fix this? Before, I try the same app but with an only one activity: MainActivity, and works fine. Now I have two activities and I don't achieve success yet. Please, any help will be gratefully.

[@GeorgeTrialonis]

Hi there! In MainActivity rvTodos is not identified. Anyone has an idea about how to fix it? I applied a suggestion posted below by someone who watched this video. This suggestion did not work for me. Also, in the the clicklistener Todo [line: Todo(title, false)] is not identified either. Thanks.

[@PhilippLackner]

Back then we had a plugin called Kotlin synthetics which allowed us to call views directly. Nowdays, you'll need to get view references using either findViewById() or ViewBinding (preferred)

[@faraday6521]

Hi Philipp is this playlist for beginners to android or for java devs transitioning to kotlin, cause i'm the former with just knowledge of kotlin bascis

[@valarmorghulisx]

i love you man! you are awesome!

[@PhilippLackner]

Thank you ❤️

[@МихаилПатин-е6п]

Right now cbDone.isChecked is not updated in todo item. When you create more items and scroll then changed cbDone will be set as default.

[@mohyddineal-lahham7620]

same prob here

[@malcolmfarrelle8591]

great video but I'm struggling with undeclared "tvTitle" when trying to populate> override fun onBindViewHolder(holder: TodoViewHolder, position: Int). I checked, double and treble checked, everything is named correctly. Any ideas?

[@megumin4625]

Check my comment on the video. You need to enable viewbinding. I just gave instructions.

[@malcolmfarrelle8591]

@@megumin4625 thanks 👍 (I had added the required statement in the module grade script but at the wrong scope level)

[@megumin4625]

@@malcolmfarrelle8591 The video doesn't show how to set it up, nor is it set up properly in the video. I honestly have NO IDEA HOW it even works for him. From what I see, it shouldn't even theoretically work. Perhaps this was an old way to do it that no longer works?

[@malcolmfarrelle8591]

@@megumin4625 I happened to have it set in the module from a spinner tutorial I was following earlier. Turns out it was in the correct scope, so some other issue. I'm currently building a clone of the whole project from Philipp's GitHub, hopefully that will help

[@josantosp77]

I'm struggling with that too. It seems like learning Android dev is 10x more difficult than it should be - everything is deprecated 6 months later, so in every course or tutorial you're basically fucked trying to solve issues you shouldn't have to while learning a new framework. As a consequence, what should be a 30min tutorial ends up taking me over 3 hours trying to figure out how to make the code work. It's absolutely frustrating.

[@arthurmsiska3800]

I messed up somewhere, when I run the app, the ,list does not show up nor the recycler view item

[@rhinokyanui2702]

Me too...Did you find a fix

[@phamhung2263]

Thanks so much, Philipp. I really love all your amazing videos. Could you please create a video about using advanced RecyclerView in Android (increase performance, best practice when using RecyclerView...). I think it will be useful for any Android Developer

[@debayanghoshdastider]

Accessing the checkbox and text view using synthetics does not work anymore and to use ViewBinding we need the adapter class. I am confused here. Can you please make a video on this?

[@johnpunzak8916]

To avoid the synthetics, add the following to the inner class: init{ tvTitle = itemView.findViewById(R.id.tvTitle) cbDone = itemView.findViewById(R.id.cbDone) } Then refer to the items directly in onBindViewHolder, like this: override fun onBindViewHolder(holder: TodoViewHolder, position: Int) { holder.tvTitle.text = todos[position].title holder.cbDone.isChecked = todos[position].isChecked }

[@saeedyaftian66]

thanks a lot you explain this unit very good

[@mohamedzaarir1122]

does it save ? i mean if i close the app and open it again , does it save the ToDos that i added or not ?

[@guestalt00]

late 1 year and xml is outdated, and i know you already knew the answer, but the answer is "no", you need to write another code to save something to your phone.

[@wowovanmbothen]

You take the data from list in Main Activity (todolist), what if i want to take the data from some class? For example i have data class book that contain title, author, year released etc

[@crateer]

Well then you take the items from the Book Class, store them in a list, and you're done =)

[@АльфредАхметгалеев]

HI! How delete item (position) ?

[@youcantbebored2988]

If we search for the xml views in onBindViewHolder wont it search for the view for every item ? this is exactly why we have ViewHolder class, so that the activity don't have to search for the view for every item 😅😅correct me if i am wrong

[@gangardarwagle8938]

Why is that only first data is shown

[@dluca182]

the learning curve is steep on this one....

[@dfmayes]

Thanks for the video. Is the code on github?

[@olayiwolaosho4989]

Great video man Thanks for this Have a question The how does the view holder know the XML view item it should hold is gotten from the todoitemxml didn't see any reference to it Thanks 😊

[@Anonymous-nx9fh]

The ViewHolderclass is a inner class of the Adapter so the viewholder can get the refernce from there . Hope this helps :)

[@GiridharaSaiPavanKumarGurram]

Hey, Great tutorial Can you do a video on layout manager in recyclerview ?

[@vuyaninxele2301]

recyclerviews do this for you

[@jaywye]

Thank you for this video. Very helpful.

