I have an app which loads a boatload of images and displays them in a TableLayout which is inside a ScrollView. At run time I get the width of the layout parent and use that to determine how many images can go in each TableRow (all of the images are of a set size).
I'm concerned about memory issues when loading more and more images. I know ListView recycles its views but I don't know how to dynamically change number of views in each item. I am only aware of inflating XML which isn't going to change the number of views per item at run time.
So my question is what is easier - figuring out how to recycle views in my table by myself, or making a list's items change based on screen size? Just a link to a tutorial on how to do whichever is easier is good enough an answer for me.
I suggest you to use ListView with the ViewHolder approach (you can see it here: How to load the Listview "smoothly" in android).
The ListView, when scrolled, removes the views that are no more visible and gets the views that are about to become visible. This way, it's better than using a ScrollView and a TableLayout.
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I understand we always use listview to display list of items instead of Scrollview. But I know we can do it with scrollview also. I understand that performance of list view is better than ScrollView when you want to display list of items. My question is there are any reason for that also? And why nobody use scrollview to display list of items? Please give me your opinion. Thank you.
I often use Scrollview for displaying a limit of items, this number rarely be changed on runtime, such as in a configuration page. Otherwise, ListView is for display a lot of items. Those items may be the same type such as a list of Students, Messages, etc.
ListView uses a concept of dequeueing that is removing view from the view hierarchy when they are not visible. For example if you have 20 items and only 10 are visible at a time.
The listview will remove the top 1st element when 11th element comes
into view using scrolling. This reduces memory load and gives smoother
performance. Battery consumption is major factor of phone these days
and no one wants a app that consumes all the phone battery.
Scrollview on the other hand keeps all the view added in it in the view heirarchy all the time therefore increased memory usage and performance issues when the number of views added are huge.
ScrollView is used to put different or same child views or layouts and the all can be scrolled.
ListView is used to put same child view or layout as multiple items. All these items are also scrollable.
A scrollview on the other hand is quite different. You add other views to a scrollview which allows you to have more elements than what would fit on screen. Say, for example, you wanted to have 50 buttons or a large chunk of text. By using a listview you have a container that is the size of the screen but allows the user to scroll up and down to see the other views.
Am trying to create a page with a scrollable list. Features would be a normal list to remove item by clicking on it. Number of items in that list are limited and added dynamically by user. You can consider a to do list as example. Now which would be a better approach to implement it? Recycler view with data bound to its adapter? Or the normal linear layout with items added as children at run time?
My current implementation is recycler view. But,I found it lagging and animations are not performing well. So a linear layout is auto animated by specifying it xml -- by setting animate layout changes to true.
FYI data is local and syncs in background.
Never use a LinearLayout for anything longer than a single screen. The whole point of ListView and RecyclerView is to efficiently reuse views instead of needing to hold things in memory when they're not visible. Maybe you can refine or reask your question so people can help you with whatever difficulty you're having with animations, rather than avoiding the issue.
I have an Android fragment in which contains a Vertical LinearLayout with two layouts inside it: Another inner Vertical LinearLayout (which takes at least half of the screen) and a ListView (which shows a number of smaller Views). A good way to think about it is something like a facebook post along with several comments showing below it.
The problem I am facing is that the the inner LinearLayout is not scrollable and therefore parts of the ListView stays outside of the screen and there is no way to scroll the screen up to see the entire ListView (the inner layout could possibly take up the entire screen). Placing the entire layout inside a ScrollView is also known to be a bad practice.
I know one solution is to make the entire layout to be a ListView with the first cell to be the inner LinearLayout, followed by the cells from the original ListView. That however has its own issues: It is harder to recycle the views in the ListView, and generally I also see it as a bad practice where one cell has a different behavior from all other cells in the ListView.
Is there a better solution to this? I can imagine this is a typical problem and I hope to find a better solution than above.
This may help you:
ListView yourListView = new ListView(this);
yourListView.addHeader(getHeaderView());
You can also add footer to a ListView. When you do this, the header(or footer) will become part of the ListView, and so it will be scrollable. You can find the document here: http://developer.android.com/reference/android/widget/ListView.html.
I know how to populate a ListView or any other list types, but now I am facing an issue where I should implement a ListView in a ScrollView. So, I decided to use a LinearLayout ( myLinearLayout.addView( adapter.getView(position, null, null) ). As you can see, I am retrieving data from adapter and adding as a new view to my LinearLayout. Everything is working, but if the list is being populated with 30+ rows the application freezes. Each row contains an ImageView and this way the virtual machine can't allocate enough memory.
How I should recycle linearlayout rows?
It doesn't look like a good idea to put a listview inside a scrollview. How are your users gonna use that ? Which gesture will scroll the scrollview and which one will scroll the listview ? It's not going to be usable.
Android components are well designed, you should really consider sticking to a listview that every one knows how to use and is pretty well optimized.
If you have troubles displaying many images in a list, refer this docs from google.
Once you populate the row into a linear layout the views aren't recycled by the adapter. As you wrote its also not possible to have to scroll components one inside the other. Why do you need to show list inside scroll? Did you considered populate the list "on top" of the scroll view? For example in a different fragment?
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.