I have a need for both horizontal and vertical scrolling of some data in my app. I've overridden HorizontalScrollView and I've allowed it to take an Adapter to populate its data. It behaves much like a horizontal ListView would behave, except I'm not doing any view recycling. Each item in my custom HorizontalScrollView is a ListView whose items are also populated with an Adapter. Each item in the ListView is a complex view.
I'm able to scroll horizontally, and vertically just fine except that it's performance is a bit chunky. The getView() method in the adapter for populating the custom HorizontalScrollView is only called when the Adapter is first set on the view. However, I noticed that getView() is constantly being called for the ListViews in the HorizontalScrollView. I'm wondering is this is the performance problem?
This question points out a supposed documentation bug pertaining to using a ListView inside of a HorizontalScrollView, but the same warning is not given in the documentation for the vertically scrolling ScrollView documentation.
Will I have performance issues if I put ScrollViews inside of the HorizontalScrollView?
Giving the ListView a dip value for layout_height did the trick. Not setting a height was causing the ListView to keep measuring, calling getView, etc.
Related
I have created a listview inside scrollview. Atfirst it was not scrolling but when it started scrolling then layouts below list view started disappearing from screen. is there any solution to dynamically calculated he height of list view and assign it or is it possible that some how the scrolling of listvew is disabled so that only its items appear on screen like normal layouts or any tags and it does not scrolls???
ListView is deprecated. I would suggest you to use RecyclerView and add nestedScrollingEnabled="true" to your xml or call RecyclerView.setNestedScrollEnabled(true) if you want to wrap adapterview with a scroller. You can also try NestedScrollView for support compability.
Good luck
I have a ScrollView that contains several other views and I would like for one of these views to be a grid of other views having the same layout (e.g. ImageView).
Since having one scrollable view inside another is not recommended, I would like this grid view not to be scrollable, otherwise I would have used GridView or RecyclerView.
Surely I can place the grid views inside one of the standard layouts (e.g. TableLayout) but this may cause memory issues when many grid items exist.
Is there any standard approach or a library that allows to recycle views for a non scrollbale view inside ScrollView?
If you try to force GridView or RecyclerView to be non-scrollable (so basically you would have to force the dimensions of the view to display all the elements) you will end up in the same situation as if you used TableLayout (so you would need to watch out for memory issues).
If you disable the scrolling of scrollable (recycling) elements like GridView/RecyclerView you disable the most important part that makes those things work efficiently (that makes those things reuse their views).
The way you should solve your issue is to implement your other Views of your ScrollView as a part of the RecyclerView. Your RecyclerView should be equipped with the adapter that can inflate multiple types of Views (you can read about it for example here).
Since you are using RecyclerView you could use NestedScrollView instead of ScrollView They should play more nicely since RecyclerView extends from NestedScrollingChild and NestedScrollView extends from NestedScrollingParent.
Other views you can use are VerticalGridView or HorizontalGridView but as you said you are worried about performance issues and you can provide a GridLayoutManager to the RecyclerView I would stick with that.
I have a LinearLayout with a nested listview which looks like this:
<LinearLayout ... >
<LinearLayout>
</LinearLayout>
<ListView>
</ListView>
</LinearLayout>
The problem is that the listview owns the scrollbar (so only content in the listview is scrollable) but i actually want the parent LinearLayout to own the scrollbar (so making the entire content scrollable).
Wrapping parent ListView in a ScrollView hasn't been successful because the ScrollView doesn't recognize ListView height (which looks like is rendered at running time)
Thanks
Edit: SOLVED My perfect solution was using a MergeAdapter, as advised by Barak
You can use CommonWares MergeAdapter which allows you to define views and list adapters, pour them into the MergeAdapter and get a single list adapter out, containing everything you poured in, and it scrolls as one list.
A previous answer about MergeAdapter I gave with some instructions is here
You could replace the Listview with a Tableview instead, as long as the listview does not have too many items in it. You can still use a childview with the tableview in much the same way as the listview, you just won't be able to databind it in the same way as you can with a listview, and the items won't recycle either.
Since the listview is designed to contain more items than can be displayed the height will never exceed the screen size (best case) which is the intent of the control, though I suppose you could force it to be larger that seems generally like a bad idea for a lot of reasons.
I suspect what you should do is either create a custom listview adapter, and based on position in the list create the view you want, this would allow all items to scroll like you want.
Listview with different view types per row
This may or may not work depending on what exactly you are trying to do, otherwise you might just want to add views to a linear view inside a scroll view san's the listview.
It just depends on the use case (how many items in the list view, memory issues etc) and what the purpose of the other views are.
I'm making a GUI with two different parts. The first part (at the top) is composed of some banners, several fixed buttons. So I think using LinearLayout is the most straightforward way to implement. The second part is composed of several similar items grouped together which can be implemented by using ExpandableListView, I think.
However the problem is that the content exceeds the screen size. So I intend to put two of them into a ScrollView. I checked several sources, it seems that putting "ExpandableListView" inside a ScroolView is NOT possible, or not efficent, so I'm afraid...
Would you help to confirm if this is possible? efficient ?
If no, would you give me some recommendations for this layout design?
I'm indeed looking forward to your supports.
Sincerely.
If you have a fixed header at the top of a list, use ListView's header view feature.
Putting ListViews in ScrollViews fundamentally makes no sense and here is why:
ListView has one purpose: to efficiently display unbounded data sets. Since these can be extremely large (tens of thousands of items and more) you do not want to create a View for each item up front. Instead, ListView asks its Adapter for Views only for the items that currently fit in the ListView's measured space on screen. When an item's View is scrolled out of sight, ListView disconnects that View and hands it back to the adapter to fill out with new data and reuse to show other items. (This is the convertView parameter to an Adapter's getView method.)
ScrollView also has one purpose: to take a single child view and give it "infinite" vertical space to fit within. The user can then scroll up and down to see the full content.
Now given this, how many item Views would a ListView create for a 100,000 item Adapter if it had infinite height available to fill? :)
By putting a ListView inside a ScrollView you defeat ListView's key purpose. The parent ScrollView will give the ListView effectively infinite height to work with, but ListView wants to have a bounded height so that it can provide a limited window into a large data set.
Well Expandable List View itself has scrollable property by placing it in scroll view is really undesirable.As the both scroll would contradict and smooth scrolling can't be obtained in that case..
If we have any data to be shown prior or later to list...
Best way is to use header and footer view to list...
I recommend you use header and footer in your case.
The documentation for HorizontalScrollView has the following:
You should never use a
HorizontalScrollView with a ListView,
since ListView takes care of its own
scrolling. Most importantly, doing
this defeats all of the important
optimizations in ListView for dealing
with large lists, since it effectively
forces the ListView to display its
entire list of items to fill up the
infinite container supplied by
HorizontalScrollView.
The reasoning here seems to apply to a (vertically scrolling) ScrollView, since ListView also scrolls vertically. But ScrollView doesn't have any such caveat. Did Google put this warning in the wrong class, or am I not understanding something?
Looks like it is a bug indeed: http://code.google.com/p/android/issues/detail?id=2781