TweetFollow Us on Twitter

Apr 97 Top 10

Volume Number: 13 (1997)
Issue Number: 4
Column Tag: Symantec Top Ten

Symantec Top 10

By Matthew Hopkins

In this month's column, we are focusing on customer issues pertaining to our C++ and Java development environments, including the newly released Visual Café. Let's warm up with a question regarding Visual Page, a dynamic web-authoring utility

Q: In Visual Page, how do you tell what size a document is before you save it?

A: By selecting Download Statistics... from the Edit menu, you can see a dialog box which not only tells you the total document size, but also tells you how long (on the average) it will take to download your page, depending upon the speed of your modem.

Q: I am using Visual Café, and I am having a problem getting the GridLayout to work properly. For instance, when I set the number of columns to 3 in the Property Manager, the applet doesn't respond at all visually. What's going on here?

A: Visual Café behaves in this manner because of how GridLayout is implemented in Java. When the rows and columns are both defined to anything other than 0, the Layout Manager will ignore the number of columns you have specified and calculate them based upon the number of rows and the number of elements. If you are interested in having the Layout Manager organize your elements according to a certain number of columns, set the number of rows to 0 (meaning "any"), and the Layout Manager will make the number of rows dependent upon the number of columns.

Q: I am getting an error of type -43 when running my Java application in Symantec Café. How do I correct this?

A: In an application, the main function needs to be static, and the main class needs to be set in the Project Options window.

Q: I am running the following program in Symantec Café and it does nothing but hang. Could you tell me why?

class PrintThread implements Runnable {
         String str;
         
         public PrintThread (String str) {
                 this.str = str;
         } 

         public void run() {
                 for (;;)
                         System.out.print(str);
         } 
} 

class ConcurrencyTest {
         public static void main(String argv[]) {
                 new Thread(new PrintThread("A")).start();
                 new Thread(new PrintThread("B")).start();
          } 
} 

A: This does not actually cause a freeze. It just appears that way because the System.out.print never receives a "" character, so it never shows you what's going on; it adds characters to the print stream indefinitely. To achieve the results you intended (mainly, seeing A and B printed forever), either call PrintThread with "A" and "B", or change the line reading System.out.print(str) to System.out.println(str).

Q: Which folder do you put packages into in Symantec Café for the Mac?

A: You have two options:

1) Place any additional class packages into the {java libraries} folder.

2) Place them in whatever folder you like as long as you open the Preferences:Paths window and add the search path to the upper window so that Café will know to search that folder.

Q: I am developing an application in Café that includes HTML text and embedded Applets. Some of the applets need to read local files whose names are supplied by the user, but the applet security rules prevent applets from reading local files. Is there a standard way of reading user-OK'ed local files that I am missing?

A: The names of the files have to be "fully qualified" (i.e. volume/folder/file), and there can be no non-standard characters anywhere in the path (like ƒ after folder names.) You can use something like this

FileDialog file_dialog_open;
file_dialog_open = new FileDialog(this, "Open A File", FileDialog.LOAD);

public void loadFile() {
 file_dialog_open.pack();
 file_dialog_open.show();
   if (file_dialog_open.getFile() != null) {
      currentFolder = file_dialog_open.getDirectory();
      selectedFile = new String(file_dialog_open.getFile());
      fullPath = currentFolder + "/" + selectedFile;
   } 
} 

This lets the user select a file and then pass the fully qualified path name for the file to the method that actually accesses the data.

Q: Is there a simple way to use ImageMaps for applets in Java? I need to write an applet that loads a graphic file at the proper coordinates when the mouse is moved over a certain location.

