I'd like to use a JavaScript library from within a ScheduledTaskAgent on Windows Phone 8. We use this library across our mobile platforms so we don't have to write N versions of it.
I thought I'd be able to do that with a WebBrowser within a ScheduledTaskAgent but I'm running into cross threading issues if I execute this outside of a Dispatcher.BeginInvoke and a System.UnauthorizedAccess exception (claiming I need ID_CAP_WEBBROWSERCOMPONENT despite having that in my application's WMAppManifest.xml) when inside of Dispatcher.BeginInvoke like so:
static ScheduledAgent()
{
// Subscribe to the managed exception handler
Deployment.Current.Dispatcher.BeginInvoke(delegate
{
Application.Current.UnhandledException += UnhandledException;
client = new WebBrowser();
client.NavigateToString("<html><body><script src='https://...path to library...'/></body></html>");
});
}
Has anyone done anything like this before successfully? I can't believe I'm the first person to want to run JavaScript from a background scheduled task on Windows Phone.
As it turns out, the WebBrowser control is not supported in a background task, see: http://msdn.microsoft.com/en-us/library/windowsphone/develop/hh202962(v=vs.105).aspx
Related
First some background:
My setup uses a Service, which implements BeaconConsumer and binds to the BeaconManager. I have additional handling so when my app leaves the foreground, I move my Service to run in foreground, and when my app enters the foreground, I move my Service to run in background. That way, the persistent notification should display if and only if the app isn't displaying. In accordance, I am using the pattern here to tell BeaconManager I'm running this Service in the foreground, to allow for more frequent scanning. The link above isn't quite clear about this, but I believe this pattern should work without alterations needed on both pre-Android 8 as well as Android 8+. It shouldn't be strictly necessary on pre-Android 8, since the OS is more lenient. However, using this setup across all versions has the collateral benefit of ensuring that the OS does not kill the Service. If the app is in the foreground, the Service is background but has priority by virtue of the app, and if the app is not in the foreground, the Service is, and therefore has priority.
Now the problem: On pre-Android 8 devices, my Service is not seeing didEnterRegion called when the app is not in the foreground (but the Service is). It works fine on Android 8+.
some code snippets:
In my Service, set up the BeaconManager, set scan intervals
_beaconManager = BeaconManager.getInstanceForApplication(this);
_beaconManager.getBeaconParsers().add(new BeaconParser().
setBeaconLayout(IBEACON_PATTERN_1));
_beaconManager.setEnableScheduledScanJobs(false);
_beaconManager.setBackgroundBetweenScanPeriod(0);
_beaconManager.setBackgroundScanPeriod(1100);
Function in my Service I invoke to send the service to the foreground, and background:
private void sendServiceToForeground() {
this.startForeground(NOTIFICATION_ID, _notification);
if (_beaconManager != null) {
if (_beaconManager.isBound(this)) {
_beaconManager.unbind(this);
}
_beaconManager.enableForegroundServiceScanning(_notification, NOTIFICATION_ID);
_beaconManager.bind(this);
}
}
private void sendServiceToBackground() {
if (_beaconManager != null) {
if (_beaconManager.isBound(this)) {
_beaconManager.unbind(this);
}
_beaconManager.disableForegroundServiceScanning();
_beaconManager.bind(this);
}
this.stopForeground(true);
}
I can provide more code as requested. Not sure what all is relevant.
Calls to unbind() and bind() are asynchronous, so calling them one after another will be a problem unless you first wait for the unbind() operation to complete. This is tricky, because the library's BeaconManager does not provide a callback to tell you when unbind is complete (indeed, this is because the underlying Android service APIs also do not provide such a callback. You essentially don't know when the library's scanning service has stopped so you can safely restart it again in a different mode.)
It's a bit of a hack, but you might try adding a delay between unbind() and bind() to see if that makes a difference.
We are evaluating FiddlerCore for a use-case. Basically, for now we just want to catch all of the endpoints/urls being requested on a system. This works fine in Fiddler, no issues. But we only want to catch them while a certain vendor software is open. So we want to write a plugin to that software that will run when it launches, and then exit when it exits. Hence, using FiddlerCore (hopefully).
As proof-of-concept, I just made a simple app, one form with a textbox, that it should just append each url into the textbox. Simple as simple can be. However, it's not doing anything. I run the app, then refresh a page in my browser, and ... nothing.
