Java Reference
In-Depth Information
now. The original
BudgetPro
constructor took a
JFrame
argument, now it
will have to get a
Display
and a
Shell
. So we have to allocate a local
Display
and a local
Shell
. We also need to add the
Display
argument to the
BudgetPro
constructor.
After this is done, we modify the call to the constructor to pass the local
Display
and
Shell
to our class instance.
Next, we have to set a layout manager. The original application used the
Swing
BorderLayout
layout manager. SWT doesn't have such a critter.
Fortunately, the original used only the north, center, and south positions
of the
BorderLayout
. SWT has a simple layout manager called a
FillLayout
that puts its contained controls in a single row or column, equally
sized. Putting the three controls in a column will end up looking much like
using the north, center, and south of a
BorderLayout
. So we change the call
to the
frame.setLayout()
to pass in a new
FillLayout
and add the
SWT.VERTICAL
attribute.
The
SWT
Class
The
SWT
class is pretty bare-bones. Its primary use is a library of named
constants used for attributes to
Widget
(and other) constructors. You'll
see such
SWT.
xxxx
constants all over your typical SWT application.
There are a handful of methods that the
SWT
class provides, all of
them static, including
error()
, which throws an
SWTException
,
getPlatform()
, which returns a string with the name of the platform
on which SWT is running, and
getVersion()
, which returns an
int
version number.
It also has a subclass, called
OLE
, which is a Windows-only class that
provides ActiveX support for SWT. Obviously, such use is nonportable
and non-Linux, so we won't talk any more about it.
The next block of code in
main()
sets the Swing look and feel. SWT has
nothing like this. All SWT applications look like native applications (we seem
to be saying that a lot), so all of this code may be removed.
The next block of code calls methods on the application object (
app
) that,
in the original, construct the three “chunks” of UI and add them to the frame
using the
BorderLayout
attributes. Since, as we explained earlier, all SWT
controls must be explicitly joined to a parent control when they are constructed,
