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Android Recyclerview vs ListView with Viewholder
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I was reading about the difference b/w recyclerview and listview and found out that recyclerview is faster than listview.
I tried to search online but not found any satisfactory answer I know it is used ViewHolder pattern and Notifying adapter but what does it does intearlly so it is faster?
Recycler View you could say is an efficient way to create list of views.
If you have 1000 items like ur contact list , and If ur visible screen can show only 10 items at once, it will Create only 10+1 (or +2) Views and as u scroll , items/views that left will be reused (not create) to show new data.
Recycler View by default does this, where as List View by default doesn't do.
There are some differences between these two views.
ListView is a bit heavy and it has a lot of responsibilities. Whenever we have to handle the list, such as to configure it in some way, the only way to do this is through the ListView object or inside the adapter.
A lot of bad things in the ListView were fixed or changed in the RecyclerView. It’s more efficient by default, the layout is separated and we have more possibilities over the data set inside the adapter.
These are some crucial differences between ListView and RecyclerView:
1 ViewHolder
The ViewHolder pattern allows us to make our list scrolling act smoothly. It stores list row views references and, thanks to this, calling the findViewById() method only occurs a couple of times, rather than for the entire dataset and on each bind view.
The RecyclerView’s adapter forces us to use the ViewHolder pattern. The creating part (inflating the layout and finding views) and updating the views is split into two methods — onCreateViewHolder() and onBindViewHolder().
The ListView, on the other hand, doesn’t give us that kind of protection by default, so without implementing the ViewHolder pattern inside the getView() method, we’ll end with inefficient scrolling in our list.
2 LayoutManager
The LayoutManager takes responsibility for layouting row views. Thanks to this, RecyclerView doesn’t have to think about how to position the row view. This class gives us the opportunity to choose the way that we want to show the row views and how to scroll the list. For example, if we want to scroll our list vertically or horizontally, we can choose LinearLayoutManager. For grids, it is more suitable to choose the GridLayoutManager.
Previously, with the use of the ListView, we were only able to create a vertical-scrolling list, so it wasn’t that flexible. If we wanted grids on our list, we had to choose the other widget for that — GridView.
3 ItemDecoration
A duty of the ItemDecoration is simple in theory – add some decorations for the list row views – but in practice, it’s that simple to implement if we want to create a custom one. In this case, we should extend the ItemDecoration class and implement our solution. For example, the RecyclerView list has no dividers between rows by default and it’s consistent with the Material Design guidelines. However, if we want to add a divider for some reason, we can use DividerItemDecoration and add it to the RecyclerView. In case we use the ListView, we have to figure out rows decorations by ourselves. There is no helper class like ItemDecoration for this widget.
4 ItemAnimator
The last but not least component of RecyclerView that I want to mention is ItemAnimator. As we can expect, it’s handling row views animations like list appearance and disappearance, adding or removing particular views and so on. By default, RecyclerView’s list animations are nice and smooth. Of course, we can change that by creating our own ItemAnimator, which is also not that easy. To make it easier, we should extend the SimpleItemAnimator class and implement the methods that we need (just add animations to a ViewHolder’s views). To be honest, implementing animations on the ListView was a pain. Again, we had to figure out how we want to handle them.
5 Notifying adapter
We have a couple of cool notifiers on the RecyclerView’s adapter. We are still able to use notifyDataSetChanged() but there are also ones for particular list elements, like notifyItemInserted(), notifyItemRemoved() or even notifyItemChanged() and more. We should use the most appropriate ones for what is actually happening, so the proper animations will fire correctly.
Using ListView, we were able to use just notifyDataSetChanged() on the adapter and then had to handle the rest ourselves, again.
Because of ViewHolder Pattern.
Thats was the simplest answer. Now for some details.
What recycler view does is what it's name indicates "Recycle", yes it recycles items, and it does it with the help of ViewHolder Pattern.
By Using ViewHolder we do-not need to call findViewByID() every time we go through getView()method. The reference for all rows are stored in-memory. This increases the performance significantly, as findViewByID()is a heavy process.
Hope this clears your confusion.
I am developing an android app which will allow users to create polls. A user can create a question and provide a set of options.
I wanted to provide a feature in which users can add or remove options dynamically.
I can't decide which layout would be best.
TableLayout - Each row can contain an option.
Vs
RecyclerView - Each item can be an option.
(Note that each option actually would be an EditText View where the user has to enter the option content.)
