Symantec Visual Cafe for Java 2.5/symantec-visual-cafe-2.5-database-dev-edition.iso/Visual Cafe Pro v1.0/SOURCE.BIN/InvisibleHTMLLink.java

Java Source | 1997-06-19 | 4.7 KB | 174 lines

package symantec.itools.awt;


import java.net.URL;
import java.awt.Event;
import java.awt.Container;
import java.applet.*;


/**
 * Use this component to create an invisible rectangular button, usually within
 * an image, that links to a URL address when clicked. Specifically, use
 * InvisibleHTMLLink to:
 * <UL>
 * <DT>╖ Accept or yield focus.</DT>
 * <DT>╖ Respond to a user event.</DT>
 * <DT>╖ Send an action event to another component.</DT>
 * </UL>
 * Button tips:
 * <UL>
 * <DT>╖ Buttons accept and yield focus automatically by default.</DT>
 * <DT>╖ Buttons accept clicked events automatically by default.</DT>
 * <DT>╖ To send an action event to another component, use the Interaction
 * Wizard. Optionally, you can override the InvisibleButtonÆs click event in
 * project source code.</DT>
 * </UL>
 * Implements the Runnable interface to support threads. An InvisibleHTMLLink
 * can be set from the Property List window to post continuous action events
 * when the button is clicked.
 * <p>
 * @version 1.0, Nov 26, 1996
 * @author Symantec
 */
public class InvisibleHTMLLink
    extends InvisibleButton
{
    /**
     * URL to show when the button is clicked.
     */
    protected URL url;
    /**
     * Applet context that shows the URL.
     */
    protected AppletContext context;
    /**
     * Frame specifier for showing a URL document in a browser or applet
     * viewer. It is interpreted as follows:
     * <UL>
     * <DT>"_self"  show document in the current frame</DT>
     * <DT>"_parent"    show document in the parent frame</DT>
     * <DT>"_top"   show document in the topmost frame</DT>
     * <DT>"_blank" show document in a new unnamed toplevel window</DT>
     * <DT>all others   show document in a new toplevel window with the given name</DT>
     * </UL>
     */
    protected String frame;

    /**
     * Constructs a default InvisibleHTMLLink.
     */
    public InvisibleHTMLLink()
    {
        frame = null;
    }

    /**
     * Returns the URL to show when the button is clicked.
     * @see #setURL
     */
    public URL getURL()
    {
        return url;
    }

    /**
     * Sets the URL to show when the button is clicked.
     * @param u the URL to show when the button is clicked
     * @see #getURL
     */
    public void setURL(URL u)
    {
        url = u;
        context = null;
    }

    /**
     * Sets the title displayed on the applet frame while showing
     * the URL.
     * @param f applet frame title
     * @see #getFrame
     */
    public void setFrame(String f)
    {
        frame = f;
    }

    /**
     * Returns the title that is displayed on the applet frame while showing
     * the URL.
     * @see #setFrame
     */
    public String getFrame()
    {
        return frame;
    }

    /**
     * Handles internal actions for this component.
     * This is a standard Java AWT method which usually gets called by the AWT
     * method handleEvent() in response to receiving an ACTION_EVENT event. In those
     * cases the o parameter contains the value in the event's arg field.
     *
     * @param e the event that caused this action
     * @param o the action
     * @return true if the action was handled
     * @see java.awt.Component#handleEvent
     */
    public boolean action(Event event, Object what)
    {
        if (context != null)
        {
            if (frame == null || frame.length() == 0)
                context.showDocument(url);
            else
                context.showDocument(url, frame);

            return true;
        }

        return false;
    }

    /**
     * Ensures that this component is laid out properly, as needed.
     * This is a standard Java AWT method which gets called by the AWT to
     * make sure this component and its subcomponents have a valid layout.
     * If this component was made invalid with a call to invalidate(), then
     * it is laid out again.
     *
     * It is overridden here to locate the applet containing this component.
     *
     * @see java.awt.Component#invalidate
     */
    public void validate()
    {
        // On validation, try to find the containing applet.  If we can find
        // it, we don't bother doing the link...
        Container c;

        c = getParent();

        while (c != null)
        {
            if (c instanceof Applet)
            {
                setAppletContext(((Applet) c).getAppletContext());
                break;
            }

            c = c.getParent();
        }
    }

    /**
     * Sets the applet context to use for showing the URL.
     * @param c the applet context
     */
    protected void setAppletContext(AppletContext c)
    {
        context = c;
    }
}