API 结果未显示 C# UWP

Question

Hello everyone,

I'm trying to use an API to show the current Bitcoin price. The API returns the result and everything but it just won't show it on the UWP application.

The strange thing is that it did show the result one time but after that it never showed the result again.

• Yes the API is really fast.

Here is my MainPage code:

public sealed partial class MainPage : Page, INotifyPropertyChanged
{
    public string Price { get; set; }

    private DispatcherTimer _timer;

    public event PropertyChangedEventHandler PropertyChanged;

    public MainPage()
    {
        this.InitializeComponent();

        this._timer = new DispatcherTimer();
        this._timer.Interval = TimeSpan.FromSeconds(20);
        this._timer.Tick += OnUpdate;

        this._timer.Start();
    }

    private async void OnUpdate(object sender, object e)
    {
        this.Price = (await API.GetData(1))[0]["price_eur"];
        this.PropertyChanged?.Invoke(this, new PropertyChangedEventArgs("Price"));
    }
}

Here is my API class code:

class API
{
    public static async Task<List<Dictionary<string, string>>> GetData(int limit)
    {
        var url = "https://api.coinmarketcap.com/v1/ticker/?convert=EUR&limit=" + limit;

        using (var client = new HttpClient())
        {
            var response = await client.GetAsync(url);

            if (response.IsSuccessStatusCode)
            {
                var result = await response.Content.ReadAsStringAsync();

                return JsonConvert.DeserializeObject<List<Dictionary<string, string>>>(result);
            }
            else
            {
                return null;
            }
        }
    }
}

Here is my MainPage xaml code:

<RelativePanel>
        <Rectangle x:Name="rctOrange" Fill="Orange" RelativePanel.AlignRightWithPanel="True" RelativePanel.AlignBottomWithPanel="True" Stretch="UniformToFill"/>
        <TextBlock x:Name="tbPrice" FontSize="80" Text="{x:Bind Price, Mode=OneWay}" RelativePanel.AlignVerticalCenterWith="rctOrange" RelativePanel.AlignHorizontalCenterWith="rctOrange"/>
</RelativePanel>

I hope you guys can find the problem because I'm getting crazy.

Thanks in advance!

Answer 1

You shouldn't implement INotifyPropertyChanged on your page. You should create an ViewModel that implements INotifyPropertyChanged.

private async void OnUpdate(object sender, object e)
{
    this.Price.Value = (await API.GetData(1))[0]["price_eur"];
}

class PriceModel : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;
    private string _value;
    public string Value
    {
        get { return _value; }
        set
        {
            _value = value;
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs("Value"));
        }
    }
}