Question

我已将自定义拖动行为添加到网格上的TextBlock

XAML

<Grid>
    <TextBlock Text="{Binding Description}"  >
        <i:Interaction.Behaviors>
            <flowfieldVisualiser:DragBehavior/>
        </i:Interaction.Behaviors>        
    </TextBlock>
</Grid>

行为代码

public class DragBehavior : Behavior<UIElement>
    {
        private Point _elementStartPosition;
        private Point _mouseStartPosition;
        private readonly TranslateTransform _transform = new TranslateTransform();

        protected override void OnAttached()
        {
            AssociatedObject.RenderTransform = _transform;
            AssociatedObject.MouseLeftButtonDown += AssociatedObject_MouseLeftButtonDown;
            AssociatedObject.MouseLeftButtonUp += AssociatedObject_MouseLeftButtonUp;
            AssociatedObject.MouseMove += AssociatedObject_MouseMove;
        }

        void AssociatedObject_MouseLeftButtonDown(object sender, System.Windows.Input.MouseButtonEventArgs e)
        {
            var parent = Application.Current.MainWindow;
            _elementStartPosition = AssociatedObject.TranslatePoint(new Point(), parent);

            var vector = e.GetPosition(parent) - _elementStartPosition;
            _mouseStartPosition = new Point(vector.X, vector.Y);

            AssociatedObject.CaptureMouse();
        }

        void AssociatedObject_MouseMove(object sender, System.Windows.Input.MouseEventArgs e)
        {
            var parent = Application.Current.MainWindow;
            _elementStartPosition = AssociatedObject.TranslatePoint(new Point(), parent);
            var diff = e.GetPosition(parent) - _mouseStartPosition;
            if (AssociatedObject.IsMouseCaptured)
            {
                _transform.X = diff.X;
                _transform.Y = diff.Y;
            }
        }

        void AssociatedObject_MouseLeftButtonUp(object sender, System.Windows.Input.MouseButtonEventArgs e)
        {
            AssociatedObject.ReleaseMouseCapture();
        }
    }

这很好用，我可以拖动文本框。问题是，我需要知道我的datacontext中的新值是什么。如何将TranslateTransform x和y绑定到我的数据上下文的x和y属性？

Answer 1

这是一个示例

    Binding bindingX = new Binding("DataContext.X");
    bindingX.Source = AssociatedObject;
    bindingX.Mode = BindingMode.OneWayToSource;
    BindingOperations.SetBinding(_transform, TranslateTransform.XProperty, bindingX);

假设DataContext视图模型在代码上面有一个名为X的属性，将为TranslateTransform.XProperty的_transform设置一个绑定，这将把值推送到源绑定，即AssociatedObject的DataContext.X。因此将值推送到VM的属性。

您可能还需要为Y属性设置相同的内容。

信息UIElement没有DataContext，因此除非AssociatedObject的类型为FrameworkElement，否则可能无法正常工作。

您也可以将其更改为Behavior<FrameworkElement>以获得更好的可靠性

如何绑定到translatetransform

1 个答案: