I try to get my code working with catching certain errors. I store the token for a user after he or she grants permission to my app (this is a WP7 app). When I try to post on the wall by using the stored token it works. When I remove the permissions on facebook it throws an OAuthException. I can't catch it it seems. My app just crashes. This is the code I used:
private object PostToFacebook()
{
_fbApp = new FacebookClient(_appsettings.faceBookToken);
FacebookAsyncCallback callback = new FacebookAsyncCallback(this.postResult);
var parameters = new Dictionary<string, object>();
parameters.Add("message", "message on wall");
try
{
_fbApp.PostAsync("me/feed", parameters, callback);
}
catch (Exception ex)
{
}
return null;
}
private void postResult(FacebookAsyncResult asyncResult)
{
if (asyncResult.Error == null)
{
status = "succes";
}
else
{
status = "error" + asyncResult.Error.Message;
}
}
The try catch doesn't catch anything and the generic exception handler in my app.xaml.cs either.
Any ideas how to catch this error so I can ask the user to authenticate again?
Put your try..catch in the callback.
You can also catch exceptions globally by handling the UnhandledException event on the App object.
Related
I'm make an app which get data from API, but sometimes error will occur.
I have throw exception in my code when StatusCode is not Ok. But i have to handle it.
So, my question is how to get the exception on another thread and throw it with message box in xamarin.
ProductsNew = await Task.Run(() =>
{
ProductViewData productNewViewData = new ProductViewData();
return productNewViewData.GetProductNew("5");
});
Thanks for any help.
Put your code in try and catch block and show the error on message box.
try
{
//code
}
catch(Exception ex)
{
DisplayAlert("Error",ex.Message,"Ok");
}
I am busy writing an application where the user needs to capture a lot of images and then they get packaged together with some text data and then they get uploaded to a local server. I want to implement the uploading on the Android platform through an Intent Service but I cannot find a good Xamarin Forms PCL example to show me how.
This is the method where I initialize the Intent to pass to the IntentService:
public async Task<bool> UploadAsync(Uri serviceAddress,
CaptureEntity capture,
List<ImageEntity> images)
{
try
{
Intent uploadIntent = new Intent();
uploadIntent.PutExtra("serviceAddress", serviceAddress.ToString());
uploadIntent.PutExtra("captureId", capture.WorkflowId.ToString());
StartService(uploadIntent);
return true;
}
catch (Exception exc)
{
App.logger.LogError(DateTime.Now, "Uploader", exc.ToString());
throw exc;
}
}
And this is the IntentService itself.
[Service]
public class ServiceIntent : IntentService
{
public ServiceIntent() : base("ServiceIntent")
{
}
//[return: GeneratedEnum]
public override StartCommandResult OnStartCommand(Intent intent, [GeneratedEnum] StartCommandFlags flags, int startId)
{
return base.OnStartCommand(intent, flags, startId);
}
public override void OnCreate()
{
base.OnCreate();
}
protected override void OnHandleIntent(Intent intent)
{
Uri serviceAddress = new Uri(intent.GetStringExtra("serviceAddress"));
Guid captureId = Guid.Parse(intent.GetStringExtra("captureId"));
CaptureEntity capture = new DatabaseConnection_Android().CreateConnection().Query<CaptureEntity>("SELECT * FROM [CaptureEntity]").Single(c => c.WorkflowId == captureId);
var images = new DatabaseConnection_Android().CreateConnection().Query<ImageEntity>("SELECT * FROM [ImageEntity]").Where(i => i.CaptureEntityId == capture.Id);
try
{
MultipartFormDataContent content = new MultipartFormDataContent();
StringContent strContent = new StringContent(
capture.XmlData,
Encoding.UTF8,
"text/xml");
IImageHandler handler = new ImageHandler_Droid();
HttpRequestMessage request = new HttpRequestMessage();
request.Headers.Add("workflow", capture.WorkflowId.ToString());
request.Method = HttpMethod.Post;
request.RequestUri = serviceAddress;
foreach (var image in images)
{
byte[] imageByte = handler.ReadAllBytes(image.ImagePath);
ByteArrayContent byteContent = new ByteArrayContent(imageByte);
byteContent.Headers.Add("Content-Type", "image/jpeg");
content.Add(byteContent, "file", image.ImageName);
}
content.Add(strContent, "text/xml");
request.Content = content;
using (HttpClient client = new HttpClient())
{
client.Timeout = TimeSpan.FromSeconds(180);
var response = client.SendAsync(
request,
HttpCompletionOption.ResponseContentRead).Result;
var readResponse = response.Content.ReadAsStringAsync().Result;
if (readResponse == "File uploaded.")
