MVVMcross Command Binding fire Exception - mvvmcross

Question

I experience an issue when i try to use a command to open a Second View Model V4.0.Beta5.
I followed the Exemple described in N+1 Video series https://www.youtube.com/playlist?list=PLR6WI6W1JdeYSXLbm58jwAKYT7RQR31-W
First ViewModel
public class FirstViewModel
: MvxViewModel
{
private string _hello = "Hello MvvmCross";
public string Hello
{
get { return _hello; }
set
{
_hello = value;
RaisePropertyChanged(() => Hello);
}
}
private Cirrious.MvvmCross.ViewModels.MvxCommand _goSecondViewCommand;
public System.Windows.Input.ICommand GoSecondViewCommand
{
get
{
_goSecondViewCommand = _goSecondViewCommand ??
new Cirrious.MvvmCross.ViewModels.MvxCommand(DoGoSecondView);
return _goSecondViewCommand;
}
}
private void DoGoSecondView()
{
base.ShowViewModel<SecondViewModel>();
}
}
Second View model
public class SecondViewModel :MvxViewModel
{
private string _hello2 = "Hello2 MvvmCross";
public string Hello2
{
get { return _hello2; }
set
{
_hello2 = value;
RaisePropertyChanged(() => Hello2);
}
}
}
First View
<views:MvxWindowsPage
x:Class="TestCommand.UWP.Views.FirstView"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:TestCommand.UWP"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:views="using:Cirrious.MvvmCross.WindowsUWP.Views"
mc:Ignorable="d">
<Grid>
<TextBox x:Name="textBox" HorizontalAlignment="Left" Margin="70,92,0,0" TextWrapping="Wrap" Text="FirstView" VerticalAlignment="Top" Width="223"/>
<Button x:Name="button" Command="{Binding GoSecondViewCommand}" Content="Button" HorizontalAlignment="Left" Height="108" Margin="70,346,0,0" VerticalAlignment="Top" Width="223"/>
</Grid>
Second view
<views:MvxWindowsPage
x:Class="TestCommand.UWP.Views.SecondView"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:TestCommand.UWP.Views"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:views="using:Cirrious.MvvmCross.WindowsUWP.Views"
mc:Ignorable="d"
d:DesignHeight="300"
d:DesignWidth="400">
<Grid />
Setup Class:
public class Setup : MvxWindowsSetup
{
public Setup(Frame rootFrame) : base(rootFrame)
{
}
protected override IMvxApplication CreateApp()
{
return new TestCommand.Core.App();
}
}
If you want you can download the solution Here:
https://onedrive.live.com/redir?resid=A5D9789788DE33CB!36079&authkey=!AKs9nsG28iI6nQQ&ithint=file%2czip.

Answer 1

The possible reason is you don't use Setup correctly in your UWP app, here is what I do to make this work:
1) Create two ViewModels in the UWP app: FirstViewModel and SecondViewModel
2) Create a Setup class in Setup.cs file:
public class Setup : MvxWindowsSetup
{
public Setup(Frame rootFrame) : base(rootFrame)
{
}
protected override IMvxApplication CreateApp()
{
return new AppSetup();
}
}
public class AppSetup : MvxApplication
{
public override void Initialize()
{
RegisterAppStart<FirstViewModel>();
}
}
3) FirstView.xaml:
<StackPanel>
<TextBox x:Name="textBox" HorizontalAlignment="Left" Margin="70,92,0,0" TextWrapping="Wrap" Text="FirstView" VerticalAlignment="Top" Width="223"/>
<TextBlock Height="50" Text="{Binding Hello}" />
<Button x:Name="button" Command="{Binding GoSecondViewCommand}" Content="Button" HorizontalAlignment="Left" VerticalAlignment="Top" Width="223" Height="50" />
</StackPanel>
4) SecondView.xaml:
<StackPanel>
<TextBox x:Name="textBox" HorizontalAlignment="Left" Margin="70,92,0,0" TextWrapping="Wrap" Text="SecondView" VerticalAlignment="Top" Width="223"/>
<TextBlock Height="50" Text="{Binding Hello2}" />
</StackPanel>
5) In App.xaml.cs file, make the following changes in OnLaunched method:
protected override void OnLaunched(LaunchActivatedEventArgs e)
{
......
if (rootFrame.Content == null)
{
var setup = new Setup(rootFrame);
setup.Initialize();
var start = Mvx.Resolve<IMvxAppStart>();
start.Start();
}
// Ensure the current window is active
Window.Current.Activate();
}
By the way, the MvvmCross version is 3.5.1
Check the Completed sample on Github
Update for exception in OnNavigationFailed method:
Please comment this line in FirstView and SecondView's code behind:
ViewModel = new FirstViewModel();
ViewModel = new SecondViewModel();
The MvvmCross has set the ViewModel automatically.