VBNet - Форум - События (Events)

Вопрос: События (Events) Добавлено: 21.02.03 10:30

Автор вопроса: Vit | Web-сайт: www.home-soft.jino-net.ru

Подскажите, пожалуйста, как создать событие?

Меня, в частности, интересует синтаксис обявления.

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CyRax

Разработчик Offline Client

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Профиль | | #1 Добавлено: 21.02.03 13:10

Из MSDN'а

Event Statement Example

The following example uses events to count off seconds during a demonstration of the fastest 100 meter race. The code illustrates all of the event-related methods, properties, and statements, including the Event statement.

The class that raises an event is the event source, and the classes that implement the event are the sinks. An event source can have multiple sinks for the events it generates. When the class raises the event, that event is fired on every class that has elected to sink events for that instance of the object.

The example also uses a form (Form1) with a button (Command1), a label (Label1), and two text boxes (Text1 and Text2). When you click the button, the first text box displays "From Now" and the second starts to count seconds. When the full time (9.84 seconds) has elapsed, the first text box displays "Until Now" and the second displays "9.84"

The code for Form1 specifies the initial and terminal states of the form. It also contains the code executed when events are raised.

Option ExplicitPrivate WithEvents mText As TimerStatePrivate Sub Command1_Click()Text1.Text = "From Now"    Text1.Refresh    Text2.Text = "0"    Text2.RefreshCall mText.TimerTask(9.84)End SubPrivate Sub Form_Load()    Command1.Caption = "Click to Start Timer"    Text1.Text = ""    Text2.Text = ""    Label1.Caption = "The fastest 100 meter run took this long:"    Set mText = New TimerState    End SubPrivate Sub mText_ChangeText()    Text1.Text = "Until Now"    Text2.Text = "9.84"End SubPrivate Sub mText_UpdateTime(ByVal dblJump As Double)    Text2.Text = Str(Format(dblJump, "0"))    DoEventsEnd Sub

The remaining code is in a class module named TimerState. The Event statements declare the procedures initiated when events are raised.

Option ExplicitPublic Event UpdateTime(ByVal dblJump As Double)Public Event ChangeText()Public Sub TimerTask(ByVal Duration As Double)    Dim dblStart As Double    Dim dblSecond As Double    Dim dblSoFar As Double    dblStart = Timer    dblSoFar = dblStart        Do While Timer < dblStart + Duration        If Timer - dblSoFar >= 1 Then            dblSoFar = dblSoFar + 1            RaiseEvent UpdateTime(Timer - dblStart)        End If    Loop        RaiseEvent ChangeText    End Sub

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