Question

我正在使用带有状态图像的VB.NET制作联系人列表。我正在从MSSQL加载这个列表但是当我重新加载列表时它会闪烁。

此列表是一个带有动态创建的图片框和标签的TableLayoutPanel。

我的问题是：

当您重新加载我的联系人而不是重新加载整个列表时，如何在动态图片框中更改我的图像。

我创建表格的代码：

While UserData.Read

    If UserData("Status").ToString = "Online" Then

        If UserData("NieuwBericht").ToString = "Ja" Then

            Dim newPictureBox As New PictureBox
            newPictureBox.Image = My.Resources.greenchat
            newPictureBox.Visible = True
            newPictureBox.Width = 30
            newPictureBox.Height = 30
            newPictureBox.SizeMode = PictureBoxSizeMode.Zoom
            newPictureBox.Name = UserData("Username").ToString
            ChatContactList.Controls.Add(newPictureBox)

            Dim newPictureBox2 As New PictureBox
            newPictureBox2.Image = My.Resources.greenbubblechat
            newPictureBox2.Visible = True
            newPictureBox2.Width = 30
            newPictureBox2.Height = 30
            newPictureBox2.SizeMode = PictureBoxSizeMode.Zoom
            newPictureBox2.Name = UserData("Username").ToString
            ChatContactList.Controls.Add(newPictureBox2)

            Dim newLabel As New Label
            AddHandler newLabel.Click, AddressOf Chatbox
            newLabel.Text = UserData("Voornaam").ToString & " " & UserData("Achternaam").ToString
            newLabel.Name = UserData("Username").ToString
            newLabel.Font = New Font("Microsoft sans serif", 12)
            newLabel.Dock = DockStyle.Fill
            newLabel.TextAlign = ContentAlignment.MiddleLeft
            newLabel.Visible = True
            ChatContactList.Controls.Add(newLabel)

        ElseIf UserData("NieuwBericht").ToString = "Nee" Then

            Dim newPictureBox As New PictureBox
            newPictureBox.Image = My.Resources.greenchat
            newPictureBox.Visible = True
            newPictureBox.Width = 30
            newPictureBox.Height = 30
            newPictureBox.SizeMode = PictureBoxSizeMode.Zoom
            newPictureBox.Name = UserData("Username").ToString
            ChatContactList.Controls.Add(newPictureBox)

            Dim newPictureBox2 As New PictureBox
            newPictureBox2.Image = My.Resources.greybubblechat
            newPictureBox2.Visible = True
            newPictureBox2.Width = 30
            newPictureBox2.Height = 30
            newPictureBox2.SizeMode = PictureBoxSizeMode.Zoom
            newPictureBox2.Name = UserData("Username").ToString
            ChatContactList.Controls.Add(newPictureBox2)

            Dim newLabel As New Label
            AddHandler newLabel.Click, AddressOf Chatbox
            newLabel.Text = UserData("Voornaam").ToString & " " & UserData("Achternaam").ToString
            newLabel.Name = UserData("Username").ToString
            newLabel.Font = New Font("Microsoft sans serif", 12)
            newLabel.Dock = DockStyle.Fill
            newLabel.TextAlign = ContentAlignment.MiddleLeft
            newLabel.Visible = True
            ChatContactList.Controls.Add(newLabel)

        End If

    ElseIf UserData("Status").ToString = "Afwezig" Then

        If UserData("NieuwBericht").ToString = "Ja" Then

            Dim newPictureBox As New PictureBox
            newPictureBox.Image = My.Resources.orangechat
            newPictureBox.Visible = True
            newPictureBox.Width = 30
            newPictureBox.Height = 30
            newPictureBox.SizeMode = PictureBoxSizeMode.Zoom
            newPictureBox.Name = UserData("Username").ToString
            ChatContactList.Controls.Add(newPictureBox)

            Dim newPictureBox2 As New PictureBox
            newPictureBox2.Image = My.Resources.greenbubblechat
            newPictureBox2.Visible = True
            newPictureBox2.Width = 30
            newPictureBox2.Height = 30
            newPictureBox2.SizeMode = PictureBoxSizeMode.Zoom
            newPictureBox2.Name = UserData("Username").ToString
            ChatContactList.Controls.Add(newPictureBox2)

            Dim newLabel As New Label
            AddHandler newLabel.Click, AddressOf Chatbox
            newLabel.Text = UserData("Voornaam").ToString & " " & UserData("Achternaam").ToString
            newLabel.Name = UserData("Username").ToString
            newLabel.Font = New Font("Microsoft sans serif", 12)
            newLabel.Dock = DockStyle.Fill
            newLabel.TextAlign = ContentAlignment.MiddleLeft
            newLabel.Visible = True
            ChatContactList.Controls.Add(newLabel)

