Question

它返回一个Geometry，但这是一个抽象类。我正在创建一个文本形状，并希望缓存此几何 BuildGeometry可以返回不同的类型，感到怀疑，因此我可能做错了。我可以破解代码（一旦运行就会执行）但是我怎么能确定它总是会是同一类型的呢？

public class Label : ShapeBase
    {
        RectangleGeometry geometry = new RectangleGeometry();

        protected override Geometry DefiningGeometry
        {
            get { return geometry; }
        }

        protected override Size MeasureOverride(Size constraint)
        {
            return constraint;
        }

        public string Text
        {
            get { return (string)GetValue(TextProperty); }
            set { SetValue(TextProperty, value); }
        }

        public static readonly DependencyProperty TextProperty =
            DependencyProperty.Register("Text", typeof(string), typeof(Label), new UIPropertyMetadata(string.Empty, OnTextChanged));

        private static void OnTextChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            Label label = (Label)d;
            label.SetGeometry(label.Text);
            label.InvalidateVisual();
        }

        private void SetGeometry(string text)
        {
            FormattedText formattedtext = new FormattedText(text, CultureInfo.CurrentCulture, FlowDirection.LeftToRight, new Typeface("Tahoma"), 16, Brushes.Black);
            GeometryGroup group = (GeometryGroup)formattedtext.BuildGeometry(new Point(0, 0));
        }
    }

Answer 1

如果您在formattedtext.BuildGeometry设置断点并检查返回的值，您会发现它是GeometryGroup：

var geometry = formattedText.BuildGeometry(new Point());
var geometryGroup = geometry as GeometryGroup;

if (geometryGroup != null)
{
    foreach (var childGeometry in geometryGroup.Children)
    {
        // do something with the child geometries...
    }
}

当我使用简单的FormattedText测试时，顶级GeometryGroup的子节点本身就是GeometryGroups，PathGeometries作为它们的子节点。我的假设是，二级GeometryGroups每个都包含FormattedText对象的一个文本行，而PathGeometries包含单个字符或字形。

Answer 2

从您的代码中看起来像RectangleGeometry。

    RectangleGeometry geometry = new RectangleGeometry();

    protected override Geometry DefiningGeometry
    {
        get { return geometry; }
    }

FormattedText.BuildGeometry返回哪个几何？

2 个答案: