XAML ProgressRing 不会停止

Question

我的问题是 ProgressRing 一直在运行。我使用 MVVM。 ProgressRing 只能在应用获取新数据时激活。

我在 VM 中有代码（我更新了 ViewModel）：

public class MainPageViewModel : ObservableCollection<AdModel>, ISupportIncrementalLoading{
    private Visibility _loaderVisibility;
    public Visibility LoaderVisibility
    {
        get { return _loaderVisibility; }
        private set
        {
            _loaderVisibility = value;

        }}
    public IAsyncOperation<LoadMoreItemsResult> LoadMoreItemsAsync(uint count)
    {
        CoreDispatcher coreDispatcher = Window.Current.Dispatcher;

        return Task.Run<LoadMoreItemsResult>(async () =>
        {
            await coreDispatcher.RunAsync(CoreDispatcherPriority.Normal,
                () =>
                {
                    this.LoaderVisibility = Visibility.Visible;
                });

            var NewAds = new ObservableCollection<AdModel>();

            do{NewAds = await LoadAds();//get data from API}
            while (NewAds == null);

            await coreDispatcher.RunAsync(CoreDispatcherPriority.Normal,
                () =>
                {
                    foreach (AdModel item in NewAds)
                    {
                        this.Add(item);
                    }
                    this.LoaderVisibility = Visibility.Collapsed;
                });

            return new LoadMoreItemsResult() { Count = count };
        }).AsAsyncOperation<LoadMoreItemsResult>();}}

Answer 1

首先，您需要在更改 LoaderVisibility 属性时触发 PropertyChanged 事件，以便通知 UI 新值。请参阅有关如何Implement Property Change Notification 的示例。

LoaderVisibility 属性应该如下所示（这个 VM 类需要实现INotifyPropertyChanged 接口，所以你有PropertyChanged 事件）。

private Visibility _loaderVisibility; 
public Visibility LoaderVisibility 
{
    get { return _loaderVisibility; }
    set 
    {
        _loaderVisibility = value;
        OnPropertyChanged(new System.ComponentModel.PropertyChangedEventArgs("LoaderVisibility"));
    }
}

其次，不要在后面的代码中设置 ProgressRing's Visibility 属性，这会破坏您在 XAML 中连接的数据绑定。