        ElseIf UserData("NieuwBericht").ToString = "Nee" Then

            Dim newPictureBox As New PictureBox
            newPictureBox.Image = My.Resources.orangechat
            newPictureBox.Visible = True
            newPictureBox.Width = 30
            newPictureBox.Height = 30
            newPictureBox.SizeMode = PictureBoxSizeMode.Zoom
            newPictureBox.Name = UserData("Username").ToString
            ChatContactList.Controls.Add(newPictureBox)

            Dim newPictureBox2 As New PictureBox
            newPictureBox2.Image = My.Resources.greybubblechat
            newPictureBox2.Visible = True
            newPictureBox2.Width = 30
            newPictureBox2.Height = 30
            newPictureBox2.SizeMode = PictureBoxSizeMode.Zoom
            newPictureBox2.Name = UserData("Username").ToString
            ChatContactList.Controls.Add(newPictureBox2)

            Dim newLabel As New Label
            AddHandler newLabel.Click, AddressOf Chatbox
            newLabel.Text = UserData("Voornaam").ToString & " " & UserData("Achternaam").ToString
            newLabel.Name = UserData("Username").ToString
            newLabel.Font = New Font("Microsoft sans serif", 12)
            newLabel.Dock = DockStyle.Fill
            newLabel.TextAlign = ContentAlignment.MiddleLeft
            newLabel.Visible = True
            ChatContactList.Controls.Add(newLabel)

        End If

    ElseIf UserData("Status").ToString = "Offline" Then

        If UserData("NieuwBericht").ToString = "Ja" Then

            Dim newPictureBox As New PictureBox
            newPictureBox.Image = My.Resources.redchat
            newPictureBox.Visible = True
            newPictureBox.Width = 30
            newPictureBox.Height = 30
            newPictureBox.SizeMode = PictureBoxSizeMode.Zoom
            newPictureBox.Name = UserData("Username").ToString
            ChatContactList.Controls.Add(newPictureBox)

            Dim newPictureBox2 As New PictureBox
            newPictureBox2.Image = My.Resources.greenbubblechat
            newPictureBox2.Visible = True
            newPictureBox2.Width = 30
            newPictureBox2.Height = 30
            newPictureBox2.SizeMode = PictureBoxSizeMode.Zoom
            newPictureBox2.Name = UserData("Username").ToString
            ChatContactList.Controls.Add(newPictureBox2)

            Dim newLabel As New Label
            AddHandler newLabel.Click, AddressOf Chatbox
            newLabel.Text = UserData("Voornaam").ToString & " " & UserData("Achternaam").ToString
            newLabel.Name = UserData("Username").ToString
            newLabel.Font = New Font("Microsoft sans serif", 12)
            newLabel.Dock = DockStyle.Fill
            newLabel.TextAlign = ContentAlignment.MiddleLeft
            newLabel.Visible = True
            ChatContactList.Controls.Add(newLabel)

        ElseIf UserData("NieuwBericht").ToString = "Nee" Then

            Dim newPictureBox As New PictureBox
            newPictureBox.Image = My.Resources.redchat
            newPictureBox.Visible = True
            newPictureBox.Width = 30
            newPictureBox.Height = 30
            newPictureBox.SizeMode = PictureBoxSizeMode.Zoom
            newPictureBox.Name = UserData("Username").ToString
            ChatContactList.Controls.Add(newPictureBox)

            Dim newPictureBox2 As New PictureBox
            newPictureBox2.Image = My.Resources.greybubblechat
            newPictureBox2.Visible = True
            newPictureBox2.Width = 30
            newPictureBox2.Height = 30
            newPictureBox2.SizeMode = PictureBoxSizeMode.Zoom
            newPictureBox2.Name = UserData("Username").ToString
            ChatContactList.Controls.Add(newPictureBox2)

            Dim newLabel As New Label
            AddHandler newLabel.Click, AddressOf Chatbox
            newLabel.Text = UserData("Voornaam").ToString & " " & UserData("Achternaam").ToString
            newLabel.Name = UserData("Username").ToString
            newLabel.Font = New Font("Microsoft sans serif", 12)
            newLabel.Dock = DockStyle.Fill
            newLabel.TextAlign = ContentAlignment.MiddleLeft
            newLabel.Visible = True
            ChatContactList.Controls.Add(newLabel)

        End If

    End If

End While

我的联系人列表的图片

Answer 1

UserControl有点像子窗体。它是各种控件的容器，它们共同起作用或代表某个逻辑单元。在这种情况下，它将是一些用户状态（属性）的可视化表示。您可以将它们放在一个UC上，并封装多少代码来管理它们，而不是创建和管理单个控件。

在解决方案资源管理器窗口中，右键单击，选择添加，然后选择 UserControl 。我添加了一个TableLayoutPanel，2个PictureBoxes和一个Label（当然都有正确的名称）。 ~~还有ImageList快速抓取你的图像~~：

此单独取代了许多代码行，您可以创建新控件，然后一遍又一遍地设置相同的属性。要使它们充当逻辑对象，您可以添加抽象选择图像等细节的属性：

Public Class Chatter

    Public Enum ChatStatus
        Unknown
        Online
        Away
        Offline
    End Enum

    Public Enum ChatMsgStatus
        Undefined      ' kludge to force the initial state
        Unknown
        [New]
        Read
    End Enum

    ' one set of images for all chatter instances
    Private Shared Imgs As Image()

    Public Property ChatId As Int32         ' or guid?

