【发布时间】：2021-02-10 18:16:36
【问题描述】：
我有一个自定义控件，它在下拉列表中显示颜色选择，效果很好。
我发现同一表单上的多个控件的性能很差，因此我将其更改为将 Color 索引存储在 Items 集合中。
这很好用，但是设计器会填充大量值，这会导致控件中的项目为空。
如何阻止设计师存储项目？
这是我不想要的设计器代码：
Me.cboCWarcColor.Items.AddRange(New Object()
{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,
19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35,
36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52,
53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69,
70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86,
87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102,
103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115,
116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128,
129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140}
)
这是自定义控件代码：
Imports System.Collections.Generic
Public Class ColorCombo
Inherits System.Windows.Forms.ComboBox
Private mSelectedColor As Color = Nothing
Private Shared myColors As New List(Of Color)
Private Shared myColorsIndices As New List(Of Object)
Private Sub ColorCombo_DrawItem(ByVal sender As Object, ByVal e As System.Windows.Forms.DrawItemEventArgs) Handles Me.DrawItem
Try
If e.Index < 0 Or e.Index >= myColors.Count Then
e.DrawBackground()
e.DrawFocusRectangle()
Exit Try
End If
' Get the Color object from the Items list
Dim aColor As Color = myColors.Item(e.Index) 'myColors.Item(e.Index)
' get a square using the bounds height
Dim rect As Rectangle = New Rectangle(4, e.Bounds.Top + 2, CInt(e.Bounds.Height * 1.5), e.Bounds.Height - 4)
' call these methods first
e.DrawBackground()
e.DrawFocusRectangle()
Dim textBrush As Brush
' change brush color if item is selected
If e.State = DrawItemState.Selected Then
textBrush = Brushes.White
Else
textBrush = Brushes.Black
End If
' draw a rectangle and fill it
Dim p As New Pen(aColor)
Dim br As New SolidBrush(aColor)
e.Graphics.DrawRectangle(p, rect)
e.Graphics.FillRectangle(br, rect)
' draw a border
rect.Inflate(1, 1)
e.Graphics.DrawRectangle(Pens.Black, rect)
' draw the Color name
e.Graphics.TextRenderingHint = Drawing.Text.TextRenderingHint.ClearTypeGridFit
e.Graphics.DrawString(aColor.Name, Me.Font, textBrush, rect.Width + 5, ((e.Bounds.Height - Me.Font.Height) \ 2) + e.Bounds.Top)
p.Dispose()
br.Dispose()
Catch ex As Exception
e.DrawBackground()
e.DrawFocusRectangle()
End Try
End Sub
Public Sub New()
' This call is required by the Windows Form Designer.
InitializeComponent()
Try
Dim aColorName As String
Me.BeginUpdate()
Items.Clear()
SelectedItem = Nothing
If myColors.Count = 0 Then
Dim names() As String = System.Enum.GetNames(GetType(System.Drawing.KnownColor))
For Each aColorName In names
If aColorName.StartsWith("Active") _
Or aColorName.StartsWith("Button") _
Or aColorName.StartsWith("Window") _
Or aColorName.StartsWith("Inactive") _
Or aColorName.StartsWith("HighlightText") _
Or aColorName.StartsWith("Control") _
Or aColorName.StartsWith("Scroll") _
Or aColorName.StartsWith("Menu") _
Or aColorName.StartsWith("Gradient") _
Or aColorName.StartsWith("App") _
Or aColorName.StartsWith("Desktop") _
Or aColorName.StartsWith("GrayText") _
Or aColorName.StartsWith("HotTrack") _
Or aColorName.StartsWith("Transparent") _
Or aColorName.StartsWith("Info") Then
Else
AddColor(Color.FromName(aColorName))
End If
Next
Else
Me.Items.AddRange(myColorsIndices.ToArray)
End If
Catch
Finally
Me.EndUpdate()
End Try
' Add any initialization after the InitializeComponent() call.
End Sub
Public Function AddColor(clr As Color) As Integer
myColors.Add(clr)
Dim idx As Integer = myColors.Count - 1
myColorsIndices.Add(idx)
Me.Items.Add(idx)
Return idx
End Function
''' <summary>
''' Returns a named color if one matches else it returns the passed color
''' </summary>
Public Function GetKnownColor(ByVal c As Color, Optional ByVal tolerance As Double = 0) As Color
For Each clr As Color In myColors
If ColorDistance(c, clr) <= tolerance Then
Return clr
End If
Next
Return c
End Function
''' <summary>
''' Returns index if one matches
''' </summary>
Public Function ContainsColor(ByVal c As Color) As Integer
Dim idx As Integer = 0
For Each clr As Color In myColors
If c.ToArgb = clr.ToArgb Then
Return idx
End If
idx += 1
Next
Return -1
End Function
Sub ColorCombo_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.SelectedIndexChanged
If SelectedIndex >= 0 Then
mSelectedColor = myColors.Item(SelectedIndex)
End If
End Sub
Public Property SelectedColor() As Color
Get
'If mSelectedColor.Name = "Transparent" Then
' Return Color.Black
'End If
Return mSelectedColor
End Get
Set(ByVal value As Color)
Try
Dim smallestDist As Double = 255
Dim currentDist As Double = 0
Dim bestMatch As Integer = 0
Dim idx As Integer = -1
For Each c As Color In myColors
idx += 1
currentDist = ColorDistance(c, value)
If currentDist < smallestDist Then
smallestDist = currentDist
bestMatch = idx
End If
Next
If Me.Items.Count >= bestMatch Then
Me.SelectedIndex = bestMatch
End If
Catch ex As Exception
Debug.Print(ex.Message)
End Try
End Set
End Property
Private Function ColorDistance(ByRef clrA As Color, ByRef clrB As Color) As Double
Dim r As Long, g As Long, b As Long
r = CShort(clrA.R) - CShort(clrB.R)
g = CShort(clrA.G) - CShort(clrB.G)
b = CShort(clrA.B) - CShort(clrB.B)
Return Math.Sqrt(r * r + g * g + b * b)
End Function
End Class
【问题讨论】：
标签： vb.net winforms graphics combobox user-controls