A: The key to this problem is the Component action method mouseEnter(). This works for all components, including buttons, windows, etc. In order to implement ImageMaps, I find the canvas component to work the best, being invisible. Here is a small snippet of code written in Visual Café that illustrates this

import java.awt.*;
import java.applet.*;

public class Applet1 extends Applet {    
        public void init() {
                super.init();
                setLayout(null);
                addNotify();
                resize(426,266);
                theMap = new ImageMap("myMap", 50, 50, getGraphics());
                theMap.reshape(60,31,186,150);
                add(theMap);
        } 

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

class ImageMap extends Canvas {
        boolean on;
        String label;
        Graphics g;
        

        ImageMap(String label, int sizex, int sizey, Graphics g) {
                this.label=label;
                this.g=g;
                resize(sizex, sizey);
        } 
        
        public void paint(Graphics g) {
                update(g);
        } 
        
        public void update(Graphics g) {
                if(on) {
                        this.g.drawString("Hello, World!", 25, 25);
                } 
        } 
        
        public boolean mouseEnter(Event evt, int x, int y) {
                on=true;
                repaint();
                return true;
        } 
} 

Here, the text Hello, World! has been substituted for the image that should be displayed. In case you wish to remove the image when the mouse is removed from the area, use the method mouseExit() in the same way.

Q: I am using a HashTable to keep track of a number of Button objects in Symantec Café, but every time I click on the button and look up the corresponding HashTable entry, it returns null.

import java.applet.*;
import java.awt.*;
import java.util.*;

public class HashTblTest extends Applet {
        Hashtable ht = new Hashtable();
        Button[] b = new Button[3];

        public void init()       {
                for (int i = 0;i < 3;i++) {
                        b[i] = new Button("Button " + i);
                        add(b[i]);
                        ht.put(b[i], new Integer(i));    
                }   
        } 
        public boolean action(Event e, Object o){
                System.out.println(ht.get(o));
                return false;
        }      
} 

What am I doing wrong?

A: The problem here is that the Button action method counter-intuitively provides as its Object parameter a STRING which is the button's name, not the button object itself. You have entered the buttons themselves into the HashTable, but the action method is looking up a string, not a button in your table. The best way to work around this is to change your action code to read: System.out.println(ht.get(e.target)); This will achieve your desired results.

Q: I have written a program in the Think Project Manager 7.0.5 that runs in the debugger, but when I try to run it in the Finder or without the debugger, the main window does not even come up. What do I need to do to get it to work?

A: This usually indicates a failure to initialize the Macintosh toolbox. Your code seems to work in the debugger because the debugger initializes the toolbox for you.

Q: I have written a program that uses two-dimensional and three-dimensional arrays. It seems to look fine but I keep getting link errors. What can I do to fix this problem?

A: It sounds like you are putting some huge arrays on the stack! Space is allocated for these arrays prior to run-time, and if your arrays are large enough, you could be causing a stack overflow that is posing some problems for the linker. There is an excellent example on how to put these arrays on the heap (allocating them at run time) in the Think Reference under Arrays Bigger than 32k.

Special thanks to Mark Baldwin, Ted Flug, Richard Hill, Steve Howard, Scott Morrison, Kevin Kenan, and Kevin Quah.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

