I need to display a complicated list in my app. On each row there will be a checkbox and some TextView.
I know this could be done via ListView/Adapter, but I was worried it requires too much tweaking to make it fits my specific requirement, so I just created my own customized MyListView inheriting LinearLayout. On initiating, it adds MyListViewItem (inherited from RelativeLayout) dynamically.
The customized view functions fine. However, I notice that the rendering speed of MyListView is a little too slow, so I wondered will it be faster if I use ListView/Adapter instead?
Thanks,
The benefit of using ListView rather than a great big LinearLayout is that the OS can do a better job of optimizing when views are inflated, and the recycling of views, based on what is actually visible to the user. It also makes it easier to perform common actions such as scrolling to a particular row.
ListView recycles its items. So, yes, it will work much more efficiently in case of a large number of list items. And as a result you'll obtain a less complicated view hierarchy.
Related
I am trying to achieve a gridview with a different number of items in each row, depending on the width of each item. I want it to look like the one on the Medium app, as shown below:
How can i achieve this?
You can approach the problem in two main ways:
Use ScrollView with a Linear- or RelativeLayout inside. Then you would add the items in your code, measuring each and putting them into new rows when required. This will require some logic to be created, but is achievable. The ScrollView will take care of the scrolling in case the contents exceed the screen height. The problem with this solution is that you will not have a recycling mechanism, which can lead to problems with memory when the list gets long.
Use RecyclerView! :-D One of the awesome features of the RecyclerView is the fact that while providing the standard Adapter-based concept of the list of items, it also allows you to implement a custom LayoutManager. Create your own implementation of LayoutManager which positions the items based on their measured with and you are done, the RecyclerView will take care of scrolling and recycling the items for you! :-D This will take some getting used to, especially if you have no experience with RecyclerView, but the whole thing should take no more than several hours and is, in my humble opinion, really worth it.
You are free to choose either, but the second approach is more modern and, in general, easier to implement. In general, you should learn to use the RecyclerView, it helps a lot and is quicker to implement than the good old List- and GridViews, once you get the hang of it.
Do we get any benefits of implementing a ListView for which every item would have different layout? Would it be a better idea to put those items into ScrollView with LinearLayout instead?
Intuitively, it seems like using a ListView may still give better performance, though it might be negligible depending on the size of your content. Because the ListView inflates the views as it needs them, it seems like you might save some time by not parsing/rendering views that a user might never see. A long ScrollView with a bunch of views inside seems like it would take additional time when first launched, since the view hierarchy is more complex.
I do think Michael is mostly correct though, that the main advantage of a ListView is that views are reused, which saves on memory/processing. Unless you have a ton of content in the ScrollView, I suspect the performance difference is not significant, and will almost definitely be more complex -- in particular, having to create an adapter that knows how to create each view type for each row.
I don't understand why you may use ListView for this. Listview is a list of common data using the same layout if you click on it. Users depend on same/similar GUI patterns.
How about Sliding Tabs or the newer navigation drawer, link NavigationDrawer.
If you like sliding tabs, then I can give you more details.
I´m facing the implementation of a View where I have to load perhaps almost 100 items in a list. I have a doubt in which maybe the best way to implement it.
I already know that ListView recycles the views and ScrollView keeps all in memory. The point is that I was thinking in apply paging to the Scrollview to avoid huge loading times when the app inflates all items.
Applications as Google+, Facebook, twitter or Linkedin, Do you think they use ListView?
Thanks
ListView is definitely the way to go. It's easier to use than ScrollView, and a paging system doesn't fit in with the style of android.
ListView is meant to create a list of varrying lengths based of an array of information. ScrollView is for having a (usually) set amount of children in the View (defined in the layout xml).
ListViews do not inflate all items, they inflate however many can fit on a page at a time. Your fastest option, with or without paging is a ListView. However, if each child is completeley different, then ScrollView is the way to go.
I have a ListView with each item being a custom layout with multiple Views (including a large image of ~445x250, a smaller image of ~40x40, etc). While scrolling, the animation is extremely choppy.
Can someone recommend how I can improve performance?
One approach I tried was to eliminate any transparency in the images being used. This did improve it slightly, though there is still a noticeable lag when before a new item scrolls into view.
Update:
Here's the View heirarchy for the custom layout (for each item) - http://pastie.org/3333903
Looking at the layout provided, there are a few things that may cause performance issues:
Your View Hierarchy has a depth of 4. You should make your View Hierarchy as shallow as possible. Consider using a RelativeLayout/TableLayout where possible instead of nested LinearLayouts.
You have nested weights. Try to avoid having nested weighted views.
You have a lot of views for a row item. Remember the purpose of a ListView - if your rows start becoming complex, it may be a sign to look at something else to display this information.
A GestureOverlayView seems a bit heavy for a ListView row item. Is this necessary? Considering ListViews a scrollable by touch, having custom gestures on row items may be a bit confusing.
You can also try using android:persistentDrawingCache="scrolling" and the ViewHolder pattern to squeeze out a bit more performance.
If you download the latest version of ADT, it will also guide you in optimising your layouts.
Apart from layout optimisations, minimal work should be done in the getView method of your ListAdapter.
Additionally, you can use android:hardwareAccelerated="true" to take advantage of hardware in Android 3.0+.
You can use the dynamic table layout instead using the List view. It will improve the performance. Dynamic table layout will adjust the large image and smaller image. It will be of help to you.
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.