Question

我的问题是ProgressRing一直在运行。我使用MVVM。只有当app获取新数据时，ProgressRing才会处于活动状态。

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(Activity)context).runOnUiThread(new Runnable() { public void run() { // your code Toast.makeText(magContext, "hi", Toast.LENGTH_SHORT).show(); } });属性时触发PropertyChanged事件，以便可以通知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（此VM类需要实现LoaderVisibility接口，因此您有INotifyPropertyChanged事件。

PropertyChanged

其次，不要在代码后面设置private Visibility _loaderVisibility; public Visibility LoaderVisibility { get { return _loaderVisibility; } set { _loaderVisibility = value; OnPropertyChanged(new System.ComponentModel.PropertyChangedEventArgs("LoaderVisibility")); } }属性，这会破坏你在XAML中连接的数据绑定。

XAML ProgressRing不会停止

1 个答案: