Table scroll not working as expected

Question

I am working on a certain table with fixed headers in LWUIT. Let me come straight to the problem. When I run it on the emulator, the touch interface works very fine and the scrolling of the form works flawless, but when I try to navigate it with the navigation keys, the LEFT key pressed creates a glitch. The glitch is that when I navigate to the right and then back to the left, the left scroll fezzes on 2nd column and it doesn't move to the extreme left no matter how many times i press the left key. After many efforts I found a combination that on randomly pressing the UP and LEFT key continuously, then the form scrolls to the extreme left. I cant get why is this happening. I tried it on all emulators and 2 actual handsets, but still the same problem. Could there be some code which creates this kind of problem? I'm not sure of that. Any help on this will be appreciated. Moreover I am posting the whole source code so that anyone interested may try it as it is and can see if this problem comes on his emulator or not.

import com.sun.lwuit.Button;
import com.sun.lwuit.Component;
import com.sun.lwuit.Display;
import com.sun.lwuit.Form;
import com.sun.lwuit.Label;
import com.sun.lwuit.events.ActionEvent;
import com.sun.lwuit.events.ActionListener;
import com.sun.lwuit.geom.Dimension;
import com.sun.lwuit.layouts.BorderLayout;
import com.sun.lwuit.table.DefaultTableModel;
import com.sun.lwuit.table.Table;
import com.sun.lwuit.table.TableModel;
import javax.microedition.lcdui.Canvas;
import javax.microedition.midlet.MIDlet;

public class FixedTableDemo extends MIDlet implements ActionListener {

private static final String[] TITLES = {"Title 1", "Title 2", "Title 3", "Title 4", "Title 5"};
private static final int ROWS = 100;
private static Dimension[] TITLE_SIZES;
Button b[][];



static class MirroredTable extends Table {

   private MirroredTable mirrorTo;

   public MirroredTable(TableModel m) {

       super(m);

   }



   public MirroredTable(TableModel m, boolean b) {

       super(m, b);

   }

   public void setScrollX(int x) {

       super.setScrollX(x);

       if(isDragActivated()) {
           mirrorTo.setScrollX(x);
       }

   }



   /**

    * @param mirrorTo the mirrorTo to set

    */

   public void setMirrorTo(MirroredTable mirrorTo) {
       this.mirrorTo = mirrorTo;
   }



   public Component createCell(Object value, int row, int column, boolean editable) {

       Component c = super.createCell(value, row, column, editable);

       if(TITLE_SIZES != null && TITLE_SIZES[column] != null) {
           c.setPreferredSize(TITLE_SIZES[column]);
       }

       return c;

   }

}

MirroredTable titlesTable;

MirroredTable bodyTable;

public void startApp() {

   Display.init(this);



   Form f = new Form("Table Title");

   titlesTable = new MirroredTable(new DefaultTableModel(TITLES, new Object[0][0]));

   //TITLE_SIZES = new Dimension[TITLES.length];

   /*for(int iter = 0 ; iter < TITLES.length ; iter++) {
    * 
    * TITLE_SIZES[iter] = titlesTable.createCell(TITLES[iter], -1, iter, false).getPreferredSize();
    * 
    * }*/

   titlesTable.removeAll();

   Button bt[]=new Button[5];

   for(int i=0;i<5;i++)
   {
       bt[i]=new Button("Title  "+i);
       bt[i].setUIID("");
       titlesTable.addComponent(bt[i]);
   }


   Object[][] body = new Object[ROWS][TITLES.length];

   /* for(int rows = 0 ; rows < body.length ; rows++) {
    * 
    * for(int cols = 0 ; cols < body[rows].length ; cols++) {
    * 
    * body[rows][cols] = "" + rows + ", " + cols;
    * 
    * }
    * 
    * }*/

   bodyTable = new MirroredTable(new DefaultTableModel(TITLES, body), false);

   bodyTable.setMirrorTo(titlesTable);

   titlesTable.setMirrorTo(bodyTable);

   bodyTable.setScrollable(true);

   titlesTable.setScrollableX(true);

   f.setScrollable(false);

   f.setLayout(new BorderLayout());

   titlesTable.setTensileDragEnabled(false);

   bodyTable.setTensileDragEnabled(false);

   titlesTable.setIsScrollVisible(false);

   f.addComponent(BorderLayout.NORTH, titlesTable);

   f.addComponent(BorderLayout.CENTER, bodyTable);


   f.addGameKeyListener(Canvas.LEFT, this);
   f.addGameKeyListener(Canvas.RIGHT, this);
   f.addGameKeyListener(Canvas.UP, this);

   f.setCyclicFocus(false);


   /**
    * buttons adding and their listener
    */
   b=new Button[50][5];
   //Label l[][]=new Label[50][5];

   for(int i=0;i<50;i++)
     {
     for(int j=0; j<5;j++)
     {
     b[i][j]=new Button("Title "+i);
     b[i][j].setUIID("");
     //l[i][j]=new Label("Title 1");
     bodyTable.addComponent(b[i][j]);

     }
     }





   f.show();

 }

 public void actionPerformed(ActionEvent evt) {
    if(evt.getKeyEvent()==Canvas.LEFT)
    {
        System.out.println(bodyTable.getScrollX());
        titlesTable.setScrollX(bodyTable.getScrollX());

