scroller.java

新闻滚动播出Java小程序

/*
    Basic horizontal scrolling text applet, with optional URL link

    Parameters (see also WebBase):
        SCROLLTEXT      Message to display
            def: "No message supplied!"
        SHADOW          "Shadow" text
            def: false (no shadow)
        URL             the URL to jump to when the applet is clicked
                            by a mouse
            def: none - if none supplied or invalid, it's just a scrolling
                text applet

    Copyright 1998 by E. A. Graham, Jr.
    Free to use or modify.
 */

import java.awt.*;
import java.applet.*;
import java.net.URL;
import java.net.MalformedURLException;

public class Scroller extends WebBase {
    String message;

    int messageX = 0,messageY = 0;          // Coordinates of the scrolling text
    int messageW = 0;                       // Width of the message in pixels

    public Font messageF;                   // Font for the message (TimesRoman only)
    boolean font3D;                         // draw a drop-shadow on the message

    String  urlName;                        // string for URL to link to
    URL     nextURL = null;                 // the actual URL

    // initialization time!
    public void init() {
        super.init();

        // get the HTML parameters or set to defaults
        String  tparam;
        tparam = readMessage();
        message = (tparam == null) ? new String("No message supplied!") : new String(tparam);

        tparam = ReadText("SHADOW");
        font3D = (tparam == null) ? false : tparam.equalsIgnoreCase("true");

        urlName = ReadText("URL");
        if (urlName != null) {
            try {
                if (urlName.indexOf("http://") < 0) {
                    nextURL = new URL(getDocumentBase(),urlName);
                }
                else {
                    nextURL = new URL(urlName);
                }
            }
            catch (MalformedURLException e) {};
        }
        borderWidth = Math.abs(borderWidth);

        // set up the font and initial positions
        setFontValues();
    }

    public void stop() {
        super.stop();
        messageX = maxWidth;
    }

    // draw the stuff
    public synchronized void update(Graphics g) {
        if(loaded) {
            super.update(g);

           //...then draw shadow copy of text...
           if (font3D) {
               Color foreColorD1,foreColorD2;
               foreColorD1 = foreColor.darker();
               foreColorD2 = foreColorD1.darker();
               appGC.setColor(foreColorD2);
               appGC.drawString(message, messageX+2, messageY+2);
               appGC.setColor(foreColorD1);
               appGC.drawString(message, messageX+1, messageY+1);
           }

            //...then draw the text...
            appGC.setColor(foreColor);
            appGC.setFont(messageF);
            appGC.drawString(message, messageX, messageY);         // clipping is wonderful!

            //...next comes the border...
            drawBorder(maxWidth,maxHeight,borderWidth);

            //...fade the edges
            g.drawImage(appImage, 0, 0, this);
        }
    }

    public boolean handleEvent(Event event) {
        return super.handleEvent(event);
    }

    // method that can be over-ridden to supply the message text
    protected String readMessage() {
        String tmsg;
        tmsg = ReadText("ScrollText");
        return tmsg;
    }

    void setFontValues() {
        messageF = appFont((maxHeight - (2 * borderWidth)),Font.BOLD);
        FontMetrics fm = getFontMetrics(messageF);
        messageX = maxWidth;
        messageY = ((maxHeight-fm.getHeight()) >> 1) + fm.getAscent() - 1;
        messageW = fm.stringWidth(message);
    }

    synchronized void doAppThing() {
        messageX -= scrollUnit;         //scrollUnit is the incremental distance of scrolling
        if((messageX + messageW) < 0) messageX = maxWidth;
    }
    public boolean mouseDown(Event e,int x, int y) {
        borderWidth = -borderWidth;
        return true;
    }
    public boolean mouseUp(Event e,int x, int y) {
        borderWidth = -borderWidth;
        if (nextURL !=null) {
            getAppletContext().showDocument(nextURL,frameTarget);
        }
        return true;
    }
    public boolean mouseEnter(Event e,int x,int y) {
        if (nextURL != null) showStatus("Link to " + urlName);
        return true;
    }
    public boolean mouseExit(Event e,int x,int y){
        showStatus("");
        return true;
    }
}