SWT: A Developer's Notebook

Supplying the SWT Package to the Java Compiler

First, you’ve got to let javac know where to find the SWT libraries so that it can compile your applications.

How do I do that?

You first need to create a Java project, and then specify the Java Build Path for that project.

Note

The Java Build Path in Eclipse is the equivalent of specifying the -classpath option for the javac compiler on the command line.

The Java Build Path in Eclipse may be specified either at the time the project is created, or later by selecting Project Properties from the Eclipse menu. Either way, you will invoke a dialog similar to that shown in Figure 1-6, the Project Properties dialog. Select Java Build Path from the list on the left side of the dialog, which will reveal the set of tabs shown in the figure. Click the Libraries tab to specify the SWT packages required for your project.

Figure 1-6. Specifying the Java Build Path

On the Libraries tab, click the Add External JARs button and use the dialog shown in Figure 1-7 to locate the JAR file that contains the SWT classes (you should have these from Section 1.1 Section 1.1. This file is normally called swt.jar and will be located in the directory where you extracted the SWT development files.

Figure 1-7. Locating the swt.jar file

Note

Make sure you include swt.jar in your final distribution so that your code can locate the SWT classes at runtime.

Navigate to the JAR file and click Open; this adds swt.jar into the Java Build Path for the project and returns you to the Project Properties dialog, as shown in Figure 1-8. You should see a reference to swt.jar listed under JARs and class folders on the build path.

If you need them, you can proceed to add other custom libraries to your project. For our purposes, the SWT classes are all that are needed. Make certain that your properties appear as shown in Figure 1-8 before clicking OK to save these settings in your project.

Figure 1-8. 

To test your configuration, simply create a Java class and enter the following lines of code:

import org.eclipse.swt.*;
import org.eclipse.swt.custom.*;
import org.eclipse.swt.graphics.*;
import org.eclipse.swt.widgets.*;
import org.eclipse.swt.layout.*;

If these lines appear in the Eclipse editor with red lines underneath the package identifiers, the project still can’t locate the SWT classes and you should repeat the preceding steps. If the problem persists, try downloading the SWT classes again, as the original download may have been corrupt.

Note

If you don’t see swt.jar listed, repeat these steps, making sure to highlight swt.jar in the File dialog after clicking Add External JARs..

What about...

if your import statements have yellow lines underneath them? That’s okay—those mean only that you haven’t yet referred to any of those classes in your code, which is normal at this stage of the process.

Note

Having unused imports in your code when it’s completed is bad form; though it won’t cause any problems, it’s considered unprofessional.