Visual Inheritance

• Inherit from any Shell, Composite, JFrame, JDialog, JApplet or JPanel subclass
• All inherited widgets are visible
• Access inherited widgets exposed via public or protected accessors
• Access inherited custom properties
• Inherited widgets appear in tree with the "exposed" decorator

The following is an example of two Composites in an inheritance hierarchy. The first Composite uses a GridLayout and has two Labels, two Text widgets, a Button and an inner Composite widget.

The inner Composite widget has been exposed as a public component using the Expose Component command. Expose Component converts a component to a field and adds a public accessor for it. Finally, the background color property of the first Text widget and the text property of the Button have been exposed as a public properties of the Composite using the Expose Property command. Expose Property adds a pair of accessors for getting and setting the desired property of the target widget.

import org.eclipse.swt.SWT;

import org.eclipse.swt.graphics.Color;

import org.eclipse.swt.layout.*;

import org.eclipse.swt.widgets.*;

 

public class ParentComposite extends Composite {

private Button browseButton;

private Composite composite;

private Text secondField;

private Text firstField;
 

public ParentComposite(Composite parent, int style) {

super(parent, style);

createContents();

}
 

public void createContents() {

final GridLayout gridLayout = new GridLayout();

gridLayout.numColumns = 3;

setLayout(gridLayout);
 

final Label firstFieldLabel = new Label(this, SWT.NONE);

firstFieldLabel.setText("First Field");
 

firstField = new Text(this, SWT.BORDER);

final GridData gd_firstField = new GridData(SWT.FILL, SWT.CENTER, true, false);

firstField.setLayoutData(gd_firstField);
 

browseButton = new Button(this, SWT.NONE);

browseButton.setLayoutData(new GridData(SWT.FILL, SWT.CENTER, false, false));

browseButton.setText("Browse...");
 

final Label secondFieldLabel = new Label(this, SWT.NONE);

secondFieldLabel.setText("Second Field");
 

secondField = new Text(this, SWT.BORDER);

final GridData gd_secondField = new GridData(SWT.FILL, SWT.CENTER, true, false, 2, 1);

secondField.setLayoutData(gd_secondField);
 

composite = new Composite(this, SWT.NONE);

composite.setLayoutData(new GridData(SWT.FILL, SWT.FILL, false, true, 3, 1) );

}
 

public Composite getComposite() {

return composite;

}
 

public String getBrowseButtonText() {

return browseButton.getText();

}
 

public void setBrowseButtonText(String text) {

browseButton.setText(text);

}
 

public Color getFirstFieldBackground() {

return firstField.getBackground();

}
 

public void setFirstFieldBackground(Color background) {

firstField.setBackground(background);

}

}

The second Composite inherits from the first and sets the inner Composite's layout manager via its accessor from the superclass and then adds several new widgets to the inner Composite. It also adds several new widgets that appear after the inherited widgets and use the GridLayout layout manager inherited from the superclass. Finally, it overrides the background color for the first Text widget and the text setting of the Button using the accessors defined in the first Composite.

Note that the exposed and inherited inner Composite from the superclass shows up in the component tree with a small overlay icon. The other widgets defined in the first Composite do not show up in the tree because they are private to that Composite.

import org.eclipse.swt.SWT;

import org.eclipse.swt.layout.*;

import org.eclipse.swt.widgets.*;

 

public class ChildComposite extends ParentComposite {

private List list;

private Text sixthField;

private Text fifthField;

private Text fourthField;

private Text thirdField;
 

public ChildComposite(Composite parent, int style) {

super(parent, style);

}
 

public void createContents() {

super.createContents();
 

setFirstFieldBackground(Display.getCurrent().getSystemColor(SWT.COLOR_YELLOW));

setBrowseButtonText("Find...");
 

final GridLayout gridLayout = new GridLayout();

gridLayout.numColumns = 2;

getComposite().setLayout(gridLayout);
 

final Label thirdFieldLabel = new Label(getComposite(), SWT.NONE);

thirdFieldLabel.setText("Third Field");
 

thirdField = new Text(getComposite(), SWT.BORDER);

final GridData gd_thirdField = new GridData(SWT.FILL, SWT.CENTER, true, false);

thirdField.setLayoutData(gd_thirdField);
 

final Label fourthFieldLabel = new Label(getComposite(), SWT.NONE);

fourthFieldLabel.setText("Fourth Field");
 

fourthField = new Text(getComposite(), SWT.BORDER);

final GridData gd_fourthField = new GridData(SWT.FILL, SWT.CENTER, true, false);

fourthField.setLayoutData(gd_fourthField);
 

list = new List(getComposite(), SWT.BORDER);

list.setItems(new String[] {"First Item", "Second Item"});

list.setLayoutData(new GridData(SWT.FILL, SWT.FILL, false, true, 2, 1));
 

final Label fifthFieldLabel = new Label(this, SWT.NONE);

fifthFieldLabel.setLayoutData(new GridData());

fifthFieldLabel.setText("Fifth Field");
 

fifthField = new Text(this, SWT.BORDER);

final GridData gd_fifthField = new GridData(SWT.FILL, SWT.CENTER, true, false, 2, 1);

fifthField.setLayoutData(gd_fifthField);
 

final Label sixthFieldLabel = new Label(this, SWT.NONE);

sixthFieldLabel.setText("Sixth Field");
 

sixthField = new Text(this, SWT.BORDER);

final GridData gd_sixthField = new GridData(SWT.FILL, SWT.CENTER, true, false);

sixthField.setLayoutData(gd_sixthField);
 

final Button searchButton = new Button(this, SWT.NONE);

searchButton.setText("Search...");

}

}