MessagingCenter.Send<CaptureEntity, string>(
capture,
"Completed",
"Success");
else if (readResponse.Contains("An error has occurred."))
MessagingCenter.Send<CaptureEntity, string>(
capture,
"Uploader",
String.Format(CultureInfo.InvariantCulture,
"Failed: {0}",
readResponse));
else
MessagingCenter.Send<CaptureEntity, string>(
capture,
"Uploader",
String.Format(CultureInfo.InvariantCulture,
"Failed: {0}",
readResponse));
}
}
catch (WebException webExc)
{
MessagingCenter.Send<string, string>("Uploader", "Failed",
String.Format(CultureInfo.InvariantCulture,
"{0} upload failed.\n{1}",
capture.DisplayName,
webExc.Message));
}
catch (TimeoutException timeExc)
{
MessagingCenter.Send<string, string>("Uploader", "Failed",
String.Format(CultureInfo.InvariantCulture,
"{0} upload failed.\n{1}",
capture.DisplayName,
timeExc.Message));
}
catch (Exception exc)
{
MessagingCenter.Send<string, string>("Uploader", "Failed",
String.Format(CultureInfo.InvariantCulture,
"{0} upload failed.\n{1}",
capture.DisplayName,
exc.Message));
}
}
}
Can anyone tell me what I am doing wrong as I am getting the following error when I want to start the service:
Java.Lang.NullPointerException: Attempt to invoke virtual method 'android.content.ComponentName android.content.Context.startService(android.content.Intent)' on a null object reference
In your Intent declaration you need to tell the service you want to call
Something like this:
var uploadIntent = new Intent(this, typeof(ServiceIntent));
Note: this represents the Context.
Update:
As mentioned in the comments your interface implementation cannot derive from Activity class. In order to have access to the Context to be able to call the StartService method and also create your Intent you can make it in two ways:
Using the Xamarin.Forms.Forms.Context:
public async Task<bool> UploadAsync(Uri serviceAddress,
CaptureEntity capture,
List<ImageEntity> images)
{
try
{
var context = Xamarin.Forms.Forms.Context;
var uploadIntent = new Intent(context, typeof(ServiceIntent));
uploadIntent.PutExtra("serviceAddress", serviceAddress.ToString());
uploadIntent.PutExtra("captureId", capture.WorkflowId.ToString());
context.StartService(uploadIntent);
return true;
}
catch (Exception exc)
{
App.logger.LogError(DateTime.Now, "Uploader", exc.ToString());
throw exc;
}
}
If you are using latest versions of Xamarin.Forms this global context was deprecated and they suggest to you local context instead. You can still use it though but in future updates of XF your app might break.
using CurrentActivity plugin:
public async Task<bool> UploadAsync(Uri serviceAddress,
CaptureEntity capture,
List<ImageEntity> images)
{
try
{
var context = CrossCurrentActivity.Current.Activity;
var uploadIntent = new Intent(context, typeof(ServiceIntent));
uploadIntent.PutExtra("serviceAddress", serviceAddress.ToString());
uploadIntent.PutExtra("captureId", capture.WorkflowId.ToString());
context.StartService(uploadIntent);
return true;
}
catch (Exception exc)
{
App.logger.LogError(DateTime.Now, "Uploader", exc.ToString());
throw exc;
}
}
This plugin can be installed from nugget and the setup is very straight forward. Basically it gives you access to the current activity and you can use it as your context to call the IntentService
Hope this helps.-
Here is the IntentService.
