Windows Phone 7进度条，用于列表框加载数据

问题描述

| 列表框完成数据加载后，我可以监听事件吗？我有一个文本框和一个列表框，当用户单击Enter时，该列表框将填充Web服务的结果。我想在列表框加载时运行进度栏，并在完成时折叠它。 更新

    <controls:PivotItem Header=\"food\" Padding=\"0 110 0 0\">

            <Grid x:Name=\"ContentFood\" Grid.Row=\"2\" >

                <StackPanel>
                    ...
                    ...

                    <toolkit:PerformanceProgressBar Name=\"ppbFoods\" HorizontalAlignment=\"Left\" 
                        VerticalAlignment=\"Center\"
                        Width=\"466\" IsIndeterminate=\"{Binding IsDataLoading}\" 
                        Visibility=\"{Binding IsDataLoading,Converter={StaticResource BoolToVisibilityConverter}}\"
                        />


                    <!--Food Results-->
                    <ListBox x:Name=\"lbFoods\" ItemsSource=\"{Binding Foods}\" Padding=\"5\" 
                             SelectionChanged=\"lbFoods_SelectionChanged\" Height=\"480\" >
                        ....
                    </ListBox>

                </StackPanel>
            </Grid>


        </controls:PivotItem>

这是我的辅助转换器类...。

    public class BoolTovalueConverter<T> : IValueConverter
{
    public T FalseValue { get; set; }
    public T TrueValue { get; set; }

    public object Convert(object value,Type targettype,object parameter,System.Globalization.CultureInfo culture)
    {
        if (value == null)
            return FalseValue;
        else
            return (bool)value ? TrueValue : FalseValue;
    }

    public object ConvertBack(object value,System.Globalization.CultureInfo culture)
    {
        return value != null ? value.Equals(TrueValue) : false;
    }
}

public class BoolToStringConverter : BoolTovalueConverter<String> { }
public class BoolToBrushConverter : BoolTovalueConverter<Brush> { }
public class BoolToVisibilityConverter : BoolTovalueConverter<Visibility> { }
public class BoolToObjectConverter : BoolTovalueConverter<Object> { }

在我的App.xaml中...

    xmlns:HelperClasses=\"clr-namespace:MyVirtualHealthCheck.HelperClasses\"
    ...
    <HelperClasses:BoolToVisibilityConverter x:Key=\"BoolToVisibilityConverter\" TrueValue=\"Visible\" FalseValue=\"Collapsed\" />

viewmodel...。

    ...
    public bool IsDataLoading
    {
        get;
        set;
    }
    ...
    public void GetFoods(string strSearch)
    {
        IsDataLoading = true;
        WCFService.dcFoodInfoCollection localFoods = IsolatedStorageCacheManager<WCFService.dcFoodInfoCollection>.Retrieve(\"CurrentFoods\");

            if (localFoods != null)
            {
                Foods = localFoods;
            }
            else
            {
                GetFoodsFromWCF(strSearch);
            }
    }


    public void GetFoodsFromWCF(string strSearch)
    {
        IsDataLoading = true;
        wcfProxy.GetFoodInfosAsync(strSearch);
        wcfProxy.GetFoodInfosCompleted += new EventHandler<WCFService.GetFoodInfosCompletedEventArgs>(wcfProxy_GetFoodInfosCompleted);
    }

    void wcfProxy_GetFoodInfosCompleted(object sender,WCFService.GetFoodInfosCompletedEventArgs e)
    {
        WCFService.dcFoodInfoCollection foods = e.Result;
        if (foods != null)
        {
            //set current foods to the results from the web service
            this.Foods = foods;
            this.IsDataLoaded = true;

            //save foods to phone so we can use cached results instead of round tripping to the web service again
            SaveFoods(foods);
        }
        else
        {
            Debug.WriteLine(\"Web service says: \" + e.Result);
        }
        IsDataLoading = false;
    }

    

解决方法

        没有内置功能。完成加载数据后，您将必须更新进度条。 或者，在视图模型中更新布尔依赖项属性，然后将进度条绑定到该属性。 更新资料 一些基于注释的粗糙示例代码。这是在此处编写的，未经检查，但您应该了解一下： 虚拟机：

public class MyViewModel : INotifyPropertyChanged
{
    private bool isLoading;
    public bool IsLoading
    {
        get { return isLoading; }

        set
        {
            isLoading = value;
            NotifyPropertyChanged(\"IsLoading\");
        }
    }

    public void SimulateLoading()
    {
        var bw = new BackgroundWorker();

        bw.RunWorkerCompleted += (s,e) => 
            Deployment.Current.Dispatcher.BeginInvoke(
                () => { IsLoading = false; });

        bw.DoWork += (s,e) =>
        {
            Deployment.Current.Dispatcher.BeginInvoke(() => { IsLoading = true; });
            Thread.Sleep(5000);
        };

        bw.RunWorkerAsync();
    }

    public event PropertyChangedEventHandler PropertyChanged;

    private void NotifyPropertyChanged(String propertyName)
    {
        PropertyChangedEventHandler handler = PropertyChanged;
        if (null != handler)
        {
            handler(this,new PropertyChangedEventArgs(propertyName));
        }
    }
}

XAML：

<toolkit:PerformanceProgressBar IsEnabled=\"{Binding IsLoading}\" 
                                IsIndeterminate=\"{Binding IsLoading}\"/>

将页面的DataContext设置为视图模型的实例，然后在视图模型实例上调用ѭ6。 再次更新： 我的错误“ 7”是个布尔值，因此不需要转换器。     ,        您可以创建一个新的窗体，该窗体将带有进度条。 进度表单将具有计时器和进度栏。

Private Sub tProgress_Tick(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles tProgress.Tick
        Count = (Count + 1) Mod ProgressBar1.Maximum
        ProgressBar1.Value = Count
    End Sub

Public Sub KillMe(ByVal o As Object,ByVal e As EventArgs)

        Me.Close()

    End Sub

要从主窗体调用进度表，请使用以下代码

Dim ProgressThread As New Threading.Thread(New Threading.ThreadStart(AddressOf StartProgress))
ProgressThread.Start()

Public Sub ProgressSplash()
        \'Show please wait splash
        Progress = New frmProgress
        Application.Run(Progress)

End Sub

要关闭进度表，请使用此代码

Public Sub CloseProgress()

        If Progress IsNot Nothing Then

            Progress.Invoke(New EventHandler(AddressOf Progress.KillMe))
            Progress.Dispose()
            Progress = Nothing
        End If

    End Sub

由于Progress表单在其他线程上运行，因此不会冻结UI。 对不起，代码在VB.NET中