很多 Windows 程序使用的窗口都帶有使用拆分器分隔的窗格。你可以拖動拆分器來擴大其中一個窗格同時縮小其它的窗格——而這個過程無須更改父窗口的大小。雖然 Visual Basic 6 不提供用于這一用途的控件,但是你可以自己實現這一效果。
創建窗格拆分器的方法是使用一個 Picture Box 控件作為其它控件的容器。在設計窗體時,放兩個 Picture Box 控件到窗體上,每個代表一個窗格。例如,對于上部窗格和下部窗格,可以將它們叫做pbTop和pbBotton。然后,將其它控件放在每個窗格對應的 Picture Box 上。
在程序運行時,程序代碼調整兩個 Picture Box 控件(即兩個窗格)的大小從而以預定義的尺寸填充窗口。Picture Box 控件的尺寸會被精確地計算,以使窗體在兩個 Picture Box 之間顯示一個窄帶;這個窄帶就作為拆分器。
將窗體的MousePointer屬性設計為“7 - Size NS”,以使得在鼠標置于拆分器之上時光標形狀變為調整上/下大小的樣式。將每個 Picture Box 控件的MousePointer屬性設置為“1 - Arrow”。程序還需要一些常量設置拆分器的高度和每個窗格允許的最小高度。
下面拆分器的工作方式:在用戶開始拖到拆分器時,拆分器的新位置由鼠標光標的位置所決定。這由MouseMove事件過程實現。在MouseMove事件過程中首先一個叫做ChangePaneSizes的過程被調用;該過程使用新的拆分器位置相應地更改兩個窗格的尺寸。任何一個窗格的尺寸都不能小于指定的最小尺寸。
下面的完成這一動作的代碼。你可以創建一個 VB 程序親自試一下這段代碼,首先在窗體上放置兩個 Picture Box 控件,分別命名為pbTop和pbBottom;然后,將這段代碼粘貼到窗體的代碼窗口中。這個例子展示的是一個水平拆分器分隔兩個窗格,但是你可以對它進行修改,從而得到其它的窗格排列樣式。
Option Explicit
Const SPLITTER_HEIGHT = 40 Const MIN_PANE_HEIGHT = 400
' The percentage of the window height ' occupied by the top pane. Dim TopPanePercent As Single ' True when the splitter is being dragged. Private Dragging As Boolean
Private Sub ChangePaneSizes()
' Arrange the panes according to the new splitter position. Dim TopHeight As Single Dim BottomHeight As Single
' Do nothing if window is minimized. If WindowState = vbMinimized Then Exit Sub
TopHeight = (ScaleHeight - SPLITTER_HEIGHT) * TopPanePercent If TopHeight < MIN_PANE_HEIGHT Then TopHeight = MIN_PANE_HEIGHT pbTop.Move 0, 0, ScaleWidth, TopHeight BottomHeight = (ScaleHeight - SPLITTER_HEIGHT) - TopHeight If BottomHeight >= MIN_PANE_HEIGHT Then pbBottom.Move 0, TopHeight + SPLITTER_HEIGHT, ScaleWidth, BottomHeight End If
End Sub
Private Sub Form_Load() ' Initially each pane gets half the window. TopPanePercent = 0.5 End Sub
Private Sub Form_MouseDown(Button As Integer, Shift As Integer, X As Single, _ Y As Single) ' Start dragging the splitter. Dragging = True End Sub
Private Sub Form_MouseMove(Button As Integer, Shift As Integer, X As Single, _ Y As Single) ' As the splitter is dragged. ' Do nothing if we're not dragging. If Not Dragging Then Exit Sub
TopPanePercent = Y / ScaleHeight If TopPanePercent < 0 Then TopPanePercent = 0 If TopPanePercent > 1 Then TopPanePercent = 1 ChangePaneSizes End Sub
Private Sub Form_MouseUp(Button As Integer, Shift As Integer, X As Single, _ Y As Single) ' End dragging the splitter. Dragging = False End Sub
Private Sub Form_Resize() ' Change pane sizes if the window is resized. ChangePaneSizes End Sub
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