在C＃中每5秒调用一次API

Question

I'm trying to develop a mobile app on Xamarin Forms platform.I'm getting data from API.API call only happened once only when the application is opened. I'm Listing livescores between teams in a ListView . For example the minutes of the match 25 for now.I'm waiting 2 minutes and nothing changed. The minute is the same on my ListView.When I close and open the app again minute is changing.I just want to make call every 5 second to refresh the data without close the application. Here is my code.

public List<liveScoreData>liveScore() 
    {
        var result = new List<liveScoreData>();
        try
        {

            Guid guidSifre = Guid.NewGuid();
            string guid = guidSifre.ToString();
            string result = CreateMD5forChecksum(guid);

            using (var client = new WebClient())
            {
                var values = new NameValueCollection();
                values["result"] = result;
                values["guid"] = guid;

                var response = client.UploadValues("http://abcd.com/admin/LiveScore", values);

                var responseString = Encoding.Default.GetString(response);


                var responseResult = JsonConvert.DeserializeObject(responseString);
                result = JsonConvert.DeserializeObject<List<liveScoreData>>(responseResult.ToString());

                Mehmet.liveScoreDataList = result;

            }
        }
        catch (Exception ex)
        {
            var exc = ex;
        }

        return result;

    }

Answer 1

What you can do is implement my special PollingTimer.cs class:

using System;
using System.Threading;
using Xamarin.Forms;

namespace AppNamespace.Helpers
{
    /// <summary>
    /// This timer is used to poll the middleware for new information.
    /// </summary>
    public class PollingTimer
    {
        private readonly TimeSpan timespan;
        private readonly Action callback;

        private CancellationTokenSource cancellation;

        /// <summary>
        /// Initializes a new instance of the <see cref="T:CryptoTracker.Helpers.PollingTimer"/> class.
        /// </summary>
        /// <param name="timespan">The amount of time between each call</param>
        /// <param name="callback">The callback procedure.</param>
        public PollingTimer(TimeSpan timespan, Action callback)
        {
            this.timespan = timespan;
            this.callback = callback;
            this.cancellation = new CancellationTokenSource();
        }

        /// <summary>
        /// Starts the timer.
        /// </summary>
        public void Start()
        {
            CancellationTokenSource cts = this.cancellation; // safe copy
            Device.StartTimer(this.timespan,
                () => {
                    if (cts.IsCancellationRequested) return false;
                    this.callback.Invoke();
                    return true; // or true for periodic behavior
            });
        }

        /// <summary>
        /// Stops the timer.
        /// </summary>
        public void Stop()
        {
            Interlocked.Exchange(ref this.cancellation, new CancellationTokenSource()).Cancel();
        }
    }
}

Then what you can do following that is in your page that you want to make a call every 5 seconds from, in the constructor at the end of it you can write this line of code:

timer = new PollingTimer(TimeSpan.FromSeconds(5), liveScore);

This will run your method every 5 seconds. To make your method work with the pollingtimer you must edit your method to a void and return the value to a global variable like so:

//Make a global variable for your method to access
  List<liveScoreData> globalLiveScore = new List<liveScoreData>();

      public void liveScore() 
        {
            var result = new List<liveScoreData>();
            try
            {

                Guid guidSifre = Guid.NewGuid();
                string guid = guidSifre.ToString();
                string result = CreateMD5forChecksum(guid);



                using (var client = new WebClient())
                {
                    var values = new NameValueCollection();
                    values["result"] = result;
                    values["guid"] = guid;



                    var response = client.UploadValues("http://abcd.com/admin/LiveScore", values);

                    var responseString = Encoding.Default.GetString(response);



                    var responseResult = JsonConvert.DeserializeObject(responseString);
                    result = JsonConvert.DeserializeObject<List<liveScoreData>>(responseResult.ToString());



                    Mehmet.liveScoreDataList = result;


                }
            }
            catch (Exception ex)
            {
                var exc = ex;
            }


            globalLiveScore = result;



        }

Then from there you can check your live score data in other methods. Then in your OnAppearing method you can run

timer.Start();

and in your OnDisappearing method you can run

timer.Stop();

have a play with it and see if you can put it in better places for optimal performance etc.

Answer 2

You could use the System.Threading.Timer object

and simply initialize it like this

`System.Threading.Timer myTimer = new System.Threading.Timer((e) =>
{
    liveScore(); //your function call
}, null, 
TimeSpan.FromSeconds(0), //start immediately
TimeSpan.FromSeconds(5)); //execute every 5 secs`