I'm confused if we use the two methods to tell the adapter that data you point were changed so what is the difference between them.
notifyDataSetChanged() can be thought of as a "major" change. You're telling the adapter that everything in the data set has changed, and so it should re-bind every single child.
notifyItemInserted() (and the other methods like notifyItemRemoved() etc) can all be thought of as "minor" changes. You're telling the adapter exactly how the data set has changed, and so it can perform optimizations (like only re-binding the affected children).
Notably, using the "minor" change methods will also give you nice animations by default, which makes it a lot easier for the user to see what changed in the list.
Based on the documentation
notifyDataSetChanged():
This event does not specify what about the data set has changed, forcing any observers to assume that all existing items and structure may no longer be valid. LayoutManagers will be forced to fully rebind and relayout all visible views.
notifyItemInserted()
Representations of other existing items in the data set are still considered up to date and will not be rebound, though their positions may be altered.
Main difference is that notifyDataSetChanged() will cause more overhead since it will force LayouManagers to full rebind the views where as notifyItemInserted() will not rebound all the views again but rather alter positions for them.
For better performance, rely on notifyDataSetChanged() as a last resort. Use the more specific change events (like notifyItemInserted()) wherever possible for better efficiency.
notifyItemInserted(int position) takes the position of your inserted item as an argument, notifies about that item insert and thus also shifts positions after that item.
notifyDataSetChanged() notifies that the data set connected to the adapter has changed.
Related
after update android studio to arctic fox, I get this warning. But I dont know what is the efficient way to notify data change.
in my code I'm filling the adapter from network call and then I notifydatasetchange, but the compiler gave me this:
It will always be more efficient to use more specific change events if you can. Rely on notifyDataSetChanged as a last resort. RecycleView
edit question:
the want us to use
DiffUtil docs
instead of notifyDataSetChanged() because it much faster.
check this article on medium.
It means that if you need to change the whole item list at once in the recyclerview, then use notifyDataSetChanged().
If you need to change the specific item, then it's better to use notifyItemChanged(position) so that it won't refresh & rebind the whole dataset which can impact the performance if the dataset is large.
So it's just a normal suggestion or maybe a warning, nothing to worry about. :)
The function notifyDataSetChanged essentially considers all data in your dataset has changed. This causes all VISIBLE views using this data to be redrawn. This is unnecessary when only some data has changed.
You need to identify the position that data has change and notify your adapter to update only those items.
you can notify change of the particular position using this methods
notifyItemChanged(int)
notifyItemInserted(int)
notifyItemRemoved(int)
notifyItemRangeChanged(int, int)
notifyItemRangeInserted(int, int)
notifyItemRangeRemoved(int, int)
It's just a suggestion by Android studio to update data in RecyclerView.
This advice to notify change in the Recycler view items using particular postion update only like, notifyItemChanged(int), notifyItemInserted(int), notifyItemRemoved(int) ,notifyItemRangeChanged(int, int), notifyItemRangeInserted(int, int), notifyItemRangeRemoved(int, int).
notifyDataSetChanged() should be used as the last resort or as the final course of action. This function will reinitialize and rebind all views once again which can decrease the performance.
Must notifyItemRangeChanged be called after calling notifyItemInserted in an RecyclerView.Adapter?
There are so many examples on SO where they always call notifyItemRangeChanged after notifyItemInserted but I am not sure this is really correct? If this is correct what would be the explanation? What would the case be where you don't need to call notifyItemRangeChanged, otherwise it would be part of notifyItemInserted?
There are no rules as one method should always precede the other.
If there is an addition of a new item, then call notifyItemInserted. If items are changed, then call notifyItemRangeChanged.
If some items are added and some are changed, you have to call both methods with respective positions as arguments. You can call the methods in any order, but based on the order the animations and the position that you have to pass to the methods might change.
Based on the documentation for RecyclerView:
There are two different classes of data change events, item changes and structural changes. Item changes are when a single item has its data updated but no positional changes have occurred. Structural changes are when items are inserted, removed or moved within the data set.
notifyItemInserted
Is a structural change event
notifyItemRangeChanged
Is a item change event
What would the case be where you don't need to call
notifyItemRangeChanged, otherwise it would be part of
notifyItemInserted?
Well its not necessary to always call notifyItemRangeChanged when notifyItemInserted since they both serve different purposes.
To put it in a simple way, if you add a new row/data to existing adapter's dataset then you should call notifyItemInserted.
If you modify certain data in bulk in the adapter's dataset, without adding, moving or deleting the adapter's dataset's content then call notifyItemRangeChanged. For single item change use notifyItemChanged
So I have an activity with RecyclerView and I want to change TextView of every item in the RecyclerView by pressing button that has onClickListener() in the activity.
