I'm trying to make a change to sample project Cirrious.Conference. In particular in the Touch View at SessionView class and at this class
https://github.com/slodge/MvvmCross-Tutorials/blob/master/Sample%20-%20CirriousConference/Cirrious.Conference.Core/ViewModels/SessionLists/BaseSessionListViewModel.cs
on method
protected void NavigateToSession(Session session)
{
ShowViewModel<SessionViewModel>(new { key = session.Key });
}
I'd like to openl a UIWebView (in app) binding LoadRequest with a property of class Session (suppose to have a Property URL...). I have created a UIWebView object in the SessionView but it's not possible to create a Swisse Binding...Maybe it's possible with a customBinding...
How could i'll do it?
Since UIWebView doesn't expose a property for the LoadRequest, then you can't bind directly to it.
If you want to use binding for LoadRequest, then 3 options available to you are:
Inherit MyWebView from UIWebView, add a C# property that drives LoadRequest and then use that class in your UI and that property in your Swiss binding - e.g.:
[Register("MyWebView")]
public class MyWebView : UIWebView
{
public MyWebView()
{
}
public MyWebView(IntPtr handle) : base(handle)
{
}
private string _myUrl;
public string MyUrl
{
get { return _myUrl; }
set
{
if (_myUrl == value) return;
_myUrl = value;
LoadRequest(value); // or similar (I've not checked the syntax!)
}
}
}
Implement a custom target Swiss binding and add it to your Setup.cs. The process for this is described in this Custom Bindings presentation - which also includes links to some examples (one of them is in the Conference app)
If this property will never change, then don't use binding and instead just call LoadRequest in your MvxViewController ViewDidLoad - e.g.
public void ViewDidLoad()
{
base.ViewDidLoad();
var myViewModel = (MyViewModel)ViewModel;
var url = myViewModel.Url;
TheWebView.LoadRequest(url);
}
Related
I need to change the Visibility of a Button on a View from method call from within a class.
I have tried accessing the VeiwModel by exposing it in the class, and then had success in changing the Property "ShowRedHat" from true to false, but this does not update the Visibility of the Button in the View. This also double loads the ViewModel, which is not acceptable in my solution.
Any help is appreciated.
The class:
public class HatEngine
{
public void SetShowRedHat()
{
????.ShowRedHat = false;
}
}
The Property in the ViewModel:
public class MyViewModel : ObservableObject
{
private bool _showRedHat;
public bool ShowRedHat
{
get { return _showRedHat; }
set
{
OnPropertyChanged(ref _showRedHat, value);
}
}
}
The Button in the View:
<Button Content="Red Hat"
Command="{Binding RedHatCommand}"
Visibility="{Binding ShowRedHat, Converter={StaticResource BoolToVis}}"/>
If the purpose of HatEngine is to be a service that is used by MyViewModel, then something like the following be the start of getting what you need.
This example uses dependency injection via the constructor; this is common in MVVM and if you're not familiar with it, I would highly recommend looking into it further.
// define delegate for event to be fired from HatEngine instances
public delegate void HatEngineNotifyEventHandler(object sender, bool shouldShow);
// interface declaration for HatEngine - this is important for injecting mocks for unit testing
public interface IHatEngine
{
event HatEngineNotifyEventHandler Notify;
void SetShowRedHat(bool show);
}
// simple IHatEngine implementation
public sealed class HatEngine : IHatEngine
{
public event HatEngineNotifyEventHandler Notify;
public void SetShowRedHat(bool show) => OnNotify(show);
private void OnNotify(bool shouldShow) =>
Notify?.Invoke(this, shouldShow);
}
public class MyViewModel : ObservableObject
{
private readonly IHatEngine _hatEngine;
private bool _showRedHat;
// MyViewModel consumes an IHatEngine instance and subscribes to its Notify event
public MyViewModel(IHatEngine hatEngine = null)
{
// many MVVM frameworks include a DI container that should be used here
// to resolve an IHatEngine instance; however, for simplicity for this
// example just create HatEngine() directly
_hatEngine = hatEngine ?? new HatEngine();
// when the event is received, update ShowRedHat accordingly
_hatEngine.Notify += (_, shouldShow) => ShowRedHat = shouldShow;
}
public bool ShowRedHat
{
get => _showRedHat;
set => OnPropertyChanged(ref _showRedHat, value);
}
}
You can just bind an integer since Visibility is an Enum, check documentation since in some versions Hidden option is not available and Collapsed becomes 1, however normally you can just use these below:
Visible [0] - Display the element.
