Horizantal image scroll in J2ME form

[Dushyant Chhetri]

Hi Friends,

I have been trying to figure out if J2ME javax.microedition.lcdui.Form allows for horizontal scrolling.

When form items are added to this form, and they exceed the form area, the vertical scrollbar appears automatically. This is not the case however when an ImageItem wider than the form is placed onto it. That is, if say the form on a Nokia mobile with a screen of 125x100 takes precisely those dimensions, and an ImageItem of 200x200 is placed on it. Vertical scrolling appears automatically, but not the horizontal.

I tried with resizing the image using the code snippet attached in this url.

Image zooming.

However the reduced size of the image makes it very hazy and unusuable thu si had to discard this option.
Now I desperately need to find a way to get the horizantal scroll work.

I know it can be done using Canvas class , but then my entire code will also change so please help me out with its implementation in a Form.

Thanks,

[Aleksandar Babic]

This link might help
http://www.experts-exchange.com/Programming/Languages/Java/Q_20840864.html
(You must register to view the code. I could paste it here if you have problem with login)

[Dushyant Chhetri]

Hi Aleksandar,

I tried the link below but as you mentioned I could not log in ti view the solution.

It would be very helpful if you would paste the code out here.

Thanks in advance..

[Aleksandar Babic]

Here it is!

  package com.ossltd.scroll;

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

public class Scroller extends MIDlet implements CommandListener
{
    private Display display;
    private Command exitCommand;
    private Command viewCommand;
    private Form mainForm;
    private ScrollCanvas scrollCanvas;
   
    public Scroller()
    {
        exitCommand = new Command("Exit", Command.EXIT, 1);
        viewCommand = new Command("View", Command.SCREEN, 1);
       
        mainForm = new Form("Scroller");
        mainForm.append("Press 'View' to access the scrolling image");
        mainForm.addCommand(viewCommand);
        mainForm.addCommand(exitCommand);
        mainForm.setCommandListener(this);
       
        scrollCanvas = new ScrollCanvas();
        scrollCanvas.addCommand(exitCommand);
        scrollCanvas.setCommandListener(this);
    }
   
    public void startApp()
    {
        display = Display.getDisplay(this);
        display.setCurrent(mainForm);
    }
   
    public void pauseApp()
    {
    }
   
    public void destroyApp(boolean flag)
    {
    }
   
    public void commandAction(Command command, Displayable displayable)
    {
        if (command == viewCommand)
        {
            display.setCurrent(scrollCanvas);
        }
        else if (command == exitCommand)
        {
            destroyApp(true);
            notifyDestroyed();
        }
    }
}  

  package com.ossltd.scroll;

import java.io.*;
import javax.microedition.lcdui.*;

public class ScrollCanvas extends Canvas
{
    private static final int TOP_LEFT = Graphics.TOP | Graphics.LEFT;
    private Image bigImage;
    private int imgX;
    private int imgY;
   
    public ScrollCanvas()
    {
        try
        {
            bigImage = Image.createImage("/images/myImg.png");
        }
        catch (IOException ioe)
        {
            // Deal with failure to load image.
        }
    }
   
    public void paint(Graphics graphics)
    {
        graphics.setColor(0x000000);
        graphics.fillRect(0, 0, getWidth(), getHeight());
        graphics.drawImage(bigImage, imgX, imgY, TOP_LEFT);
    }
   
    public void keyReleased(int keyCode)
    {
        int gameKey = getGameAction(keyCode);

        if ((gameKey == UP) || (keyCode == KEY_NUM2))
        {
            imgY++;
        }
        else if ((gameKey == LEFT) || (keyCode == KEY_NUM4))
        {
            imgX++;
        }
        else if ((gameKey == RIGHT) || (keyCode == KEY_NUM6))
        {
            imgX--;
        }
        else if ((gameKey == DOWN) || (keyCode == KEY_NUM8))
        {
            imgY--;
        }

        repaint();
        serviceRepaints();
    }
}  

[Dushyant Chhetri]

Thanks Aleksandar Babic.
It is working just the way I wanted it.

[Aleksandar Babic]

Great! You're welcome