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[英]WPF button binding to a property Convertback IMultiValueConverter does not update value
[英]WPF, Property does not return value to the binding
因此,我有一個帶有滾動文本(marqee)的項目,該項目在字符串數組上旋轉。 我希望它在每次動畫迭代20秒后更改字符串值。
但是,存在一個問題,使用INotifyPropertyChanged接口綁定到文本塊(使用XAML)的屬性(ScrollingText)在第一次迭代后不會返回。 即使它正常刷新(在set部分中),它也不會在Getter部分返回。
主要類別:
class GetScrollingText : CommonBase
{
private string _scrollingtext = String.Empty;
DoubleAnimation Animation;
public GetScrollingText()
{
ScrollingText = GetScrollString();
}
public string ScrollingText
{
get
{
return _scrollingtext;
}
set
{
if (value != _scrollingtext)
{
_scrollingtext = value;
RaisePropertyChanged("ScrollingText");
}
}
} // INJECTS the string in the animated textblock {binding}.
public TextBlock scrollBlock { get; set; }
string GetScrollString()
{
.........
return scrolltext;
}
public void LeftToRightMarqee(double from, double to)
{
Animation = new DoubleAnimation();
Animation.From = from;
Animation.To = to;
Animation.Duration = new Duration(TimeSpan.FromSeconds(20));
Animation.Completed += animation_Completed;
scrollBlock.BeginAnimation(Canvas.LeftProperty, Animation);
}
void animation_Completed(object sender, EventArgs e)
{
ScrollingText = GetScrollString();
scrollBlock.BeginAnimation(Canvas.LeftProperty, Animation);
}
}
由於某種原因,animation_Completed事件僅更改值ScrollingText,但不調用Getter部分,因此不會返回到{binding}。
XAML:
<Window
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:vm="clr-namespace:AnnouncingSys"
x:Class="AnnouncingSys.MainWindow"
x:Name="Window"
Width="1280" Height="720" MinHeight="566" MinWidth="710">
<Window.Resources>
<vm:GetScrollingText x:Key="ScrollingText"/>
</Window.Resources>
<Canvas x:Name="MainCanvas" ClipToBounds="True" Margin="0,0,0,0" Grid.Row="5" Background="Black" Grid.ColumnSpan="5" >
<TextBlock x:Name="ScrollBlock" TextWrapping="Wrap" VerticalAlignment="Top" Height="113" Width="5147" Canvas.Left="-1922" Text="{Binding ScrollingText, Source={StaticResource ScrollingText}}"/>
</Canvas>
</Window>
代碼如下:
public partial class MainWindow : Window
{
GetScrollingText scrolling = new GetScrollingText();
public MainWindow()
{
InitializeComponent();
scrolling.scrollBlock = this.ScrollBlock;
scrolling.LeftToRightMarqee(2000, -3000);
}
}
最后是輔助類CommonBase:
public class CommonBase : INotifyPropertyChanged
{
protected CommonBase()
{
}
public event PropertyChangedEventHandler PropertyChanged;
protected void RaisePropertyChanged(string PropertyName)
{
PropertyChangedEventHandler handler = this.PropertyChanged;
if (handler != null)
{
PropertyChangedEventArgs e = new PropertyChangedEventArgs(PropertyName);
handler(this, e);
}
}
}
我什至在Getter的返回塊上放置了一個斷點,但僅在第一個斷點上激活:“ ScrollingText = GetScrollString()”。 我的意思是,每次更改值后都不應該返回嗎???
您正在使用GetScrollingText
類的兩個不同實例,一個實例在XAML中作為StaticResource,另一個在后面的代碼中作為類MainWindow中的scrolling
字段。
除了在XAML中創建StaticResource之外,您還可以設置MainWindow的DataContext
屬性:
public partial class MainWindow : Window
{
GetScrollingText scrolling = new GetScrollingText();
public MainWindow()
{
InitializeComponent();
scrolling.scrollBlock = this.ScrollBlock;
scrolling.LeftToRightMarqee(2000, -3000);
DataContext = scrolling; // here
}
}
現在,您無需顯式設置綁定的Source
屬性,因為DataContext用作默認綁定源:
<TextBlock ... Text="{Binding ScrollingText}"/>
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