Hidden [1] Do not display the element, but reserve space for the
element in layout.
Collapsed [2] Do not display the element, and do not reserve space for
it in layout.
In order to get PropertyChanged to fire in NUnit tests, I had to set ShouldAlwaysRaiseInpcOnUserInterfaceThread(false). Are there any repercussions to this when I later use the class as a ViewModel? Maybe I should be setting up a user interface thread in NUnit? Help!
public interface ISomething : INotifyPropertyChanged
{
}
public class Something : MvxNotifyPropertyChanged, ISomething
{
public Something()
{
ShouldAlwaysRaiseInpcOnUserInterfaceThread(false);
}
private int _num;
public int Num
{
get { return _num; }
set { if (_num != value) { _num = value; RaisePropertyChanged(() => Num); }
}
}
By default MvvmCross marshals calls like RaisePropertyChanged onto the UI thread for the convenience of developers.
If you want to disable this on an individual object, you can call ShouldAlwaysRaiseInpcOnUserInterfaceThread(false); for that object (this is a method call rather than a property as properties on ViewModel objects are generally reserved for INotifyPropertyChanged use)
If you want to disable this by default on all objects then you can use Mvx.Resolve<IMvxSettings>().AlwaysRaiseInpcOnUserInterfaceThread = false;
If during testing you want to provide a mock implementation for the UI thread marshalling, then see for example the N=29 video in http://mvvmcross.blogspot.co.uk/ - with some MockDispatcher code inside https://github.com/MvvmCross/NPlus1DaysOfMvvmCross/tree/master/N-29-TipCalcTest/TipCalcTest.Tests
There is such ability to bind buttons actions directly like this:
var set = this.CreateBindingSet<...
set.Bind(button).To(x => x.Go);
but what's about UITapGestureRecognizer, for instance. How should I bind it (it's tap action) in such elegant way?
Thank you!
Just for reference. Newer version of MvvMcross includes a UIView method extension (see MvxTapGestureRecognizerBehaviour) out of the box that you can use to bind the tap gesture:
using Cirrious.MvvmCross.Binding.Touch.Views.Gestures;
// in this case "Photo" is an MvxImageView
set.Bind(Photo.Tap()).For(tap => tap.Command).To("OpenImage");
You could add this yourself if you wanted to.
e.g. something like
public class TapBehaviour
{
public ICommand Command { get;set; }
public TapBehaviour(UIView view)
{
var tap = new UITapGestureRecognizer(() =>
{
var command = Command;
if (command != null)
command.Execute(null);
});
view.AddGestureRecognizer(tap);
}
}
public static class BehaviourExtensions
{
public static TapBehaviour Tap(this UIView view)
{
return new TapBehaviour(view);
}
}
// binding
set.Bind(label.Tap()).For(tap => tap.Command).To(x => x.Go);
I think that would work - but this is coding live here!
Advanced> If you wanted to, you could also remove the need for the For(tap => tap.Command) part by registering a default binding property for TapBehaviour - to do this override Setup.FillBindingNames and use:
registry.AddOrOverwrite(typeof (TapBehaviour), "Command");
After this, then the binding could be:
set.Bind(label.Tap()).To(x => x.Go);
I am new to MvvmCross and I have a question.
I noticed that the following binding code works in one way only:
{ this, "{'CurrentIndex':{'Path':'CurrentIndex','Mode':'TwoWay'}}" }
CurrentIndex is an Int Property in the View
CurrentIndex is also an Int Property in the ViewModel
This way works!
ViewModel => View
But not this way!
View => ViewModel
I have a collection of ViewControllers and my goal was to call a DeleteCommand for the CurrentIndex in the viewModel.
