使用API建立窗體（類似VC的建立過程） (轉)

使用API建立窗體（類似VC的建立過程） (轉)[@more@]

在VB中用建立窗體和VC中的步驟是一樣的，只不過用環境建立是把過程都封裝起來，現在我們用API方式建立，大致讓我們瞭解一個窗體的產生過程，讓我們使用VB的員對的機制多一些瞭解.

先所以下用C++建立窗體的過程：

程式的入口：int APIENTRY WinMain(HINSTANCE hInstance,
  HINSTANCE hPrevInstance,
  LPSTR  lpCmdLine,
  int  nCmdShow)

進入後先初始化結構WNDCLASSEX wcex;

APIRegisterClassEx,註冊窗體結構，如果成功一次呼叫CreateWindow、ShowWindow、UpdateWindow這樣一個主窗體就成功的建立並顯示給，下面就缺少一個處理訊息的死迴圈。

那麼我們我們可以按照這個步驟在VB中實現一樣的效果：

在C++因為API宣告已經被包涵到頭所以直接用就可以，但是在VB中就要逐個宣告一下用到的API，結構。

Public Declare Function RegisterClass Lib "user32" Alias "RegisterClassA" (Class As WNDCLASS) As Long
Public Declare Function UnregisterClass Lib "user32" Alias "UnregisterClassA" (ByVal lpClassName As String, ByVal hInstance As Long) As Long
Public Declare Function DefWindowProc Lib "user32" Alias "DefWindowProcA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
Public Declare Function GetMessage Lib "user32" Alias "GetMessageA" (lpMsg As Msg, ByVal hwnd As Long, ByVal wMsgFilten As Long, ByVal wMsgFilterMax As Long) As Long
Public Declare Function TranslateMessage Lib "user32" (lpMsg As Msg) As Long
Public Declare Function DispatchMessage Lib "user32" Alias "DispatchMessageA" (lpMsg As Msg) As Long
Public Declare Function ShowWindow Lib "user32" (ByVal hwnd As Long, ByVal nCmdShow As Long) As Long
Public Declare Function LoadCursor Lib "user32" Alias "LoadCursorA" (ByVal hInstance As Long, ByVal lpCursorName As Any) As Long
Public Declare Function LoadIcon Lib "user32" Alias "LoadIconA" (ByVal hInstance As Long, ByVal lpIconName As String) As Long
Public Declare Function CreateWindowEx Lib "user32" Alias "CreateWindowExA" (ByVal dwExStyle As Long, ByVal lpClassName As String, ByVal lpWindowName As String, ByVal dwStyle As Long, ByVal x As Long, ByVal y As Long, ByVal nWidth As Long, ByVal nHeight As Long, ByVal hWndParent As Long, ByVal hMenu As Long, ByVal hInstance As Long, lpParam As Any) As Long
Public 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
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 GetWindowLong Lib "user32" Alias "GetWindowLongA" (ByVal hwnd As Long, ByVal nIndex As Long) As Long
Public Declare Function MessageBox Lib "user32" Alias "MessageBoxA" (ByVal hwnd As Long, ByVal lpText As String, ByVal lpCaption As String, ByVal wType As Long) As Long
Public Declare Sub PostQuitMessage Lib "user32" (ByVal nExitCode As Long)

Public Type WNDCLASS
  style As Long
  lpfnwndproc As Long
  cbClsextra As Long
  cbWndExtra2 As Long
  hInstance As Long
  hIcon As Long
  hCursor As Long
  hbrBackground As Long
  lpszMenuName As String
  lpszClassName As String
End Type

Public Type POINTAPI
  x As Long
  y As Long
End Type

Public Type Msg
  hwnd As Long
  message As Long
  wParam As Long
  lParam As Long
  time As Long
  pt As POINTAPI
End Type

Public Const CS_VREDRAW = &H1
Public Const CS_HREDRAW = &H2

Public Const CW_USEDEFAULT = &H80000000

Public Const ES_MULTILINE = &H4&

Public Const WS_BORDER = &H800000
Public Const WS_CHILD = &H40000000
Public Const WS_OVERLAPPED = &H0&
Public Const WS_CAPTION = &HC00000 ' WS_BORDER Or WS_DLGFRAME
Public Const WS_SYSMENU = &H80000
Public Const WS_THICKFRAME = &H40000
Public Const WS_MINIMIZEBOX = &H20000
Public Const WS_MAXIMIZEBOX = &H10000
Public Const WS_OVERLAPPEDWINDOW = (WS_OVERLAPPED Or WS_CAPTION Or WS_SYSMENU Or WS_THICKFRAME Or WS_MINIMIZEBOX Or WS_MAXIMIZEBOX)

Public Const WS_EX_CLIENTEDGE = &H200&

Public Const COLOR_WINDOW = 5

Public Const WM_DESTROY = &H2
Public Const WM_LBUTTONDOWN = &H201
Public Const WM_LBUTTONUP = &H202

Public Const IDC_ARROW = 32512&

Public Const IDI_APPLICATION = 32512&

Public Const GWL_WNDPROC = (-4)

Public Const SW_SHOWNORMAL = 1

Public Const MB_OK = &H0&
Public Const MB_ICONEXCLAMATION = &H30&

宣告幾個我們需要的變數、常量：

Public Const gClassName = "MyClassName"
Public Const gAppName = "My Window Caption"