    }
    else if(evt.getKeyEvent()==Canvas.RIGHT)
    {
        System.out.println(bodyTable.getScrollX());
        titlesTable.setScrollX(bodyTable.getScrollX());
    }
    else if(evt.getKeyEvent()==Canvas.UP)
    {
        System.out.println("Up:"+bodyTable.getScrollX()+","+bodyTable.getScrollY());
    }
 }

 public void pauseApp() {

 }



 public void destroyApp(boolean unconditional) {

 }

}

Answer 1

I do not know it is accurate way to achieve this or not. But i have made some changes in your code. Check it out.

import com.sun.lwuit.Button;
import com.sun.lwuit.Component;
import com.sun.lwuit.Display;
import com.sun.lwuit.Form;
import com.sun.lwuit.events.ActionEvent;
import com.sun.lwuit.events.ActionListener;
import com.sun.lwuit.geom.Dimension;
import com.sun.lwuit.layouts.BorderLayout;
import com.sun.lwuit.table.DefaultTableModel;
import com.sun.lwuit.table.Table;
import com.sun.lwuit.table.TableModel;
import javax.microedition.lcdui.Canvas;
import javax.microedition.midlet.MIDlet;

public class FixedTableDemo extends MIDlet implements ActionListener {

private static final String[] TITLES = {"Title 1", "Title 2", "Title 3", "Title 4", "Title 5"};
private static final int ROWS = 100;
private static Dimension[] TITLE_SIZES;
Button b[][];
int screenWidth;
int lastMove = 0;
int lastModifiedMove = 1;
int temp;

static class MirroredTable extends Table {

    private MirroredTable mirrorTo;

    public MirroredTable(TableModel m) {

        super(m);

    }

    public MirroredTable(TableModel m, boolean b) {

        super(m, b);

    }

    public void setScrollX(int x) {

        super.setScrollX(x);

        if (isDragActivated()) {

            mirrorTo.setScrollX(x);

        }

    }

    /**
     *
     * @param mirrorTo the mirrorTo to set
     *
     */
    public void setMirrorTo(MirroredTable mirrorTo) {

        this.mirrorTo = mirrorTo;

    }

    public Component createCell(Object value, int row, int column, boolean editable) {

        Component c = super.createCell(value, row, column, editable);

        if (TITLE_SIZES != null && TITLE_SIZES[column] != null) {

            c.setPreferredSize(TITLE_SIZES[column]);

        }

        return c;

    }
}
MirroredTable titlesTable;
MirroredTable bodyTable;

public void startApp() {

    Display.init(this);


    screenWidth = Display.getInstance().getDisplayWidth();

    Form f = new Form("Table Title");

    titlesTable = new MirroredTable(new DefaultTableModel(TITLES, new Object[0][0]));
    titlesTable.removeAll();

    Button bt[] = new Button[5];

    for (int i = 0; i < 5; i++) {
        bt[i] = new Button("Title" + (i + 10));
        bt[i].setUIID("");
        titlesTable.addComponent(bt[i]);
    }


    Object[][] body = new Object[ROWS][TITLES.length];

    bodyTable = new MirroredTable(new DefaultTableModel(TITLES, body), false);

    bodyTable.setMirrorTo(titlesTable);

    titlesTable.setMirrorTo(bodyTable);

    bodyTable.setScrollable(true);

    titlesTable.setScrollableX(true);

    f.setScrollable(false);

    f.setLayout(new BorderLayout());

    titlesTable.setTensileDragEnabled(false);

    bodyTable.setTensileDragEnabled(false);

    titlesTable.setIsScrollVisible(false);

    f.addComponent(BorderLayout.NORTH, titlesTable);

    f.addComponent(BorderLayout.CENTER, bodyTable);


    f.addGameKeyListener(Canvas.LEFT, this);
    f.addGameKeyListener(Canvas.RIGHT, this);
    f.addGameKeyListener(Canvas.UP, this);

    f.setCyclicFocus(false);


    /**
     * buttons adding and their listener
     */
    b = new Button[50][5];
    //Label l[][]=new Label[50][5];

    for (int i = 0; i < 50; i++) {
        for (int j = 0; j < 5; j++) {
            b[i][j] = new Button("Title" + (i + 10));
            b[i][j].setUIID("");
            //l[i][j]=new Label("Title 1");
            bodyTable.addComponent(b[i][j]);

        }
    }





    f.show();

}

public void actionPerformed(ActionEvent evt) {


    if (evt.getKeyEvent() == Canvas.LEFT) {
        if (lastMove != 0) {

            lastMove -= 20;

            bodyTable.setScrollX(lastMove);
            titlesTable.setScrollX(lastMove);
        }

    } else if (evt.getKeyEvent() == Canvas.RIGHT) {
        if (lastMove != lastModifiedMove) {

            lastMove += 20;


            bodyTable.setScrollX(lastMove);

            titlesTable.setScrollX(lastMove);

            if (temp == bodyTable.getScrollX()) {

                lastModifiedMove = temp;
                lastMove = temp;

            } else {
                temp = bodyTable.getScrollX();
            }

        } else {
            lastMove = lastModifiedMove;
        }
    } else if (evt.getKeyEvent() == Canvas.UP) {
    }
}

public void pauseApp() {
}

public void destroyApp(boolean unconditional) {
}
}