My application is in MVVM architecture.
I Have photo.xaml page in which i have one 1 ListView whoose bindingcontext is ObservableCollection listphoto of photos which is defined in its viewmodel.cs file.
now i have to redirect to BarcodeScan.cs from button click of photo.xaml .
my que i how can i add item to listphoto from here(BarcodeScan.cs )??
I tried to define new list in BarcodeScan like this
public ObservableCollection<JobPhoto> ListSerialNumbers { get; set; }
and intialised in its constructor like this
ListSerialNumbers = new ObservableCollection<JobPhoto>();
but it dont update list on photo.xaml page.
how can i achieve this. I am new to MVVM.Please Help.
Thank you.
You should use messaging center for this
First get it method registered as :
MessagingCenter.Subscribe<YourObjectClassComesHere>(this, "Any Message or empty string will be okay", (Obj) =>
{
//Code you want to execute
});
After this you can invoke it from another page as
MessagingCenter.Send(YourObject(of type "YourObjectClassComesHere"), "Any Message or empty string will be okay");
Hope it helps.
More details are available at : https://developer.xamarin.com/guides/xamarin-forms/application-fundamentals/messaging-center/
You can try MessageCenter https://developer.xamarin.com/guides/xamarin-forms/application-fundamentals/messaging-center/
In Phonepage you subscript message and send a message from another page.
I Have photo.xaml page in which i have one 1 ListView whoose bindingcontext is ObservableCollection listphoto of photos which is defined in its viewmodel.cs file.
Firstly it would be worth showing your XAML code.
You say in the quote above that you set the bindingcontext of the listview to the collection. You should be setting the ItemSource property of the ListView to the collection.
Related
I have a Xamarin.Forms app with a master-detail page and it works well.
But I've recently needed to add a parameter to the constructor of the master page (AttendPageMaster), but now I need to pass this constructor.
How do I add a parameter to the xaml?
<MasterDetailPage.Master>
<pages:AttendPageMaster x:Name="MasterPage" />
</MasterDetailPage.Master>
The code behind page with constructor:
public AttendPageMaster(AttendanceViewModel viewModel)
{
}
Let me know if you need any more info.
You do not have to pass ViewModel to Page via constructor, you can set the Page's BindingContext:
<MasterDetailPage.Master>
<pages:AttendPageMaster x:Name="MasterPage">
<pages:AttendPageMaster.BindingContext>
<myViewModels:AttendanceViewModel />
</pages:AttendPageMaster.BindingContext>
</pages:AttendPageMaster>
</MasterDetailPage.Master>
This solution will work if your ViewModel does not expect any parameters in constructor. Otherwise you may consider using ViewModelLocator and DI to inject the constructor parameters.
Please note that myViewModels should be defined in the header of your XAML page as xmlns:myViewModels.
P.S.: Previously you mentioned that you got an exception while trying to use code behind approach. You could easily solve it by setting the Title property of the AttendPageMaster. Example:
new AttendPageMaster(new AttendanceViewModel()){ Title = " " };
I managed to do this from the code behind by creating the menu page in the constructor of the masterdetail and assigning it to the "Master" property:
AttendMasterPageMaster MasterPage;
public AttendMasterPage(AttendanceViewModel viewModel)
{
MasterPage = new AttendMasterPageMaster(viewModel);
Detail = new NavigationPage((Page)Activator.CreateInstance(typeof(StartPage), viewModel));
Master = MasterPage;
I'm trying to bind CheckedChange from monodroid CheckBox to a command, but I get an error.
I want to unselect another item when a particular one is checked.
I think it is possible to do it with EventTrigger in wp7, but MvvmCross for android doesn't seem to support this feature.
Is MvvmCross limited to Button only ?
Thanks in advance for your help.
CheckedChanged is an EventHandler<CompoundButton.CheckedChangeEventArgs> so it isn't one of the delegate types that MvvmCross automatigically knows about.
However, there is a custom binding in place for this...
https://github.com/slodge/MvvmCross/blob/vnext/Cirrious/Cirrious.MvvmCross.Binding.Droid/Target/MvxCompoundButtonCheckedTargetBinding.cs
And this custom binding should be registered using:
registry.RegisterFactory(new MvxSimplePropertyInfoTargetBindingFactory(typeof(MvxCompoundButtonCheckedTargetBinding), typeof(CompoundButton), "Checked"));
in https://github.com/slodge/MvvmCross/blob/vnext/Cirrious/Cirrious.MvvmCross.Binding.Droid/MvxAndroidBindingBuilder.cs
So if you have a ViewModel with a property IsSpecial
private bool _isSpecial;
public bool IsSpecial
{
get { return _isSpecial; }
set
{
_isSpecial = value;
RaisePropertyChanged(() => IsSpecial);
// your custom code here
}
}
then this binding should work:
'Checked':{'Path':'IsSpecial'}
And that should work for any CompoundButton - CheckBox, Switch, or your own compounds...
