As with menus (and,
in fact, all widgets), you must now add a
listener for each button and code the
widgetSelected()
method for each
SelectionListener to take the appropriate action.
The Listener code for the four toolbar buttons
created by Example 4-1 is shown here:
openToolItem.addSelectionListener(new SelectionListener( ) {
public void widgetSelected(SelectionEvent event) {
System.out.println("Open");
}
public void widgetDefaultSelected(SelectionEvent event)
{
}
});
saveToolItem.addSelectionListener(new SelectionListener( ) {
public void widgetSelected(SelectionEvent event) {
System.out.println("Save");
}
public void widgetDefaultSelected(SelectionEvent event)
{
}
});
cutToolItem.addSelectionListener(new SelectionListener( ) {
public void widgetSelected(SelectionEvent event) {
System.out.println("Cut");
}
public void widgetDefaultSelected(SelectionEvent event)
{
}
});
copyToolItem.addSelectionListener(new SelectionListener( ) {
public void widgetSelected(SelectionEvent event) {
System.out.println("Copy");
}
public void widgetDefaultSelected(SelectionEvent event)
{
}
});
pasteToolItem.addSelectionListener(new SelectionListener( ) {
public void widgetSelected(SelectionEvent event) {
System.out.println("Paste");
}
public void widgetDefaultSelected(SelectionEvent event)
{
}
});Adding the preceding code to the constructor for
ToolbarShellExample results in the toolbar buttons
becoming functional—at least to the point of printing a message
to the Console when they are pressed, as shown in Figure 4-2.
all that
duplicate code in the
SelectionListener classes? One of the goals of
object-oriented programming is to reduce the amount of code that is
duplicated in an application, yet as you see, the
widgetSelected( ) code added to the
ToolItem objects is identical to that added to the
MenuItem objects created in Example 4-1.
This can be corrected by creating named inner classes that implement
the SelectionListener interface, as shown in
Example 4-2.
Example 4-2. Using named inner classes for SelectionListeners
import org.eclipse.swt.SWT;
import org.eclipse.swt.events.SelectionEvent;
import org.eclipse.swt.events.SelectionListener;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.widgets.*;
public class ToolbarShellExample {
Display d;
Shell s;
ToolbarShellExample( ) {
d = new Display( );
s = new Shell(d);
s.setSize(300,300);
s.setImage(new Image(d, "c:\\icons\\JavaCup.ico"));
s.setText("A Shell Toolbar Example");
final ToolBar bar = new ToolBar(s,SWT.HORIZONTAL);
bar.setSize(500,70);
bar.setLocation(0,0);
// create images for toolbar buttons
final Image saveIcon = new Image(d, "c:\\icons\\save.jpg");
final Image openIcon = new Image(d, "c:\\icons\\open.jpg");
final Image childIcon = new Image(d, "c:\\icons\\userH.ico");
final Image cutIcon = new Image(d, "c:\\icons\\cut.jpg");
final Image copyIcon = new Image(d, "c:\\icons\\copy.jpg");
final Image pasteIcon = new Image(d, "c:\\icons\\paste.jpg");
// create and add the button for performing an open operation
final ToolItem openToolItem = new ToolItem(bar, SWT.PUSH);
openToolItem.setImage(openIcon);
openToolItem.setText("Open");
openToolItem.setToolTipText("Open File");
//create and add the button for performing a save operation
final ToolItem saveToolItem = new ToolItem(bar, SWT.PUSH);
saveToolItem.setImage(saveIcon);
saveToolItem.setText("Save");
saveToolItem.setToolTipText("Save File");
final ToolItem sep1 = new ToolItem(bar, SWT.SEPARATOR);
//create and add the button for performing a cut operation
final ToolItem cutToolItem = new ToolItem(bar, SWT.PUSH);
cutToolItem.setImage(cutIcon);
cutToolItem.setText("Cut");
cutToolItem.setToolTipText("Cut");
// create and add the button for performing a copy operation
final ToolItem copyToolItem = new ToolItem(bar, SWT.PUSH);
copyToolItem.setImage(copyIcon);
copyToolItem.setText("Copy");
copyToolItem.setToolTipText("Copy");
// create and add the button for performing a paste operation
final ToolItem pasteToolItem = new ToolItem(bar, SWT.PUSH);
pasteToolItem.setImage(pasteIcon);
pasteToolItem.setText("Paste");
pasteToolItem.setToolTipText("Paste");
// create inner classes for SelectionListeners
class Open implements SelectionListener
{
public void widgetSelected(SelectionEvent event) {
System.out.println("Open");
}
public void widgetDefaultSelected(SelectionEvent event)
{
}
}
class Save implements SelectionListener
{
public void widgetSelected(SelectionEvent event) {
System.out.println("Save");
}
public void widgetDefaultSelected(SelectionEvent event)
{
}
}
class Cut implements SelectionListener
{
public void widgetSelected(SelectionEvent event) {
System.out.println("Cut");
}
public void widgetDefaultSelected(SelectionEvent event)
{
}
}
class Copy implements SelectionListener
