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Why first click event of button not working

I have app(net4.7.2) like this:
Program is simple, when user presses OK, im sending request to steam market to get informations about item which user entered (item steam market url) to textbox.
But when im trying to send request, first click event of button not working:
private void btnOK_Click(object sender, EventArgs e)
{
if (txtItemURL.Text.StartsWith("https://steamcommunity.com/market/listings/730/") == true)
{
Helpers.Helper.BuildURL(txtItemURL.Text);
SteamMarketItem SMI = Helpers.Helper.GetItemDetails();
lblPrice.Text = SMI.LowestPrice.ToString() + "$";
pbItemImage.ImageLocation = SMI.ImagePath;
Helpers.Helper.Kontrollar_BerpaEt();
}
else
{
Helpers.Helper.Kontrollar_SifirlaYanlisDaxilEdilib();
}
}
Method GetItemDetails():
public static SteamMarketItem GetItemDetails()
{
WinForms.Control.CheckForIllegalCrossThreadCalls = false;
Task.Run(() =>
{
try
{
using (HttpClient client = new HttpClient())
{
JavaScriptSerializer serializer = new JavaScriptSerializer();
/* Get item info: */
var ResultFromEndpoint1 = client.GetAsync(ReadyEndpointURL1).Result;
var Json1 = ResultFromEndpoint1.Content.ReadAsStringAsync().Result;
dynamic item = serializer.Deserialize<object>(Json1);
marketItem.LowestPrice = float.Parse(((string)item["lowest_price"]).Replace("$", "").Replace(".", ","));
/* Get item image: */
var ResultFromEndpoint2 = client.GetAsync(ReadyEndPointURL2).Result;
var Json2 = ResultFromEndpoint2.Content.ReadAsStringAsync().Result;
var html = ((dynamic)serializer.Deserialize<object>(Json2))["results_html"];
HtmlDocument htmlDoc = new HtmlDocument();
htmlDoc.LoadHtml(html);
marketItem.ImagePath = htmlDoc.DocumentNode.SelectSingleNode("//img[#class='market_listing_item_img']").Attributes["src"].Value + ".png";
Kontrollar_BerpaEt();
}
}
catch
{
Kontrollar_SifirlaYanlisDaxilEdilib();
}
});
return marketItem;
}
Class SteamMarketItem:
public class SteamMarketItem
{
public string ImagePath { get; set; }
public float LowestPrice { get; set; }
}
When im using Task.Run() first click not working, without Task.Run() working + but main UI thread stopping when request not finished.
I have no idea why this happens, I cant find problem fix myself, I will be glad to get help from you. Thanks.

If you want to use async you need to change your event handler to async so you can use await, please see the following:
1. Change your Event handler to async void, async void is acceptable on event handler methods, you should try to use async Task in place of async void in most other cases, so change your method signature to the following:
private async void btnOK_Click(object sender, EventArgs e)
{
if (txtItemURL.Text.StartsWith("https://steamcommunity.com/market/listings/730/") == true)
{
Helpers.Helper.BuildURL(txtItemURL.Text);
//here we use await to await the task
SteamMarketItem SMI = await Helpers.Helper.GetItemDetails();
lblPrice.Text = SMI.LowestPrice.ToString() + "$";
pbItemImage.ImageLocation = SMI.ImagePath;
Helpers.Helper.Kontrollar_BerpaEt();
}
else
{
Helpers.Helper.Kontrollar_SifirlaYanlisDaxilEdilib();
}
}
2. You shouldn't need to use Task.Run, HttpClient exposes async methods and you can make the method async, also, calling .Result to block on an async method is typically not a good idea and you should make the enclosing method async so you can utilize await:
//Change signature to async and return a Task<T>
public async static Task<SteamMarketItem> GetItemDetails()
{
WinForms.Control.CheckForIllegalCrossThreadCalls = false;
//what is marketItem?? Where is it declared?
try
{
using (HttpClient client = new HttpClient())
{
JavaScriptSerializer serializer = new JavaScriptSerializer();
/* Get item info: */
var ResultFromEndpoint1 = await client.GetAsync(ReadyEndpointURL1);
var Json1 = await ResultFromEndpoint1.Content.ReadAsStringAsync();
dynamic item = serializer.Deserialize<object>(Json1);
marketItem.LowestPrice = float.Parse(((string)item["lowest_price"]).Replace("$", "").Replace(".", ","));
/* Get item image: */
var ResultFromEndpoint2 = await client.GetAsync(ReadyEndPointURL2);
var Json2 = await ResultFromEndpoint2.Content.ReadAsStringAsync();
var html = ((dynamic)serializer.Deserialize<object>(Json2))["results_html"];
HtmlDocument htmlDoc = new HtmlDocument();
htmlDoc.LoadHtml(html);
marketItem.ImagePath = htmlDoc.DocumentNode.SelectSingleNode("//img[#class='market_listing_item_img']").Attributes["src"].Value + ".png";
Kontrollar_BerpaEt();
}
}
catch
{
Kontrollar_SifirlaYanlisDaxilEdilib();
}
//what is marketItem?? Where is it declared?
return marketItem;
}

