Is there a way to use MVVM Light to handle application events like Closed, Deactivated, Activated, etc?
Thanks to Matt Casto for sending me in the right direction.
Here is the working code:
App.xaml.cs:
private void Application_Activated(object sender, ActivatedEventArgs e)
{
Messenger.Default.Send(new NotificationMessage<AppEvents>(AppEvents.Activated, string.Empty));
}
private void Application_Deactivated(object sender, DeactivatedEventArgs e)
{
Messenger.Default.Send(new NotificationMessage<AppEvents>(AppEvents.Deactivated, string.Empty));
}
private void Application_Closing(object sender, ClosingEventArgs e)
{
Messenger.Default.Send(new NotificationMessage<AppEvents>(AppEvents.Closing, string.Empty));
}
ViewModel:
Messenger.Default.Register<NotificationMessage<AppEvents>>(this, n =>
{
switch (n.Content)
{
case AppEvents.Deactivated:
_sessionPersister.Persist(this);
break;
case AppEvents.Activated:
var model = _sessionPersister.Get<TrackViewModel>();
break;
}
});
One thing you could do is handle these events in the App.xaml.cs and have them send a message using the default Messenger instance. Then just have any view models register to receive the message. If you need to cancel the event, use the message with a callback telling the application to cancel.
Related
I need to refresh webView control when the ui size changed. I used SizeChanged event in some controls like Border, WebView, etc SizeChanged event. But I got this system.invalidoperationexception 'a method was called at an unexpected time error. I got this error at the beginning of running the application. The way I used:
<WebView x:Name="webView" SizeChanged="OnSizeChanged" HorizontalOptions="FillAndExpand" VerticalOptions="FillAndExpand">
<WebView.Source>
...
</WebView.Source>
</WebView>
private void OnSizeChanged(object sender, EventArgs e)
{
webView.Reload();
}
Probably I used it in wrong way, or could it be a bug?
I solved the problem when I used Reload method in try-catch:
private void OnSizeChanged(object sender, EventArgs e)
{
try
{
webView.Reload();
}
catch(Exception ex)
{
}
}
I have a Xamarin.Forms app and I am using FreshMvvm framework.
If I do this from ViewIsAppearing method of FirstPageModel:
CoreMethods.PushPageModel<SecondPageModel>();
I go the "SecondPageModel". Then, when I am in the "SecondPageModel" if I do:
CoreMethods.PopPageModel();
or press hard back button, or press title bar back button not works in Android (anything happens). I am using FreshMasterDetailNavigationContainer.
In iOS it works OK, I get back to FirstPageModel.
This is because ViewIsAppearing will always be called when the page starts displaying on the screen. When you pop the second page then go to the first page, the first page's ViewIsAppearing will fire again. It caused a dead cycle and prohibited your app from returning to the first page.
Add a property to avoid that:
bool isInitialized;
public FirstPageModel()
{
// ...
isInitialized = true;
}
protected async override void ViewIsAppearing(object sender, EventArgs e)
{
base.ViewIsAppearing(sender, e);
if (isInitialized)
{
await Task.Delay(100);
await CoreMethods.PushPageModel<SecondPageModel>();
isInitialized = false;
}
}
iOS may optimize this process, but I still recommend you to add this judgment statement.
Update:
Call it when your app has reached the main thread.
protected override void ViewIsAppearing(object sender, EventArgs e)
{
base.ViewIsAppearing(sender, e);
if (isInitialized)
{
Device.BeginInvokeOnMainThread(() =>
{
CoreMethods.PushPageModel<SecondPageModel>();
isInitialized = false;
});
}
}
I have below code written inside C# Form application where I am trying to get x,y and z co-ordinates from Leap Motion device.
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
//controller.EventContext = WindowsFormsSynchronizationContext.Current;
button1.Click += new EventHandler(button1_Click);
}
private void button2_Click(object sender, EventArgs e)
{
Application.Exit();
}
private void button1_Click(object sender, EventArgs e)
{
// Initialize the Controller object which connects to the Leap motion service
// and captures the hand tracking data
Controller controller = new Controller();
//Get the most recent tracking data using the Frame object
Frame frame = controller.Frame();
for (int h = 0; h < frame.Hands.Count; h++)
{
// Initialize the Hand in the given frame
Hand leapHand = frame.Hands[h];
// Get the "Pointer" finger of current hand which refers to where a person is pointing
Finger leapFinger = leapHand.Fingers[1];
// Prepare a vector which will store the co-ordinate values of the tip of the pointer
Vector currentPosition = leapFinger.StabilizedTipPosition;
textBox1.Text = Convert.ToString(currentPosition.x);
textBox2.Text = Convert.ToString(currentPosition.y);
textBox3.Text = Convert.ToString(currentPosition.z);
}
}
}
However, I need to explicitly click the button1 to display.
Any idea what's wrong ?