{
public void widgetSelected(SelectionEvent event) {
System.out.println("Copy");
}
public void widgetDefaultSelected(SelectionEvent event)
{
}
}
class Paste implements SelectionListener
{
public void widgetSelected(SelectionEvent event) {
System.out.println("Paste");
}
public void widgetDefaultSelected(SelectionEvent event)
{
}
}
openToolItem.addSelectionListener(new Open( ));
saveToolItem.addSelectionListener(new Save( ));
cutToolItem.addSelectionListener(new Cut( ));
copyToolItem.addSelectionListener(new Copy( ));
pasteToolItem.addSelectionListener(new Paste( ));
// create the menu system
Menu m = new Menu(s,SWT.BAR);
// create a File menu and add an Exit item
final MenuItem file = new MenuItem(m, SWT.CASCADE);
file.setText("&File");
final Menu filemenu = new Menu(s, SWT.DROP_DOWN);
file.setMenu(filemenu);
final MenuItem openMenuItem = new MenuItem(filemenu, SWT.PUSH);
openMenuItem.setText("&Open\tCTRL+O");
openMenuItem.setAccelerator(SWT.CTRL+'O');
final MenuItem saveMenuItem = new MenuItem(filemenu, SWT.PUSH);
saveMenuItem.setText("&Save\tCTRL+S");
saveMenuItem.setAccelerator(SWT.CTRL+'S');
final MenuItem separator = new MenuItem(filemenu, SWT.SEPARATOR);
final MenuItem exitMenuItem = new MenuItem(filemenu, SWT.PUSH);
exitMenuItem.setText("E&xit");
// create an Edit menu and add Cut, Copy, and Paste items
final MenuItem edit = new MenuItem(m, SWT.CASCADE);
edit.setText("&Edit");
final Menu editmenu = new Menu(s, SWT.DROP_DOWN);
edit.setMenu(editmenu);
final MenuItem cutMenuItem = new MenuItem(editmenu, SWT.PUSH);
cutMenuItem.setText("&Cut");
final MenuItem copyMenuItem = new MenuItem(editmenu, SWT.PUSH);
copyMenuItem.setText("Co&py");
final MenuItem pasteMenuItem = new MenuItem(editmenu, SWT.PUSH);
pasteMenuItem.setText("&Paste");
//create a Window menu and add Child items
final MenuItem window = new MenuItem(m, SWT.CASCADE);
window.setText("&Window");
final Menu windowmenu = new Menu(s, SWT.DROP_DOWN);
window.setMenu(windowmenu);
final MenuItem maxMenuItem = new MenuItem(windowmenu, SWT.PUSH);
maxMenuItem.setText("Ma&ximize");
final MenuItem minMenuItem = new MenuItem(windowmenu, SWT.PUSH);
minMenuItem.setText("Mi&nimize");
// create a Help menu and add an About item
final MenuItem help = new MenuItem(m, SWT.CASCADE);
help.setText("&Help");
final Menu helpmenu = new Menu(s, SWT.DROP_DOWN);
help.setMenu(helpmenu);
final MenuItem aboutMenuItem = new MenuItem(helpmenu, SWT.PUSH);
aboutMenuItem.setText("&About");
// add action listeners for the menu items
openMenuItem.addSelectionListener(new Open( ));
saveMenuItem.addSelectionListener(new Save( ));
exitMenuItem.addSelectionListener(new SelectionListener( ) {
public void widgetSelected(SelectionEvent e) {
System.exit(0);
}
public void widgetDefaultSelected(SelectionEvent e)
{
}
});
cutMenuItem.addSelectionListener(new Cut( ));
copyMenuItem.addSelectionListener(new Copy( ));
pasteMenuItem.addSelectionListener(new Paste( ));
maxMenuItem.addSelectionListener(new SelectionListener( ) {
public void widgetSelected(SelectionEvent e) {
Shell parent = (Shell)maxMenuItem.getParent( ).getParent( );
parent.setMaximized(true);
}
public void widgetDefaultSelected(SelectionEvent e)
{
}
});
minMenuItem.addSelectionListener(new SelectionListener( ) {
public void widgetSelected(SelectionEvent e) {
Shell parent = (Shell)minMenuItem.getParent( ).getParent( );
parent.setMaximized(false);
}
public void widgetDefaultSelected(SelectionEvent e)
{
}
});
aboutMenuItem.addSelectionListener(new SelectionListener( ) {
public void widgetSelected(SelectionEvent e) {
System.out.println("Help Invoked");
}
public void widgetDefaultSelected(SelectionEvent e)
{
}
});
s.setMenuBar(m);
s.open( );
while(!s.isDisposed( )){
if(!d.readAndDispatch( ))
d.sleep( );
}
d.dispose( );
}
}As you can see from Example 4-2, the number of duplicated lines is
decreased. This is accomplished by adding a named inner class for
each SelectionListener that was shared between a
menu item and a toolbar button. For example, the inner class for the
Open functionality is now written as follows:
Note
This saves a little code—how much depends on the contents of the inner classes. Remember, he who writes the fewest lines wins.
class Open implements SelectionListener
{
public void widgetSelected(SelectionEvent event) {
System.out.println("Open");
}
public void widgetDefaultSelected(SelectionEvent event)
{
}
}The inner class is then used for both the menu item and the toolbar
button by calling the addSelectionListener()
method for each:
openToolItem.addSelectionListener(new Open( )); openMenuItem.addSelectionListener(new Open( ));
Either approach is valid: choose whichever best matches your coding philosophy.
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