factorising code!!

THANK YOU!!! That works great! :-) As you can see, I'm a total novice to Java, and have to code this by June :-( I'm trying to make a "tutorial" for learning Maths...i need a miracle!

So what do you mean by wasting resources? Would it be better to factorise the text/style code into an independent class of its own, maybe using abstract method+inheritance maybe? In the superclass define the common things like menus, buttons etc, and then in the subclass define the text/style methods perhaps?

confused_girla at 2007-7-15 15:35:44 >

Hi there,

I don't have any designs at the moment, but similar to what I originally posted up. There will be lots of menu options, buttons etc, but the main concept will be as the user selects "next" or "back", the appropriate text/images are displayed within the TextArea/Scroller area, until the end of that particular topic is reached. I HATE java! One tiny mistake and the whole prog messes up!

That XML stuff sounds really interesting...thanks for the idea-i will look into this..

I'm afraid it does have to be in Java-thats one of the requirements unfortunately otherwise I would have picked something easy like HTML/Servlets!

That would be fantastic if you wouldnt mind making an example for me-whenever you have the time, I would be very grateful for any help.

Thanks again... :-)

confused_girla at 2007-7-15 15:35:44 >

Ok, I had half an hour, so here's a vey quick version that uses XML to

load your pages. STudy it, ask questions, look stuff up and find out

how it works.

To run it: java ConfusedGirl3 <file name>

where <file name> is a file containing the following xml.

Good luck!

<document>

<page title="Page 1">

<element style="regular">This is the FIRST PAGE</element>

<element style="bold">for MATHS</element>

<element style="small">learning</element>

<element style="large">tools</element>

<newline/>

<element style="regular">which suports embedded graphs...</element>

<element style="bold">...and embedded icons.</element>

</page>

<page title="Page 2">

<element style="regular">This is the next page</element>

<element style="logo"></element>

<element style="bold">of</element>

<element style="small">the</element>

<newline/>

<element style="text"></element>

<newline/>

<element style="regular">tutorial</element>

<element style="italic">click to continue</element>

</page>

</document>

Here comes the code:

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

import javax.swing.text.*;

import java.io.File;

import java.util.ArrayList;

import javax.xml.parsers.SAXParser;

import javax.xml.parsers.SAXParserFactory;

import org.xml.sax.SAXException;

import org.xml.sax.Attributes;

import org.xml.sax.helpers.DefaultHandler;

public class ConfusedGirl3

{

static class Element

{

private String mText;

private String mStyle;

public Element(String style)

{

this("", style);

}

public Element(String text, String style)

{

mText= text;

mStyle= style;

}

public String getText() { return mText; }

public String getStyle() { return mStyle; }

}

static class DisplayPane

extends JTextPane

{

public DisplayPane()

{

Style def= StyleContext.getDefaultStyleContext().getStyle(

StyleContext.DEFAULT_STYLE);

Style regular= addStyle("regular", def);

StyleConstants.setFontFamily(def, "SansSerif");

Style s= addStyle("italic", regular);

StyleConstants.setItalic(s, true);

s= addStyle("bold", regular);

StyleConstants.setBold(s, true);

s= addStyle("small", regular);

StyleConstants.setFontSize(s, 10);

s= addStyle("large", regular);

StyleConstants.setFontSize(s, 16);

s= addStyle("logo", regular);

StyleConstants.setAlignment(s, StyleConstants.ALIGN_CENTER);

JLabel label= new JLabel(new ImageIcon("pig.gif"));

StyleConstants.setComponent(s, label);

s= addStyle("text", regular);

StyleConstants.setAlignment(s, StyleConstants.ALIGN_CENTER);

JTextField txt= new JTextField(5);

StyleConstants.setComponent(s, txt);

setEditable(false);

}

public void clear()

{

try {

getDocument().remove(0, getDocument().getLength());

}

catch (Exception e) {

e.printStackTrace();

}

}

private void add(Element element)

{

try {

getDocument().insertString(

getDocument().getLength(),

element.getText() +" ",

getStyle(element.getStyle()));

}

catch (Exception e) {

e.printStackTrace();

}

}

}

static class Navigator

extends JPanel

{

private DisplayPane mPane= new DisplayPane();

private Element[][] mElements;

private int mPage= 0;

public Navigator(Element[][] elements)

{

mElements= elements;

setPage(0);

setLayout(new BorderLayout());

add(mPane, BorderLayout.CENTER);

final JButton back= new JButton("< Back");

final JButton next= new JButton("Next >");

back.setEnabled(false);

back.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {

setPage(--mPage);

if (mPage <= 0)

back.setEnabled(false);

next.setEnabled(true);

}

});

next.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {

setPage(++mPage);

if (mPage >= mElements.length -1)

next.setEnabled(false);

back.setEnabled(true);

}

});

JPanel panel= new JPanel(new BorderLayout());

JPanel btns= new JPanel(new GridLayout(1, 0));

btns.add(back);

btns.add(next);

panel.add(btns, BorderLayout.WEST);

add(panel, BorderLayout.NORTH);

}

private void setPage(int page)