However,
"Android and Touch 2 way bindings are incomplete"
Reference: MvvmCross experiences, hindsight, limitations?
My guess is the TwoWay mode only works for Controls (UILabel, UITextfield, ...) but not for Properties.
So, is there a good way to make it works in both ways? Or Are there any alternatives to my problem?
Patrick
In order for a binding to transfer any value between a View to a ViewModel, then it needs to hook into some event when the value changes.
In the ViewModel, this event is always the event in the INotifyProperty interface.
In the View/Activity, there is one single pattern employed - so each binding has to hook into a separate event. For example, the Text on EditText is hooked up using the TextChanged event (see MvxEditTextTextTargetBinding.cs) while the value in a SeekBar is hooked up using a Listener object rather than an event (see MvxSeekBarProgressTargetBinging.cs).
So if you wanted to implement this two-way binding for your activity, then you could do this by:
declaring an event - CurrentIndexChanged - in your activity (MyActivity) which is fired whenever CurrentIndex changes
declare a custom binding for your MyActivity which programmatically links CurrentIndex and CurrentIndexChanged
adding the custom binding to the binding registry during Setup
For example, your activity might include:
public event EventHandler CurrentIndexChanged;
private int _currentIndex;
public int CurrentIndex
{
get { return _currentIndex; }
set { _currentIndex = value; if (CurrentIndexChanged != null) CurrentIndexChanged(this, EventArgs.Empty); }
}
And you might then declare a binding class like:
public class MyBinding : MvxPropertyInfoTargetBinding<MyActivity>
{
public MyBinding (object target, PropertyInfo targetPropertyInfo)
: base(target, targetPropertyInfo)
{
View.CurrentIndexChanged += OnCurrentIndexChanged;
}
public override MvxBindingMode DefaultMode
{
get
{
return MvxBindingMode.TwoWay;
}
}
private void OnCurrentIndexChanged(object sender, EventArgs ignored)
{
FireValueChanged(View.CurrentIndex);
}
protected override void Dispose(bool isDisposing)
{
base.Dispose(isDisposing);
if (isDisposing)
{
View.CurrentIndexChanged -= OnCurrentIndexChanged;
}
}
}
And you'd need to tell the binding system about this binding in setup like:
registry.RegisterFactory(new MvxSimplePropertyInfoTargetBindingFactory(typeof(MyBinding), typeof(MyActivity), "CurrentIndex"));
However... at a practical level, if you are operating in C# rather than in XML, then you might be better off in this case using C# to simply update the ViewModel rather than using declarative binding in this case.
To be clear... in this case, I would most probably just write the Activity property as:
public int CurrentIndex
{
get { return _currentIndex; }
set { _currentIndex = value; ViewModel.CurrentIndex = value; }
}
Or... I'd consider not having this property in the Activity at all.
If it helps, there's some more information on custom bindings in:
MonoTouch MVVMCross binding to instance variables
In MvvmCross how do I do custom bind properties
Hope this helps! IMHO the bindings are there to help you when you're working in XML - you don't have to use them...
