SENDMESSAGE函数巧应用

g) As Long
Private Declare Function GlobalFree Lib "kernel32" (ByVal hMem As Long) As Long
Dim hItemPrv As Long
Private Sub Form_Load()
Dim ndX As Node
`加入若干Item
Set ndX = TreeView1.Nodes.Add(, , "R", "Root")
Set ndX = TreeView1.Nodes.Add("R", tvwChild, "Key1", "Node1")
Set ndX = TreeView1.Nodes.Add("Key1", tvwChild, "SubKey1", "SubNode1")
Set ndX = TreeView1.Nodes.Add("SubKey1", tvwChild, "SubKeys1", "SubNode1")
Set ndX = TreeView1.Nodes.Add("Key1", tvwChild, "SubKey2", "SubNode2")
Set ndX = TreeView1.Nodes.Add("Key1", tvwChild, "SubKey3", "SubNode3")
Set ndX = TreeView1.Nodes.Add("Key1", tvwChild, "SubKey4", "SubNode4")
End Sub
Private Sub TreeView1_MouseMove(Button As Integer, Shift As Integer, x As Single, y As Single)
Dim ptA As TPoint
Dim tf As TVHITTESTINFO
Dim tv As TVITEM
Dim hStr As Long
Dim hItem As Long
Dim astr As String ＊ 1024
Dim bstr
On Error GoTo errLab
`获得当前光标所在的位置坐标
ptA.x = Int(x / Screen.TwipsPerPixelX)
ptA.y = Int(y / Screen.TwipsPerPixelY)
tf.pt = ptA
tf.flags = TVHT_ONITEMLABEL
`获得光标所在的Item的句柄
hItem = SendMessageRef(TreeView1.hwnd, TVM_HITTEST, 0, tf)
`如果未获得句柄或者同上一次是同一个Item的句柄则退出
If ((hItem <= 0) Or (hItem = hItemPrv)) Then Exit Sub
hItemPrv = hItem
`分配一定的内存空间用以存储Item的标题
hStr = GlobalAlloc(GMEM－FIXED, 1024)
If hStr > 0 Then
tv.mask = TVIF_TEXT
`获取标题文本
tv.HTreeItem = hItem
`Item句柄
tv.pszText = hStr
tv.cchTextMax = 1023
`发送TVM_GETITEM获得标题文本
CallSendMessageRef(TreeView1.hwnd, TVM－GETITEM, 0, tv)
`将标题文本拷贝到字符串astr中
CopyMemory astr, hStr, 1024
bstr = Left＄(astr, (InStr(astr, Chr(0)) － 1))
TreeView1.ToolTipText = bstr
`释放分配的内存空间
GlobalFree hStr
End If
Exit Sub
errLab:
Resume Next
End Sub
运行上面的程序，当光标在TreeView1上面移动时，TreeView1的ToolTips就会根据光标所在的不同标题行而变动。
以上程序在Win98、Win2000，VB6下运行通过