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Xamarin.Forms有一个用于启动计时器的API,您可能会发现它对此有用,在此处记录.

Device.StartTimer (TimeSpan.FromSeconds(10), () => {
    // If you want to update UI, make sure its on the on the main thread.
    // Otherwise, you can remove the BeginInvokeOnMainThread
    Device.BeginInvokeOnMainThread(() => methodRunPeriodically());
    return shouldRunAgain;
});

根据上述问题中的代码,您将确保:

您的userdata对象实现IPropertyChange,如下所示:

//Other usings skipped for brevity
...
...
using System.ComponentModel;
using System.Runtime.CompilerServices;

// This is a simple user class that 
// implements the IPropertyChange interface.
public class DemoUser : INotifyPropertyChanged
{
    // These fields hold the values for the public properties.
    private string userName = string.Empty;
    private string phoneNumber = string.Empty;

    public event PropertyChangedEventHandler PropertyChanged;

    // This method is called by the Set accessor of each property.
    // The CallerMemberName attribute that is applied to the optional propertyName
    // parameter causes the property name of the caller to be substituted as an argument.
    private void NotifyPropertyChanged([CallerMemberName] String propertyName = "")
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }

    public DemoUser()
    {
    }
    public string Id { get; set; }
    public string UserName
    {
        get
        {
            return this.userName;
        }

        set
        {
            if (value != this.userName)
            {
                this.userName = value;
                NotifyPropertyChanged();
            }
        }
    }

    public string PhoneNumber
    {
        get
        {
            return this.phoneNumber;
        }

        set
        {
            if (value != this.phoneNumber)
            {
                this.phoneNumber = value;
                NotifyPropertyChanged();
            }
        }
    }
}

在您的ContentPage中,然后尝试以下操作(我稍微修改了上面的其他代码):

public class UserPage : ContentPage
{
    private DemoUser demoUser;
    private int intervalInSeconds;

    public UserPage()
    {
        //Assuming this is a XAML Page....
        InitializeComponent();
    }
    public UserPage(DemoUser demoUser, int intervalInSeconds = 10) : this()
    {
        this.demoUser = demoUser;
        this.intervalInSeconds = intervalInSeconds;

        this.BindingContext = this.demoUser; 

        Device.StartTimer(TimeSpan.FromSeconds(this.intervalInSeconds), () =>
        {
            Device.BeginInvokeOnMainThread(() => refreshDemoUser());
            return true;
        });
    }

    private async void refreshDemoUser()
    {
        this.demoUser = await getDemoUserById(this.demoUser.Id);
    }
}