InkCanvas 橡皮擦

Question

我的画板是InkCanvas；我想改变橡皮擦的大小，所以我写了：

Private Sub Sketchpad_KeyDown(sender As System.Object, e As System.Windows.Input.KeyEventArgs) Handles Sketchpad.KeyDown

If e.Key = Key.OemMinus Then

' Decrease size of Eraser to 5*5 

Sketchpad.EraserShape = New RectangleStylusShape(5, 5)

End If

If e.Key = Key.OemPlus Then

' Increase size of Eraser to 50*50 

Sketchpad.EraserShape = New RectangleStylusShape(50, 50)

End If

If e.Key = Key.I Then
' Change editing mode to Ink
Sketchpad.EditingMode = InkCanvasEditingMode.Ink

End If

If e.Key = Key.E Then
' Change editing mode to Eraser
Sketchpad.EditingMode = InkCanvasEditingMode.EraseByPoint

End If

End Sub

试试这个：

1. 按e选择橡皮擦，橡皮擦笔尖会出现矩形
2. 按 + 号增加大小，您不会看到任何变化。为什么？
3. 现在按 i 更改编辑模式，会出现墨迹提示。
4. 再次按 e 可重新切换到橡皮擦。您会看到橡皮擦的形状发生了变化。

为什么按 + 号后不呢？

Answer 1

来自help：

“如果更改 EraserShape，则在 InkCanvas 上呈现的光标不会更新，直到下一次 EditingMode 更改。”

我测试了以下代码，它工作正常：

if (e.Key == Key.OemMinus)
{
    ink.EraserShape = new RectangleStylusShape(5, 5);
    var editMode = ink.EditingMode;
    ink.EditingMode = InkCanvasEditingMode.None;
    ink.EditingMode = editMode;
}
if (e.Key == Key.OemPlus)
{
    ink.EraserShape = new RectangleStylusShape(50, 50);
    var editMode = ink.EditingMode;
    ink.EditingMode = InkCanvasEditingMode.None;
    ink.EditingMode = editMode;
}