I have some async calls from Init in view model. The problem is that sometimes async call returns before OnCreate, and the property in UI is not updated.
Is there proper async/await model for this case, when we have to init async data?
pseudo code:
// ViewModel
public async Task Init(string id)
{
Url = await LoadUrlAsync(id);
}
// View
protected override void OnCreate(Bundle bundle)
{
base.OnCreate(bundle);
SetContentView(Resource.Layout.ui_xml);
ViewModel.PropertyChanged += ViewModel_PropertyChanged;
}
void ViewModel_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
{
_webView.LoadUrl(ViewModel.Url);
}
I'd probably do something like this in the OnCreate method, as you might want to add additional properties to it in the future.
private bool _loaded;
protected override void OnCreate(Bundle bundle)
{
base.OnCreate(bundle);
SetContentView(Resource.Layout.ui_xml);
ViewModel.WeakSubscribe(() => ViewModel.Url, (s,e) =>
{
if (!_loaded)
_webView.LoadUrl(ViewModel.Url);
});
if (ViewModel.Url != null) //Check if the async Init has finished already
{
_webView.LoadUrl(ViewModel.Url);
_loaded = true;
}
}
Related
I'm trying to use Topshelf Framework to create a windows service. But when i try to start the service, there is this exception :
" The service failed to start... System.Service.Process.TimeoutException : the waiting period has expired and the operation has not been completed"
This is my code :
public class MyService : ServiceControl
{
private System.Timers.Timer _timer;
public void MyService()
{
_timer = new System.Timers.Timer(10);
_timer.AutoReset = false;
_timer.Elapsed += new ElapsedEventHandler(TimerOnElapsed);
}
private void TimerOnElapsed(object source, ElapsedEventArgs e)
{
//all the operation to do at the startup
}
public bool Start(HostControl hostControl)
{
_timer.Start();
return true;
}
public bool Stop(HostControl hostControl)
{
_timer.Stop();
return true;
}
}
Thanks for any help :)
There are several issues I notice:
The current code would make the timer fire only once (you have AutoReset = false)
with TopShelf, the MyService class should look like this:
using System.Timers;
using Topshelf;
namespace TopShelfTestService
{
public class MyService
{
private System.Timers.Timer _timer;
public MyService()
{
_timer = new System.Timers.Timer(10);
_timer.AutoReset = true;
_timer.Elapsed += new ElapsedEventHandler(TimerOnElapsed);
}
private void TimerOnElapsed(object source, ElapsedEventArgs e)
{
//all the operation to do at the startup
}
public bool Start(HostControl hostControl)
{
_timer.Start();
return true;
}
public bool Stop(HostControl hostControl)
{
_timer.Stop();
return true;
}
}
}
and the console app/ Program.cs will look like so:
using Topshelf;
namespace TopShelfTestService
{
class Program
{
static void Main(string[] args)
{
HostFactory.Run(x =>
{
x.Service<MyService>(s =>
{
s.ConstructUsing(name => new MyService());
s.WhenStarted((tc, hostControl) => tc.Start(hostControl));
s.WhenStopped((tc, hostControl) => tc.Stop(hostControl));
});
x.RunAsLocalSystem();
x.SetDescription("Sample Topshelf Host"); //7
x.SetDisplayName("Test Service with TopShelf"); //8
x.SetServiceName("TopShelfTestService");
});
}
}
}
I have a user control which has a button and a dependency property for the action the button is to execute. The page which contains the control sets the action in XAML.
MyUserControl.cs
A Button, and dependency property ButtonAction, of type Action. When the button is clicked it executes the ButtonAction.
MainPage.xaml.cs
Action Action1
Action Action2
MainPage.xaml
Present an instance of MyUserControl, with ButtonAction=Action1
The problem: The ButtonAction property is not assigned from the XAML
MyUserControl.cs
public sealed partial class MyUserControl : UserControl
{
public Action ButtonAction {
get { return (Action)GetValue(ButtonActionProperty); }
set { SetValue(ButtonActionProperty, value); }
}
public static readonly DependencyProperty ButtonActionProperty =
DependencyProperty.Register("ButtonAction", typeof(Action), typeof(MyUserControl), new PropertyMetadata(null,ButtonAction_PropertyChanged));
private static void ButtonAction_PropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) {
Debug.WriteLine("ButtonAction_PropertyChanged");
// Is not called!
}
public MyUserControl() {
this.InitializeComponent();
}
private void Button_Click(object sender, RoutedEventArgs e) {
if (ButtonAction != null) {
// Never reaches here!
ButtonAction();
}
}
}
MyUserControl.xaml
<Grid>
<Button Click="Button_Click">Do The Attached Action!</Button>
</Grid>
MainPage.xaml.cs
Action Action1 = (
() => { Debug.WriteLine("Action1 called"); });
Action Action2 = (() => { Debug.WriteLine("Action2 called"); });
MainPage.xaml
<Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
<local:MyUserControl x:Name="myUserControl" ButtonAction="{Binding Action1}"/>
</Grid>
It does work if in the code-behind for MainPage (MainPage.xaml.cs) I assign the action in the Loaded event.
private void Page_Loaded(object sender, RoutedEventArgs e) {
this.myUserControl.ButtonAction = Action1;
}
In this case the PropertyChanged callback in the user control is also called. (This handler is provided only for diagnostic purposes. I can't see how it can be used to support the property in practice).
The issue is in your data binding. The Action1 in ButtonAction="{Binding Action1}" should be a public property while you defined it as a private variable.
Also, you cannot just declare a normal property directly in the code behind like that. You will need either a dependency property, or more commonly, a public property inside a viewmodel which implements INotifyPropertyChanged.
If we go with the second approach, we will need to create a viewmodel class like the following with an Action1 property. Note the OnPropertyChanged stuff is just the standard way of implementing INotifyPropertyChanged.
public class ViewModel : INotifyPropertyChanged
{
private Action _action1;
public Action Action1
{
get { return _action1; }
set
{
_action1 = value;
OnPropertyChanged("Action1");
}
}
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged(string name)
{
var handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(name));
}
}
}
And then you just need to assign this to the DataContext of your main page.
public MainPage()
{
this.InitializeComponent();
var vm = new ViewModel();
vm.Action1 = (() =>
{
Debug.WriteLine("Action1 called");
});
this.DataContext = vm;
}
With these two changes, your ButtonAction callback should be firing now. :)
I am trying to save a list of backstack pages that are Tombstoned, so that when I navigate back to them, I can compare if they are present in this list. If yes, I'll restore its state.
Currently my code looks like this.
public partial class App : Application
{
public static List<PhoneApplicationPage> TombstonedPages = new List<PhoneApplicationPage>();
private void Application_Activated(object sender, ActivatedEventArgs e)
{
if(!e.IsApplicationInstancePreserved)
{
foreach (JournalEntry j in (Application.Current.RootVisual as PhoneApplicationFrame).BackStack)
{
TombstonedPages.Add(//What should i add here);
}
}
}
}
code in some PhoneApplicationPage
protected override void OnNavigatedTo(NavigationEventArgs e)
{
//checking tombstone
if(e.NavigationMode== NavigationMode.Back && App.TombstonedPages.Contains(this) )
{
//restore state and delete entry from App.TombstonedPages
}
}
protected override void OnNavigatedFrom(NavigationEventArgs e)
{
if(e.NavigationMode != NavigationMode.Back)
{
//save state
}
}
But I am unable to get a reference of pages from backstack. How should I do this? Is there a different way to do this?
How can I make the background agent execution to wait before all ImageOpened() events are fired (3 in this case) in order to update secondary live tile with custom images?
Edit 1:
In the OnInvoke() method of the ScheduledAgent I am calling my own create tile data function implemented in a shared library which in turn subscribes to 3 ImageOpened() events as I am trying to create custom images for all live tile templates i.e. small, medium and wide.
Since these being asynchronous events I have no way to check if all the events have completed successfully so that I can call NotifyComplete() to notify the background agent that its job is now done. So sometimes the tile gets updated while most of the times it doesn't. Also I am using the same function to update the live tiles every time the app is launched so there is no problem with its implementation. I have also tried to take care of all the memory limitations with the ScheduledAgent by disposing Bitmaps and calling GC.Collect() forcefully.
Please help in any possible way to fix this problem.