TechTool Pro 9.5.1 - Hard drive and syst...
TechTool Pro has long been one of the foremost utilities for keeping your Mac running smoothly and efficiently. With the release of version 9, it has become more proficient than ever. TechTool... Read more
Jamf Pro 9.99.0 - Powerful sysadmin/ente...
Jamf Pro (formerly Casper Suite) is the EMM tool that delights IT pros and the users they support by delivering on the promise of unified endpoint management for Apple devices. At Jamf, connecting... Read more
VueScan 9.5.78 - Scanner software with a...
VueScan is a scanning program that works with most high-quality flatbed and film scanners to produce scans that have excellent color fidelity and color balance. VueScan is easy to use, and has... Read more
Adobe Lightroom 6.10.1 - Import, develop...
Adobe Lightroom is available as part of Adobe Creative Cloud for as little as $9.99/month bundled with Photoshop CC as part of the photography package. Lightroom 6 is also available for purchase as a... Read more
iPhoto Library Manager 4.2.7 - Manage mu...
iPhoto Library Manager allows you to organize your photos among multiple iPhoto libraries, rather than having to store all of your photos in one giant library. You can browse the photos in all your... Read more
Smultron 9.4 - Easy-to-use, powerful tex...
Smultron 9 is an elegant and powerful text editor that is easy to use. Use it to create or edit any text document. Everything from a web page, a note or a script to any single piece of text or code.... Read more
TextSoap 8.4 - Automate tedious text doc...
TextSoap can automatically remove unwanted characters, fix up messed up carriage returns, and do pretty much anything else that we can think of to text. Save time and effort. Be more productive. Stop... Read more
Merlin Project 4.2.3 - $349.00
Merlin Project is the leading professional project management software for OS X. If you plan complex projects on your Mac, you won’t get far with a simple list of tasks. Good planning raises... Read more
QuarkXPress 13.0.0.0 - Desktop publishin...
QuarkXPress 2017 is the new version that raises the bar for design and productivity. With non-destructive graphics and image editing directly within your layout, you no longer have to choose between... Read more
Path Finder 7.5 - Powerful, award-winnin...
Path Finder makes you a master of file management. Take full control over your file system. Save your time: compare and synchronize folders, view hidden files, use Dual Pane and full keyboard... Read more

Latest Forum Discussions

See All

Zombie Gunship Survival Beginner's...
The much anticipated Zombie Gunship Survival is here. In this latest entry in the Zombie Gunship franchise, you're tasked with supporting ground troops and protecting your base from the zombie horde. There's a lot of rich base building fun, and... | Read more »
Mordheim: Warband Skirmish (Games)
Mordheim: Warband Skirmish 1.2.2 Device: iOS Universal Category: Games Price: $3.99, Version: 1.2.2 (iTunes) Description: Explore the ruins of the City of Mordheim, clash with other scavenging warbands and collect Wyrdstone -... | Read more »
Mordheim: Warband Skirmish brings tablet...
Legendary Games has just launched Mordheim: Warband Skirmish, a new turn-based action game for iOS and Android. | Read more »
Magikarp Jump splashes onto Android worl...
If you're tired ofPokémon GObut still want something to satisfy your mobilePokémon fix,Magikarp Jumpmay just do the trick. It's out now on Android devices the world over. While it looks like a simple arcade jumper, there's quite a bit more to it... | Read more »
Purrfectly charming open-world RPG Cat Q...
Cat Quest, an expansive open-world RPG from former Koei-Tecmo developers, got a new gameplay trailer today. The video showcases the combat and exploration features of this feline-themed RPG. Cat puns abound as you travel across a large map in a... | Read more »
Jaipur: A Card Game of Duels (Games)
Jaipur: A Card Game of Duels 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: ** WARNING: iPad 2, iPad Mini 1 & iPhone 4S are NOT compatible. ** *** Special Launch Price for a limited... | Read more »
Subdivision Infinity (Games)
Subdivision Infinity 1.03 Device: iOS Universal Category: Games Price: $2.99, Version: 1.03 (iTunes) Description: Launch sale! 40% Off! Subdivision Infinity is an immersive and pulse pounding sci-fi 3D space shooter. https://www.... | Read more »
Clash of Clans' gets a huge new upd...
Clash of Clans just got a massive new update, and that's not hyperbole. The update easily tacks on a whole new game's worth of content to the hit base building game. In the update, that mysterious boat on the edge of the map has been repaired and... | Read more »
Thimbleweed Park officially headed to iO...
Welp, it's official. Thimbleweed Park will be getting a mobile version. After lots of wondering and speculation, the developers confirmed it today. Thimbleweed Park will be available on both iOS and Android sometime in the near future. There's no... | Read more »
Pokémon GO might be getting legendaries...
The long-awaited legendary Pokémon may soon be coming to Pokémon GO at long last. Data miners have already discovered that the legendary birds, Articuno, Moltres, and Zapdos are already in the game, it’s just a matter of time. [Read more] | Read more »

