I try to migrate my iphone app to wp7.
On ios, UITableview is well designed, and very easy to code.
I have the some book about wp7, but there are no detail concerned about moving and removing of a row of listbox.
Welcome any comment
I'd like to think that Windows Phone is also well designed. :)
To simply remove an item from a ListBox in your codebehind, you need to get a reference to the ListItem that you want to remove. For example, to remove the currently selected item:
var myListItem = myListBox.SelectedItem;
Then you can remove it with:
myListBox.Items.Remove(myListItem);
In order to address your question about moving items, we'd need to know more about how you're populating the ListBox. Are you using databinding, or adding items with myListBox.Items.Add(myListItem)?
If I needed to move items between two lists, I would create a public List<MyItem> property for each list and databind each list to its own ListBox. Then I might do something like this (working from memory here):
var itemToMove = myList1.Remove(myListBox1.SelectedItem);
myList2.Add(itemToMove);
myListBox1.DataBind();
myListBox2.DataBind();
There's a much better way to do this, using INotifiyPropertyChanged, but I suspect you need to play around with the basics for a while to get comfortable in C#.
Bonus tip: Windows Phone is very similar to Silverlight, and you can usually find more information if you search for Silverlight examples.
In WP7, usually we set the ItemSource of listbox, when our source changes its changes automatically propagate to the UI due to data binding ( it is known as one way binding ; source to UI ).
so what ever you do ( add, update or delete) in itemsource, it reflects to UI.
databinding in wp7
Related
I am trying to build a form with a phone input that includes country codes. Essentially, I am trying to make something a lot like this:
I already found and cleaned a list of flags, countries, and their codes, and built the method that creates a DropdownMenuItem for an arbitrary index. I then construct a list of them and pass it to the DropdownButton widget. It's all very simple, so I don't think the code is necessary. However, because I have so many countries, and therefore menu items, the menu lags significantly when opening. So, I was wondering if drop down menus are capable of loading large numbers of widgets in a smarter fashion than it seems they do.
Can a drop down menu could load the first 10 or so widgets around the selected index and display them, as that is all that will be in view initially, and then load the rest of the widgets asynchronously? I suspect that this will require a custom drop down menu, but I am not very well versed in the implementation of Flutter's drop down menu, so I am unsure of how to proceed with this.
Any help is appreciated.
I don't think that "loading" is the actual problem here, more likely it's the rendering/building of the widgets. You can improve the situation by using something like a ListView.builder that builds items on demand.
It seems like the default dropdown system is not based on a ListView.
You can create your own version of the dropdown (like a complete customized copy of the classes), which will require quite quite a lot of work and research.
Or alternatively, use something like a SimpleDialog with an embedded ListView to display the list. Like this one for Android.
I'm trying to work out how to catch a data binding in the act (either intercept or post-process) to customize the display of data in the target control.
I know about IValueConvertor and understand that I can transform a simple value into another simple value, but I don't believe this is enough for my needs... which are:
The control in this case is a TextBlock and the data values from the objects in my ObservableCollection are variable length strings. I want to render the strings in multiple colours by splitting them into pieces and programatically creating a <Run Foreground="xxx" Text="yyy"/> for each piece inside the TextBlock.
Since the strings are variable length and the colours have to be programatically determined from the content of the string, I don't believe I can pre-create the <Run>s in the XAML, so I have to somehow get in on the data binding action and generate the <Run>s at bind-time (or very soon after).
Binding.NotifyOnTargetUpdated would seem to be a way to set up an event handler to do the work, but that's not available in the Windows Phone cut-down Silverlight implementation.
Any ideas? All search results seem to point to the above, but I'm looking for that little bit more.
Having apparently exhausted all the cut-down Silverlight on Windows Phone options for programmatically hooking the rendering of ListBoxItems via the data model, I ended up adding a Loaded="..." event handler to the XAML for the TextBlock.
It doesn't feel like the nicest solution, but perhaps that's just my code-preference talking and it's actually the right way to do it on Windows Phone.
In any case, because I'm hooked to the TextBlock directly, I'm not sure how to then get to the databound object on the ListBoxItem containing the TextBlock... if anyone has advice on how to get back up the tree to the generated ListBoxItem then I could use the bound object directly instead of retrieving it from elsewhere.
Note that since the ListBoxItem is generated, I didn't find where to put a Loaded="..." event handler for that in the XAML. The ListBox.ItemTemplate doesn't accept a Loaded attribute.
Update: this doesn't work!
The Loaded event handler fires when the TextBlock is first created and loaded, so the substitution works initially.
BUT
The generated ListBoxItem seems to be recycled (I guess by the ListBox.ItemContainerGenerator which doesn't want to use excessive amounts of memory by instantiating a whole new container when there are many off-screen entries in the list that won't need to be seen for a while) and when this happens, the Loaded event DOES NOT FIRE.