Xamarin Forms Play a sound Asynchronously

I can successfully play sounds using Xamarin forms (Android and iOS) however I also need to achieve the following:
I need to await so that if multiple sounds are 'played', one will complete before the next.
I need to return a boolean to indicate whether operation was a success.
Here is my current simplified code (for the iOS platform):
public Task<bool> PlayAudioTask(string fileName)
{
var tcs = new TaskCompletionSource<bool>();
string filePath = NSBundle.MainBundle.PathForResource(
Path.GetFileNameWithoutExtension(fileName), Path.GetExtension(fileName));
var url = NSUrl.FromString(filePath);
var _player = AVAudioPlayer.FromUrl(url);
_player.FinishedPlaying += (object sender, AVStatusEventArgs e) =>
{
_player = null;
tcs.SetResult(true);
};
_player.Play();
return tcs.Task;
}
To test the method, I have tried calling it like so:
var res1 = await _audioService.PlayAudioTask("file1");
var res2 = await _audioService.PlayAudioTask("file2");
var res3 = await _audioService.PlayAudioTask("file3");
I had hoped to hear the audio for file1, then file2, then file3. However I only hear file 1 and the code doesn't seem to reach the second await.
Thankyou

I think your issue here is that the AVAudioPlayer _player was being cleared out before it was finished. If you were to add debugging to your FinsihedPlaying, you'll notice that you never hit that point.
Try these changes out, I made a private AVAudioPlayer to sit outside of the Task
(I used the following guide as a reference https://developer.xamarin.com/recipes/ios/media/sound/avaudioplayer/)
public async void play()
{
System.Diagnostics.Debug.WriteLine("Play 1");
await PlayAudioTask("wave2.wav");
System.Diagnostics.Debug.WriteLine("Play 2");
await PlayAudioTask("wave2.wav");
System.Diagnostics.Debug.WriteLine("Play 3");
await PlayAudioTask("wave2.wav");
}
private AVAudioPlayer player; // Leave the player outside the Task
public Task<bool> PlayAudioTask(string fileName)
{
var tcs = new TaskCompletionSource<bool>();
// Any existing sound playing?
if (player != null)
{
//Stop and dispose of any sound
player.Stop();
player.Dispose();
}
string filePath = NSBundle.MainBundle.PathForResource(
Path.GetFileNameWithoutExtension(fileName), Path.GetExtension(fileName));
var url = NSUrl.FromString(filePath);
player = AVAudioPlayer.FromUrl(url);
player.FinishedPlaying += (object sender, AVStatusEventArgs e) =>
{
System.Diagnostics.Debug.WriteLine("DONE PLAYING");
player = null;
tcs.SetResult(true);
};
player.NumberOfLoops = 0;
System.Diagnostics.Debug.WriteLine("Start Playing");
player.Play();
return tcs.Task;
}

Repeat async task by timer in xamarin forms

i'm new to xamarin.forms development and i'm still having my first steps from the few tutorials that are found on the net.
I have an async task that returns the time from date.jsontest.com
and i have a timer that decrements a text in a label.
i want to put the async task in the timer so that it repeats itself and displays the time on the label however im getting cannot convert async lamba to func
here's my code please help me, thanks
static async Task<string> RequestTimeAsync()
{
using (var client = new HttpClient())
{
var jsonString = await client.GetStringAsync("http://date.jsontest.com/");
var jsonObject = JObject.Parse(jsonString);
return jsonObject["time"].Value<string>();
}
}
protected override async void OnAppearing()
{
base.OnAppearing();
timeLabel.Text = await RequestTimeAsync();
Device.StartTimer(TimeSpan.FromSeconds(1), () => { // i want the taks to be put
//here so that it gets repeated
var number = float.Parse(button.Text) - 1;
button.Text = number.ToString();
return number > 0;
});
}
Reloading the Content Page in the timer would do the trick, so if anybody can please help me it would be appreciated