{

mPane.clear();

for (int i= 0; i< mElements[page].length; i++)

mPane.add(mElements[page][i]);

}

}

static class Parser

{

public Element[][] parse(String fname)

{

final ArrayList pages= new ArrayList();

try {

SAXParser parser= SAXParserFactory.newInstance().newSAXParser();

parser.parse(new File(fname), new DefaultHandler() {

String text;

String style;

ArrayList elements= new ArrayList();

public void startElement(String uri, String localName, String qName, Attributes attributes)

throws SAXException

{

if (qName.equals("page")) {

elements= new ArrayList();

pages.add(elements);

}

else if (qName.equals("element")) {

text= "";

style= attributes.getValue(attributes.getIndex("style"));

}

}

public void characters(char ch[], int start, int length)

throws SAXException

{

text += new String(ch).substring(start, start+length);

}

public void endElement(String uri, String localName, String qName)

throws SAXException

{

if (qName.equals("newline"))

elements.add(new Element("\n", "regular"));

else if (qName.equals("element"))

elements.add(new Element(text, style));

}

});

}

catch (Exception e) {

e.printStackTrace();

}

Element[][] elements= new Element[pages.size()][];

for (int i= 0; i< elements.length; i++)

elements[i]= (Element[]) ((ArrayList) pages.get(i)).toArray(new Element[0]);

return elements;

}

}

public static void main(String[] argv)

{

Element[][] elements= new Parser().parse(argv[0]);

JFrame frame= new JFrame("ConfusedGirl3");

frame.getContentPane().add(new Navigator(elements));

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

frame.pack();

frame.setSize(600,480);

frame.setVisible(true);

}

}

dchswa at 2007-7-15 15:35:44 >

wow! i just tried this out!! its fantastic! thank you soooo much! you have saved me so much time..this way is so much simpler as opposed to hard-coding the entire content into the program...i can work so much better with this as a foundation! i totally understand how you did it-new pages can be added into the xml file..you really don't know how grateful I am! originally i had planned to code the entire content as in the original program that i initially sent out (using that long-winded "creatTextPane()" method), but this really has made my day! if you don't mind me asking, how many years experience do you have in Java? My pathetic attempts to code must have made you cry with laughter!!!are you a regular user of this forum? I would like to keep you informed of my progress if thats ok by you? Seeing as you have helped me so much already, and if I need help again?!...

confused_girla at 2007-7-15 15:35:44 >

Ok, looks like you've got the idea of using an xml document to store the dynamic content of your system, so let me answer some of your questions, and pose a few for you.

If your system will include just a handful of pages, you're xml document will probably remain manageable; i.e. it will be possible to edit it in a simple text editor when changes are required. If you need many hundreds of pages, editing the xml by hand becomes a real pain as you need to run your app to validate your changes.

If you define an XML Schema for your document (you'll have to research what one of these is and what it does for you - btw, do not use a DTD, they are old technology and not worth getting familiar with) then commercial XML editors will be able to enforce the validity of your document as you write it.

Even then, we've essentially re-invented a rather fundamental wheel.

What we have in this example XML is the beginnings of a simple mark-up language. Add an XML Schema and it becomes formalised. To put it another way, we've just re-invented HTML. The application code is a simplistic re-invention of an internet browser.

This comes back to the original point of the exercise, what is it? You said you had to write something in Java but I don't know if you are a student with an assignment or working on a commercial system.

Depending on the requirements, you could ditch XML all together and simply write the tutorial pages in HTML. You could still write a simple browser in Java and provide a config file that defines the navigation order (Introduction.html, Page1.html, Page2.html, etc.).

It all depends on what you're trying to accomplish.

Your question about adding a login screen demonstrates the challenges of answering questions in this forum. When I give a solution here it always has a top level class named after the user who posted the question - hence ConfusedGirl3.java. The individual classes used to illustrate the solution are declared static so they can be used by the other classes and the main method on the outer class.

This scheme makes it simple for anyone to cut out the code into a single file, compile it and see what the code does.

In the real world, the static inner classes would be public classes in their own files. In this case you would have: Element.java, DispayPane.java, Navigator.java, Parser.java and some other class with the main method.

To add you login screen, you would create Login.java and hook that in by calling it from the main method/class. When you get a good login, you fire up an instance of Navigator inside a JFrame just as we do now.

In terms of my experience with Java, I first used it in 1996 whilst working on another OO language for a database vendor. I've been using it almost exclusively since 1997. Don't worry about your code appearing pathetic - I see much worse on a daily basis from people who claim to know what they're doing :)

I'm happy to provide ongoing help as your project progresses. However, this forum probably isn't the best place to provide it. I do login on a reasonably regular basis, but if I'm busy I may not wander by for months.

If you want to contact me with questions, I suggest you create a temporary e-mail address on hotmail (or similar), post that address here in "account AT hotmail DOT com" format - don't use "@" and "." then when I mail you there, stop using that new account. After a couple of months inactivity, hotmail will delete it.

The point being, don't post your real email address here unless you get some perverted pleasure from wading through spam!

dchswa at 2007-7-19 12:27:09 >