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3.10. Take Control of Window Layout
.NET 2.0 includes two new container
controls that can lay out all the controls they contain in a set
pattern. Both of these controls extend the Panel
class with additional layout logic. The
FlowLayoutPanel arranges controls evenly over
several rows (from left to right), or in multiple columns (from top
to bottom). The TableLayoutPanel places its
controls into a grid of invisible cells, allowing to you to keep
consistent column widths and row heights.
Note: The new . NET layout controls give you a way to lay out
controls in set patterns automatically, which can save a good deal of
effort with highly dynamic or configurable interfaces.
3.10.1. How do I do that?
The layout controls are used most often in the following two
scenarios:You have a dynamic interface that generates some of its elements
programmatically. Using the layout controls, you can arrange a group
of controls neatly without calculating a position for each control
(and then setting the Location property
accordingly).You have a localized interface that must adapt to different languages
that require vastly different amounts of on-screen real estate. As a
result, when the display text changes, the controls must also adjust
their size. In this case, layout controls can help you make sure the
controls remain properly arranged even when their size varies.
Example 3-4 demonstrates an implementation of the
first scenario. It starts with a form that includes an empty
FlowLayoutPanel. The
FlowLayoutPanel has its
BorderStyle set to
BorderStyle.Fixed3D so the border is visible.No controls are added to the FlowLayoutPanel at
design time. Instead, several new buttons are added programmatically
when a cmdGenerate button is clicked.
Example 3-4. Laying out buttons dynamically
Private Sub Button1_Click(ByVal sender As System.Object, _Note that the code doesn't set the
ByVal e As System.EventArgs) Handles Button1.Click
For i As Integer = 0 To 10
' Create a new button.
Dim Button As New Button
Button.Text = "Dynamic Button #" & String.Format("{0:00}", i)
' Size the button the width of the text.
Button.AutoSize = True
' Add the button to the layout panel.
FlowLayoutPanel1.Controls.Add(Button)
Next
End Sub
Location property for each button.
That's because the
FlowLayoutPanel won't use this
information. Instead, it will arrange the buttons in the order they
are added, spacing each button out from left to right and then top to
bottom. (To reverse this order, change the
FlowLayoutPanel.FlowDirection property.)There is one piece of information that the
FlowLayoutPanel does use.
That's the Margin property of
each container control. This sets the minimum border required between
this control and the next. The code above doesn't
change the Button.Margin property, because the
default setting of 3 pixels is perfectly adequate.Figure 3-10 shows what the buttons look like once
they've been added.
Figure 3-10. Laying out buttons dynamically
Note: There are actually four different components of the Margin
property: Margin.Left, Margin.Right, Margin.Top, and Margin.Bottom.
You can set these individually to specify different margins for the
control on each side.
.NET also includes a TableLayoutPanel. This panel
works like the FlowLayoutPanel, laying out
controls automatically, but it aligns them according to invisible
column and row grid lines. For example, if you have a number of
controls that were sized differently, you can use the
TableLayoutPanel to ensure that each control is
spaced out evenly in an imaginary cell.
3.10.2. What about...
...more advanced layout examples? There's a lot more
you can do with a creative use of layout controls. Of course, just
because you can doesn't mean
you should. Microsoft architects recommend you
use layout controls only in specialized scenarios where the anchoring
and docking features of Windows Forms aren't enough.
If you don't have a highly dynamic interface, layout
managers may introduce more complexity than you need.
3.10.3. Where can I learn more?
To get started with more advanced uses of layout controls, refer to
some of the information in the MSDN help library reference. Look up
"TableLayoutPanel control
about"in the index of the MSDN help reference. This displays general
information about the TableLayoutPanel control and
provides a link to two walkthroughs that show how the
TableLayoutPanel can work in a complex localizable
application.