You just need to wrap the async method call in a Task.Run(), for example:
Device.StartTimer(TimeSpan.FromSeconds(1), () =>
{
Task.Run(async () =>
{
var time = await RequestTimeAsync();
// do something with time...
});
return true;
});

Solved
as simple as that
private async void ContinuousWebRequest()
{
while (_keepPolling)
{
timeLabel.Text = "call: "+counter+" "+ await RequestTimeAsync()+Environment.NewLine;
// Update the UI (because of async/await magic, this is still in the UI thread!)
if (_keepPolling)
{
await Task.Delay(TimeSpan.FromSeconds(5));
}
}
}
static async Task<string> RequestTimeAsync()
{
using (var client = new HttpClient())
{
var jsonString = await client.GetStringAsync("http://date.jsontest.com/");
var jsonObject = JObject.Parse(jsonString);
TimePage.counter++;
return jsonObject["time"].Value<string>();
}
}

A simple clock demonstrates a one second timer action:
Device.StartTimer(TimeSpan.FromSeconds(1), doitt);
bool doitt()
{
label1.Text = DateTime.Now.ToString("h:mm:ss");
return true;
}

or you can try this:
static async Task<string> RequestTimeAsync()
{
using (var client = new HttpClient())
{
var jsonString = await client.GetStringAsync("http://date.jsontest.com/");
var jsonObject = JObject.Parse(jsonString);
return jsonObject["time"].Value<string>();
}
}
protected override async void OnAppearing()
{
base.OnAppearing();
var Text = await RequestTimeAsync();
Device.StartTimer(TimeSpan.FromSeconds(1), () => {
// i want the taks to be put
//here so that it gets repeated
var jsonDateTsk = RequestTimeAsync();
jsonDateTsk.Wait();
var jsonTime = jsonDateTsk.Result;
var number = float.Parse(Text) - 1;
var btnText = $"{number}";
return number > 0;
});
}

Waiting on the results of GetGeopositionAsync()

I'm developing a WinPhone 8 App.
On this App there is a Button 'Send SMS'.
When the user clicks on this button two things should happen:
(Method A) Get the geo-coordinate of the current Location (using Geolocator and GetGeopositionAsync).
(Method B) Compose and send an SMS with the geo-coordinate as part of the body.
The Problem: GetGeopositionAsync is an asynchronous method. Before the coordinate is detected (which takes a few seconds) the SMS is sent (of course with no coordinates).
How can I tell Method 2 to wait until the coordinates are available?
OK, here is my code:
When the user presses the button, the coordinates are determined by the first method and the second method sends the SMS which includes the coordinates in its body:
private void btnSendSms_Click(object sender, RoutedEventArgs e)
{
GetCurrentCoordinate(); // Method 1
// -> Gets the coordinates
SendSms(); // Method 2
// Sends the coordinates within the body text
}
The first method GetCurrentCoordinate() looks as follows:
...
private GeoCoordinate MyCoordinate = null;
private ReverseGeocodeQuery MyReverseGeocodeQuery = null;
private double _accuracy = 0.0;
...
private async void GetCurrentCoordinate()
{
Geolocator geolocator = new Geolocator();
geolocator.DesiredAccuracy = PositionAccuracy.High;
try
{
Geoposition currentPosition = await geolocator.GetGeopositionAsync(
TimeSpan.FromMinutes(1),
TimeSpan.FromSeconds(10));
lblLatitude.Text = currentPosition.Coordinate.Latitude.ToString("0.000");
lblLongitude.Text = currentPosition.Coordinate.Longitude.ToString("0.000");
_accuracy = currentPosition.Coordinate.Accuracy;
MyCoordinate = new GeoCoordinate(
currentPosition.Coordinate.Latitude,
currentPosition.Coordinate.Longitude);
if (MyReverseGeocodeQuery == null || !MyReverseGeocodeQuery.IsBusy)
{
MyReverseGeocodeQuery = new ReverseGeocodeQuery();
MyReverseGeocodeQuery.GeoCoordinate = new GeoCoordinate(
MyCoordinate.Latitude,
MyCoordinate.Longitude);
MyReverseGeocodeQuery.QueryCompleted += ReverseGeocodeQuery_QueryCompleted;
MyReverseGeocodeQuery.QueryAsync();
}
}
catch (Exception)
{ // Do something }
}
private void ReverseGeocodeQuery_QueryCompleted(object sender,
QueryCompletedEventArgs<IList<MapLocation>> e)
{
if (e.Error == null)
{
if (e.Result.Count > 0)
{
MapAddress address = e.Result[0].Information.Address;
lblCurrAddress.Text = address.Street + " " + address.HouseNumber + ",\r" +
address.PostalCode + " " + address.City + ",\r" +
address.Country + " (" + address.CountryCode + ")";
}
}
}
}
And the Methode 'SendSms()':
private void SendSms()
{
SmsComposeTask smsComposeTask = new SmsComposeTask();
smsComposeTask.To = "0123456";
smsComposeTask.Body = "Current position: \rLat = " + lblLatitude.Text +
", Long = " + lblLongitude.Text +
"\r" + lblCurrAddress.Text;
// -> The TextBoxes are still empty!
smsComposeTask.Show();
}
The problem is, that all these TextBoxes (lblLatitude, lblLongitude, lblCurrAddress) are still empty when the method SendSms() sets the SmsComposeTask object.
I have to ensure that the TextBoxes are already set BEFORE the method SendSms() starts.

