I have a ListView that displays a set of notes, each with varying ammounts of data (i.e. some have a due date, others don't).
Currently, each view in the list is a RelativeLayout containing a TextView for each field, plus two Button and a CheckBox. I then simply hide the unused fields by setting visible false on each one.
This has worked well, but I'm about to add a lot more data fields to the notes and inflating that many unneeded views for each row will surely kill my app. I need a more dynamic solution.
I've decided the best way to go is to create a custom view. How can I implement/design my view so that it can display a variable number of text fields without creating/destroying textviews each time (which would be quite expensive and worse than my current situation), or maintaining a large pool of hidden textviews?
You can create a class that extends LinearLayout
and use addView to dynamically place your views.
Sounds like you might want to look into a view with a stub. The stubs will save space until they are inflated, so each row will be lighter until it is used on a heftier view. If you have a relatively low number of these larger views you might save a bit of overhead.
Related
This is how my screen should look like. The problem for me here is, I should pass User object to adapter and fill those fields with user object fields. How could I know which field to update if I create child layout with one TextView?
Is it a better idea to create for example DetailsViewHolder, AddressViewHolder, etc? Or I can create details.xml with 6 Edittexts? but I don't think that's a good idea, right?
ListView is best for long lists that may change with time. For your situation I wouldn't recommend using a ListView at all, but rather a simple LinearLayout. It is much easier to work with and gets the job done perfectly. If you need scrolling, just wrap the LinearLayout inside a ScollView.
If you are creating a very dynamic list, say, where every row can have a different set of input types plus optional buttons, and the list length is based on another dynamic value, is it better to do this in a list adapter or creating a custom view in a scroll window?
After struggling with list adapters for quite a while now something finally occurred to me- this seems dumb. It seems like I am going through a lot of work keeping track of what spinner is set to what value, which row was clicked and so forth.
For example, say you are showing something like a contacts screen with various details that can be entered about a contact. Some rows will have text inputs (name, address etc), some will have spinners (ie. state, group), some will have checkboxes (like 'favorite' or something). Also, there is an 'add' button that allows you to add another field to edit. Is it worth making this in a list adapter or is it better to populate a custom view, and if the "add" button is clicked, we re-create the custom view, adding a view of the type they want to add?
I hope this is clear.
ListViews (and List Adapters) are meant for data that is to be displayed in mainly similar views. For your example, it is much easier and more natural to have a predefined layout file with the screen and use view visibility so select which views are to be shown. If you need to add views to the screen you can do this dynamically by using findViewById on the layout and then using it's addView method.
Let me know if you need more clarification or sample code...
I have a standard layout and i have to populate it at runtime with a number of controls/views i.e. TextView / EditText depending on the number of products that come back from a REST service.
Of course the control I wish to add to the layout at runtime needs to contain a number of views (textview, edittext) etc. I was thinking a custom control to bring all the controls I need I am unsure.
The other idea I had was to inflate and existing XML into my layout but I am unsure if this is possible or if it was or would I control the ID names - inserting more than 1 would cause duplicate id's?
I will try and explain in detail what I am trying to do, we can wrap it in a for loop for test which would count form 1 to 5 hence 5 controls would get populated on my layout.
The custom controls would have a TextView which describes the product. The Edit text where the user can enter freely the amount in numbers using the virtual keyboard and a spinner control to the right of the EditText which would allow the increasing of the EdtiText value.
So all pretty simple eh ? :-) but of could I class all these controls as 1 specific view and I need to a number of them on my layout hence if there were 5 products there would be 5 custom controls, each custom control contain controls i.e. TextView, EditText and Spinner.
How can I accomplish this?
The examples I have seen have been inheriting from VIEW but I need my VIEW (CUSTOM CONTROL) to be a container for a number of other controls and then later be able to dynamically add this new custom control onto my Activity Layout.
What about using a ListView with custom adapter...
check http://www.ezzylearning.com/tutorial.aspx?tid=1763429
http://www.framentos.com/en/android-tutorial/2012/07/16/listview-in-android-using-custom-listadapter-and-viewcache/
You may want to use a ListView with a custom Adapter, and update the adapter with the information from the service.
is there any type of 'repeater' type functionality in android? I have a relative layout (inside a row in a listview) and inside that I'd like to have a series of TextViews be displayed one after the other (as if they are child rows in the listview row). The issue is that the number of those "child rows" will vary. is there any way to do this, or should i just create the TextView objects in code, and programatically add them to a linear or table layout?
The closest thing (besides ListView/ListAdapter, naturally) that I can think of offhand is ViewSwitcher and ViewSwitcher.ViewFactory, but there's really nothing magical there: it's an interface that you can call to get a view.
Since it's only one line to get a view and add it to your current hierarchy anyways, though (View.inflate(context, R.layout.somelayout, myContainerViewGroup)) it feels silly to go with something heavier, but if you feel better wrapping that up in a Factory of some sort, check the AOSP source for ViewSwitcher.
One option is TextViews support Multi-line text. So you could create the text with a StringBuilder using "\n" for new lines, and not have to worry about multiple text views.
I have a RelativeLayout with different elements. I was planning to have two ListViews on it, but I have noticed there are some problems with scrolling. Since each ListView only shows a maximum of 5 rows should I try to make some kind of custom adapter to merge those ListViews? Or is it better to replace the ListView with a LinearLayout/RelativeLayout and add the rows as I get them manually? (like the first answer in here: android listview display all available items without scroll with static header ).
Which should be the proper way on doing this? or is there another way? Also, each row will have an OnClickListener.
There's two solutions if you'd like to keep your list... list-y, without having to prerender all the row Views like the above solution suggests (which can be slow to render, eats RAM and doesn't scale nicely to more than a screen or two of Views, but is a fine quick solution for smaller lists, though I'd just use a bunch of Views in a LinearLayout in a ScrollView rather than a ListView in that case).
Write a custom ListAdapter, overriding getItemViewType, getViewTypeCount and GetView to inflate the proper kind of view and recycle appropriately for your two types of views. You'll also either need to override getItem to contain custom logic for figuring out which set of source data to look in and to map the data accordingly, or mush the data down into one list of Objects (if you're using an arrayadapter) and cast in the getView method (probably a bit slower than handling it in the getItem without casting).
Just use cwac-merge, a view-and-adapter wrapping adapter. You can put two ListAdapters into a MergeAdapter and set that as your single ListView's adapter.
I had problems with scrolling. I never figured out how to have the ListView share vertical space with a different View, and have a single scrollbar for them both.
I worked around it by having everything that needs to scroll on the layout a row in the ListView.
Adding views as rows to a LinearLayout may have problems scaling up, but I think you'll be OK if you only have 10 rows in total. On 1st gen Android devices it'll probably start to get sluggish around 20 items (depends on Layout complexity obviously). ListView scales up by only inflating views as they come on screen.
So in answer to your question either of the two alternatives you suggest will be OK, but the LinearLayout option will be the easiest to code.