Question

How can I create a modal dialog box?

Answer

Modal dialog boxes are extremely useful for display alert messages, and for capturing the user's attention. You can create a simple modal dialog box, and then it will remain visible and will maintain focus until it is hidden (usually when the user clicks on a button). Here's a simple example.

import java.awt.*;
import java.awt.event.*;

public class DialogExample {
	private static Dialog d;

	public static void main(String args[])
	{
		Frame window = new Frame();

		// Create a modal dialog
		d = new Dialog(window, "Alert", true);

		// Use a flow layout
		d.setLayout( new FlowLayout() );

		// Create an OK button
		Button ok = new Button ("OK");
		ok.addActionListener ( new ActionListener()
		{
			public void actionPerformed( ActionEvent e )
			{
				// Hide dialog
				DialogExample.d.setVisible(false);
			}
		});

		d.add( new Label ("Click OK to continue"));
		d.add( ok );

		// Show dialog
		d.pack();
		d.setVisible(true);

		System.exit(0);
	}
}

The most important part of the program is the line that initializes the dialog. Notice the parameters we pass to it. The first parameter is a parameter for a window, and the second the title for the dialog. The final parameter controls whether the dialog is modal or not (true modal, false non-modal).

d = new Dialog(window, "Alert", true);

Using dialogs is easy, and can communicate information to users effectively. For those wishing to use the example, remember that it requires JDK1.1 or higher.

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