You should almost never mark a method async void unless it's a UI event handler. You're calling an asynchronous method without waiting for it to end. You are basically calling those 2 methods in parallel, so it's clear why the coordinates aren't available.
You need to make GetCurrentCoordinate return an awaitable task and await it, like this:
private async Task GetCurrentCoordinateAsync()
{
//....
}
private async void btnSendSms_Click(object sender, RoutedEventArgs e)
{
await GetCurrentCoordinateAsync();
// You'll get here only after the first method finished asynchronously.
SendSms();
}

This is one of the primary reasons you should avoid async void. void is a very unnatural return type for async methods.
First, make your GetCurrentCoordinate an async Task method instead of async void. Then, you can change your click handler to look like this:
private async void btnSendSms_Click(object sender, RoutedEventArgs e)
{
await GetCurrentCoordinate();
SendSms();
}
Your click handler is async void only because event handlers have to return void. But you should really strive to avoid async void in all other code.

There two things you're doing wrong here:
Using void returning async methods when you need to await on them. This is bad because you can't await on execution of these methods and should only be used when you can't make the method return Task or Task<T>. That's why you're not seeing anything on the text boxes when SendSmsis called.
Mixing UI and non-UI code. You should transfer data between UI and non-UI code to avoid tight coupling between code with different responsibilities. IT also makes it easy to read and debug the code.
ReverseGeocodeQuery does not have an awaitable async API but you can easily make your own:
private async Task<IList<MapLocation>> ReverseGeocodeQueryAsync(GeoCoordinate geoCoordinate)
{
var tcs = new TaskCompletionSource<IList<MapLocation>>();
EventHandler<QueryCompletedEventArgs<IList<MapLocation>>> handler =
(s, e) =>
{
if (e.Cacelled)
{
tcs.TrySetCancelled();
}
else if (e.Error != null)
{
tcs.TrySetException(e.Error);
}
else
{
tcs.TrySetResult(e.Result);
}
};
var query = new ReverseGeocodeQuery{ GeoCoordinate = geoCoordinate };
try
{
query.QueryCompleted += handler;
query.QueryAsync();
return await tcs.Task;
}
finally
{
query.QueryCompleted -= handler;
}
}
This way you'll get full cancellation and error support.
Now let's make the retrieval of the geo coordinate information all in one chunk:
private async Task<Tuple<Geocoordinate, MapLocation>> GetCurrentCoordinateAsync()
{
try
{
var geolocator = new Geolocator
{
DesiredAccuracy = PositionAccuracy.High
};
var currentPosition = await geolocator.GetGeopositionAsync(
TimeSpan.FromMinutes(1),
TimeSpan.FromSeconds(10))
.ConfigureAwait(continueOnCapturedContext: false);
var currentCoordinate = currentPosition.Coordinate;
var mapLocation = await this.ReverseGeocodeQueryAsync(
new GeoCoordinate(
currentCoordinate.Latitude,
currentCoordinate.Longitude));
return Tuple.Create(
currentCoordinate,
mapLocation.FirstOrDefault());
}
catch (Exception)
{
// Do something...
return Tuple.Create(null, null);
}
}
Now the button eventnt handler becomes much more readable:
private void btnSendSms_Click(object sender, RoutedEventArgs e)
{
var info = await GetCurrentCoordinate();
if (info.Item1 != nuil)
{
lblLatitude.Text = info.Item1.Latitude.ToString("0.000");
lblLongitude.Text = info.Item1.Longitude.ToString("0.000");
}
if (info.Item2 != null)
{
var address = info.Item2.Information.Address;
lblCurrAddress.Text = string.Format(
"{0} {1},\n{2} {3},\n{4} ({5})",
address.Street,
address.HouseNumber,
address.PostalCode,
address.City,
address.Country,
address.CountryCode);
}
SendSms(info.Item1, info.Item2);
}
Does this make sense?

