chatscreen.java

These notes are only intended as a brief guide for building and running the example.

//
// Copyright 2002 Nokia Corporation.
//
// THIS SOURCE CODE IS PROVIDED 'AS IS', WITH NO WARRANTIES WHATSOEVER,
// EXPRESS OR IMPLIED, INCLUDING ANY WARRANTY OF MERCHANTABILITY, FITNESS
// FOR ANY PARTICULAR PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE
// OR TRADE PRACTICE, RELATING TO THE SOURCE CODE OR ANY WARRANTY OTHERWISE
// ARISING OUT OF ANY PROPOSAL, SPECIFICATION, OR SAMPLE AND WITH NO
// OBLIGATION OF NOKIA TO PROVIDE THE LICENSEE WITH ANY MAINTENANCE OR
// SUPPORT. FURTHERMORE, NOKIA MAKES NO WARRANTY THAT EXERCISE OF THE
// RIGHTS GRANTED HEREUNDER DOES NOT INFRINGE OR MAY NOT CAUSE INFRINGEMENT
// OF ANY PATENT OR OTHER INTELLECTUAL PROPERTY RIGHTS OWNED OR CONTROLLED
// BY THIRD PARTIES
//
// Furthermore, information provided in this source code is preliminary,
// and may be changed substantially prior to final release. Nokia Corporation
// retains the right to make changes to this source code at any time,
// without notice. This source code is provided for informational
// purposes only.
//
//
// Nokia and Nokia Connecting People are registered trademarks of Nokia
// Corporation. Java and all Java-based marks are trademarks or registered
// trademarks of Sun Microsystems, Inc. Other product and company names
// mentioned herein may be trademarks or trade names of their respective owners.
//
// A non-exclusive, non-transferable, worldwide, limited license is hereby
// granted to the Licensee to download, print, reproduce and modify the
// source code. The licensee has the right to market, sell, distribute and
// make available the source code in original or modified form only when
// incorporated into the programs developed by the Licensee. No other
// license, express or implied, by estoppel or otherwise, to any other
// intellectual property rights is granted herein.
//


import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import java.util.*;


class ChatScreen
    extends Canvas
    implements CommandListener
{
    private final ChatMIDlet parent;
    private final Vector chatText = new Vector();
    private final Font font;
    private final int lineHeight, lineWidth, maxLines;
    private final Command toCommand, quitCommand;
    private final String prompt;

    private Command writeCommand = null;
    private int topLine = 0;


    ChatScreen(ChatMIDlet parent, String prompt)
    {
        this.parent = parent;
        this.prompt = prompt;

        font = Font.getFont(Font.FACE_PROPORTIONAL,
                            Font.STYLE_PLAIN,
                            Font.SIZE_SMALL);

        lineWidth = getWidth() - 2;
        lineHeight = font.getHeight() + 1;
        maxLines = (getHeight() - 2) / lineHeight;

        toCommand = new Command("To", Command.SCREEN, 1);
        quitCommand = new Command("Quit", Command.EXIT, 2);
        addCommand(toCommand);
        addCommand(quitCommand);
        setCommandListener(this);
    }


    void update(String text)
    {
        if (font.stringWidth(text) > lineWidth)
        {
            // seperate message text into multiple lines and
            // add each to chatText
            int offset = 0;
            int len = 1;

            do
            {
                // calculate the max lenth of substring fitting one screen line
                while (((offset + len) <= text.length()) &&
                       (font.substringWidth(text, offset, len) <= lineWidth))
                {
                    len++;
                }
                chatText.addElement(text.substring(offset, offset + len - 1));
                offset += len - 1;
                len = 1;
            } while (offset + len <= text.length());
        }
        else
        {
            chatText.addElement(text);
        }

        if (chatText.size() > maxLines)
        {
            topLine = chatText.size() - maxLines;
        }
        repaint();
    }


    public void paint(Graphics g)
    {
        g.setColor(0xFFFFFF);
        g.fillRect(0, 0, getWidth(), getHeight());
        g.setColor(0);
        g.setFont(font);

        if (chatText.size() == 0)
        {
            g.drawString(prompt, 1, 1, (Graphics.TOP | Graphics.LEFT));
        }
        else
        {
            for (int i = 0; i < maxLines && i < chatText.size(); i++)
            {
                g.drawString((String) chatText.elementAt(topLine + i),
                             1,
                             (lineHeight * i + 1),
                             (Graphics.TOP | Graphics.LEFT));
            }
        }
    }


    protected void keyReleased(int keyCode)
    {
        switch (getGameAction(keyCode))
        {
            case Canvas.UP:
                if (topLine != 0)
                {
                    topLine--;
                    repaint();
                }
                break;

            case Canvas.DOWN:
                if ((topLine + maxLines) < chatText.size())
                {
                    topLine++;
                    repaint();
                }
                break;

            default:
                break;
        }
    }


    public void commandAction(Command c, Displayable d)
    {
        if (c == toCommand)
        {
            parent.chatScreenChoosePeer();
        }
        else if (c == writeCommand)
        {
            parent.chatScreenWriteMessage();
        }
        else if (c == quitCommand)
        {
            parent.chatScreenQuit();
        }
    }


    void enableWriteCommand()
    {
        if (writeCommand == null)
        {
            writeCommand = new Command("Write", Command.SCREEN, 1);
            addCommand(writeCommand);
        }
    }
}