Since I modify the content when the TextBlock was first Loaded, this breaks the binding association so when the ListBoxItem is recycled, it now contains old/incorrect data.
Still no solution.
I'm thinking about trying to use an IValueConvertor and somehow pass a reference to the binding target... now sure how yet though.
Update 2: finally got it to work...
Sticking with the Loaded="..." event handler, it is possible to disable recycling of previously-generated ListBoxItems by configuring the VirtualizingStackPanel used by the ListBox under the covers.
In the XAML for the ListBox set VirtualizingStackPanel.VirtualizationMode="Standard" to force a new ListBoxItem to be generated each time instead of recycling previously-generated ones.
This means the Loaded event handler is called every time and I can replace the ordinary text of the TextBlock with the <Run>s to produce dynamically coloured text.
As my app gets bigger I am finding that the same type of entity is appearing more and more throughout, typically in a listbox.
When someone taps on the entity, I want to navigate to the detailed view of this entity.
An example of this would be a product: it appears in a product list by category, it appears in search results, or it might appear as a saved favourite. In my instance, all of these would come from a table in local SQLCE storage.
Every time I surface the entity in some way that someone could tap on it, I basically cut the same code: subscribe to the SelectionChange event on the listbox, extract the entity, use MVVM Light messaging to signal that the selected entity has changed, then call NavigationService to do its business.
Has anyone worked on something similar and, if so, what have you came up with? Or more importantly, if there's some MVVM Light toolkit convention that I'm overlooking, could you please point me in the right direction?
Are you calling the NavigationService from code-behind or the View Model now? If the former, you could check the WP7 Navigation arcticle by LBugnion for triggering it from the VM. If you combine that with the EventToCommand behavior (like in here) you should be able to create a nice and clean "MyEntitySelected" command in the VM which takes the entity as a parameter.
I think the question here is, how do I deal with this without cut/paste the same code each time? If this is the case, maybe trying to package the entity/listbox thing in a XAML usercontrol! Take a look at this: http://www.windowsphonegeek.com/articles/Creating-a-WP7-Custom-Control-in-7-Steps
Then if the representation needs to be different, you could have a look at this: http://www.windowsphonegeek.com/articles/Implementing-Windows-Phone-7-DataTemplateSelector-and-CustomDataTemplateSelector ( this example does different styling in one listbox, but you can change this to only apply different style on each different page with a listbox on it )
I am using the LongListSelector from the Mango Silverlight toolkit.
But I need to be able to set 'MaximumFlickVelocity' and 'BufferSize' but neither do anything.
For example:
<toolkit:LongListSelector IsFlatList="True" MaximumFlickVelocity="10" BufferSize="5" IsBouncy="False">
The properties there have no effect at all, except 'IsFlatList'.
Thanks.
EDIT: I just noticed in the documentation that all the properties I need at marked as Obsolete. So could anyone tell me what alternatives I have? Because the performance on this isn't great at all.
It depends on the kind of list you have. If you can afford to load more items into the list, as the user scrolls to the bottom of the list, you can use the StretchingBottom event on the longlistselector.
The property IsBouncy defaults to true in the latest release, so StretchingBottom is fired everytime the user scrolls to the bottom and then some.
In essence, you can play with the events and the ItemsSource property to improve the performance in an extremely long list. Well, I am not sure if it will be of much help, but it`s worth a try.
Good luck.
This is easy in .NET (not my question) but I'm trying to figure out if it is possible to simply change the text of a string in a Win32 list box control given an index.
There is a GetText function that takes an item index but nothing to change the text of an existing item/string. My workaround will be to remove it and add it back in the box (which is also a weird prospect since there is no single command to add a string + item data -- these must be done carefully by inserting the string and then setting the item data on the index of the inserted string, which is tricky (not possible?) with sorting active).
Yes, the lack of a LB_SETITEMTEXT message is a bit weird.
You should put your Delete+Insert+SetData calls between calls to WM_SETREDRAW...
At the risk of being off topic...
I tend to use the ListView control all of the time. You'll want it in report view to mimic a listbox, and, as a plus, it supports multiple columns.
Oh.. and it has a LVM_SETITEM Message :)
http://msdn.microsoft.com/en-us/library/bb761186(v=VS.85).aspx
Although this question is old, but I think this documentation presented by Microsoft will be able to answer anyone questions based on this one.
So according to Microsoft documentation which you can find here
Changes the text of a list-view item or subitem. You can use this
macro or send the LVM_SETITEMTEXT message explicitly.
void ListView_SetItemText(
hwndLV,
i,
iSubItem_,
pszText_
);
And it also presents other macros for managing the list box. You can build a wrapper around this macros to simplify handling list view controls, etc.