IntentService is a base class for Services that handle asynchronous requests (expressed as Intents) on demand. Clients send requests through startService(Intent) calls; the service is started as needed, handles each Intent in turn using a worker thread, and stops itself when it runs out of work.
In Android, we usually use IntentService to do asynchronous operator. As we all know, thread is also used to do asynchronous operator. The difference between IntentService and Thread is IntentService is Service which belongs to Android Component. So, the priority of IntentService is higher than Thread.
For example, there is a ActivityA which has a IntentService, and there is a ActivityB which has a Thread, both IntentService and Thread are working, and both ActivityA and ActivityB are al background Activity. Now, if your phone's system doesn't have extra resources, your ActivityB will be killed firstly.
About the Exception:
Java.Lang.NullPointerException: Attempt to invoke virtual method 'android.content.ComponentName android.content.Context.startService(android.content.Intent)' on a null object reference
That means you should use android.content.Context to call the StartService method. In Android, there are three kinds of Context. Application, Activity and Service. So you can call the StartService method in these three classes directly. If you are not in these three classes, you need pass the Context to your class, and then use the Context to call StartService.
I added Activity for this class' inheritance.
If you do this, your class will be a Activity, and you need to register it in your manifiest, add layout for your class, and it should have the lifecycle, and etc. It will not be what you want to get class. In Android, Activity is a Component, not normal class, so you can't inherit it unless you want your class to be a Activity.
Demo:
I have made a demo for you,
In my WebApi code, I raise a HttpResponseException which short-circuits the request pipeline and generates a valid Http response. However, I'm trying to integrate webApi with elmah logging, yet the HttpResponseExeptions aren't showing up.
I have the web.config set-up for elmah and have the following code:
In Global.asx.cs:
static void ConfigureWebApi(HttpConfiguration config)
{
config.Filters.Add(new ServiceLayerExceptionFilter());
config.Filters.Add(new ElmahHandledErrorLoggerFilter());
config.DependencyResolver = new WebApiDependencyResolver(ObjectFactory.Container);
}
Filter:
public class ElmahHandledErrorLoggerFilter : ExceptionFilterAttribute
{
public override void OnException(HttpActionExecutedContext actionExecutedContext)
{
base.OnException(actionExecutedContext);
ErrorSignal.FromCurrentContext().Raise(actionExecutedContext.Exception);
}
}
Code where exception is raised:
public Task<FileUpModel> UploadFile()
{
if (Request.Content.IsMimeMultipartContent())
{
var provider = new TolMobileFormDataStreamProvider("C:\images\");
var task = Request.Content.ReadAsMultipartAsync(provider).ContinueWith(
t =>
{
if (t.IsFaulted || t.IsCanceled)
throw new HttpResponseException(HttpStatusCode.InternalServerError);
var fileInfo = provider.FileData.FirstOrDefault();
if (fileInfo == null)
// the exception here isn't logged by Elmah?!
throw new HttpResponseException(HttpStatusCode.InternalServerError);
var uploadModel = new FileUpModel { success = true };
return uploadModel;
});
return task;
}
else
{
throw new HttpResponseException(Request.CreateResponse(HttpStatusCode.NotAcceptable, "This request is not properly formatted"));
}
}
Can anyone who has implemented this before let me know what I'm doing wrong?
