App Class

Create an entity that represents the overall application. Please note that you have to create a subclass of App in your code and add a Start() method to this class. You can't add a Start() method to the App() class inside GUI Classes like you can in VO.

Inheritance Hierarchy

Object
  VObject
    App
      VOWinFormApp

Namespace: VO
Assembly: VOGUIClasses (in VOGUIClasses.dll) Version: 2.19

Syntax

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 CLASS App INHERIT VObject

public class App : VObject

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The App type exposes the following members.

Constructors

	Name	Description
	App	Construct an application.

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Methods

	Name	Description
	Destroy	Free memory resources allocated for a VObject object and its derived objects. (Inherited from VObject.)
	Exec	Start the event handling loop for the application.
	GetAccel	This method returns the handle for the current active Accelerator Table.
	GetAccelWindow	This method gets the handle to the window for which accelerators must be translated.
	GetDialogWindow	This method gets the handle active Dialog window for which Dialog keys must be handled
	GetMdiClientWindow	This method gets the handle to the MDI Clientwindow on the active ShellWindow.
	Handle	Return the handle for an application.
	Quit	Terminate the application by instructing the application to close itself.
	Run	Invoke and execute a specified command.
	SetAccel	This method sets the handle for the current active Accelerator Table (belonging to the active menu).
	SetAccelWindow	This method sets the window for which accelerators must be translated.
	SetDialogWindow	This method sets the handle active Dialog window for which Dialog keys must be handled
	SetMdiClientWindow	This method sets the handle to the MDI Clientwindow on the active ShellWindow.

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Fields

	Name	Description
	oCargo	Cargo slot. (Inherited from VObject.)

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Remarks

The App class starts, runs, and stops the application. However, nearly all the code in an application executes in event handlers. Once you invoke the method App:Exec(), the system starts sending you events. While the term application is consistent in both the windowing and non-windowing worlds, the event-driven nature of a windowing application is designed to handle user-driven events (such as a mouse click or the resizing of a window). As a result, the function of the windowing application is relegated to an event scheduling loop. In this class, the Start() method is analogous to the entry point START() function in CA-Clipper. It is where the main elements of your application are constructed. The objects declared within App:Start() should be those which have "application wide" scope. Within the App:Start() method you must call App:Exec(). Doing so invokes the message processing loop of your underlying windowing system and begins the system event handling mechanism by activating the system dispatcher. The App:Exec() method can be thought of as a layered service with a typical "get-translate-dispatch-message" mechanism driven by your underlying windowing system and a "filter-translate-dispatch-event" mechanism being directed through the system framework by the system dispatcher. The App:Quit() method provides a way of breaking out of the application's Exec() loop to terminate the application. It is analogous to the QUIT() function in CA-Clipper.

Examples

The following example demonstrates an entire application, using the various methods of the App class:

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 1DEFINE IDM_MYMENU := "MyMenu"
 2DEFINE IDM_MYMENU_CLOCK_ID := 1000
 3DEFINE IDM_MYMENU_GETHANDLE_ID := 1001
 4DEFINE IDM_MYMENU_QUIT_ID := 1002
 5FUNCTION Start as VOID
 6LOCAL oApp as XApp
 7oApp := XApp{}
 8oApp:Start()
 9RETURN
10
11CLASS XApp INHERIT APP
12METHOD Start()
13LOCAL oWin AS Window
14oWin := MyTopAppWin{SELF}
15oWin:Show()
16SELF:Exec()
17RETURN NIL
18
19END CLASS
20
21CLASS MyTopAppWin INHERIT TopAppWindow
22
23CONSTRUCTOR(oOwnerApp)
24LOCAL lRetVal AS LONG
25SUPER(oOwnerApp)
26SELF:Menu := MyMenu{SELF}
27lRetVal := oOwnerApp:Run("Clock")
28SELF:Caption := "My Top App Window Application"
29SELF:WarningMessage("The return value of running CLOCK is :" +AsString(lRetVal))
30RETURN
31
32METHOD GetClock()
33SELF:Owner:Run("Clock")
34RETURN NIL
35
36METHOD GetHandle()
37SELF:WarningMessage("The handle of this app is :"+AsString(SELF:Handle()))
38RETURN NIL
39
40METHOD GoQuit()
41SELF:Owner:Quit()
42RETURN NIL
43END CLASS
44
45CLASS MyMenu INHERIT Menu
46CONSTRUCTOR(oOwner)
47SUPER(ResourceID{IDM_MYMENU})
48SELF:RegisterItem(IDM_MYMENU_CLOCK_ID, HyperLabel{#GetClock,,,})
49SELF:RegisterItem(IDM_MYMENU_GETHANDLE_ID, HyperLabel{#GetHandle,,,})
50SELF:RegisterItem(IDM_MYMENU_QUIT_ID, HyperLabel{#GoQuit,,,})
51END CLASS
52RESOURCE IDM_MYMENU MENU
53BEGIN
54POPUP "&Menu1"
55BEGIN
56MENUITEM "&Clock", IDM_MYMENU_CLOCK_ID
57MENUITEM "&Get App Handle", IDM_MYMENU_GETHANDLE_ID
58MENUITEM SEPARATOR
59MENUITEM "&QUIT", IDM_MYMENU_QUIT_ID
60END
61END

Reference

VO Namespace