1

我将Widtha 的 a绑定TextBox到ActualWidth其包含的Grid，如下所示：

<TextBlock
    Grid.Column="0"
    Text="WorkPortalView UserControl"
    TextTrimming="CharacterEllipsis"
    Foreground="White"
    Margin="5" 
    Width="{Binding ActualWidth, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Grid}}, Converter={StaticResource textWidthConverter}, diag:PresentationTraceSources.TraceLevel=High}" />

如图，我使用的是Converter，如下：

class TextWidthConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            double? d = value as double?;
            if (d == null)
                return null;

            return (d / 2);
        }

        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            throw new NotSupportedException("Cannot convert back");
        }
    }

奇怪的是，显示的代码工作正常。但是，如果我将return (d / 2)语句替换为return (d - 75D)，似乎会引发属性更改的无限循环。

这是 d / 2 的诊断跟踪标记的输出：

System.Windows.Data Warning: 71 :     Lookup ancestor of type Grid:  queried Grid (hash=19487651)
System.Windows.Data Warning: 70 :   RelativeSource.FindAncestor found Grid (hash=19487651)
System.Windows.Data Warning: 76 : BindingExpression (hash=35097890): Activate with root item Grid (hash=19487651)
System.Windows.Data Warning: 106 : BindingExpression (hash=35097890):   At level 0 - for Grid.ActualWidth found accessor DependencyProperty(ActualWidth)
System.Windows.Data Warning: 102 : BindingExpression (hash=35097890): Replace item at level 0 with Grid (hash=19487651), using accessor DependencyProperty(ActualWidth)
System.Windows.Data Warning: 99 : BindingExpression (hash=35097890): GetValue at level 0 from Grid (hash=19487651) using DependencyProperty(ActualWidth): '417.6'
System.Windows.Data Warning: 78 : BindingExpression (hash=35097890): TransferValue - got raw value '417.6'
System.Windows.Data Warning: 80 : BindingExpression (hash=35097890): TransferValue - user's converter produced '208.8'
System.Windows.Data Warning: 87 : BindingExpression (hash=35097890): TransferValue - using final value '208.8'

