SendMessage函数应用(一) 在Windows编程中，向文本框控件、列表控件、按钮控件等是我们最常接触的控件了。?br />窃赩B中这些控件有时无法实现我们的需要。在这时，我们只要简单的利用Windows API函数就可以扩充这些控件的功能了。顾名思义，SendMessage函数就是向窗口（这里的窗口指的是向按钮、列表框、编辑框?br />染哂衕Wnd属性的控件）发送消息的函数，该函数的定义如下:Declare Function SendMessage Lib "user32" Alias "SendMessageA" _(ByVal hwnd As Long, _ByVal wMsg As Long, _ByVal wParam As Long, _lParam As Any) As Long其中hwnd指定接受消息的窗口，参数wMsg指定消息值，参数wParam lParam分别定义传递到窗口的附加参数。而在Windows系统的很多消息中，有一些不仅仅是?br /> 峁┮桓龃翱谙⒛敲醇虻ァＫ强梢钥刂拼翱诘亩骱褪粜浴Ｏ旅嫖医执蜗蛳虼蠹医樯躍endMessage函数在扩充基本控件功能方面的应用。 一、列表（ListBox）控件在Windows中，有一系列的以LB_开头的列表消息，这里介绍的就是利用LB消息控制的ListBox的应用1、使列表中光标移动到不同的列表项上有不同的提示（ToolTip）在列表框控件中有一个ToolTipText属性，该属性决定了当光标在列表框上移动时出现的提?br />疚淖帧５侨绾问沟? 当光标在不同的列表项上移动时的提示文字也不同呢？问题的关键是要知道在光标移动时光标所在的列表项的索引，使 用SendMessage函数发送LB_ITEMFROMPOINT消息就可以获得。下面是程序范例： Option Explicit Const LB_ITEMFROMPOINT = &H1A9 Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" _(ByVal hwnd As Long, _ByVal wMsg As Long, _ByVal wParam As Long, _lParam As Any) As Long Private Sub Form_Load()Dim iFor i = 1 To 200List1.AddItem Str(i) + " Samples in this list is " + Str(i)Next iEnd Sub Private Sub List1_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)Dim lXPoint As LongDim lYPoint As LongDim lIndex As Long If Button = 0 Then '确定在移动鼠标的同时没有按下功能键或者鼠标键'获得光标的位置，以像素为单位lXPoint = CLng(X / Screen.TwipsPerPixelX)lYPoint = CLng(Y / Screen.TwipsPerPixelY)'With List1'获得 光标所在的标题行的索引lIndex = SendMessage(.hwnd, LB_ITEMFROMPOINT, 0, _ByVal ((lYPoint * 65536) + lXPoint))'将ListBox的Tooltip设置为该标题行的文本If (lIndex >= 0) And (lIndex <= .ListCount) Then.ToolTipText = .List(lIndex) 'Return the text = .list(lIndex)Else.ToolTipText = ""End IfEnd WithEnd IfEnd Sub首先在Form1中加入一个ListBox控件，然后再将上面的代码加入到Form1的代码窗口中?br />Ｔ诵谐绦颍惫獗暝?列表中移动时，可以看到根据光标所在的不同的列表项，提示文字也不相同。 2、向列表中加入横向滚动条使得可以浏览长列表项当向列表中加入的列表项超出了列表的显示范围后，列表并不会出现横向滚动条让你可以通过滚动来浏览项目 的全部内容。利用LB_SETHORIZONTALEXTENT消息可以设置列表的横向滚动条以及滚动长度。下面是范例程序：Option Explicit Private Type RECTLeft As LongTop As LongRight As LongBottom As LongEnd TypePrivate Declare Function DrawText Lib "user32" Alias "DrawTextA" _(ByVal hdc As Long, _ByVal lpStr As String, _ByVal nCount As Long, _lpRect As RECT, _ByVal wFormat As Long) As Long Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" _(ByVal hwnd As Long, _ByVal wMsg As Long, _ByVal wParam As Long, _lParam As Any) As Long Const LB_SETHORIZONTALEXTENT = &H194Const DT_CALCRECT = &H400 Public Function ListTextWidth(ByRef lstThis As ListBox) As LongDim i As LongDim tR As RECTDim lW As LongDim lWidth As LongDim lHDC As Long With lstThis.Parent.Font.Name = lstThis.Font.Name.Size = lstThis.Font.Size .Bold = lstThis.Font.Bold .Italic = lstThis.Font.ItalicEnd WithlHDC = lstThis.Parent.hdc'便历所有的列表项以找到最长的项For i = 0 To lstThis.ListCount - 1DrawText lHDC, lstThis.List(i), -1, tR, DT_CALCRECTlW = tR.Right - tR.Left + 8If (lW > lWidth) ThenlWidth = lWEnd IfNext i'返回最长列表项的长度（像素）ListTextWidth = lWidthEnd Function Private Sub Form_Load()Dim astr As StringDim iDim l As Longl = List1.FontSize * 20 / Screen.TwipsPerPixelXFor i = 1 To 10astr = astr + "我们This is a very long item " + Str(i)Next iList1.AddItem astr + "aaa"'加入一个很厂的列表项l = ListTextWidth(List1)SendMessage List1.hwnd, LB_SETHORIZONTALEXTENT, l, 0End Sub首先在Form1中加入一个ListBox控件，然后再将上面的代码加入到Form1的代码窗口中?br />Ｔ诵谐绦颍梢钥吹搅斜碇谐鱿至撕嵯蚬龆酰夜龆段д檬橇斜硐畹某ざ取?br>3、使列表可以响应用户击键有时我们需要列表根据用户的敲入字符串自动调整列表的ListIndex到最接近的列表项?br /> 拖骎B中动态感应用户输入控件属性的编辑器一样。问题的关键是如何在列表中查找含有?br /> 付ㄗ址牧斜硐睿褂肔B_FINDSTRING消息可以在列表中查找指定字符串。下面是范例：Private Declare Function SendMessageStr Lib "user32" Alias "SendMessageA" _(ByVal hwnd As Long, _ByVal wMsg As Long, _ByVal wParam As Long, _ByVal lParam As String) As Long Const LB_FINDSTRING = &H18FDim astr As String Private Sub Form_KeyPress(KeyAscii As Integer)Dim l As Longastr = astr + Chr(KeyAscii)l = SendMessageStr(List1.hwnd, LB_FINDSTRING, -1, astr)If l ThenList1.ListIndex = lEnd IfEnd Sub Private Sub Form_Load()'向List中加入列表项For i = 65 To 85For j = 65 To 85List1.AddItem Chr(i) + Chr(j)Next jNext iEnd Sub Private Sub List1_DblClick()'清除原来的查找字符串astr = ""End Sub Private Sub List1_KeyPress(KeyAscii As Integer)'如果按下的是字母键就将击键消息传递到Form1If ((KeyAscii >= 65 And KeyAscii <= 90) Or (KeyAscii >= 97 _Or KeyAscii <= 122)) ThenKeyAscii = 0End IfEnd Sub首先在Form1中加入一个ListBox控件，然后再将上面的代码加入到Form1的代码窗口中?br />２⒔獿ist1的Sorted属性设置为True。运行程序，在列表中敲入字符，例如"av" "gm"，列表就会高亮显示相近的列表项，双击列表就可以清除原来的输入。

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