Add a new class that lets you create custom events -
public class SaveImageCompleteEventArgs : EventArgs
{
public bool Success { get; set; }
public Exception Exception { get; set; }
public string ImageFileName { get; set; }
public SaveImageCompleteEventArgs(bool success, string fileName)
{
Success = success;
ImageFileName = fileName;
}
}
Initialize the events and required variables in the file you are updating the custom live tile from -
public static int countTile = 3;
public event EventHandler<SaveImageCompleteEventArgs> SaveMediumImageComplete;
public event EventHandler<SaveImageCompleteEventArgs> SaveWideImageComplete;
public event EventHandler<SaveImageCompleteEventArgs> SaveSmallImageComplete;
public event EventHandler<SaveImageCompleteEventArgs> SaveAllImagesComplete;
Fire the completion event in the ImageOpened() event handlers for all the tiles and check if the SaveAllImagesComplete event needs to be fired-
public void OnBackgroundBmpOpenedMedium(object sender, RoutedEventArgs e)
{
if (SaveMediumImageComplete != null)
{
countTile -= 1;
CheckIfAllImagesOpened();
SaveMediumImageComplete(this, new SaveImageCompleteEventArgs(true, mediumTileImageUriIronMan));
}
}
private void CheckIfAllImagesOpened()
{
if (countTile == 0)
{
if (SaveAllImagesComplete != null)
{
var args1 = new SaveImageCompleteEventArgs(true, "");
SaveAllImagesComplete(this, args1);
}
}
}
In the ScheduledAgent file -
public static ManualResetEvent evt;
public bool IsPaused { get { return !evt.WaitOne(0); } }
In the OnInvoke() function -
evt = new ManualResetEvent(false);
Deployment.Current.Dispatcher.BeginInvoke(() =>
{
//Initialize secondary tile here
if (secondaryTile != null)
{
/*
obj is a object of a helper file that contains all the
functions responsible for updating the custom live tile
Call the function that is responsible for initializing all the
tile image bitmpas and that subscribes to the ImageOpened events
*/
obj.SaveMediumImageComplete += async (s, args) =>
{
if (!IsPaused)
evt.Set();
};
obj.SaveWideImageComplete += async (s, args) =>
{
if (!IsPaused)
evt.Set();
};
obj.SaveSmallImageComplete += async (s, args) =>
{
if (!IsPaused)
evt.Set();
};
obj.SaveAllImagesComplete += async (s, args) =>
{
try
{
if (args.Success)
obj.UpdateTileIcon();
}
catch (Exception) { }
finally
{
if (!IsPaused)
evt.Set();
}
};
}
});
evt.WaitOne();
NotifyComplete();
I made my own slider as user control with some custom properties and one custom event. Everything works fine, but recently I start using Caliburn Micro, and I don't know how to capture my custom event.
Previously I used:
<my:RadialSlider x:Name="slider" WedgeAngle="270" ..... AngleChanged="slider_AngleChanged" />
and
public void slider_AngleChanged(object sender, ValueChangedEventArgs e)
{
.... something ....
}
Now, in Caliburn project I tried:
<my:RadialSlider x:Name="slider" WedgeAngle="270" ..... cal:Message.Attach="[Event AngleChanged] = [Action slider_AngleChanged($eventArgs)]" />
and in my ViewModel:
public void slider_AngleChanged(object sender, ValueChangedEventArgs e)
{
.... something ....
}
But, this doesn't work...
So, how to capture this event?
Slider UC code-behind:
public delegate void AngleChangedEventHandler(object sender, ValueChangedEventArgs e);
public sealed partial class RadialSlider : UserControl
{
public event AngleChangedEventHandler AngleChanged;
private void OnAngleChanged(ValueChangedEventArgs e)
{
if (AngleChanged != null)
AngleChanged(this, e);
}
public static readonly DependencyProperty WedgeAngleProperty = DependencyProperty.Register("WedgeAngle", typeof(double), typeof(RadialSlider), new PropertyMetadata((double)270, new PropertyChangedCallback(OnPropertyWedgeAngleChanged)));
public double WedgeAngle
{
get { return (double)this.GetValue(WedgeAngleProperty); }
set { this.SetValue(WedgeAngleProperty, value); }
}
private static void OnPropertyWedgeAngleChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
{
(sender as RadialSlider).UpdateControls();
if (e.NewValue != e.OldValue)
{
(sender as RadialSlider).OnAngleChanged(new ValueChangedEventArgs((double)e.OldValue, (double)e.NewValue));
}
}
}
You need to use a routed event. This has to do with how events bubble up the visual tree and how Caliburn.Micro attaches itself to them. Standard events should be avoided on controls or UI widgets in any tech using Xaml as the loose out on some pretty funky features (bubble up / down).