用于列表框加载数据的 Windows Phone 7 进度条 [英] windows phone 7 progress bar for a listbox loading data
问题描述
当列表框完成加载数据时,是否有我可以监听的事件?我有一个文本框和一个列表框,当用户按 Enter 键时,列表框会填充来自 Web 服务的结果.我想在列表框加载时运行进度条,并在完成时折叠它....
Is there an event I can listen for when a listbox has completed loading it's data? I have a textbox and a listbox, when the user hits enter, the listbox is populated with results from a web service. I'd like to run the progress bar while the listbox is loading and collapse it when it's finished....
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>
这是我的助手转换器类....
Here is my helper converter class....
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, Type targetType, object parameter, 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....
In my App.xaml....
xmlns:HelperClasses="clr-namespace:MyVirtualHealthCheck.HelperClasses"
...
<HelperClasses:BoolToVisibilityConverter x:Key="BoolToVisibilityConverter" TrueValue="Visible" FalseValue="Collapsed" />
视图模型....
...
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;
}
推荐答案
没有针对此的内置功能.完成数据加载后,您必须更新进度条.
或者更新视图模型中的布尔依赖属性并将进度条绑定到该属性.
There's no built in functionality for this. You'll have to update the progressbar when you've finished loading the data.
Alternatively update a boolean dependency property in your view model and bind the progress bar to that.
更新
一些粗略的示例代码,基于注释.这是写在这里并没有检查,但你应该明白:
Update
Some rough, example code, based on comments. This is written here and not checked but you should get the idea:
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 SimulateLoading()
.
Set the DataContext of the page to an instance of the view model and then call SimulateLoading()
on the view model instance.
再次更新:
我的错误 IsIndeterminate
是一个布尔值,因此不需要转换器.
Update yet again:
My mistake IsIndeterminate
is a bool so a converter isn't required.
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