I have a fragment holding several lists, as you may guess the scrolling is a mess, so I give it a try to the cwac-merge adapter, it seems to do it's job fine, but I wanted to customize some of the items, i.e. I need some of the adapters to show or hide depending on how many items they have, right now empty list adapters are showing a blank space, and I would like to make them gone until items are retrieved.
On the screenshot (please excuse its blurred but Im not allowed to show the product yet) you can see I highlighted with red rectangles the empty spaces, where I'm setting the view to have Visibility = GONE.
Also one of these empty spaces is caused because an adapter has no items.
Is there a way to hide or show certain adapters or views inside the MergeAdapter so they don't occupy space?
Thanks
where I'm setting the view to have Visibility = GONE
IIRC, having a GONE row in a ListView is problematic in general. MergeAdapter should not have an impact on it.
Also one of these empty spaces is caused because an adapter has no items.
I rather doubt that. Hierarchy View should show you what is really going on.
Is there a way to hide or show certain adapters or views inside the MergeAdapter so they don't occupy space?
An adapter returning 0 from getCount() should occupy no space, if you call notifyDataSetChanged() on the MergeAdapter so that it can tell the ListView to redraw itself.
Related
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 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.
I am trying to create something like (very poorly created in paint) in the image below:
I have only 4 items, and it won't be more. the items contains two textviews. But when you click on an item, i want it to expand, (like item 2) to the bottom with three extra buttons. It would be really nice if there would be some nice expand animation. I don't want this list to be scrollabe, it just need to fits in my screen. And only one can be expanded.
I think there are two options, but maybe i am missing something.
1) Create an itemlayout.xml, containing an linearlayout or something containing the extra buttons, set to linearlayoutbuttoncontainer.setvisibility(View.GONE). And then build a switch, which closes the others than the clicked one, and set the visibility of the clicked item to visible. This would be fairly easy to build i guess, i don't foresee a lot of problems. But is it possible creating an animation or is there only a sudden screen change?
2) expandable listview, with the buttons in the expandable item. I know its possible to make only one item expanded, by rembering the expanded one and closing it again. But is it possible to make it like this, with the buttons in the expandable part? Actually i've never used an expandable view.
Anyone know what the best solution should be?
Thanks
I would recommend using an expandable list view for this, as your second option described. For this type of list you can use a expandable listview adapter, describded here:
http://developer.android.com/reference/android/widget/ExpandableListAdapter.html
This adapter has both a getGroupView(open/close items) and a getChildView method in which you can inflate your layouts, or manually set them up. If you have used ordinary listviews I'm sure this wont be a problem for you, since it's basically the same operations.
This means you should probably inflate your childViews with a LinearLayout containing three buttons. Then you have to implement functionality for your collapse/expand logics by keeping track of which item index is opened.
I did this tutorial when I first started out with exp.list views, I found it helpful:
http://android-adda.blogspot.se/2011/06/custom-expandable-listview.html
Good luck!
You gotta check this http://udinic.wordpress.com/2011/09/03/expanding-listview-items/ it works neat. If you got any more problems, do ask...
Can any one explain the difference between Scroll View and List View? When to use which one? And which one is more efficient?
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.
Simply ScrollView is for both homogeneous and heterogeneous collection. ListView is for only homogeneous collection.
They're completely different.
A ScrollView is simple a scrolling container you can use to scroll whatever you put inside it, which might be a list of items, or it might not.
http://developer.android.com/reference/android/widget/ScrollView.html
A ListView is very specifically designed to hold lists, where items typically look the same (or at least follow a pattern, e.g. section headings). ListView is also designed to connect to a data source of some sort, SQLite, array, content provider etc. ListView can scale to handle enormous numbers of list items.
http://developer.android.com/resources/tutorials/views/hello-listview.html
If you have data you need to show in a list, use a ListView. If you just need scrolling content, then a ScrollView is probbaly enough.
ListView:-
In ListView You can manage layout of items in xml easily that you want to display in list.
You are required to tell the adapter ho many item you want in your display list.
You can design for both homogenous as well as heterogenous views depending on your requirement by overrifing getItemViewType() method of Adapter.
In ListView items in list are created according to screen size. i.e How many items can appear on screen are created additional views(items) are created when list is scrolled at runtime. The views that are displayed once are cached when they move out of screen and when list is scrolled back to previous state the same views are displayed but this time view are not created rather they are fetched from cache.
ScrollView :-
Cache concept is not applicable with ScrollView.
All views are created at once when they come to screen and are not cached when they move out of screen while scrolling. They are present in memory(main) that may lead to memory leak because the number of objects created are not being destroyed by garbage collector since they are being referenced untill you are on same page.
Although you can create both homogenous as well as heterogenous views. If there are more items to be displayed in your list it would be tedious to manage the layout whether you are designing in xml or creating dynamically using Java code.
It is preferable to use scrollview if you have a single page that does not contain list of items e.g registration form, reservation form but that view is larger than the screen size then put ScrollView as parent view also keep in mind that ScrollView can have only one direct child layout/view.
ScrollView simply places its contents in a scrollable container, you can edit it's contents only by adding views to it.
ListView is a class that uses an adapter which handles creating the views for your data objects, you only need to edit the data, and the layout modifications are done automatically by the adapter.
ScrollView should be used when you have a screen (ex: a form with multiple fields) that do not fit into one screen on small devices, as such scrollview offers the user the possibility to scroll down.
ListView should be used when representing sets of data.
You can read about these at http://developer.android.com/guide/index.html
A ListView is backed by an Adapter, which contains a DataSource. This allows you to easily display data in rows.
A ScrollView allows you to put content inside of it, and if the content exceeds the size of the ScrollView, it will allow the user to scroll.
They both have their uses, but it depends on what you are trying to do.
Since an image worth a thousand words, here are perfect real life examples:
Listview is like the Kijiji app
Scrollview is like the EBay app
Also, see a scrollview like a billboard or a wall, where you can put bunch of different stuff on it.
And a listview is more like a result page: results are all of same nature, therefore they fit perfectly in a listview. Like a contacts list: they all share the same structure; phone number name address, etc....
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.