[VB.NET]為控制項加上顯示載入動畫的機制

最近有個需求是當程式在做複雜的運算時,需要告知使用者程式仍然運作,而若用彈出單一Loading對話框的方式又不太適用,因此會想跟網頁一樣能在控制項上外加載入動畫。

在找不到更好的解法前,這邊我先考慮用擴充方法來實作這樣的需求功能。主要是利用擴充方法啟動控制項的載入畫面,啟動多執行緒去更新載入動畫。程式碼如下:

#Region “Imports”
Imports System.Runtime.CompilerServices
Imports System.Collections.Specialized
Imports System.Windows.Forms
Imports System.Drawing
Imports System.Threading
Imports System.Drawing.Imaging

#End Region

Public Module ControlLoadingExtension

#Region “Class”
Class LoadingInfo
Private _loaddingBmp As Image
Private _loaddingBmpActiveFrameIdx As Integer
Private _loaddingBmpDimension As FrameDimension
Private _loaddingBmpFrameCount As Integer
Private _displayLocation As Point

Property LoaddingBmp As Image
Get
Return _loaddingBmp
End Get
Set(ByVal value As Image)
If _loaddingBmp IsNot value Then
_loaddingBmp = value
LoaddingBmpDimension = New FrameDimension(value.FrameDimensionsList(0))
LoaddingBmpFrameCount = value.GetFrameCount(LoaddingBmpDimension)
LoaddingBmpActiveFrameIdx = 0
End If
End Set
End Property

Property LoaddingBmpActiveFrameIdx As Integer
Get
Return _loaddingBmpActiveFrameIdx
End Get
Set(ByVal value As Integer)
_loaddingBmpActiveFrameIdx = value
LoaddingBmp.SelectActiveFrame(LoaddingBmpDimension, value)
End Set
End Property

Property LoaddingBmpDimension As FrameDimension
Get
Return _loaddingBmpDimension
End Get
Private Set(ByVal value As FrameDimension)
_loaddingBmpDimension = value
End Set
End Property

Property LoaddingBmpFrameCount As Integer
Get
Return _loaddingBmpFrameCount
End Get
Private Set(ByVal value As Integer)
_loaddingBmpFrameCount = value
End Set
End Property

Property DisplayLocation As Point
Get
Return _displayLocation
End Get
Set(ByVal value As Point)
_displayLocation = value
End Set
End Property
End Class
#End Region

#Region “Var”
Private _loadingStatePool As HybridDictionary
Private _updateThread As Thread
#End Region


#Region “Private Property”
Private ReadOnly Property m_LoadingStatePool() As HybridDictionary
Get
If _loadingStatePool Is Nothing Then
_loadingStatePool = New HybridDictionary
End If
Return _loadingStatePool
End Get
End Property

Private Property m_UpdateThread As Thread
Get
If _updateThread Is Nothing Then
_updateThread = New Thread(AddressOf ThreadingUpdatePhoto) With {.IsBackground = True}
End If
Return _updateThread
End Get
Set(ByVal value As Thread)
_updateThread = value
End Set
End Property
#End Region


#Region “Private Method”
Private Sub InvalidLoaddingBmp(ByVal ctrl As Control)
Dim info As LoadingInfo = DirectCast(m_LoadingStatePool(ctrl), LoadingInfo)
ctrl.Invalidate(New Rectangle(info.DisplayLocation, info.LoaddingBmp.Size))
End Sub

Private Sub BindingControlEvent(ByVal ctrl As Control)
UnBindingControlEvent(ctrl)
AddHandler ctrl.Paint, AddressOf Control_Paint
AddHandler ctrl.HandleDestroyed, AddressOf Control_HandleDestroyed
AddHandler ctrl.Resize, AddressOf Control_Resize
End Sub

Private Sub UnBindingControlEvent(ByVal ctrl As Control)
RemoveHandler ctrl.Paint, AddressOf Control_Paint
RemoveHandler ctrl.HandleDestroyed, AddressOf Control_HandleDestroyed
RemoveHandler ctrl.Resize, AddressOf Control_Resize
End Sub

Private Function GetDisplayLocation(ByVal ctrl As Control) As Point
Dim info As LoadingInfo = DirectCast(m_LoadingStatePool(ctrl), LoadingInfo)
Dim bmp As Bitmap = info.LoaddingBmp
Return New Point(ctrl.Width \ 2 - bmp.Width \ 2, ctrl.Height \ 2 - bmp.Height \ 2)
End Function

Private Sub AdjustDisplayLocation(ByVal ctrl As Control)
Dim info As LoadingInfo = DirectCast(m_LoadingStatePool(ctrl), LoadingInfo)
Dim bmp As Bitmap = info.LoaddingBmp
info.DisplayLocation = GetDisplayLocation(ctrl)
End Sub

Private Sub PaintGraphic(ByVal g As Graphics, ByVal ctrl As Control)
Dim info As LoadingInfo = DirectCast(m_LoadingStatePool(ctrl), LoadingInfo)
Dim bmp As Bitmap = info.LoaddingBmp
info.LoaddingBmpActiveFrameIdx = (info.LoaddingBmpActiveFrameIdx + 1) Mod info.LoaddingBmpFrameCount
g.DrawImage(bmp, info.DisplayLocation)
End Sub

Private Sub ThreadingUpdatePhoto()
While True
For idx As Integer = m_LoadingStatePool.Count - 1 To 0 Step -1
InvalidLoaddingBmp(DirectCast(mLoadingStatePool.Keys(idx), Control))
Next
Thread.Sleep(100)
End While
End Sub
#End Region


#Region “Public Method”
<Extension()>

Function IsLoadingState(ByVal ctrl As Control) As Boolean
Return mLoadingStatePool.Contains(ctrl)
End Function

<Extension()>

Sub ActiveLoadingState(ByVal ctrl As Control, ByVal loaddingBmp As Image)
If loaddingBmp Is Nothing Then
Throw New ArgumentNullException(“loaddingBmp”)
End If
DeActiveLoadingState(ctrl)
m_LoadingStatePool.Add(ctrl, New LoadingInfo() With {.LoaddingBmp = loaddingBmp})
AdjustDisplayLocation(ctrl)
BindingControlEvent(ctrl)
If m_LoadingStatePool.Count = 1 Then
mUpdateThread.Start()
End If
End Sub


<Extension()>

Sub DeActiveLoadingState(ByVal ctrl As Control)
If IsLoadingState(ctrl) Then
UnBindingControlEvent(ctrl)
m_LoadingStatePool.Remove(ctrl)
ctrl.Invalidate()
End If
If m_LoadingStatePool.Count = 0 Then
Try
m_UpdateThread.Abort()
Catch ex As Exception
Finally
m_UpdateThread = Nothing
End Try
End If
End Sub
#End Region

#Region “Event Process”
Private Sub Control_Paint(ByVal sender As Object, ByVal e As PaintEventArgs)
PaintGraphic(e.Graphics, DirectCast(sender, Control))
End Sub

Private Sub Control_HandleDestroyed(ByVal sender As Object, ByVal e As EventArgs)
DeActiveLoadingState(DirectCast(sender, Control))
End Sub

Private Sub Control_Resize(ByVal sender As Object, ByVal e As EventArgs)
AdjustDisplayLocation(DirectCast(sender, Control))
End Sub
#End Region
End Module


範例介面如下:
image

範例程式碼如下:



Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
For Each c As Control In Me.Controls
c.ActiveLoadingState(My.Resources.ajaxloader__1)
Next
End Sub

Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
For Each c As Control In Me.Controls
c.DeActiveLoadingState()
Next
End Sub
End Class


運行結果如下:

image