RECYCLERVIEW - Android Fundamentals
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- เผยแพร่เมื่อ 4 มี.ค. 2020
- In this video you will learn about a very important view in Android which is the RecyclerView. It is used to implement all kinds of list in a very efficient way.
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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.
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
Thank you, it works!!! Yes, and update or at least a pinned comment is definitely needed.
@@renatovg6337 Croatia? I ask because of VG in username?
He used buildgradle:app plugin add id 'kotlin-android-extensions'
King
Thanks a lot!
I was stuck on a problem for a whole day until I saw this video! Thank you!
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!
Thank you Philipp, for the great tutorials! I follow the ANDROID FUNDAMENTALS FOR BEGINNERS and the tutorials are perfect so far.
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!
Glad it was helpful!
I havent seen the video yet but.... CAN WE TALK ABOUT HOW COOL THAT INTRO TRANSITION WAS???!!! xD
Thank you Sir! Better than my lecturer's explanation
Thanks for the great demo
On minute 18:50 , I used an inner apply :
todos[position].apply {
txtTitle.text = title
chkDone.isChecked = isChecked
}
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.
Amazing , detailed and easy to understand , thank you so much
Thank you. The way you explain things, it's really easy to follow for newbies like me - very good job!
Wow, this is such an elegant tutorial! Thank you!
My understanding is alot better now, but am sure i will get back to it once more. Thanks mate
I'm really thankful to you . This tutorial is very easy to understand and learn recycle view.
Great tutorial Phillip! The lesson is valuable and your narration is easy to understand. Thank you
Thank you, you're welcome!
Thank you very much for this video, it was really easy to follow and understand. Your explanations are clear and concise :)
Wow this is really step by step love this.
Amazing Tutorial. Keep up the good work man!
Thank you so much this was really simplified amazingly
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)
Lifesaver! Thanks!
Thanks a ton buddy,
Have a great day my friend!
This should be pinned. Wasted a headache trying to understand what was wrong
Thank you very much.
thanks
This is fantastic. Thank you so much!
Awesome tutorial! Hello from Indonesia 😁
Thank you, this actually helped me to understand recycler view :D
Congrats, you're welcome :D
awesome video , simple exemple not to much in it , perfect to understand the basics of everything 5 star this!!!!!!!!!!! good job
Very Clean Explaination Thanks
Thank you for this video. Very helpful.
Great explanation! Thanks
great lecture! Thank You!!
good dude, fundamental is important, awesome!!
Thank you!
Thank you very much man!!!
Hello Phillip! Do you plan on creating a video about recyclerview in view binding?
Your explanation is just wow! Could you pls bring a video on the same but in Java?
thanks a lot you explain this unit very good
good explanation. thanks
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
thank you, you explain really well.
Thanks!
Clear explanation. Congrats !
Can you do updates as video or as comment under the video, because there are some deprecated usages.
Thanks bro!
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
i love you man! you are awesome!
Thank you ❤️
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)).
Thanks so much for your help! You are kind of a heroe for me
People who write such comments like you are heroes for me 🙏
Great tutorial! I always look for your channel when I don't understand something in Android :) Can you do a video on ListAdapter please
Loved it!
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
why this awesome video has less number of views.?
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.
Thanks a lot man
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?
BEAUTIFUL
the learning curve is steep on this one....
Really helpful tutorial! Could I ask you if you know any places online where I could really dive deep into recycler views?
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
Thanks a lot
hey Phillip :) if you also had a Spinner with todo category how would you declare that in the data class?
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
He said in a previous video he prefers to teach XML because it has way more options than what you see in the GUI
In LayoutInflater function why attachToRoot parameter in need if its always going to be false??
does it save ? i mean if i close the app and open it again , does it save the ToDos that i added or not ?
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?
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?
do you have a video showing how you can use a button from within each recycler view?
thank you
Hey,
Great tutorial
Can you do a video on layout manager in recyclerview ?
recyclerviews do this for you
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
I just died of cringe bro🥲
Thank youu !!
really good !!!!
if i had a delete button on the template then how would i attach a function to each one?
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.
Nice tutorial, how can i implement recyclerview with snapping on start?
Hey how can i remove the todo list after i check the checkbox?
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.👍
hi just create 1 adapter then from your mainActivity pass it to any new Activity you want
Nice one!
Thanks!
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
When I run my app, I get Dublicate Classes error. What could be the problem please
Thanks for the video. Is the code on github?
hi very good and nice plz learn Recyclerview drag and drop , thx
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
just add the following one line code for that: etTodo.getText().clear()
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
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.
Make a video on deletion and onClick listeners for it please
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?...
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 😊
The ViewHolderclass is a inner class of the Adapter so the viewholder can get the refernce from there . Hope this helps :)
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
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
Well then you take the items from the Book Class, store them in a list, and you're done =)
HI! How delete item (position) ?
Hi, Thanks for the Demo. Where we can find the source code?
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.
i have the same problem , any solution ??
@@arbouchemadjber2540 I defined the fields in the holder inner class, finding them by Id, and accessed them that way.
why did u set android:height = 0dp ,
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.
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)
I have mutableListOf in red. Does anybody know how to fix this issue?
I add the layout in onCreateViewHolder method. But I can't access the components of this layout in onBindViewHolder method . Anyone please help me .......
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.
same prob here
I messed up somewhere, when I run the app, the ,list does not show up nor the recycler view item
Me too...Did you find a fix
is there a java version of this?
Where is "rvTodoItems" coming from in the main activity????
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!!!
Hi, you need add Kotlin Android Extensions to your gradle file.
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.
@@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...
@@glebshymko Thank you! Been staring at my code for 1h wondering what when wrong
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)
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?
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
}
what is """tvTitle""" ? it's not working and we didn't declare it before !!!
very hard man
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)
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
@@PhilippLackner I tried but unable to follow up! Too many things going on there.