[@movie4u978]

why did u set android:height = 0dp ,

[@celina6204]

Great tutorial! I always look for your channel when I don't understand something in Android :) Can you do a video on ListAdapter please

[@hanadanefa7837]

how can i check like if the recyclerview is empty? so i can have a textview saying no todo list something like that

[@PhilippLackner]

Either check if the list in the adapter is empty or use its layout manager to check if no items are visible. I would prefer the first option

[@hanadanefa7837]

@@PhilippLackner hello thank you for giving time in my question, I am having difficulties in data class that I want to put in recyclerview, I want to ask how can I make the data class into null? or no value at all or just say I don't want to have a default value on it, I want it to be dynamic? how can I do that using data class?

[@hanadanefa7837]

@@PhilippLackner How can I set that mutablelist to empty? then add value to the todoList mutablelistof Todo() dynamically, like what you did in the button? I don't want to have a value on it, what I want is I am the one to set the value, like adding value from a button.

[@ajaygalagali5963]

Great explanation! Thanks

[@arthurdiarealvares4829]

Thank you very much man!!!

[@jjongim3956]

great lecture! Thank You!!

[@agp1444]

good explanation. thanks

[@51bpegasi]

You're an amazing teacher, been watching a lot of your tutorials. I just downloaded Android Studio 4.2.1 and I got stuck at 17:14 because it doesn't see tvTitle, I tried Megumin's proposed fix but doesn't seem to work for me build.gradle (Module: ...) android { ... buildFeatures { viewBinding true } ...} package com.tutorial.recyclerviewtutorial import android.view.LayoutInflater import android.view.ViewGroup import androidx.recyclerview.widget.RecyclerView import com.tutorial.recyclerviewtutorial.databinding.ItemTodoBinding class ToDoAdapter(var todos: List): RecyclerView.Adapter() { inner class TodoViewHolder(val itemView: ItemTodoBinding): RecyclerView.ViewHolder(itemView.root) override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): TodoViewHolder { val inflater = LayoutInflater.from(parent.context) val view = ItemTodoBinding.inflate(inflater, parent, false) return TodoViewHolder(view) } override fun onBindViewHolder(holder: TodoViewHolder, position: Int) { holder.itemView.apply { tvTitle.text = todos[position].title // tvTitle is unresolved reference here } } override fun getItemCount(): Int { return todos.size } Not sure how to fix this to continue.

[@51bpegasi]

oh wait, itemView seems to be reserved, works when i change it to itemview

[@martianly808]

same question.How to fix?

[@olafpl99999]

@@51bpegasi Didnt fix it for me, can you elaborate on your solution?

[@matthewkilmurray8437]

is there a java version of this?

[@ericpalmer4103]

Your explanation is just wow! Could you pls bring a video on the same but in Java?

[@bhupeshpattanaik7150]

thanks a lot for this video, please let me know is their any video in which this is done via internet i.e. data is fetched from net

[@PhilippLackner]

check my news app playlist

[@bhupeshpattanaik7150]

@@PhilippLackner 😀👍

[@simonegli3622]

This video helped me a lot! But everytime i restart the app the points on the list, that i added are gone, how can I keep them(bc thats pretty much the point of a list, where you can write things down)

[@PhilippLackner]

For that you need to save them to a database so they are not lost when the activity gets destroyed. Check out my MVVM Playlist for that. There I show exactly that

[@ajaygalagali5963]

@@PhilippLackner I tried but unable to follow up! Too many things going on there.

[@meghanabasutkar363]

Loved it!

[@nicholastzane3466]

Very nice video. Could you also make a video focusing on Emulator Devices. For example in this tutorial my app worked by i got the error Emulator: socketTcpLoopbackClientFor: error: fd 69252 above FD_SETSIZE (32768) and I don't know how i can fix it.

[@gdstardust]

Nice tutorial, how can i implement recyclerview with snapping on start?

[@Marinakulichok]

Add this line to clean the text in the EditText after it was added, otherwise you can not understand whether text was added or not

[@SaifAli-ij2xt]

just add the following one line code for that: etTodo.getText().clear()

[@mrpi230]

thank you, you explain really well.

[@PhilippLackner]

Thanks!

[@lukalukovic5082]

Can you tell me how to delete the item in recycler view

[@PhilippLackner]

By deleting the item from your list in the activity and then calling adapter.notifyItemDeleted(deletedIndex)

[@javieer]

Thanks so much for your help! You are kind of a heroe for me

[@PhilippLackner]

People who write such comments like you are heroes for me 🙏

[@tcpro0902]

Hi, Thanks for the Demo. Where we can find the source code?

[@prakashm5711]

why this awesome video has less number of views.?

[@navinkodam412]

Nice one!

[@PhilippLackner]

Thanks!

[@shahbaztariq2837]

Thanks bro!

[@randy4443]

What is 0dp mean?

[@rochmanramadhanichieftoira2695]

Watch the ConstraintLayout Series again 😉 it means that the EditText(View) will stretch a whole layout when you link the dot to the parent/another view in horizontal/vertically

[@4585329]

19:56 Did you ever ask your crush out Philipp?

[@facucancian7875]

BEAUTIFUL