I'm wondering what is better in terms of performance:
Use notifyDataSetChanged ones.
Use loop with condition like int i is less than List.size() where notifyItemChanged would be called few times.
In both cases I create boolean variable in RecyclerView Adapter which is used by onBindViewHolder to know how to update item. By default it's false and after button click it becomes true so onBindViewHolder updates item in different way.
Also I would like to know if this approach is suitable at all.
If you are simply updating one part of the view, use the notifyItemRangeChanged()or notifyItemChanged() instead of notifiyDataSetChanged(). The difference here has to do with structural changes vs item changes. This is on the android developers RecyclerView.Adapter documentation found here.
Here is another tidbit on the differences between the two types of changes:
There are two different classes of data change events, item changes
and structural changes. Item changes are when a single item has its
data updated but no positional changes have occurred. Structural
changes are when items are inserted, removed or moved within the data
set.
This is taken from that aforementioned page,
If you are writing an adapter it will always be more efficient to use
the more specific change events if you can. Rely on
notifyDataSetChanged() as a last resort.
So just to clarify use notifyDataSetChanged() as a last resort, and instead ask yourself if you can preform one of these methods instead, and if you can use it instead:
notifyItemChanged(int)
notifyItemInserted(int)
notifyItemRemoved(int)
notifyItemRangeChanged(int, int)
notifyItemRangeInserted(int, int)
notifyItemRangeRemoved(int, int)
which makes sense because notifyDataSetChanged() will pretty much try to redraw everything based on the data and make no previous assumptions on it, while the other methods will just look for changes. That means the adapter has to do a lot more work that is not necessary. This is what notifyDataSetChanged() does:
This event does not specify what about the data set has changed,
forcing any observers to assume that all existing items and structure
may no longer be valid. LayoutManagers will be forced to fully rebind
and relayout all visible views.
This also makes sense to use the incremental or range approach, because you are changing the text, you need to go get each new text and when you do that you should tell the adapter you changed it. Now, if you do a button click and get all new text values, and create a new list or something then call heavy notifyDataSetChanged().
I would definitely call notifyDataSetChanged() if all of the data items ar no longer valid. When you call notifyItemChanged(mPos), it is equivalent to a call to notifyItemRangeChanged(mPos, 1), and every time it is called, requestLayout() is also called. On the other hand, when you call notifyDataSetChanged() or notifyItemRangeChanged(0, mList.size()), there is only one call to requestLayout().
Your question should now be, what is better, a call to notifyDataSetChanged() or notifyItemRangeChanged(0, mList.size())? For that one I don't have an answer.
I've noticed that notifyItemChanged(mPos) triggers onBindVieHolder for corresponding position even it's currently not visible.
For me, calling it in a loop for all elements was more costly than notifyDatasetChanged which redrawn only visible ones.
So be careful with large datasets.
I am running into an issue with the RecyclerView#Adapter regarding notifyItemRangeChanged. It seems that if the Adapter thinks it has a size of 0 from the last call to getItemCount, and then I call Adapter#notifyItemRangeChanged(0, 1), the Adapter will simply ignore the call (it doesn't result in the new item being inserted, for example).
Is this the expected behavior?
Is this the expected behavior?
Short answer: yes.
From the docs on notifyDataSetChanged() (yes, different method, I know, but just referencing it here since it explains the difference between item changes and structural changes):
There are two different classes of data change events, item changes and structural changes. Item changes are when a single item has its data updated but no positional changes have occurred. Structural changes are when items are inserted, removed or moved within the data set.
Now have a read through the documentation on notifyItemRangeChanged() (my emphasis):
This is an item change event, not a structural change event. It indicates that any reflection of the data in the given position range is out of date and should be updated. The items in the given range retain the same identity.
That should answer your question. You're making a structural change (that is, you're adding an item), hence notifyItemRangeChanged() is not the appropriate method to call. Instead, you should call notifyItemRangeInserted() (or its singular equivalent), which does indicate a structural change was made.
I am extending the ArrayAdapter and I provided my own OnItemClickListener where I update certain states of my data which reflects on multiple items in the list so to update the current states of those items in the list, I am calling the notifyDataSetChanged. Its working properly as how I want it to my worry is if there are any issues or negative effects on doing so. Like when the user taps many items which results in consecutive calls to notifyDataSetChanged.
If the user interaction requires views to be updated then you do need to be calling notifyDataSetChanged each time. If you're really worried you can look at debounce algorithms but that's kind of overkill, but as long as you don't have a huge number of elements and don't add a bunch of data change listeners it shouldn't be a problem.
don't worried about calling notifyDataSetChanged it only notify adapter about data change