I have seen people generally use the RecyclerView for very large data sets but for my use case, a user can add a maximum of 5 or 6 options. Apart from that, I'll be using a recycler view to collect the data.
For such a use case, is it a good option to use the RecyclerView or something else?
Please provide suggestions
Definitely RecyclerView.
With a RecyclerView you can easily add and remove items dynamically.
Use the TableLayout if you have a static amount of rows (TableRow), that you declare in XML.
Use RecyclerView even if your rows are such little (5 or 6). By doing that, you will facilitate navigation for user with just one screen.
Suppose I have RecyclerView with hundreds of items. There are a few different view types. When I click on an item it has to change its UI. As I see it there are two options:
change the item to a different view type and notify the adapter that it changed so that it can inflate a new view to display the new state.
have both views in a single xml file. only one is visible at any time. Toggle between them using the setVisibility function when the state changes.
there are a lot of articles online about heterogeneous RecyclerViews using lots of view types, but i have yet seen one about the best practices when item views dynamically change and the RecyclerView becomes more heterogeneous over time.
which method is best to change an existing view in a recycler view? what are the tradeoffs?
The tradeoffs are pretty obvious.
Both UIs in a single View: depending on your views, this might:
Make the Views heavy to inflate and layout
Slow down the binding process, since you have to bind both UIs
Eventually, lag down the scrolling process.
On the other hand, you have a fast, precise control over what Views should change appearance at a certain time. Having both UIs in the same place allows for finer animations and transitions between one state and another.
Different View types: I think your case is not why view types were created in the first place - they are meant for having different childs at the same time, in different positions of the list. This:
Might slow down the transition. You have to be extremely careful on how you tell the adapter to reload the objects. As you can read anywhere, you might want to avoid notifyDataSetChanged(), which reloads any object, and rather use notifyItemChanged() or such. This requires some work and attention.
Does not allow (not easily, at least) for visual transition between one state and another.
The answer is that, IMO, only you can know. You should ask yourself:
Are these Views complex? Do they have a deep hierarchy? Would having both of them reduce performance (e.g. in the binding part)?
Would it be easy to understand which views are changed, and call notifyItemChanged(int position) in the second case? Reloading the whole dataset has a huge impact on performance, if you have lots of items.
Do you need some visual transition between one state and another? Maybe you want both UIs to fit into a single container (like different informations in a CardView)? If this is mandatory, then option 1 is better.
Do you have more than 2 UIs? If so, I would go with view types, so as not to host too many views in a single child layout.
and similar questions.
There is object array received from server
there are two ways to show items :
Adapt Objects To ListView
Use Scroll View
So If I use scroll View and add items programmatically, There are some Questions:
Does Adding Items Programmatically Cause Out Of Memory ?
Does It Need To Remove Items from memory ? or it will remove automatic after onDestroy Called or Items moved out of screen?
Regards
If the data set is large, a ListView won't stop OOMs by itself, you will have to avoid loading the entire data set in memory by using a CusorAdapter backed by some non-memory data store (like a sql database).
A ListView will reduce the amount of memory that the Views use to represent the data to the user, since it will only initialise Views that the user can see (and recycle Views if possible when the user scrolls).
Since only the Views visible are loaded with a ListView, performance should* also be better since the layout process will be quicker.
In most cases, a ListView would be better for this type of thing.
(*) If the adapter's getView or bindView e.t.c. are complex, or each row in the list has its own view type, the scrolling performance could actually be worse.
Listview is the Best case for you. and I will prefer to use volly library of android . It is easy to use and very handy and helpfull.
From android developer (Creating Lists and Cards):
The RecyclerView widget is a more advanced and flexible version of
ListView.
Okay, it sounds cool, but when I saw this example picture, I got really confused about the difference between these two.
The picture above can be easily created by ListView using custom adapter.
So, in what situation should one use RecyclerView?
RecyclerView was created as a ListView improvement, so yes, you can create an attached list with ListView control, but using RecyclerView is easier as it:
Reuses cells while scrolling up/down - this is possible with implementing View Holder in the ListView adapter, but it was an optional thing, while in the RecycleView it's the default way of writing adapter.
Decouples list from its container - so you can put list items easily at run time in the different containers (linearLayout, gridLayout) with setting LayoutManager.
Example:
mRecyclerView = (RecyclerView) findViewById(R.id.my_recycler_view);
mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
//or
mRecyclerView.setLayoutManager(new GridLayoutManager(this, 2));
Animates common list actions - Animations are decoupled and delegated to ItemAnimator.