Stuart
UPDATE If you are going to do lots of these and follow the same name pattern - using property named X with changed EventHandler event named XChanged then something like this might work - it uses reflection to find the event automagically:
public class MyBinding<T> : MvxPropertyInfoTargetBinding<T>
where T : class
{
private readonly PropertyInfo _propertyInfo;
private readonly EventInfo _eventInfo;
public MyBinding(object target, PropertyInfo targetPropertyInfo)
: base(target, targetPropertyInfo)
{
_propertyInfo = targetPropertyInfo;
var eventName = _propertyInfo.Name + "Changed";
_eventInfo = View.GetType().GetEvent(eventName);
if (_eventInfo == null)
{
throw new MvxException("Event missing " + eventName);
}
if (_eventInfo.EventHandlerType != typeof(EventHandler))
{
throw new MvxException("Event type mismatch for " + eventName);
}
var addMethod = _eventInfo.GetAddMethod();
addMethod.Invoke(View, new object[] { new EventHandler(OnChanged) });
}
public override MvxBindingMode DefaultMode
{
get
{
return MvxBindingMode.TwoWay;
}
}
private void OnChanged(object sender, EventArgs ignored)
{
var value = _propertyInfo.GetValue(View, null);
FireValueChanged(value);
}
protected override void Dispose(bool isDisposing)
{
base.Dispose(isDisposing);
if (isDisposing)
{
var removeMethod = _eventInfo.GetRemoveMethod();
removeMethod.Invoke(View, new object[] { new EventHandler(OnChanged) });
}
}
}
The Navigation framework in Windows Phone 7 is a cut down version of what is in Silverlight. You can only navigate to a Uri and not pass in a view. Since the NavigationService is tied to the View, how do people get this to fit into MVVM. For example:
public class ViewModel : IViewModel
{
private IUnityContainer container;
private IView view;
public ViewModel(IUnityContainer container, IView view)
{
this.container = container;
this.view = view;
}
public ICommand GoToNextPageCommand { get { ... } }
public IView { get { return this.view; } }
public void GoToNextPage()
{
// What do I put here.
}
}
public class View : PhoneApplicationPage, IView
{
...
public void SetModel(IViewModel model) { ... }
}
I am using the Unity IOC container. I have to resolve my view model first and then use the View property to get hold of the view and then show it. However using the NavigationService, I have to pass in a view Uri. There is no way for me to create the view model first. Is there a way to get around this.
Instead of passing the view through the constructor. You could construct the view first via the NavigationService and pass it into the view-model. Like so:
public class ViewModel : IViewModel
{
private IUnityContainer container;
private IView view;
public ViewModel(IUnityContainer container)
{
this.container = container;
}
public ICommand GoToNextPageCommand { get { ... } }
public IView
{
get { return this.view; }
set { this.view = value; this.view.SetModel(this); }
}
public void GoToNextPage()
{
// What do I put here.
}
}
PhoneApplicationFrame frame = Application.Current.RootVisual;
bool success = frame.Navigate(new Uri("View Uri"));
if (success)
{
// I'm not sure if the frame's Content property will give you the current view.
IView view = (IView)frame.Content;
IViewModel viewModel = this.unityContainer.Resolve<IViewModel>();
viewModel.View = view;
}
If you are using Mvvm Light you could try:
Windows Phone 7 — Navigation between pages using MVVM Light Messaging
(See similar post: Silverlight Navigation using Mvvm-light(oobe)+MEF?)
My opinion is that the view-model should be created and registered at application startup. By placing it inside the root DataContext all pages will automatically get a reference to it without any code-behind or IoC tricks.
// Code to execute when the application is launching (eg, from Start)
// This code will not execute when the application is reactivated
private void Application_Launching(object sender, LaunchingEventArgs e)
{
m_ViewModel = new PrimaryViewModel(RootFrame) ;
RootFrame.DataContext = m_ViewModel;
}
// Code to execute when the application is activated (brought to foreground)
// This code will not execute when the application is first launched
private void Application_Activated(object sender, ActivatedEventArgs e)
{
m_ViewModel = new PrimaryViewModel(RootFrame) ;
m_ViewModel.Activated(PhoneApplicationService.Current.State);
RootFrame.DataContext = m_ViewModel;
}
If you are using MVVM architecture,then you can pass navigationPage after registering using Messenger. Create a model class (say NavigateToPageMessage) with a string(say PageName) variable. You want to pass string from homepage.xaml to newpage.xaml,then in Homepage viewmodel just send the message like this under the command you binded (say HomeNavigationCommand)
private void HomeNavigationCommandHandler()
{
Messenger.Default.Send(new NavigateToPageMessage {PageName = "newpage"});
}
In the newpage Viewmodel,you should register the messenger like this,
Messenger.Default.Register<NavigateToPageMessage>(this, (action) => ReceiveMessage(action));
private object ReceiveMessage(NavigateToPageMessage action)
{
var page = string.Format("/Views/{0}.xaml", action.PageName);
NavigationService.Navigate(new System.Uri(page,System.UriKind.Relative));
return null;
}
//Assuming your views are in View Folder