怎么判断一个数组是空数组？dim a() as byte

damomo 2003-07-15 03:20:14

dim a() as byte

在某些条件下我会给a调用函数赋值，我怎么知道a是否变化？
如a不变我怎么判断？
ubound(a)出错。

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boywang 2003-07-16

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在调用函数的返回值中说明。

Sean918 2003-07-16

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参考：
http://expert.csdn.net/Expert/topic/1677/1677965.xml?temp=.5621759

damomo 2003-07-16

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up

progame 2003-07-15

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.

专业VB课件这个程序的目的是为了实现得到文本框1中的数组b 和内置数组a 的交集，并以交集元素的个数作为文本框二显示可以执行的条件。代码如下： Private Sub Command1_Click() Dim a(0 To 9) As String '定义一个内置的数组 Dim b(0 To 3) As String '文本框中输入的数组 Dim c() As String '数组a与数组b的交集 Dim m As Byte '定义数组a的循环变量 Dim n As Byte '定义数组b的循环变量 Dim i As Byte '定义交集c的元素数量 a(0) = "01": a(1) = 10: a(2) = 11: a(3) = 35: a(4) = 47: a(5) = 56: a(6) = 67: a(7) = 76: a(8) = 83: a(9) = 99 '给数组a赋值 b(0) = Mid(Text1.Text, 1, 2): b(1) = Mid(Text1.Text, 4, 2): b(2) = Mid(Text1.Text, 7, 3): b(3) = Mid(Text1.Text, 10, 3) '给数组b赋值 For m = 0 To 9 For n = 0 To 3 i = 0 If a(m) = b(n) Then c(i) = a(m): i = i + 1: Exit For End If Next n Next m '循环得到交集 c If UBound(c) + 1 >= 2 Then '获得交集c中元素的个数 Text2.Text = 可以执行 End If End Sub 运行时，当我输入四个两位的数据，点击按钮 1 显示提示下标越界。请求各位达人帮助，我如何才可以达到自己的目的，最好有完整的代码问题补充：按照一楼的说法做了，代码如下： Private Sub Command1_Click() Dim a(0 To 9) As String '定义一个内置的数组 Dim b(0 To 3) As String '文本框中输入的数组 Dim c() As String '数组a与数组b的交集 ReDim Preserve c(i) Dim m As Byte '定义数组a的循环变量 Dim n As Byte '定义数组b的循环变量 a(0) = "01": a(1) = 10: a(2) = 11: a(3) = 35: a(4) = 47: a(5) = 56: a(6) = 67: a(7) = 76: a(8) = 83: a(9) = 99 '给数组a赋值 b(0) = Mid(Text1.Text, 1, 2): b(1) = Mid(Text1.Text, 4, 2): b(2) = Mid(Text1.Text, 7, 2): b(3) = Mid(Text1.Text, 10, 2) '给数组b赋值 i = 0 For m = 0 To 9 For n = 0 To 3 If a(m) = b(n) Then ReDim Preserve c(i) c(i) = a(m): i = i + 1: Exit For End If Next n Next m '循环得到交集 c If UBound(c) + 1 >= 2 Then '获得交集c中元素的个数 Text2.Text = "可以执行" End If End Sub

MCGS昆仑通态的触摸屏的脚本串口驱动 DIM strTmp as STRING '临时字符变量 DIM strData as STRING ' '定义HEXE协议格式命令收发帧使用变量 dim SendByteArr(0) as byte '存放发送命令字节数组 dim RecByteArr(0) as byte '存放接收命令字节数组 dim DataByteArr(0) as byte '存放解析数据临时字节数组 DIM nReturn as INTEGER '函数返回判断标志 DIM nTmp as INTEGER '开关型临时变量 DIM 数值数据 as SINGLE '解析数值型数据，对数值型通道赋值 DIM 开关数据 as INTEGER '解析开关型数据，对开关型通道赋值 DIM setFlag as SINGLE DIM start as INTEGER DIM j as SINGLE DIM crc as SINGLE 'CRC校验值 DIM nCrc as INTEGER DIM cstrTmp as STRING DIM crcTmp as INTEGER DIM csendTmp as STRING nIndex = 0 nChlIndex = 0 setFlag = 0 j=0 '数据个数（包括CRC） '------------------第0帧收发脚本-------------------- '发送和接收数据按如下方式: if i=0 then strSend = "*" + "!$$$$$$$$$$$$$$$$$$$$$Y" + "#" !DevWriteStr(strSend) sendnum=sendnum+1 !SetSingleChannelValueByNum(66,sendnum) endif

通过本源码可了解下初始socket、对发送的消息数据进行编码、当发送数据完后关闭socket、禁用某 Socket 上的发送和接收、判断给定的IP地址的合法性、异常处理、判断给定的IP地址的合法性。这个程序由客户端和服务端组成，两者互相配合。　　If TextBox1.Text = Nothing Then 　　 MsgBox("禁止发送空的信息", MsgBoxStyle.YesNo) 　　End If 　　Dim bytes(1024) As Byte '声明字节数组　　'初始化socket 　　Dim msg As Byte() = System.Text.Encoding.Unicode.GetBytes(TextBox1.Text) 　　'对发送的数据进行编码　　Dim bytesSent As Integer = sender2.Send(msg) '发送数据　　TextBox1.Text = "" 　　'当发送数据完后关闭socket 　　sender2.Shutdown(Net.Sockets.SocketShutdown.Both) 　　'禁用某 Socket 上的发送和接收　　sender2.Close() 　　'关闭socket

由于使用了一些新的函数，本程序必须在Windows2000下运行。 Option Explicit Public Declare Function GetObjectAPI Lib "gdi32" Alias "GetObjectA" (ByVal hObject As Long, ByVal nCount As Long, lpObject As Any) As Long Public Declare Function DeleteObject Lib "gdi32" (ByVal hObject As Long) As Long Public Declare Function SetWindowRgn Lib "user32" (ByVal hwnd As Long, ByVal hRgn As Long, ByVal bRedraw As Boolean) As Long Public Declare Function CreateRectRgn Lib "gdi32" (ByVal X1 As Long, ByVal Y1 As Long, ByVal X2 As Long, ByVal Y2 As Long) As Long Public Declare Function CombineRgn Lib "gdi32" (ByVal hDestRgn As Long, ByVal hSrcRgn1 As Long, ByVal hSrcRgn2 As Long, ByVal nCombineMode As Long) As Long Public Const RGN_OR = 2 Public Declare Function GetBitmapBits Lib "gdi32" (ByVal hBitmap As Long, ByVal dwCount As Long, lpBits As Any) As Long Public Declare Function SetBitmapBits Lib "gdi32" (ByVal hBitmap As Long, ByVal dwCount As Long, lpBits As Any) As Long Public Type BITMAP bmType As Long bmWidth As Long bmHeight As Long bmWidthBytes As Long bmPlanes As Integer bmBitsPixel As Integer bmBits As Long End Type Public Const BITMAP_SIZE = 24 '=Len(BITMAP) Dim bmByte() As Byte Public Declare Function ReleaseCapture Lib "user32" () As Long Public Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long Public Const HTCAPTION = 2 Public Const WM_NCLBUTTONDOWN = &HA1; Public Declare Function GetWindowLong Lib "user32" Alias "GetWindowLongA" (ByVal hwnd As Long, ByVal nIndex As Long) As Long Public Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" (ByVal hwnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long Public Declare Function SetLayeredWindowAttributes Lib "user32" (ByVal hwnd As Long, ByVal crKey As Long, ByVal bAlpha As Byte, ByVal dwFlags As Long) As Long Public Const WS_EX_LAYERED = &H80000; Public Const GWL_EXSTYLE = (-20) Public Const LWA_ALPHA = &H2; Public Const LWA_COLORKEY = &H1; Public Sub SetAutoRgn(hForm As Form, Optional transColor As Byte = vbNull) Dim X As Long, Y As Long Dim Rgn1 As Long, Rgn2 As Long Dim SPos As Long, EPos As Long Dim bm As BITMAP Dim hbm As Long Dim Wid As Long, Hgt As Long Dim xoff As Long, yoff As Long '获取窗体背景图片尺寸 hbm = hForm.Picture GetObjectAPI hbm, Len(bm), bm Wid = bm.bmWidth Hgt = bm.bmHeight With hForm .ScaleMode = vbPixels xoff = (.ScaleX(.Width, vbTwips, vbPixels) - .ScaleWidth) / 2 yoff = .ScaleY(.Height, vbTwips, vbPixels) - .ScaleHeight - xoff '改变窗体尺寸 .Width = (Wid + xoff * 2) * Screen.TwipsPerPixelX .Height = (Hgt + xoff + yoff) * Screen.TwipsPerPixelY End With ReDim bmByte(1 To Wid, 1 To Hgt) GetBitmapBits hbm, Wid * Hgt, bmByte(1, 1) '获取图像数组 '如果没有传入transColor参数，则用第一个像素作为透明色 If transColor = vbNull Then transColor = bmByte(1, 1) Rgn1 = CreateRectRgn(0, 0, 0, 0) For Y = 1 To Hgt '逐行扫描 X = 0 Do X = X + 1 While (bmByte(X, Y) = transColor) And (X < Wid) X = X + 1 '跳过是透明色的点 Wend SPos = X While (bmByte(X, Y) <> transColor) And (X < Wid) X = X + 1 '跳过不是透明色的点 Wend EPos = X - 1 '这一段是合并区域 If SPos <= EPos Then Rgn2 = CreateRectRgn(SPos - 1 + xoff, Y - 1 + yoff, EPos + xoff, Y + yoff) CombineRgn Rgn1, Rgn1, Rgn2, RGN_OR DeleteObject Rgn2 End If Loop Until X >= Wid Next Y SetWindowRgn hForm.hwnd, Rgn1, True '设定窗体形状区域 DeleteObject Rgn1 End Sub Option Explicit Private Sub Form_DblClick() Unload Me End Sub Private Sub Form_Load() 'Me.Show Dim t As Single Dim rtn As Long rtn = GetWindowLong(hwnd, GWL_EXSTYLE) rtn = rtn Or WS_EX_LAYERED SetWindowLong hwnd, GWL_EXSTYLE, rtn SetLayeredWindowAttributes hwnd, 0, 192, LWA_ALPHA '半透明 'SetLayeredWindowAttributes hwnd, &H0;, 0, LWA_COLORKEY '去除透明色 t = Timer If Me.Picture <> 0 Then Call SetAutoRgn(Me) ', 0) End If 'MsgBox "运行时间：" & Timer - t & "秒", vbInformation End Sub Private Sub Form_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single) If Button = vbLeftButton Then ReleaseCapture SendMessage Me.hwnd, WM_NCLBUTTONDOWN, HTCAPTION, 0& End If End Sub

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