Visual Basic 6 Black Book:Scroll Bars And Sliders
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Visual Basic 6 Black Book
(Publisher: The Coriolis Group)
Author(s): Steven Holzner
ISBN: 1576102831
Publication Date: 08/01/98
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Creating Slider Controls
The Aesthetic Design Department is on the phone again. They’ve heard about slider controls in Visual Basic and like their look. Is there any way you can add them to your program, SuperDuperTextPro?
Adding a slider to a program is easy; just follow these steps:
1. Select the Project|Components menu item, and click the Controls tab in the Components box that opens.
2. Select the Microsoft Windows Common Controls item.
3. Close the Components box by clicking on OK.
4. The Slider tool appears in the toolbox at this point. Add a slider to your form in the usual way.
5. Set the slider’s Orientation property to ccOrientationHorizontal (value 0, the default) or ccOrientationVertical (value 1) to specify the orientation you want.
6. Set the slider’s Min, Max, SmallChange, and LargeChange values as you want them.
7. Set the slider’s TickFrequency property to the number of units between tics on the slider’s scale.
8. Add the code you want to the slider event you want, Change or Scroll. For example, here we add code to a slider’s Change event, setting the blue color of a text box, Text1, to match the slider’s setting, using the Visual Basic RGB function:
Private Sub Form_Load()
Slider1.Max = 255
Slider1.Min = 0
End Sub
Private Sub Slider1_Click()
Text1.BackColor = RGB(0, 0, Slider1.Value)
End Sub
Running this program yields the result you see in Figure 9.8. Now we’re using sliders in Visual Basic.
Figure 9.8 Adding a slider to a program.
Setting A Slider’s Orientation
Like scroll bars, sliders can be horizontal or vertical, but unlike scroll bars, horizontal and vertical sliders are not two different controls. Instead, you set a slider’s Orientation property to make it horizontal or vertical.
You can set the Orientation at design time or run-time; this property takes these values:
• ccOrientationHorizontal (value 0, the default) orients the slider horizontally.
• ccOrientationVertical (value 1) orients the slider vertically.
Can you change a slider’s orientation in code? You certainly can. In this example, we make a slider’s orientation vertical when the user clicks a button:
Private Sub Command1_Click()
Slider1.Orientation = ccOrientationVertical
End Sub
TIP: Besides reorienting sliders, you can move them around a form using their Move method.
Setting A Slider’s Range
You’ve added a new slider to your environment control program to let users set the temperature they want in their homes, but now they have a complaint. Why does the slider return values of up to 32,767 degrees?
It’s time to reset the slider’s range of possible values, and you use the Min (default value 0) and Max (default value 10) properties to do that. You can set a slider’s range at design time or runtime.
For example, here’s how we set a slider’s range to a more reasonable span of temperatures:
Private Sub Form_Load()
Slider1.Max = 90
Slider1.Min = 50
End Sub
After setting the Min and Max properties, you’ll probably want to set the slider’s tick frequency so the ticks on the slider’s scale look appropriate for the new range (see “Adding Ticks to a Slider” in this chapter).
Setting Up Slider Groove Clicks
Besides dragging the knob along the groove in a slider, you can click the groove itself to move the knob (just as you can click the area of a scroll bar between the thumb and arrow buttons). The amount the knob moves each time the user clicks the groove is set with the slider’s LargeChange property (just as it is in scroll bars). The default value for this property is 5.
You can set the LargeChange property at design time or runtime. For example, here’s how we set a slider’s LargeChange property to 5 when the form containing the slider first loads:
Private Sub Form_Load()
Slider1.Max = 255
Slider1.Min = 0
Slider1.LargeChange = 5
End Sub
If you change a slider’s range of possible values (in other words, the Min and Max properties), keep in mind that you might also have to change the LargeChange property as well. For example, if you change the possible range of slider values from 0 to 32767 to 1 to 100 but leave LargeChange at 4096, there’s going to be a problem when the user clicks the slider’s groove.
TIP: Sliders also have a SmallChange property, but this seems to be one of the mystery properties you run across occasionally in Visual Basic, because there just is no way to use it in a slider. (Even looking it up in the Visual Basic documentation reveals nothing—it’s undocumented, although it appears in the Properties window.) When you click a slider’s groove, the slider moves by the LargeChange amount, but there aren’t any arrow buttons in sliders to cause SmallChange events.
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