    Private chName As String = ""
    Public ReadOnly Property ChatName As String
        Get
            Return chName
        End Get
    End Property

    Private mStatus As ChatMsgStatus = ChatMsgStatus.Undefined
    Public Property MsgStatus As ChatMsgStatus
        Get
            Return mStatus
        End Get
        Set(value As ChatMsgStatus)
            If (value <> mStatus) Then
                Select Case value
                    Case ChatMsgStatus.New
                        pbMStatus.Image = Imgs(3) 
                    Case ChatMsgStatus.Read
                        pbMStatus.Image = Imgs(4)
                    Case Else
                        pbMStatus.Image = Imgs(4)
                End Select
            End If
            mStatus = value
        End Set
    End Property

    Private chStatus As ChatStatus = ChatStatus.Unknown
    Public Property Status As ChatStatus
        Get
            Return chStatus
        End Get
        Set(value As ChatStatus)
            If value <> chStatus Then
                Select Case value
                    Case ChatStatus.Online
                        pbUStatus.Image = Imgs(0)
                    Case ChatStatus.Away
                        pbUStatus.Image = Imgs(1)
                    Case ChatStatus.Offline
                        pbUStatus.Image = Imgs(2)
                    Case Else
                End Select
            End If
            chStatus = value
        End Set
    End Property

    Public Sub New()
        ' This call is required by the designer.
        InitializeComponent()

        If Imgs Is Nothing Then
            Imgs = New Image() {My.Resources.ChatUserGrn, My.Resources.ChatUserYlw, 
               My.Resources.ChatUserRed, My.Resources.ChatBalloonGrn,
               My.Resources.ChatBalloonGry}

               ' see note
        End If
    End If
        ' Add any initialization after the InitializeComponent() call.
    End Sub
    ' no need to create one without Identifiers
    Public Sub New(n As Int32, cname As String)
        MyClass.New()
        ' default intitial values:
        chName = cname
        ChatId = n

        lblChName.Text = cname
        Me.Status = ChatStatus.Online
        Me.MsgStatus = ChatMsgStatus.Unknown
    End Sub
End Class

（编辑）我不喜欢使用ImageList的结果。此版本从资源加载一系列图像。除了只加载一个GreenUser副本供所有用户使用外，它还允许您根据需要进行定制。例如，将背景颜色更改为SystemColors.Window以匹配用户的主题。如果您还使用标签而不是图片框，则可以将Text属性用于“？”或者甚至指出新消息的号。

我相信还有更多功能，我可以想到我会想要知道的一些事情（比如用未读数覆盖绿色气球）消息）。但这里的重点是封装，DRY和可重用代码的概念。

编译时，工具箱中会有一个新的Chatter控件。使用公开的属性在运行时添加一些：

Dim c As New Chatter(42, "Ziggy von Hausen")
flpChat.Controls.Add(c)

c = New Chatter(14, "ThDutoit")
c.MsgStatus = Chatter.ChatMsgStatus.New
flpChat.Controls.Add(c)

c = New Chatter(78, "Plutonix")
c.Status = Chatter.ChatStatus.Offline
flpChat.Controls.Add(c)

c = New Chatter(4, "Codexer")
c.MsgStatus = Chatter.ChatMsgStatus.New
c.Status = Chatter.ChatStatus.Away
flpChat.Controls.Add(c)

ID可以唯一标识每个聊天参与者。该名称通常不够（SO已超过50 pages of people named "Steve"），您将需要一种方法来识别将控件链接到用户。（另一种方法是用户列表中的ChatterBox引用，它是对相关UserControl的引用：

Dim user = "Codexer"

Dim chatter = flpChat.Controls.
            OfType(Of Chatter).
            FirstOrDefault(Function(c) c.ChatName.StartsWith(user))
If chatter IsNot Nothing Then
    chatter.Status = chatter.ChatStatus.Online
End If

每次搜索都是次优的，Id优于单纯名称。理想情况是ChatUser类，其中包含应用必须由用户存储的所有其他内容。该类应包含对控件的引用，以便在状态发生变化时或类似情况下，该类可以简单地：

myChatterBox.Status = myStatus

结果：

当然可以使用相当少的代码创建它们。在这些过程中，您只需设置相关属性即可更改任一图像的状态。

作为一项额外的好处，因为您不再创建单独的控件，并且因为UserControl继承自Component，所以如果/何时删除它们，您不必担心泄漏。

必读：
Creating a Windows Form User Control

从多个动态图片框

1 个答案: