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用Visual Basic编写托盘程序

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用Visual Basic编写托盘程序



  在WINDOWS98里,右下角有许多应用程序的图标。而程序本身的窗口是隐藏的,若你需要调用应用程序的窗口,则双击该图标即可。这种程序称为托盘程序。这是WINDOWS98操作系统的一大特色。使用户能够更加快捷的显示和隐藏应用程序,可以使任务栏不致于太乱。托盘程序在Visual Basic里是怎么实现的呢?
    编写托盘程序主要解决两个问题:(1)创建、修改、删除托盘;(2)如何对托盘接收到的消息进行处理。这就要用到几个Windows API函数。
    首先,Shell_NotifyIcon是用于托盘的Shell API。该API用到一个NOTIFYICONDATA结构.
  Type NOTIFYICONDATA
    cbSize As Long '该结构所占字节数
    hwnd As Long '接收托盘图标消息的窗口指针
    uID As Long '由程序定义的图标识别符,因为有的程序有多个图标
    uFlags As Long '对托盘图标操作的标志,包括添加、删除、修改
    uCallbackMessage As Long '标志应用程序的消息
    hIcon As Long '托盘图标指针
    szTip As String * 64 '当鼠标指到托盘图标时提示字符串
  End Type
    其次,应该考虑怎样在VB中接收、处理托盘的消息(双击、单击、左键、右键)。C++、Delphi等语言对消息循环的处理较简单,但在VB中处理消息循环时必须应用Win32的SetWindowLong、CallWindowProc这两个API函数。SetWindowLong 函数利用GWL_WNDPROC 索引来创建窗口类的子类(窗口类是用来创建窗口的),它使用AddressOf关键字和回调函数(WindowProc)来截取消息并根据消息来执行相应的功能,如窗口的最大化、最小化、隐藏、退出等。CallWindowProc函数调用原窗口类缺省的指针,程序最后退出时可通过SetWindowLong来关闭子类,重新使原来的Windows过程成为回调函数。
    本程序项目包括一个模块和一个窗体
    1、模块源代码为:
   Option Explicit '强制定义每个使用的变量
    Type NOTIFYICONDATA '定义结构NOTIFYICONDATA
     cbSize As Long
     hwnd As Long
     uID As Long
     uFlags As Long
     uCallbackMessage As Long
     hIcon As Long
     szTip As String * 64
    End Type
    '以下为 Shell_NotifyIcon将用到的常量
    Public Const NIF_ICON = &H2
    Public Const NIF_MESSAGE = &H1
    Public Const NIF_TIP = &H4
    Public Const NIM_ADD = &H0
    Public Const NIM_DELETE = &H2
    Public Const NIM_MODIFY = &H1
    'Shell_NotifyIcon的函数声明
    Declare Function Shell_NotifyIcon Lib "shell32.dll" Alias "Shell_NotifyIconA"
    (ByVal dwMessage As Long, lpData As NOTIFYICONDATA) As Long
   '处理消息将用到的结构、常量、API声明
    Type POINTAPI
     x As Long
     y As Long
    End Type
    Type Msg
     hwnd As Long
     message As Long
     wParam As Long
     lParam As Long
     time As Long
     pt As POINTAPI
    End Type
     Public Const WM_USER = &H400
  Public Const WM_RBUTTONDOWN = &H204
  Public Const WM_LBUTTONDBLCLK = &H203
    Public Const GWL_WNDPROC = -4
    Public trayflag As Boolean '定义托盘图标是否在桌面上
    Global lpPrevWndProc As Long
    Global gHW As Long
  Declare Function CallWindowProc Lib "user32" Alias "CallWindowProcA" (ByVal lpPrevWndFunc As Long, ByVal hwnd As Long, ByVal Msg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
  Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" (ByVal hwnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long
   '以下过程为消息循环处理
  Function WindowProc(ByVal hw As Long, ByVal uMsg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
   If hw = Form1.hwnd And uMsg = WM_USER+100 Then'检测到鼠标点动托盘图标
    Select Case lParam
      Case WM_RBUTTONDOWN '鼠标右键按下
     Form1.PopupMenu
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