Here is the entire (non-generated) code of my program...
using Fiddler;
using System;
using System.Windows.Forms;
namespace ScratchCSharp {
public partial class Form1 : Form {
public Form1() {
InitializeComponent();
FiddlerApplication.AfterSessionComplete += FiddlerApplication_AfterSessionComplete;
FiddlerApplication.Startup(8888, FiddlerCoreStartupFlags.Default);
}
private void FiddlerApplication_AfterSessionComplete(Session s) {
textBox1.Invoke((Action)delegate () {
AddText(s.fullUrl);
});
}
public void AddText(string text) {
textBox1.Text += $"{text}\n";
}
}
}
After a little more poking around, I see that FiddlerApplication.IsSystemProxy is returning false. Seems to have to do with that the Startup flag to set as system proxy is no longer honored, and it tells you now to use the Telerik.NetworkConnections.NetworkConnectionManager to set it as the system proxy. But I can't find anywhere that actually says how to do that. The closest thing I could find is this thread which seems to be their official answer to this question. However, it only goes into a lot of talk about WHY they deprecated the flag, and what their thinking was in how they designed its replacement, but not actually into HOW TO USE the replacement. The Demo app also does NOT use these libraries (probably why it doesn't catch anything either).
The biggest problem though, is that the NetworkConnectionsManager class has no public constructor, so you can't create an instance. It is not inheritable, so you can't make a subclass instance. All of the methods on it are instance methods, not static/shared. And there seems to be no method in the libraries which will create an instance of NetworkConnectitonsManager for you.
So while the class is clearly designed to be used as an instance (hence the methods not being static/shared, there doesn't actually seem to be any way to create an instance.
Any help on how to set this thing up to catch all the outgoing URLs on the system?
You can use the following code for starting Fiddler Core and registering it as a system proxy:
FiddlerCoreStartupSettings startupSettings =
new FiddlerCoreStartupSettingsBuilder()
.ListenOnPort(fiddlerCoreListenPort)
.RegisterAsSystemProxy()
.ChainToUpstreamGateway()
.DecryptSSL()
.OptimizeThreadPool()
.Build();
FiddlerApplication.Startup(startupSettings);
Some of the methods are obsolete for now, but I would recommend to stick with them until the NetworkConnectionManager API is improved and finalized.
Also, there is a sample application (that FiddlerCore installer installs on the Desktop), which is useful for a starting point with the development.
I'm actually working on a Xamarin Forms application that need push notifications. I use the Plugin.PushNotification plugin.
When the app is running in the foreground or is sleeping (OnSleep), I have no problem to open a specific page when I click on a notification that I receive. But I was wondering how can I do that when the app is closed. Thanks!
I finally found the answer by myself and I want to share it in case someone needs it.
Nota bene: according to the official documentation of the plugin, it's Xam.Plugin.PushNotification that is deprecated. I use the new version of this plugin, Plugin.PushNotification which uses FCM for Android and APS for iOS.
There is no significant differences to open a notif when the app is running, is sleeping or is closed. Just add the next callback method in the OnCreate method (MyProject.Droid > MainApplication > OnCreate) and FinishedLaunching method (MyProject.iOS > AppDelegate > FinishedLaunching):
CrossPushNotification.Current.OnNotificationOpened += (s, p) =>
{
// manage your notification here with p.Data
App.NotifManager.ManageNotif(p.Data);
};
Common part
App.xaml.cs
// Static fields
// *************************************
public static NotifManager NotifManager;
// Constructor
// *************************************
public App()
{
...
NotifManager = new NotifManager();
...
}
NotifManager.cs
public class NotifManager
{
// Methods
// *************************************
public void ManageNotif(IDictionary<string, object> data)
{
// 1) switch between the different data[key] you have in your project and parse the data you need
// 2) pass data to the view with a MessagingCenter or an event
}
}
Unfortunately there is no succinct answer for either platform. Generally speaking, you need to tell the OS what to do when it starts the app as a result of the push notification. On both platforms, you should also consider what API level you are targeting, otherwise it won't work or even crash the app.
On iOS, you will need to implement this method in AppDelegate appropriately: FinishedLaunching(UIApplication application, NSDictionary launchOptions). The launchOptions will have the payload from the push notification for you to determine what to do with it (e.g. what page to open). For more information on iOS, Xamarin's documentation is a good place to start.
Android has a more complicated topology in terms of more drastic differences between API levels, whether you are using GCM/FCM, as well as requiring more code components. However, to answer the question directly, you will need to handle this in OnCreate(Bundle savedInstanceState) of your main Activity. If you are using Firebase, the push notification payload is available in Intent.Extras. Again, Xamarin's documentation has a good walkthrough.
Finally, note that the Plugin.PushNotification library you are using has been deprecated. I suggest you either change your library and/or your implementation soon. Part of the reason that library has been deprecated is because Google has deprecated the underlying Google Cloud Messaging (GCM) service, which will be decommissioned on April 11, 2019.