How do I create a background thread

I'm currently working toward a mobile android application. The main thing that this app will have trouble with for load times is a Webservice json string that at this current stage is taking too long to load and sometimes causing the app to force close (stalling for too long).
Splash -> MainActivity -> HomeActivity This is how our application starts.
First we display a Splash, and behind that we run the MainActivity, which consists of the following code:
public class HomeActivity : Activity
{
NewsObject[] news;
protected override void OnCreate (Bundle bundle)
{
base.OnCreate (bundle);
SetContentView (Resource.Layout.Main);
var request = HttpWebRequest.Create(string.Format(#"http://rapstation.com/webservice.php"));
request.ContentType = "application/json";
request.Method = "GET";
using (HttpWebResponse response = request.GetResponse() as HttpWebResponse)
{
if (response.StatusCode != HttpStatusCode.OK)
Console.Out.WriteLine("Error fetching data. Server returned status code: {0}", response.StatusCode);
using (StreamReader reader = new StreamReader(response.GetResponseStream()))
{
var content = reader.ReadToEnd();
if(string.IsNullOrWhiteSpace(content)) {
Console.Out.WriteLine("Response contained empty body...");
Toast toast = Toast.MakeText (this, "No Connection to server, Application will now close", ToastLength.Short);
toast.Show ();
}
else {
news = JsonConvert.DeserializeObject<NewsObject[]>(content);
}
}
Console.Out.WriteLine ("Now: \r\n {0}", news[0].title);
}
var list = FindViewById<ListView> (Resource.Id.list);
list.Adapter = new HomeScreenAdapter (this, news);
list.ItemClick += OnListItemClick;
var Listen = FindViewById<Button> (Resource.Id.btnListen);
var Shows = FindViewById<Button> (Resource.Id.btnShows);
Listen.Click += (sender, e) => {
var second = new Intent (this, typeof(RadioActivity));
StartActivity (second);
};
Shows.Click += (sender, e) => {
var second = new Intent (this, typeof(ShowsActivity));
StartActivity (second);
};
}
protected void OnListItemClick(object sender, AdapterView.ItemClickEventArgs e)
{
var listView = sender as ListView;
var t = news[e.Position];
var second = new Intent (this, typeof(NewsActivity));
second.PutExtra ("newsTitle", t.title);
second.PutExtra ("newsBody", t.body);
second.PutExtra ("newsImage", t.image);
second.PutExtra ("newsCaption", t.caption);
StartActivity (second);
Console.WriteLine("Clicked on " + t.title);
}
}
The problem I am running into is the app will stick on the Splash page and the Application output will tell me that I am running too much on the Main thread.
What is a way to separate the download request to work in the background?

private class myTask extends AsyncTask<Void, Void, Void> {
#Override
protected void onPreExecute() {
}
#Override
protected Void doInBackground(Void... params) {
// Runs on the background thread
return null;
}
#Override
protected void onPostExecute(Void res) {
}
}
and to run it
new myTask().execute();

Yes there is, you need to use AsyncTask, this should help too.

If the .Net/Mono version you're using supports async/await then you can simply do
async void DisplayNews()
{
string url = "http://rapstation.com/webservice.php";
HttpClient client = new HttpClient();
string content = await client.GetStringAsync(url);
NewsObject[] news = JsonConvert.DeserializeObject<NewsObject[]>(content);
//!! Your code to add news to some control
}
if Not, then you can use Task's
void DisplayNews2()
{
string url = "http://rapstation.com/webservice.php";
Task.Factory.StartNew(() =>
{
using (var client = new WebClient())
{
string content = client.DownloadString(url);
return JsonConvert.DeserializeObject<NewsObject[]>(content);
}
})
.ContinueWith((task,y) =>
{
NewsObject[] news = task.Result;
//!! Your code to add news to some control
},null,TaskScheduler.FromCurrentSynchronizationContext());
}