As mentioned above, the Elmah filter does not catch and log anything when you raise a HttpResponseException. More specifically, if the following syntax is used:
return Request.CreateErrorResponse(HttpStatusCode.BadRequest, "It was a bad request");
or
throw new HttpResponseException(Request.CreateResponse(HttpStatusCode.NotAcceptable, "HttpResponseException - This request is not properly formatted"));
I wanted to trap and log an error in both cases. The way to do it is to use an "ActionFilterAttribute", override "OnActionExecuted", and check actionExecutedContext.Response.IsSuccessStatusCode.
public override void OnActionExecuted(HttpActionExecutedContext actionExecutedContext)
{
// when actionExecutedContext.Response is null, the error will be caught and logged by the Elmah filter
if ((actionExecutedContext.Response != null) && !actionExecutedContext.Response.IsSuccessStatusCode)
{
try
{
var messages = (System.Web.Http.HttpError)((System.Net.Http.ObjectContent<System.Web.Http.HttpError>)actionExecutedContext.Response.Content).Value;
StringBuilder stringBuilder = new StringBuilder();
foreach (var keyValuePair in messages) {
stringBuilder.AppendLine("Message: Key - " + keyValuePair.Key + ", Value - " + keyValuePair.Value);
}
Elmah.ErrorSignal.FromCurrentContext().Raise(new Exception("Web API Failed Status Code returned - " + stringBuilder.ToString()));
}
catch (Exception ex)
{
Elmah.ErrorSignal.FromCurrentContext().Raise(new Exception("Error in OnActionExecuted - " + ex.ToString()));
}
}
}
On a side note, I also overwrote "OnActionExecuting" to validate the model state. This allowed me to remove all of the checks within my actions.
public override void OnActionExecuting(System.Web.Http.Controllers.HttpActionContext actionContext)
{
if (actionContext.ModelState != null && !actionContext.ModelState.IsValid)
{
StringBuilder stringBuilder = new StringBuilder();
foreach (var obj in actionContext.ModelState.Values)
{
foreach (var error in obj.Errors)
{
if(!string.IsNullOrEmpty(error.ErrorMessage)) {
stringBuilder.AppendLine("Error: " + error.ErrorMessage);
}
}
}
Elmah.ErrorSignal.FromCurrentContext().Raise(new Exception("Invalid Model State -- " + stringBuilder.ToString()));
actionContext.Response = actionContext.Request.CreateErrorResponse(HttpStatusCode.BadRequest, actionContext.ModelState);
}
}
Of course, you will need to add the filter using "config.Filters.Add".
Web API special cases HttpResponseException thrown in action and converts into HttpResponseMessage and hence you are not seeing your exception filter getting invoked.
This is not true in the case of throwing HttpResponseException from filters. However, ideally one need not throw HttpResponseException from filters as you could short-circuit a request by setting the Response property on the supplied input context.
You need to turn on Elmah for HttpFilters in order to get this to work as you expect for WebApi.
Use Elmah.Contrib.WebApi available as a NuGet Package, it will wire include a class that you can then wire up following the instructions on the Elmah.Contrib.WebApi project site.
If you want to do this yourself, Capturing Unhandled Exceptions in ASP.NET Web API's with ELMAH walks you through what the Elmah.Contrib.WebApi is doing for you.
Additionally, I had to change the way that the error response is thrown for it to be picked by Elmah to:
throw new HttpException((int)HttpStatusCode.NotAcceptable, "This request is not properly formatted");
I would also recommend the use of the Elmah.MVC NuGet Package.
To start off with, this might be tagged as a duplicate of the following thread:
Wait for HttpWebRequest.BeginGetResponse to finish in Windows Phone 7, however, the responses in that thread did not help me get over my problem.
To begin with, I am collecting user data on the UI Thread in order to process application registration, where I also have an instance of ManualResetEvent:
private static ManualResetEvent registrationEvent = new ManualResetEvent(false);
I have another thread which handles the registration process (and includes the HttpWebRequest.BeginGetResponse() and its corresponding callback method.)
