examples/org.eclipse.swt.snippets/src/org/eclipse/swt/snippets/Snippet363.java

/*******************************************************************************
 * Copyright (c) 2012, 2016 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.swt.snippets;

/*
 * Accessibility example snippet: Declare a message area to be a "live region",
 * and send "changed" events to a screen reader when the message area is updated.
 * Note: This snippet will only work with Windows screen readers.
 *
 * For a list of all SWT example snippets see
 * http://www.eclipse.org/swt/snippets/
 */
import org.eclipse.swt.*;
import org.eclipse.swt.accessibility.*;
import org.eclipse.swt.graphics.*;
import org.eclipse.swt.layout.*;
import org.eclipse.swt.widgets.*;

public class Snippet363 {
	static final String errorMessage = "Error: Number expected.";
	static Label icon;
	static Image errorIcon;
	static Text liveLabel;

public static void main(String [] args) {
	Display display = new Display();
	errorIcon = display.getSystemImage(SWT.ICON_ERROR);
	Shell shell = new Shell(display);
	shell.setText("Snippet 363");
	shell.setLayout(new GridLayout(2, false));
	shell.setText("LiveRegion Test");

	icon = new Label(shell, SWT.NONE);
	icon.setLayoutData(new GridData(32, 32));

	liveLabel = new Text(shell, SWT.READ_ONLY);
	GC gc = new GC(liveLabel);
	Point pt = gc.textExtent(errorMessage);
	GridData data = new GridData(SWT.FILL, SWT.CENTER, true, false);
	data.minimumWidth = (int) (pt.x + gc.getFontMetrics().getAverageCharacterWidth() * 2);
	gc.dispose();
	liveLabel.setLayoutData(data);
	liveLabel.setText("");
	liveLabel.getAccessible().addAccessibleAttributeListener(new AccessibleAttributeAdapter() {
			@Override
			public void getAttributes(AccessibleAttributeEvent e) {
					e.attributes = new String[] {
									"container-live", "polite",
									"live", "polite",
									"container-live-role", "status",
							};
			}
	});

	final Label textFieldLabel = new Label(shell, SWT.NONE);
	textFieldLabel.setText("Type a number:");
	textFieldLabel.setLayoutData(new GridData(SWT.FILL, SWT.CENTER, true, false, 2, 1));

	final Text textField = new Text(shell, SWT.SINGLE | SWT.BORDER);
	textField.setLayoutData(new GridData(SWT.FILL, SWT.CENTER, true, false, 2, 1));

	final Button okButton = new Button(shell, SWT.PUSH);
	okButton.setText("OK");
	okButton.setLayoutData(new GridData(SWT.END, SWT.CENTER, false, false, 2, 1));
	okButton.setEnabled(false);

	textField.addModifyListener(e -> {
			boolean isNumber = false;
			String textValue = textField.getText();
			try {
					Integer.parseInt(textValue);
					isNumber = true;
					setMessageText(false, "Thank-you");
			} catch (NumberFormatException ex) {
					if (textValue.isEmpty()) {
							setMessageText(false, "");
					} else {
							setMessageText(true, "Error: Number expected.");
					}
			}
			okButton.setEnabled(isNumber);
	});

	textField.setFocus();
	shell.pack();
	shell.open();
	while (!shell.isDisposed()) {
			if (!display.readAndDispatch()) display.sleep();
	}
	display.dispose();
}

static void setMessageText(boolean error, String newMessage) {
	String oldMessage = liveLabel.getText();
	icon.setImage(error ? errorIcon : null);
	liveLabel.setText(newMessage);
	liveLabel.getAccessible().sendEvent(ACC.EVENT_ATTRIBUTE_CHANGED, null);
	liveLabel.getAccessible().sendEvent(ACC.EVENT_TEXT_CHANGED, new Object[] {ACC.TEXT_DELETE, 0, oldMessage.length(), oldMessage});
	liveLabel.getAccessible().sendEvent(ACC.EVENT_TEXT_CHANGED, new Object[] {ACC.TEXT_INSERT, 0, newMessage.length(), newMessage});
}

}