What I am trying to achieve here is a global loading indicator with MvvmCross.
From what I gathered so far it appears that I can implement this by using a BaseView and BaseViewModel. The BaseViewModel should contain an IsLoading property that the BaseView can Bind to. Therefore, I can set IsLoading to true in any of my ViewModels to cause the indicator to be displayed.
The BaseViewModel looks like this:
public abstract class BaseViewModel : MvxViewModel
{
private bool _isLoading = false;
public bool IsLoading
{
get { return _isLoading; }
set { _isLoading = value; RaisePropertyChanged(() => IsLoading); }
}
private string _loadingMessage = "Loading...";
public string LoadingMessage
{
get { return _loadingMessage; }
set { _loadingMessage = value; RaisePropertyChanged(() => LoadingMessage); }
}
}
As for binding to the ViewModel, this issue was addressed here: https://stackoverflow.com/a/10930788
I was successfully able to listen to IsLoading by attaching to the PropertyChanged event, however, since this is not a "real" binding it will not fire if IsLoading is set to true before you attach to the event (Such as before the view is loaded).
Next I attempted to call AddBindings to attach to my BaseViewModel in order to create a real binding between the two properties, although this does not appear to work (no errors).
Here is what my BaseView currently looks like for iOS:
public abstract class BaseView<TViewModel> : MvxViewController where TViewModel : BaseViewModel
{
public TViewModel ViewModel
{
get { return (TViewModel)base.ViewModel; }
set { base.ViewModel = value; }
}
protected BaseView(string nib, NSBundle bundle) : base(nib, bundle)
{
}
private LoadingOverlay _loadingOverlay;
public override void ViewDidLoad()
{
base.ViewDidLoad();
_loadingOverlay = new LoadingOverlay(View.Frame);
this.AddBindings(new Dictionary<object, string>()
{
{this, "{'IsLoading':{'Path':'IsLoading'}}"},
{_loadingOverlay, "{'LoadingMessage':{'Path':'LoadingMessage'}}"}
});
}
public bool IsLoading
{
set
{
if (value)
View.Add(_loadingOverlay);
else
_loadingOverlay.Hide();
}
}
}
Are there any pitfalls to AddBindings that I may be unaware of? or is there a newer method altogether that I should be using?
I Appreciate the help, Thanks.
