#眉標=Silverlight 3.0、Multi-Touch、RIA
#副標=Silverlight 3.0技術應用（3）
#大標=Silverlight 3多點觸控程式開發
#作者=文／圖 董大偉



===<反灰>=============
Public Sub New()
  InitializeComponent()
  'Hook FrameReported事件    
  AddHandler Touch.FrameReported, AddressOf Touch_FrameReported
End Sub
==<end>==============





===<反灰>=============
'Touch事件
Sub Touch_FrameReported(ByVal sender As Object, ByVal e As TouchFrameEventArgs)
  …略…
End Sub
==<end>==============




===<反灰>=============
For Each p As TouchPoint In e.GetTouchPoints(Nothing)
   (…p為每一個點…)
Next
==<end>==============




==<表>===========
表1：TouchPoint物件重要參數
屬性
功能
值
Action
回傳該觸控點目前的行為
Down/Move/Up
Position
回傳該觸控點的座標
Point物件
TouchDevice. DirectlyOver
回傳該觸控點點選到的物件(UIElement)
UIElement==<end>==============





==<box>===========
程式1

For Each p As TouchPoint In e.GetTouchPoints(Nothing)
'取得點選物件
  Dim element As UIElement = p.TouchDevice.DirectlyOver
  Select Case p.Action  '當動作為點選
    Case TouchAction.Down
      '取得Touch點原座標
      originalPointPosistions(i).X = p.Position.X
      originalPointPosistions(i).Y = p.Position.Y
      '取得物件原座標
      If element IsNot Nothing Then
       originalElementPosistions(i).X = element.GetValue(Canvas.LeftProperty)
       originalElementPosistions(i).Y = element.GetValue(Canvas.TopProperty)
       ElementLastDistance(i) = 0
      End If
    Case TouchAction.Move '當動作為移動
      If p.Action = TouchAction.Move Then                       
       '移動
       '取得新座標
       Dim x, y As Integer
       x = p.Position.X - originalPointPosistions(i).X
       y = p.Position.Y - originalPointPosistions(i).Y
       If element IsNot Nothing Then
        element.SetValue(Canvas.LeftProperty, originalElementPosistions(i).X + x)
        element.SetValue(Canvas.TopProperty, originalElementPosistions(i).Y + y)
      End If
    End If 
    Case TouchAction.Up     '當動作為放開
      originalPointPosistions(i) = Nothing
      originalElementPosistions(i) = Nothing
      ElementLastDistance(i) = 0
    End Select
   i += 1
  Next
==<end>==============






==<box>===========
程式2

Public Sub New()
  InitializeComponent()
  'Hook FrameReported事件
  AddHandler Touch.FrameReported, AddressOf Touch_FrameReported
End Sub

'同時支援的點數
Const MaxTouchPoints As Integer = 10
'保留每一個點的Stroke
Dim NewStroke(MaxTouchPoints) As System.Windows.Ink.Stroke
'觸控事件
Sub Touch_FrameReported(ByVal sender As Object, ByVal e As TouchFrameEventArgs)
  Dim i As Integer = 0
  '處理每一個點
  For Each p As TouchPoint In e.GetTouchPoints(Nothing)
   Select Case p.Action  '當動作為點選
    Case TouchAction.Down
     '建立新Stroke
     NewStroke(i) = New System.Windows.Ink.Stroke
     '加入InkPresenter1
     InkPresenter1.Strokes.Add(NewStroke(i))
    Case TouchAction.Move '當動作為移動
     '將每一個點加入Stroke
     NewStroke(i).StylusPoints.Add(New StylusPoint(p.Position.X, p.Position.Y))
  End Select
 i += 1
Next
End Sub
==<end>==============





==<box>===========
程式3


Case TouchAction.Move '當動作為移動
  If p.Action = TouchAction.Move Then
  '是否還有其他點在同一個物件身上?
   If isMultiPoints(p.TouchDevice.DirectlyOver, e) Then
    '縮放
    '如果第一點是空值
    If ElementLastDistance(i) = 0 Then
     ElementLastDistance(i) = getFirst2PointsDistance(p.TouchDevice.DirectlyOver, e)
    Else
Dim offset As Integer = getFirst2PointsDistance(p.TouchDevice.DirectlyOver, e) - ElementLastDistance(i)
     ElementLastDistance(i) = getFirst2PointsDistance(p.TouchDevice.DirectlyOver, e)
'rectangle
    If element.GetType() Is GetType(Image) Then
     CType(element, Rectangle).Height = CType(element, Rectangle).Height * (1 + offset / SenseValue)
     CType(element, Rectangle).Width = CType(element, Rectangle).Width * (1 + offset / SenseValue)
    End If
   End If            
 Else
'移動
'取得新座標
Dim x, y As Integer
  x = p.Position.X - originalPointPosistions(i).X
  y = p.Position.Y - originalPointPosistions(i).Y
   If element IsNot Nothing Then
      element.SetValue(Canvas.LeftProperty, originalElementPosistions(i).X + x)
      element.SetValue(Canvas.TopProperty, originalElementPosistions(i).Y + y)
   End If
  End If
 End If
==<end>==============