| anvas - ScrollingUpdate (Version 1.1) ScrollingUpdate is canvas sub-class that can be used to vertically scroll text over a static background image. The text is read from a file on the host, and the host text file is subsequently read periodically for updates. If an update to the text file occurs, then the vertically scrolling text displayed by the applet is dynamically updated.
| peration The following documentation describes how the ScrollingUpdate canvas class is used. Also available is the ScrollingUpdateApplet which can be used to plug the canvas directly into a web page. The ScrollingUpdateApplet class is documented separately. ScrollingUpdate.class requires NetworkTextFile.class. Both of these objects are included in the download package. During initialization, ScrollingUpdate loads the GIF or JPEG image that will be used as the background image, and reads a specified file on the host to retrieve the text that is to be scrolled vertically over the image. The are a number of parameters (documented below) that control how the text will be rendered over the background. Both the font characteristics and the location of the scroll region within the background image can be specified. The number of words that appear on a single line in the scroll region is automatically determined based upon the font characteristics and the width of the scroll region. Because each line of text is automatically formatted, the text entered in the text file does not need to be manually formatted with carriage returns. If you wish to create a line break in the text, enter the `<BR>` code or the `<P>` code in the text file where the line break should be placed. The code should be entered on a single line or with a least one space on either side of the code. The `<BR>` code will place a line break in the text at the location of the code. The `<P>` code will insert a blank line in addition to inserting the line break. The frequency at which the class checks for changes to the text file can be specified, as well as whether or not a notification indicator should be displayed whenever an update check occurs. The class determines if the text file has been changed by reading the very first line of text in the file (the file header) and comparing it to the header that was read on the previous read. Note that the header is never displayed, so the header line in the file can be can be anything that you wish, such as the date and time that the file was last changed. When you want to indicate that the text in the file has changed, simply modify the header and save the file. The next time that the class checks the text file, it will find that the header has changed and will then reload and re-render the text to be scrolled. Scrolling text can be paused by clicking anywhere within the boundries of the Canvas. A second click will start the text scrolling once again.
| ample
|  | If your browser supports Java, you should see a demonstration of the ScrollingUpdateApplet (which uses ScrollingUpdate). You can view the text file that is being read to create the scrolling text.
| onstructor The constructor and the parameters for the class constructor are listed below.
    public ScrollingUpdate(
       URL base, String textFile, int maxSizeKB,
       int refresh, boolean notifyOnRead,
       String font, int fontSize, int fontStyle,
       Color fontColor, int justification,
       int frameDelay, String background,
       Rectangle displayRegion
    ) throws MalformedURLException
URL | base | The base directory for locating the textFile and background files.
String | textFile | The name of the text file that contains the text to be vertically scrolled. The file must reside in the same directory as the Java applet.
int | maxSizeKB | The maximum size that the text file can be in kilobytes.
int | refresh | The frequency in seconds that the text file should be checked for updates.
boolean | notifyOnRead | If this parameter is set to "true", then a small red square indicator will blink in the top left corner of the screen each time that the text file is checked for updates. If set to "false", then no indication will be displayed that the text file has been checked.
String | font | The name of the font to use when rendering the text to be scrolled. It is recommended that only the standard fonts for Java be specified unless you are certain that the font that you specify will be available on all clients.
int | fontSize | The size of the font used to render the text to be scrolled.
int | fontStyle | This parameter can be set to any of the valid style constants defined in the Font class (e.g., Font.bold, Font.italic, Font.plain, etc.).
Color | fontColor | The color of the scrolled text .
int | justification | 1= justify left, 2=justify center, and 3=justify right.
int | frameDelay | The number of milliseconds to delay between each frame of animation (this controls how quickly the text scrolls).
String | background | The file name of a GIF or JPEG image that will be drawn behind the scrolling text. The file path is based starting with the directory in which the Java applet is located.
Rectangle | displayRegion | A rectangle bounding the region in which the text is scrolled. Note that text can be scrolled over any portion of the background image.
| ublic Methods This section lists the methods that can be called from a Java program to control or alter the behavior of the class. `public void start()` Starts the vertical text scroll and the text file monitoring. `public void stop()` Stops the vertical text scroll and the text file monitoring. `public void setFrameRate(int milliSeconds)` Changes the number of milliseconds to delay between each frame of animation (this controls how quickly the text scrolls).
| ownload The object code for the applet ScrollingUpdateApplet and the canvas class ScrollingUpdate along with a copy of this documentation are available for download.
| opyright This documentation and the object code for ScrollingUpdateApplet and ScrollingUpdate may be copied and distributed freely for non-commercial purposes so long as neither the code nor the documentation is altered in any way. If the object code is distributed with any documentation whatsoever, then this unaltered document must accompany the code. Copyright © 1997 by Modern Minds, Inc.