Price Scanner via MacPrices.net

Huawei Unveils New ‘Business-Styled’ MateBook...
Huawei has introduced a trio of new MateBook laptops, expanding its mobile portfolio and building on its success in delivering attractive and powerful high-end devices. The company claims the HUAWEI... Read more
Deal! Gold 12-inch 1.2GHz Retina MacBook for...
Amazon has the 2016 Gold 12″ 1.2GHz Retina MacBook (MLHF2LL/A) on sale for $350 off MSRP for a limited time. Shipping is free: - 12″ 1.2GHz Gold Retina MacBook: $1249.99 $350 off MSRP We expect this... Read more
13-inch 2.0GHz MacBook Pros on sale for $100...
B&H has the non-Touch Bar 13″ 2.0GHz MacBook Pros in stock today and on sale for $100 off MSRP. Shipping is free, and B&H charges NY & NJ sales tax only: - 13″ 2.0GHz MacBook Pro Space... Read more
15-inch 2.2GHz Retina MacBook Pro, Apple refu...
Apple has Certified Refurbished 2015 15″ 2.2GHz Retina MacBook Pros available for $1699. That’s $300 off MSRP, and it’s the lowest price available for a 15″ MacBook Pro. An Apple one-year warranty is... Read more
Apple refurbished 9-inch and 12-inch iPad Pro...
Apple has Certified Refurbished 9″ and 12″ Apple iPad Pros available for up to $160 off the cost of new iPads. An Apple one-year warranty is included with each model, and shipping is free: - 32GB 9″... Read more
Apple Certified Refurbished iMacs available f...
Apple has Certified Refurbished 2015 21″ & 27″ iMacs available for up to $350 off MSRP. Apple’s one-year warranty is standard, and shipping is free. The following models are available: - 21″ 3.... Read more
Sale! 15-inch 2.6GHz Silver Touch Bar MacBook...
DataVision has the 15″ 2.6GHz Silver Touch Bar MacBook Pro (MLW72LL/A) on sale for $2199 including free shipping. Their price is $200 off MSRP, and it’s the lowest price available for this model (... Read more
A Kaby Lake Processor Upgrade For The MacBook...
Now they tell me! Well, actually Apple hasn’t said anything official on the subject, but last week Bloomberg News’s Mark Gurman and Alex Webb cited unnamed “people familiar with the matter”... Read more
Kodak’s Camera-First Smartphone EKTRA Launche...
The Eastman Kodak Company and Bullitt Group have announced the availability of a U.S. GSM version of the KODAK EKTRA Smartphone. The U.S. launch coincides with a software update addressing requests... Read more
Apple Launches App Development Curriculum for...
Apple today launched a new app development curriculum designed for students who want to pursue careers in the fast-growing app economy. The curriculum is available as a free download today from Apple... Read more

Jobs Board

Data Engineer - *Apple* Media Products - Ap...
Changing the world is all in a day's work at Apple . If you love innovation, here's your chance to make a career of it. You'll work hard. But the job comes with more Read more
*Apple* Store Leader Program - Apple, Inc (U...
…Summary Learn and grow as you explore the art of leadership at the Apple Store. You'll master our retail business inside and out through training, hands-on Read more
*Apple* Integration Specialist - A3 Solution...
Apple Integration Specialist Contract-To-HireWe are searching for dedicated, well-experienced and energetic individuals for an information technology corporation Read more
Sr. Software Engineer, *Apple* Online Store...
Changing the world is all in a day's work at Apple . If you love innovation, here's your chance to make a career of it. You'll work hard. But the job comes with more Read more
Senior Engineering Project Manager, *Apple*...
Changing the world is all in a day's work at Apple . If you love innovation, here's your chance to make a career of it. You'll work hard. But the job comes with more Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.