是否可以使用CrystalDecisions.Windows.Forms.CrystalReportViewer上的组合ctrl +鼠标滚轮启用或实现放大/缩小功能?
MouseWheel用于滚动。建议的想法可能是处理mouseevent,中止滚动并使用delta调整缩放...但我无法处理mousewheel事件。
我已经尝试处理CrystalReportViewer.MouseWheel,它编译但从未引发过。我还尝试继承控件CrystalDecisions.Windows.Forms.CrystalReportViewer并重写OnMouseWheel方法,它永远不会被调用。有什么想法吗?
答案 0 :(得分:0)
我发现了一个类似的问题here。然后我解决了我的问题,实现IMessageFilter接口,以便在按下Ctrl键时拦截MouseWheel消息。我在CrystalReportViewer控件之前处理了消息,并根据delta调整了缩放级别。 我发布我的解决方案,希望这对其他人有用。 让我知道如果您找到更好的解决方案或错误。
Imports System.Drawing
'Imports System.Runtime.InteropServices
Imports System.Windows.Forms
Imports CrystalDecisions.CrystalReports.Engine
Imports CrystalDecisions.Windows.Forms
Public Class CrystalReportViewerMouseWheelZoom
Implements IMessageFilter
Private WithEvents _viewer As CrystalDecisions.Windows.Forms.CrystalReportViewer
Private _viewerForm As Form = Nothing
Private _ZoomLevel As Integer
Public Sub New(viewer As CrystalDecisions.Windows.Forms.CrystalReportViewer)
Me._viewer = viewer
Application.AddMessageFilter(Me)
End Sub
Private Sub _viewer_Disposed(sender As Object, e As EventArgs) Handles _viewer.Disposed
Application.RemoveMessageFilter(Me)
_viewer = Nothing
End Sub
Private Sub _viewer_ViewZoom(source As Object, e As ZoomEventArgs) Handles _viewer.ViewZoom
_ZoomLevel = e.NewZoomFactor
End Sub
'<DllImport("user32.dll")>
'Private Shared Function WindowFromPoint(ByVal p As Point) As IntPtr
'End Function
Private Const ZOOM_LEVEL_DELTA_PERC As Double = 5D
Public Function PreFilterMessage(ByRef m As Message) As Boolean Implements IMessageFilter.PreFilterMessage
If (m.Msg <> &H20A) Then Return False
If Not My.Computer.Keyboard.CtrlKeyDown Then Return False
Dim mouseAbsolutePosition = New Point(m.LParam.ToInt32())
Dim mouseRelativePosition = _viewer.PointToClient(mouseAbsolutePosition)
'DOEW NOT WORK, Control.FromHandle return always null
'Dim hControlUnderMouse As IntPtr = WindowFromPoint(mouseAbsolutePosition)
'Dim controlUnderMouse = Control.FromHandle(hControlUnderMouse)
'If Not Equals(controlUnderMouse, _viewer) Then Return False
If Not IsViewerFormActive() Then Return False
Dim _documentControl = FindFirstDocumentControl(_viewer)
If _documentControl Is Nothing Then Return False
Dim screenRectangle = _documentControl.RectangleToScreen(_documentControl.ClientRectangle)
If Not screenRectangle.Contains(mouseAbsolutePosition) Then Return False
Dim delta = m.WParam.ToInt32() >> 16
Dim newZoomLevel As Integer = CalcNewZoomLevel(_documentControl, delta)
If (newZoomLevel < 3) Then Return False
_viewer.Zoom(newZoomLevel)
Return True
End Function
Private Function IsViewerFormActive() As Boolean
Dim active As Boolean = False
If _viewerForm Is Nothing Then _viewerForm = _viewer.FindForm
Dim activeForm = Form.ActiveForm
If activeForm IsNot Nothing AndAlso activeForm.IsMdiContainer AndAlso _viewerForm.IsMdiChild Then
active = Equals(activeForm.ActiveMdiChild, _viewerForm)
Else
active = Equals(activeForm, _viewerForm)
End If
Return active
End Function
Private Function CalcNewZoomLevel(_documentControl As DocumentControl, delta As Integer) As Integer
Dim newZoomLevel = _ZoomLevel
If newZoomLevel < 3 Then
Dim rpt = TryCast(_viewer.ReportSource, ReportDocument)
If rpt Is Nothing Then Return -1
Using g = _viewer.CreateGraphics()
If _ZoomLevel = 1 Then
newZoomLevel = CInt((_documentControl.ClientSize.Width / GetPageWith(rpt, g)) * 100)
ElseIf _ZoomLevel = 2 Then
newZoomLevel = CInt((_documentControl.ClientSize.Height / GetPageHeight(rpt, g)) * 100)
End If
End Using
End If
newZoomLevel += (If(delta < 0, -1, 1) * CInt(newZoomLevel * ZOOM_LEVEL_DELTA_PERC / 100))
Return newZoomLevel
End Function
Private Function GetPageHeight(rpt As ReportDocument, g As Graphics) As Integer
Dim twips = rpt.PrintOptions.PageContentHeight + rpt.PrintOptions.PageMargins.topMargin + rpt.PrintOptions.PageMargins.bottomMargin
Return CInt(CDbl(twips) * (1.0 / 1440.0) * g.DpiY)
End Function
Private Function GetPageWith(rpt As ReportDocument, g As Graphics) As Integer
Dim twips = rpt.PrintOptions.PageContentWidth + rpt.PrintOptions.PageMargins.leftMargin + rpt.PrintOptions.PageMargins.rightMargin
Return CInt(CDbl(twips) * (1.0 / 1440.0) * g.DpiX)
End Function
Private Function FindFirstDocumentControl(parent As Control) As DocumentControl
Dim docCrtl As DocumentControl = Nothing
For Each c As Control In parent.Controls
If TypeOf c Is DocumentControl Then
docCrtl = DirectCast(c, DocumentControl)
Exit For
Else
docCrtl = FindFirstDocumentControl(c)
End If
If docCrtl IsNot Nothing Then Exit For
Next
Return docCrtl
End Function
End Class