Thread t = new Thread(() => RegistrationHandler.sendRegistrationData(url));
t.Start();
Right after this call, I block the current (UI) thread with a call to
registrationEvent.WaitOne();
//Process the response, update some UI elements and navigate to a different page.
httpSessionCompleted(response);
Once the thread handling the registration process starts, I am instantiating HttpWebRequest and invoking the BeginGetResponse() method on it.
try
{
HttpWebRequest request = HttpWebRequest.CreateHttp(url);
request.Method = "POST";
request.ContentType = mimeType;
request.BeginGetResponse(new AsyncCallback(GetRequestCallback), request);
}
catch (Exception ex)
{
Console.WriteLine("Exception caught in sendData(): {0}", ex.Message);
}
Now the issue is that the callback method (code below) is never invoked, and the application just freezes. There also doesn't seem to be any exception(s) thrown either.
try
{
HttpWebRequest request = (HttpWebRequest)asyncResult.AsyncState;
if (request != null)
{
using (HttpWebResponse response = (HttpWebResponse)request.EndGetResponse(asyncResult))
{
using (StreamReader reader = new StreamReader(response.GetResponseStream()))
{
String result = reader.ReadToEnd();
Globals.HostResponse = result;
//Signalling the calling thread to continue execution
RegistrationPage.RegistrationEvent.Set();
}
}
}
}
catch (Exception ex)
{
Console.WriteLine("Exception caught in GetRequestCallback(): {0}", ex.Message);
}
I ideally want my application to continue from httpSessionCompleted() after the callback method finishes execution. Can someone please help me with some guidance/suggestions?
Sorry for being verbose. Thanks!
You should not block UI thread, use callback pattern instead. Look at this: Windows Phone 7 - wait for Webclient to complete . Hope this helps
We have implemented a Custom Membership provider and have a change password control on a webpage that uses this provider. The ChangePassword method in this membership provider class checks some business logic about password strength and validity by connecting to an external webservice. The webservice has the ability to return exactly what is wrong with the new password if any (length problems, special character required etc.).
Now, the signature of the ChangePassword method that has to be overriden by a custom provider is:
public override bool ChangePassword(string username, string oldPassword, string newPassword)
So even though I know the exact problem with the new password the user supplies, I am not able to display it on the webpage because I can only return a true or false from this method and the change password control then takes over and does its own magic depending on the boolean return value. I can hook up the OnChangePasswordError event of the ChangePassword control to show a static error message, or I can even setup the FailureText property of this control to some hard-coded string when an error occurs, but I am unable to provide to the user what exactly is wrong with the password they supplied.
protected void OnPasswordChangeError(object sender, EventArgs e)
{
throw new MembershipPasswordException("Tell user what exactly is wrong with the password they supplied");
}
The MembershipProvider class has a ValidatingPassword event, that is raised BEFORE the password is changed, and I can throw an exception here by checking if the password meets the criteria, but still that exception does not seem to be passed to the ChangePassword control. Here is the code for the ValidatingPassword eventHandler:
void MyMembershipProvider_ValidatingPassword(object sender, ValidatePasswordEventArgs e)
{
//if password not valid
e.Cancel = true;
e.FailureInformation = new MembershipPasswordException();
e.FailureInformation;
}
how to send specific information from the ChangePassword method of the Membership provider class to the ChangePassword control to display the correct, non static/hardcoded password change error messages to the user? Is there a way to hook up the ValidatePasswordEventArgs to the EventArgs in the EventHandler for the OnChangePassword method so that I can get the FailureInformation in the ChangePassword control?
From my initial research this does not seem to be possible. Though I feel that the MS team would not have overlooked this and there should be a way.
A few pointers:
MembershipUser.ChangePassword fails without warning
http://forums.asp.net/t/983613.aspx
OK, so I finally figured a workaround. It is not the cleanest, but the only one I could come up with or found anywhere that was close to what should have been inclued by default.
Note: I did not have the option to persist this in a database or a cookie.
I created a ChangePasswordNew method that has the same behavior as the MembershipProvider ChangePassword method, but returns string instead of bool. So my new method would look like this:
public string ChangePasswordNew(string username, string oldPassword, string newPassword)
{
//if password rules met, change password but do not return bool as MembershipProvider method does,
//return Success or the exact error for failure instead
if(passwordChangeRequirementsMet == true)
{
//change the password
return "success";
}
else
return "exact reason why password cannot be changed";
}
Now, subscribe to the onPasswordChanging event of the ChangePassword Control:
protected void PasswordIsChanging(object sender, LoginCancelEventArgs e)
{
try
{
string response = Provider.ChangePasswordNew(username, currentPass, newPass);
if(response != "success")
{
changePwdCtrl.FailureText = response;
}
else
{
//cancel call to the default membership provider method that will attempt to
//change the password again. Instead, replicate the 'steps' of AttemptChangePassword(),
//an internal method of the ChangePassword control.
//Performing all the steps instead of calling the method because just calling method
//does not work for some reason
e.Cancel = true;
FormsAuthentication.SetAuthCookie(username, false);
OnPasswordChanged(sender, e);
MethodInfo successMethodInfo = changePwdCtrl.GetType().GetMethod("PerformSuccessAction", BindingFlags.NonPublic | BindingFlags.Instance);
successMethodInfo.Invoke(changePwdCtrl, new object[] { "", "", changePwdCtrl.NewPassword });
}
}
catch(Exception ex)
{
LogException(ex);
throw;
}
}
Note: In this case, if there is an error on password change, i.e. response is not "success", the Memebership Provider ChangePassword method will still be called and will return an error again. But I am already setting the FailureText property to the descriptive error returned from response in the first call, which was my objective. I did not mind two method calls in my case. Your case may be different.
Hope this helps someone!
You can do this instead, that way you are not calling the changepassword method twice.
if(response != "success")
{
e.Cancel = true;
((Literal)changePwdCtrl.ChangePasswordTemplateContainer.FindControl("FailureText")).Text = response;
}
I created a custom membershipprovider class that handles this, the changepassword method in the membership class throws and error message of the specific message and I return that back to the control literal of the change password control.
protected void ChangePassword1_ChangingPassword(object sender, LoginCancelEventArgs e)
{
try
{
ChangePassword c = (ChangePassword)sender;
MembershipUser mu = Membership.GetUser(c.UserName);
bool response;
try
{
response = mu.ChangePassword(c.CurrentPassword, c.NewPassword);
}
catch (Exception ex)
{
response = false;
e.Cancel = true;
//ChangePassword1.ChangePasswordFailureText = ex.Message;
//ChangePassword1_ChangePasswordError(sender, e);
//((Literal)ChangePassword1.ChangePasswordTemplateContainer.FindControl("FailureText")).Visible = true;
((Literal)ChangePassword1.ChangePasswordTemplateContainer.FindControl("FailureText")).Text = ex.Message;
}
if (response)
{
//cancel call to the default membership provider method that will attempt to
//change the password again. Instead, replicate the 'steps' of AttemptChangePassword(),
//an internal method of the ChangePassword control.
//Performing all the steps instead of calling the method because just calling method
//does not work for some reason
e.Cancel = true;
FormsAuthentication.SetAuthCookie(c.UserName, false);
ChangePassword1_ChangedPassword(sender, e);
MethodInfo successMethodInfo = ChangePassword1.GetType().GetMethod("PerformSuccessAction", BindingFlags.NonPublic | BindingFlags.Instance);
successMethodInfo.Invoke(ChangePassword1, new object[] { "", "", ChangePassword1.NewPassword });
}
}
catch (Exception ex)
{
throw;
}
At one time I needed to pass info out of a provider and ended up just setting a cookie before returning your bool to be picked up on the other end of the call. Worked fine.
I believe a cleaner workaround is for the ChangePassword method to throw an exception. The exception contains the error message!