When we initialise adapters, we have method getView. As I understand, each time it is called, It redraws the UI. Is there other ways to redraw UI?
calling adapater.notifyDataSetChanged()
From the documentation
Notifies the attached observers that the underlying data has been
changed and any View reflecting the data set should refresh itself.
notifyDataSetChanged() will redraw all views in your adapter.
A neat trick if you want to redraw only one view from your adapter is to call getView manually for it if its position is visible - i.e. when you have multiple rows and each one updates independently from the others. In such a scenario, it would be a waste to call notifyDataSetChanged every time a single row gets updated.
you can use notifyDataSetChanged() method for adapter.
Which is called as adapter.notifyDataSetChanged();
Which informs Adapter that background task is completed and now the data set is changed.
you can refer this
Related
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.
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
I'm using recycler view with grid view (every item contains a grid) with thumbnail images after adding images in view it start uploading, and i need to change some values (status) in model at the time of start and finish upload.
What I'm currently doing is change values in model and call notifyDataSetChanged, but it causes to slow down application (hang some times) because it updating every child of list :(
Can any one help me with this?
Call notifydatasetchanged() for particular Gridview adapter only. Don't call notifydatasetchanged() for complete recyclerview adapter.
Try setting it again to the adapter.
gridview.setAdapter(your adapter)
-passing your new list to your adapter.
I believe notifyDataSetChanged updates all of your values regardless if they have a change or not that is why it is slow. I suggest you try using notifyItemChanged(int position) instead.
According to recyclerview docs 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.
Old question but similar to what I'm experiencing.
RecyclerView is usually incredibly fast when changing list details. But manipulating a lot of images can really slow it down if you're not careul.
I'd recommend you try removing the images and repeat it so you can see if that is just as slow. I suspect this will be a lot faster.
If so, make sure you're handling the images off the UI thread. The Android docs recommend you use a library such as Glide which also handles sub-sampling the image to make sure it's the right size.
Hope that helps!
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 have an Activity that hosts a GridView. When the Activity is resumed, in the OnResume method, I want to update the UI of some item views (but not all) of the GridView because their underlying data has changed. I know that the GridView has the invalidateViews() method, but that is overkill because it recreates all views. In my case, I just want to update some views.
Is there an efficient way to achieve this?
Thanks
After changing the data of gridview call adpter with notifydatachanged() after that only it update the gridview with fresh dara
adapter.notifyDataSetChanged();
If you use invalidate views it will create view again