Here is an overly simple example of one way to do it. I'm not saying it's the best way, but you should be able to modify this sample code with your code.
In this example, there is a simple "HelloWorld" method that is called when the form is initialized as well as whenever you press the button. Let me know if this gets you close to what you're after.
namespace WindowsFormsApp1
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
button1.Click += new EventHandler(button1_Click);
HelloWorldTest();
}
private void button1_Click(object sender, EventArgs e)
{
HelloWorldTest();
}
private void HelloWorldTest()
{
MessageBox.Show("Hello World!");
}
}
}
For what it's worth, I didn't use your code because I don't have the Leap libraries installed and if there was a typo, I wouldn't be much help to resolve it. Nonetheless, hopefully it gets you going down the right path.
The accelerometer is activated (if I set ReadingChanged it works).
Why the shaking event isn't handled?
namespace AppExample
{
public sealed partial class MainPage : Page
{
private Accelerometer accel;
public MainPage()
{
this.InitializeComponent();
this.NavigationCacheMode = NavigationCacheMode.Required;
accel = Accelerometer.GetDefault();
//accel.ReadingChanged += accel_ReadingChanged;
accel.Shaken += accel_Shaken;
}
void accel_Shaken(Accelerometer sender, AccelerometerShakenEventArgs args)
{
Debug.WriteLine("shaken");
}
}
}
If you mind, there is helper librairy called ShakeGestures to handle shake gestures for windows phone 8. check this question
If you're running Windows Phone 8 , Shaken event won't trigger and does not raise any errors according to MSDN page.
Otherwise it seems like a weird bug to me , I couldn't find any information about it.
You can call the Dispatcher in order to show the result on the main thread.
namespace AppExample
{
public sealed partial class MainPage : Page
{
Accelerometer accel;
public MainPage()
{
this.InitializeComponent();
accel = Accelerometer.GetDefault();
accel.ReadingChanged += accel_ReadingChanged;
accel.Shaken += accel_Shaken;
}
await this.Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
{
LabelTest.Text = "Shaken!! " + args.Reading.AccelerationX.ToString();
});
async private void accel_Shaken(object sender, AccelerometerShakenEventArgs e)
{
await Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
{
_shakeCount++;
ScenarioOutputText.Text = _shakeCount.ToString();
});
}
}
}
I'm new to WP7 and coming from iPhone development. On iPhone I'm used to use NSNotificationCenter to notify my program of something. NSNotificationCenter is build-in the framework out of the box. Is there something similar in WP7? I stumbled uppon MVVM-Light Toolkit but I'm not sure how to use it correctly.
What I want to do:
Register to an Notification-Id and do something when Notification-Id is received
Send Notification with Notification-Id and a context (object to pass to observers)
Everyone who registers to the same Notification-Id will be notified
So something like: Registering
NotificationCenter.Default.register(receiver, notification-id, delegate);
Sending:
NotificationCenter.Default.send(notification-id, context);
Example for Registering:
NotificationCenter.Default.register(this, NotifyEnum.SayHello, m => Console.WriteLine("hello world with context: " + m.Context));
Sending ...
NotificationCenter.Default.send(NotifyEnum.SayHello, "stackoverflow context");
Here is how to do with the MVVM Light Toolkit:
Registering:
Messenger.Default.Register<string>(this, NotificationId, m => Console.WriteLine("hello world with context: " + m.Context));
Sending:
Messenger.Default.Send<string>("My message", NotificationId);
Here http://www.silverlightshow.net/items/Implementing-Push-Notifications-in-Windows-Phone-7.aspx you will find a great example on how to use push notification on windows phone 7.
I'm pretty sure that you archive the same result as NSNotificationCenter by creating a singleton which holds a list of observables that implements a specific interface based on your bussiness requirements, or call a lamba, or trigger an event, for each message sent by this singleton you will interate the list of observables and checking the message id, once you find one or more, you can call the interface method, or execute the lambda expression or trigger the event defined to digest the message contents.
Something like below:
public class NotificationCenter {
public static NotificationCenter Default = new NotificationCenter();
private List<KeyValuePair<string, INotifiable>> consumers;
private NotificationCenter () {
consumers = new List<INotifiable>();
}
public void Register(string id, INotifiable consumer) {
consumers.Add(new KeyValuePair(id, consumer));
}
public void Send(String id, object data) {
foreach(KeyValuePair consumer : consumers) {
if(consumer.Key == id)
consumer.Value.Notify(data);
}
}
}
public interface INotifiable {
void Notify(object data);
}
public class ConsumerPage : PhoneApplicationPage, INotifiable {
public ConsumerPage() {
NotificationCenter.Default.Register("event", this);
}
private Notify(object data) {
//do what you want
}
}
public class OtherPage : PhoneApplicationPage {
public OtherPage() {
NotificationCenter.Default.Send("event", "Hello!");
}
}