I'm trying to add ListItems to a ListBox (ListBox3) depending on the selectedItem of another ListBox (ListBox1). The problem is , The Items aren't added to the Listbox.
Here's the code :
private void createlist()
{
if (listBox1.SelectedValue.ToString().Equals("EPL"))
{
ListBoxItem manchesterunited = new ListBoxItem();
manchesterunited.Content = "Manchester United";
listBox3.Items.Add(manchesterunited);
}
}
private void listBox1_SelectionChanged(object sender, System.Windows.Controls.SelectionChangedEventArgs e)
{
createlist();
}
createlist() does the changes and is called in the SelctionChanged() event of ListBox1.
New to C# and WP7 programming , any help will be much appreciated.
Create the lists in your viewmodel and bind the listbox to a list<> in your viewmodel say SelectedList. When the user selects the item from ListBox1 just change the value of SelectedList with the appropriate List and Notify the property changed event. And it will be done.!
i think you program not run in mvvm structure.
make sure your logic is right. you can make a breakpoint at the line
ListBoxItem manchesterunited = new ListBoxItem();
Ensure run those code in if code block.
the way add a control in a listbox is correct.
I've read some topics/questions/google results before but still don't know how to solve my problem.
In my case I consume json and what I do is deserializing JSON into objects. Then using ListboxName.ItemsSource I bind them to listbox.
The problem is that my server gives me only 20 top results, but also I receive a link to next 20.
Theoretically, I would like to bind this link to LoadMore button which I would put at the end of the list. Then what? Merge new result to existing ObservableCollection? (I assume that I have to use ObservableCollection)
Create an
ObservableCollection<Items> Items {get;set;}
then in XAML bind to it and add items to this collection. It will notify a list box to update a view.
XAML
<ListBox x:Name="ListboxName" ItemsSource="{Binding Items}"/>
in .cs file:
//After you have parsed json
private void OnNewDataDownloaded(List<Items> parsedItems)
{
foreach(var item in parsedItems)
{
Items.Add(item);
}
}
Here you can find an elegant way to add LoadMore button
I'm writing an MVC 3 app and I have tried to code a control in the Controller (due to permissions, different menu items will be visible for different users) and use the object in the Razor page. For example, in the Controller I do something like:
public ActionResult Index()
{
var menu = "#(Html.Telerik().Menu().Name("menu").Items("menus => { menus.Add().Text("Home").Action("Index", "Home"); menus.Add().Text("Deliveries").Action("Index", "Delivery"); }))";
var model = new MenuModel()
{
Menu = menu
};
return View(model);
}
And in the View I try to render the Menu using #Model.Menu but I just get the string value rather than an actual menu. Is what I'm trying to do possible?
Extend the HtmlHelper class and use the newly created method to render your menu in the View:
Helper:
public static string RenderMenu(this HtmlHelper html)
{
var menu = new StringBuilder();
/* ... menu rendering logic ... */
return menu.ToString();
}
View:
#Html.RenderMenu();
Nevertheless, it is fine to put this logic in the view. Using the HtmlHelper extension just separates/cleans the code.
I wouldn't want to do it that way even if it were possible!
You should decouple your controller and view more than you are currently doing.
The controller should only pass data the view requires. If the view needs a menu with different menu items then use the controller to decide what menu items the view should have then add them to a list object and pass that list to the view. The view will then build a menu based on the list of menu items.
Also when I say "menu items" I don't mean markup! I mean create a new MenuItemViewModel object to persist your data between your controller and your view e.g pseudo code:
public class MenuItemViewModel { string url, string text }
List<MenuItemViewModel> menuitems ...
return View(menuitems)
Why would you want to do this? This is breaking the separation of concerns in MVC - your controller shouldn't worry about how the menu is displayed, just getting the right data to the view for display.
If you want to do security trimming, don't pass in a builder string. There are other methods available.
You could try the MVC SiteMap provider which can handle security trimming against the [Authorize] controller attributes (bit of work to learn and setup, but great once its there).
Pass in your own collection of flags or pre-build menu items, like what Greg suggested.
Make a HtmlHelper extension, something like 'IsAuthorized()' that will check against the controller authorize attributes. Here's a gist of one I used to use before switching to the MVC Sitemap.
With the html helper, you can do this:
#(Html.Telerik().Menu()
.Name("Menu")
.Items(m =>
{
#* Publicly Accessible Controller *#
m.Add()
.Text("Home").Url(Url.Action("Index", "Home"));
#* Secure Controller *#
if (Html.IsAuthorized<MyProject.Controllers.SecureController>(c => c.Index()))
{
//m.Add()....
}
.....