There is more about RecyclerView, but I think these points are the main ones.
So, to conclude, RecyclerView is a more flexible control for handling "list data" that follows patterns of delegation of concerns and leaves for itself only one task - recycling items.
For list views to have good performance you'll need to implement the holder pattern, and that's easy to mess up especially when you want to populate the list with several different kinds of views.
The RecyclerView bakes this pattern in, making it more difficult to mess up. It's also more flexible, making it easier to handle different layouts, that aren't straight linear, like a grid.
ListView is the ancestor to RecyclerView. There were many things that ListView either didn't do, or didn't do well. If you were to gather the shortcomings of the ListView and solved the problem by abstracting the problems into different domains you'd end up with something like the recycler view. Here are the main problem points with ListViews:
Didn't enforce View Reuse for same item types (look at one of the adapters that are used in a ListView, if you study the getView method you will see that nothing prevents a programmer from creating a new view for every row even if one is passed in via the convertView variable)
Didn't prevent costly findViewById uses(Even if you were recycling views as noted above it was possible for devs to be calling findViewById to update the displayed contents of child views. The main purpose of the ViewHolder pattern in ListViews was to cache the findViewById calls. However this was only available if you knew about it as it wasn't part of the platform at all)
Only supported Vertical Scrolling with Row displayed Views (Recycler view doesn't care about where views are placed and how they are moved, it's abstracted into a LayoutManager. A Recycler can therefore support the traditional ListView as shown above, as well as things like the GridView, but it isn't limited to that, it can do more, but you have to do the programming foot work to make it happen).
Animations to added/removed was not a use case that was considered. It was completely up to you to figure out how go about this (compare the RecyclerView. Adapter classes notify* method offerings v. ListViews to get an idea).
In short RecyclerView is a more flexible take on the ListView, albeit more coding may need to be done on your part.
The RecyclerView is a new ViewGroup that is prepared to render any
adapter-based view in a similar way. It is supossed to be the
successor of ListView and GridView, and it can be found in the
latest support-v7 version. The RecyclerView has been developed
with extensibility in mind, so it is possible to create any kind of
layout you can think of, but not without a little pain-in-the-ass
dose.
Answer taken from Antonio leiva
compile 'com.android.support:recyclerview-v7:27.0.0'
RecyclerView is indeed a powerful view than ListView .
For more details you can visit This page.
Following are few key points/differences between RecyclerView & ListView. Take your call wisely.
If ListView works for you, there is no reason to migrate. If you are
writing a new UI, you might be better off with RecyclerView.
RecylerView has inbuilt ViewHolder, doesn't need to implement our own
like in listView. It support notify at particular index as well
Things like animating the addition or removal of items are already
implemented in the RecyclerView without you having to do anything
We can associate a layout manager with a RecyclerView, this can be
used for getting random views in recycleview while this was limitation
in ListView In a ListView, the only type of view available is the
vertical ListView. There is no official way to even implement a
horizontal ListView. Now using a RecyclerView, we can have a
i) LinearLayoutManager - which supports both vertical and horizontal
lists, ii) StaggeredLayoutManager - which supports Pinterest like
staggered lists, iii) GridLayoutManager - which supports displaying
grids as seen in Gallery apps.
And the best thing is that we can do all these dynamically as we want.
Major advantage :
ViewHolder is not available by default in ListView. We will be creating explicitly inside the getView().
RecyclerView has inbuilt Viewholder.
Advantages of RecyclerView over listview :
Contains ViewHolder by default.
Easy animations.
Supports horizontal , grid and staggered layouts
Advantages of listView over recyclerView :
Easy to add divider.
Can use inbuilt arrayAdapter for simple plain lists
Supports Header and footer .
Supports OnItemClickListner .
I think the main and biggest difference they have is that ListView looks for the position of the item while creating or putting it, on the other hand RecyclerView looks for the type of the item. if there is another item created with the same type RecyclerView does not create it again. It asks first adapter and then asks to recycledpool, if recycled pool says "yeah I've created a type similar to it", then RecyclerView doesn't try to create same type. ListView doesn't have a this kind of pooling mechanism.
RecyclerView info
The RecyclerView was introduced with Android 5.0 (Lollipop). it is included in the Support Library. Thus, it is compatible with Android API Level 7.