My solution when I leave the application or leave it in the background gives an error 'The test application stopped', I can not find out where this queue comes from. Does anyone know where this trigger comes from the moment it leaves in the background
Is it something in this part of the code?
protected override void OnStart()
{
Debug.WriteLine("OnStart");
}
protected override void OnResume()
{
Debug.WriteLine("OnResume");
}
protected override void OnSleep()
{
Debug.WriteLine("OnSleep");
}
This type of errors came along with a specific part of your code, like #apineda mentioned maybe you are using an Android service that is updating some data on your application or it may be there to show a local notification who knows? but the thing I want to imply is that you need to take a look at your code and investigate further which is the part that is making the crash. Here are some tips:
1.- If you are using push notifications that may lead to something!
2.- Check you MainActivity.cs class since this is the one responsible of the Xamarin.Forms activity life cycle.
3.- If you have any timers on your shared code or even a background Task created with Task.Run or a Task.Factory.StartNew() check those too, deadlocks on Xamarin.Forms applications between the UI thread and background threads are a common thing on Xamarin.Forms.
I hope this helps!
I have a SignalR hub and two clients (Windows and PCL for Android and iOS). Neither of the clients is able to call some methods on the server. This behaviour is quite odd, since the methods look very similar. Moreover, a colleague of mine is able to call methods I cannot call, and vice versa, does not invoke methods that I invoke with no problems.
Here is an example of a method, which works for me and does not work for my colleague:
public override async Task<bool> RefreshArray(User user, int waitMilis)
{
var cts = new CancellationTokenSource();
try
{
cts.CancelAfter(waitMilis);
await Proxy.Invoke("RefreshArray", user);
return true;
}
catch (Exception ex)
{
OnExceptionOccured(ex);
return false;
}
}
And a method which does not work for me, but works for my colleague:
public override async Task<bool> RequestInformation(User user, Product product, int waitMilis)
{
var cts = new CancellationTokenSource();
try
{
cts.CancelAfter(waitMilis);
await Proxy.Invoke("RequestInformation", user, product);
return true;
}
catch (Exception ex)
{
OnExceptionOccured(ex);
return false;
}
}
Yes, me and my colleague have exactly the same code. And no, there are no typos or different arguments. I have tried to get as much data from the client connection as possible, by setting _connection.TraceLevel = TraceLevels.All; However, I did not get any information on the invoked methods, just on the replies from the hub. When calling RefreshArray, I got exactly the data I requested. When calling RequestInformation, the debugger never even hit the breakpoint in the hub method and the _connection.Trace displayed only this: 11:22:45.6169660 - 7bc57897-489b-49a2-8459-3fcdb8fcf974 - SSE: OnMessage(Data: {})
Has anybody solved a similar issue? Is there a solution?
UPDATE 1
I just realized that I have encountered almost the same issue about a year ago (Possible SignalR bug in Xamarin Android). StackOverflow has also pointed me to a question with almost the same issue (SignalR on Xamarin.iOS - randomly not able to call Hub method), just related to iOS and Azure. However, I got the same proble even outside Xamarin, on Windows Phone 8.1 and and Windows 10 Universal App. Moreover, I am running the server just locally, so it is not an issue od Azure. Is it really possible, that a 2 years old bug has no solution?
UPDATE 2
I have just created a simple console application with SignalR.Client. In the console application every method worked just fine. Amazingly, also the Windows 10 Universal Application started to behave as expected - every hub method was invoked correctly. Windows Phone 8.1 also improved its behaviour (all hub methods invoked). However, every now and then the connection tried to reconnect periodically (for no apparent reason), leading to Connection started reconnecting before invocation result was received. error. The Android application still behaved as before.
So I tried to replicate my previous steps and created another console application, but this time with SignalR.Client.Portable library. To my dissapointment, there was no change in the Android application behaviour.
Next week we will start to test our application on iOS, so I really wonder what new oddities will we encounter.
I have managed to solve the problem (at least so it seems). As it turned out, there is some weird stuff going around, when an application receives an answer from SignalR hub. It seems as if the HubProxy was blocked for a certain period of time on Android, while it drops the connection and starts to reconnect periodically on Windows Phone, not waiting for an asnwer from the hub.
The implementation of RefreshArray on the hub was something like this:
public async Task RefreshArray(User user)
{
await Clients.Caller.SendArray(_globalArray);
await Clients.Caller.SendMoreInformation(_additionalInfo);
}
Because the method sent two methods as an answer, the client Proxy got stuck and each platform handled it in its own unexpected way. The reason why some methods were called on my computer and not on colleagues was, simply, because we had different position of breakpoints, which enabled the application to resolve at least some requests and responses.
The ultimate solution was to add some synchronization into the invokation of methods. Now my hub calls only await Clients.Caller.SendArray(_globalArray);. This is then handled on the client with a ArraySent(string[] array) event, which then subsequently invokes the SendMoreInformation() method on the hub.