以下是 d - 75D 的诊断跟踪标记的输出：

System.Windows.Data Warning: 94 : BindingExpression (hash=58235710): Got PropertyChanged event from Grid (hash=43090134) for ActualWidth
System.Windows.Data Warning: 99 : BindingExpression (hash=58235710): GetValue at level 0 from Grid (hash=43090134) using DependencyProperty(ActualWidth): '429.6'
System.Windows.Data Warning: 78 : BindingExpression (hash=58235710): TransferValue - got raw value '429.6'
System.Windows.Data Warning: 80 : BindingExpression (hash=58235710): TransferValue - user's converter produced '354.6'
System.Windows.Data Warning: 87 : BindingExpression (hash=58235710): TransferValue - using final value '354.6'
System.Windows.Data Warning: 94 : BindingExpression (hash=58235710): Got PropertyChanged event from Grid (hash=43090134) for ActualWidth
System.Windows.Data Warning: 99 : BindingExpression (hash=58235710): GetValue at level 0 from Grid (hash=43090134) using DependencyProperty(ActualWidth): '441.6'
System.Windows.Data Warning: 78 : BindingExpression (hash=58235710): TransferValue - got raw value '441.6'
System.Windows.Data Warning: 80 : BindingExpression (hash=58235710): TransferValue - user's converter produced '366.6'
System.Windows.Data Warning: 87 : BindingExpression (hash=58235710): TransferValue - using final value '366.6'
System.Windows.Data Warning: 94 : BindingExpression (hash=58235710): Got PropertyChanged event from Grid (hash=43090134) for ActualWidth
System.Windows.Data Warning: 99 : BindingExpression (hash=58235710): GetValue at level 0 from Grid (hash=43090134) using DependencyProperty(ActualWidth): '453.6'
System.Windows.Data Warning: 78 : BindingExpression (hash=58235710): TransferValue - got raw value '453.6'
System.Windows.Data Warning: 80 : BindingExpression (hash=58235710): TransferValue - user's converter produced '378.6'
System.Windows.Data Warning: 87 : BindingExpression (hash=58235710): TransferValue - using final value '378.6'
System.Windows.Data Warning: 94 : BindingExpression (hash=58235710): Got PropertyChanged event from Grid (hash=43090134) for ActualWidth
System.Windows.Data Warning: 99 : BindingExpression (hash=58235710): GetValue at level 0 from Grid (hash=43090134) using DependencyProperty(ActualWidth): '465.6'
System.Windows.Data Warning: 78 : BindingExpression (hash=58235710): TransferValue - got raw value '465.6'
System.Windows.Data Warning: 80 : BindingExpression (hash=58235710): TransferValue - user's converter produced '390.6'
System.Windows.Data Warning: 87 : BindingExpression (hash=58235710): TransferValue - using final value '390.6'
System.Windows.Data Warning: 94 : BindingExpression (hash=58235710): Got PropertyChanged event from Grid (hash=43090134) for ActualWidth
System.Windows.Data Warning: 99 : BindingExpression (hash=58235710): GetValue at level 0 from Grid (hash=43090134) using DependencyProperty(ActualWidth): '477.6'
System.Windows.Data Warning: 78 : BindingExpression (hash=58235710): TransferValue - got raw value '477.6'
System.Windows.Data Warning: 80 : BindingExpression (hash=58235710): TransferValue - user's converter produced '402.6'
System.Windows.Data Warning: 87 : BindingExpression (hash=58235710): TransferValue - using final value '402.6'
System.Windows.Data Warning: 94 : BindingExpression (hash=58235710): Got PropertyChanged event from Grid (hash=43090134) for ActualWidth
System.Windows.Data Warning: 99 : BindingExpression (hash=58235710): GetValue at level 0 from Grid (hash=43090134) using DependencyProperty(ActualWidth): '489.6'
System.Windows.Data Warning: 78 : BindingExpression (hash=58235710): TransferValue - got raw value '489.6'
System.Windows.Data Warning: 80 : BindingExpression (hash=58235710): TransferValue - user's converter produced '414.6'
System.Windows.Data Warning: 87 : BindingExpression (hash=58235710): TransferValue - using final value '414.6'
System.Windows.Data Warning: 94 : BindingExpression (hash=58235710): Got PropertyChanged event from Grid (hash=43090134) for ActualWidth
System.Windows.Data Warning: 99 : BindingExpression (hash=58235710): GetValue at level 0 from Grid (hash=43090134) using DependencyProperty(ActualWidth): '501.6'
System.Windows.Data Warning: 78 : BindingExpression (hash=58235710): TransferValue - got raw value '501.6'
System.Windows.Data Warning: 80 : BindingExpression (hash=58235710): TransferValue - user's converter produced '426.6'
System.Windows.Data Warning: 87 : BindingExpression (hash=58235710): TransferValue - using final value '426.6'
System.Windows.Data Warning: 94 : BindingExpression (hash=58235710): Got PropertyChanged event from Grid (hash=43090134) for ActualWidth
System.Windows.Data Warning: 99 : BindingExpression (hash=58235710): GetValue at level 0 from Grid (hash=43090134) using DependencyProperty(ActualWidth): '513.6'
System.Windows.Data Warning: 78 : BindingExpression (hash=58235710): TransferValue - got raw value '513.6'
System.Windows.Data Warning: 80 : BindingExpression (hash=58235710): TransferValue - user's converter produced '438.6'
System.Windows.Data Warning: 87 : BindingExpression (hash=58235710): TransferValue - using final value '438.6'
System.Windows.Data Warning: 94 : BindingExpression (hash=58235710): Got PropertyChanged event from Grid (hash=43090134) for ActualWidth
System.Windows.Data Warning: 99 : BindingExpression (hash=58235710): GetValue at level 0 from Grid (hash=43090134) using DependencyProperty(ActualWidth): '525.6'
System.Windows.Data Warning: 78 : BindingExpression (hash=58235710): TransferValue - got raw value '525.6'
System.Windows.Data Warning: 80 : BindingExpression (hash=58235710): TransferValue - user's converter produced '450.6'
System.Windows.Data Warning: 87 : BindingExpression (hash=58235710): TransferValue - using final value '450.6'
System.Windows.Data Warning: 94 : BindingExpression (hash=58235710): Got PropertyChanged event from Grid (hash=43090134) for ActualWidth
System.Windows.Data Warning: 99 : BindingExpression (hash=58235710): GetValue at level 0 from Grid (hash=43090134) using DependencyProperty(ActualWidth): '537.6'
System.Windows.Data Warning: 78 : BindingExpression (hash=58235710): TransferValue - got raw value '537.6'
System.Windows.Data Warning: 80 : BindingExpression (hash=58235710): TransferValue - user's converter produced '462.6'
System.Windows.Data Warning: 87 : BindingExpression (hash=58235710): TransferValue - using final value '462.6'
System.Windows.Data Warning: 94 : BindingExpression (hash=58235710): Got PropertyChanged event from Grid (hash=43090134) for ActualWidth
System.Windows.Data Warning: 99 : BindingExpression (hash=58235710): GetValue at level 0 from Grid (hash=43090134) using DependencyProperty(ActualWidth): '549.6'
System.Windows.Data Warning: 78 : BindingExpression (hash=58235710): TransferValue - got raw value '549.6'
System.Windows.Data Warning: 80 : BindingExpression (hash=58235710): TransferValue - user's converter produced '474.6'
System.Windows.Data Warning: 87 : BindingExpression (hash=58235710): TransferValue - using final value '474.6'
System.Windows.Data Warning: 94 : BindingExpression (hash=58235710): Got PropertyChanged event from Grid (hash=43090134) for ActualWidth
System.Windows.Data Warning: 99 : BindingExpression (hash=58235710): GetValue at level 0 from Grid (hash=43090134) using DependencyProperty(ActualWidth): '561.6'
System.Windows.Data Warning: 78 : BindingExpression (hash=58235710): TransferValue - got raw value '561.6'
System.Windows.Data Warning: 80 : BindingExpression (hash=58235710): TransferValue - user's converter produced '486.6'
System.Windows.Data Warning: 87 : BindingExpression (hash=58235710): TransferValue - using final value '486.6'

关于什么解释了转换器的这种行为的任何想法？

4

2 回答 2

1

显然，网格需要为文本块提供更多空间。您可能能够在 d-87D 找到此行为的截止点，因为网格似乎需要在每个文本块宽度更改时额外增加 12 像素。

顺便说一句，如果您只想为文本块提供相对大小，则最好对网格列使用星号大小。

于 2012-05-10T18:26:01.637 回答
0

这似乎是一个错误。该行为对于一次“自动调整”迭代是合理的，但不应导致无限循环。请参阅上面的讨论。

我最终切换到DockPanel实现所需的布局。

于 2012-05-10T18:44:41.360 回答