Similarly to the ListView, RecyclerView’s main idea is to provide listing functionality in a performance friendly manner. The ‘Recycler’ part of this view’s name is not there by coincidence. The RecyclerView can actually recycle the items with which it’s currently working. The recycling process is done thanks to a pattern called View Holder.
Pros & Cons of RecyclerView
Pros:
integrated animations for adding, updating and removing items
enforces the recycling of views by using the ViewHolder pattern
supports both grids and lists
supports vertical and horizontal scrolling
can be used together with DiffUtil
Cons:
adds complexity
no OnItemClickListener
ListView info
The ListView has been around since the very beginning of Android. It was available even in API Level 1 and it has the same purpose as the RecyclerView.
The usage of the ListView is actually really simple. In this aspect, it’s not like its successor. The learning curve is smoother than the one for the RecyclerView. Thus, it is easier to grasp. We don’t have to deal with things like the LayoutManager, ItemAnimator or DiffUtil.
Pros & Cons of ListView
Pros:
simple usage
default adapters
available OnItemClickListener
it’s the foundation of the ExpandableListView
Cons:
doesn’t embrace the usage of the ViewHolder pattern
In addition to above differences following are few more:
RV separates view creation and binding of data to view.
In LV, you need to check if convertView is null or not for creating view, before binding data to it.
So, in case of RV, view will be created only when it is needed but in case of LV, one can miss the check for convertview and will create view everytime.
Switching between Grid and List is more easy now with LayoutManager.
No need to notify and update all items, even if only single item is changed.
One had to implement view caching in case of LV.
It is provided in RV by default. (There is difference between view caching n recycling.)
Very easy item animations in case of RV.
In my opinion RecyclerView was made to address the problem with the recycle pattern used in listviews because it was making developer's life more difficult.
All the other you could handle more or less.
For instance I use the same adapter for ListView and GridView it doesn't matter in both views the getView, getItemCount, getTypeCount is used so it's the same.
RecyclerView isn't needed if ListView with ListAdapter or GridView with grid adapters is already working for you.
If you have implemented correctly the ViewHolder pattern in your listviews then you won't see any big improvement over RecycleView.
I worked a little with RecyclerView and still prefer ListView.
Sure, both of them use ViewHolders, so this is not an advantage.
A RecyclerView is more difficult in coding.
A RecyclerView doesn't contain a header and footer, so it's a minus.
A ListView doesn't require to make a ViewHolder. In cases where you want to have a list with sections or subheaders it would be a good idea to make independent items (without a ViewHolder), it's easier and doesn't require separate classes.
You can use an interface to provide a click listener. I use this
technique with ListViews, too.
No divider: Simply add in your row a View with a width of
match_parent and a height of 1dp and give it a background color.
Simply use a StateList selector for the row background.
addHeaderView can be avoided in ListViews, too: simply put the
Header outside the View.
So, if efficiency is your concern, then yes, it's a good idea to replace a ListView with a RecyclerView.
Simple answer: You should use RecyclerView in a situation where you want to show a lot of items, and the number of them is dynamic. ListView should only be used when the number of items is always the same and is limited to the screen size.
You find it harder because you are thinking just with the Android library in mind.
Today there exists a lot of options that help you build your own adapters, making it easy to build lists and grids of dynamic items that you can pick, reorder, use animation, dividers, add footers, headers, etc, etc.
Don't get scared and give a try to RecyclerView, you can starting to love it making a list of 100 items downloaded from the web (like facebook news) in a ListView and a RecyclerView, you will see the difference in the UX (user experience) when you try to scroll, probably the test app will stop before you can even do it.
I recommend you to check this two libraries for making easy adapters:
FastAdapter by mikepenz
FlexibleAdapter by davideas
There are many differences between ListView and RecyclerView, but you should be aware of the following in particular:
The ViewHolder pattern is entirely optional in ListView, but it’s baked into RecyclerView.
ListView only supports vertical scrolling, but RecyclerView isn’t limited to vertically scrolling lists.
I want just emphasize that RecyclerView is a part of the compatibility package. It means that instead of using the feature and code from OS, every application carries own RecyclerView implementation. Potentially, a feature similar to RecyclerView can be a part of a future OS and using it from there can be beneficial. For example Harmony OS will be out soon.The compatibility package license can be changed in the future and it can be an implication. Summery of disadvantages:
licensing
a bigger foot print especially as a part of many apps
losing in efficiency if some feature coming from OS can be there
But on a good note, an implementation of some functionality, as swiping items, is coming from RecyclerView.
All said above has to be taken in a consideration.