Public gButOldProc As Long
Public gHwnd As Long, gButtonHwnd As Long, gEditHwnd As Long

 

入口：

Sub Main

程式碼如下：

Public Sub Main()

  Dim wMsg As Msg

  ''Call procedure to register window classname. If false, then exit.
  If RegisterWindowClass = False Then Exit Sub
 
  ''Create window
  If Create Then
  ''L will exit when WM_QUIT is sent to the window.
  Do While GetMessage(wMsg, 0&, 0&, 0&)
  ''TranslateMessage takes keyboard messages and converts
  ''them to WM_CHAR for easier processing.
  Call TranslateMessage(wMsg)
  ''Dispatchmessage calls the default window procedure
  ''to process the window message. (WndProc)
  Call DispatchMessage(wMsg)
  Loop
  End If

  Call UnregisterClass(gClassName$, App.hInstance)

End Sub

Public Function RegisterWindowClass() As Boolean

  Dim wc As WNDCLASS
 
 
  wc.style = CS_HREDRAW Or CS_VREDRAW
  wc.lpfnwndproc = GetAddress(AddressOf WndProc) ''Address in memory of default window procedure.
  wc.hInstance = App.hInstance
  wc.hIcon = LoadIcon(0&, IDI_APPLICATION) ''Default application icon
  wc.hCursor = LoadCursor(0&, IDC_ARROW) ''Default arrow
  wc.hbrBackground = COLOR_WINDOW ''Default a color for window.
  wc.lpszClassName = gClassName$

  RegisterWindowClass = RegisterClass(wc) <> 0
 
End Function
Public Function CreateWindows() As Boolean
 
  ''開始建立窗體

主窗體.
  gHwnd& = CreateWindowEx(0&, gClassName$, gAppName$, WS_OVERLAPPEDWINDOW, CW_USEDEFAULT, CW_USEDEFAULT, 208, 150, 0&, 0&, App.hInstance, ByVal 0&)
  ''建立一個按鈕
  gButtonHwnd& = CreateWindowEx(0&, "Button", "Click Here", WS_CHILD, 58, 90, 85, 25, gHwnd&, 0&, App.hInstance, 0&)
  ''建立一個(WS_EX_CLIENTEDGE、ES_MULTILINE風格的TextBox
  gEditHwnd& = CreateWindowEx(WS_EX_CLIENTEDGE, "Edit", "This is the edit control." & vbCrLf & "As you can see, it's multiline.", WS_CHILD Or ES_MULTILINE, 0&, 0&, 200, 80, gHwnd&, 0&, App.hInstance, 0&)

"Button ","Edit"系統中已經註冊過了所以這裡直接用 
 建立完別忘了顯示出來否則是隱藏的

  Call ShowWindow(gHwnd&, SW_SHOWNORMAL)
  Call ShowWindow(gButtonHwnd&, SW_SHOWNORMAL)
  Call ShowWindow(gEditHwnd&, SW_SHOWNORMAL)

記下按鈕處理過錯的當前所在地址 

gButOldProc& = GetWindowLong(gButtonHwnd&, GWL_WNDPROC)
 
 
  ''Set default window procedure of button to ButtonWndProc. Different
  ''settings of windows is listed in the MSDN Library. We are using GWL_WNDPROC
  ''to set the address of the window procedure.

指向新的處理過程地址
  Call SetWindowLong(gButtonHwnd&, GWL_WNDPROC, GetAddress(AddressOf ButtonWndProc))

  CreateWindows = (gHwnd& <> 0)
 
End Function

'窗體執行的主函式，在註冊這個窗體時已經指定的
Public Function WndProc(ByVal hwnd As Long, ByVal uMsg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long

  Dim strTemp As String

處理訊息，這裡指處理了WM_DESTROY訊息

  Case uMsg&
  Case WM_DESTROY:
  ''Since DefWindowProc doesn't automatically call
  ''PostQuitMessage (WM_QUIT). We need to do it ourselves.
  ''You can use DestroyWindow to get rid of the window manually.
  Call PostQuitMessage(0&)
  End Select
 

  ''Let windows call the default window procedure since we're done.
  WndProc = DefWindowProc(hwnd&, uMsg&, wParam&, lParam&)

End Function

又新增了一個Button的處理過程

Public Function ButtonWndProc(ByVal hwnd As Long, ByVal uMsg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long

  Select Case uMsg&
  Case WM_LBUTTONUP:
  Call MessageBox(gHwnd&, "You clicked the button!", App.Title, MB_OK Or MB_ICONEXCLAMATION)
  End Select
 
  ButtonWndProc = CallWindowProc(gButOldProc&, hwnd&, uMsg&, wParam&, lParam&)
 
End Function

Public Function GetAddress(ByVal lngAddr As Long) As Long
  GetAddress = lngAddr&
End Function

以上一個完整的簡單的應用程式就產生了。我們不需要IDE環境也可以建立我們想要的風格的窗體。透過這個例子對於VB程式設計師是不是對系統的機制有了一些瞭解。

雖然這個例子實際意義並不大，但是我們認為很有用，讓我們能瞭解一些封裝背後隱藏的事實，使我們的思路很自由。

最後要宣告這個想法並不是我一人想出來的，我參考一段程式碼（具體出處不祥）說想到，想與VB程式設計師共同分享一下，其實只要用活VB並沒有我們所說的那麼多限制，關鍵在使用者能否跳出這個範疇。