Re: Custom JScrollPane - Double JScrollBars

From:

"David A. Redick" <tinyweldingtorch@gmail.com>

Newsgroups:

comp.lang.java.programmer

Date:

Tue, 29 Apr 2008 07:07:18 -0700 (PDT)

Message-ID:

<5e0d073f-cf02-40f3-8671-797e289dc3a4@59g2000hsb.googlegroups.com>

I played around some more this morning and I think I figured it out.
Just add the SpringyScrollBar class and replace the DoubleScrollPane
class.
The rest is the same.

class SpringyScrollBar extends JScrollBar
{
    public SpringyScrollBar(int iOrientation)
    {
        super(iOrientation);

        setMaximum(99);
        setMinimum(0);
        moveToMid();
    }

    public int getMid()
    {
        int iMid = getMaximum() - getMinimum() + 1;
        iMid /= 2;

        int iSize = getVisibleAmount()/2;

        iMid -= iSize;

        return iMid;
    }

    public void moveToMid()
    {
        setValue(getMid());
    }

    public int getSpeed()
    {
        int i = getValue();
        i -= getMid();

        if(i < 0)
            i *= -1;

        return i;
    }

    public int getDir()
    {
        int i = getValue();
        i -= getMid();

        if(i < 0)
            return -1;

        return 1;
    }
}

// 2 horiz. bars and 2 vert. bars.
class DoubleScrollPane extends JScrollPane implements
AdjustmentListener
{
    protected SpringyScrollBar m_pHSB2;
    protected SpringyScrollBar m_pVSB2;

    DoubleScrollPane(Component pView)
    {
        super(pView);

setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);

setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_ALWAYS);

        m_pHSB2 = new SpringyScrollBar(JScrollBar.HORIZONTAL);
        m_pVSB2 = new SpringyScrollBar(JScrollBar.VERTICAL);

        m_pHSB2.addAdjustmentListener(this);
        m_pVSB2.addAdjustmentListener(this);

        m_pHSB2.setVisible(true);
        m_pVSB2.setVisible(true);

        add(m_pHSB2);
        add(m_pVSB2);

        setLayout(new DoubleScrollPaneLayout(m_pHSB2, m_pVSB2));
    }

    public void adjustmentValueChanged(AdjustmentEvent e)
    {
        SpringyScrollBar p = (SpringyScrollBar) e.getAdjustable();
        boolean bIsHoriz = p.equals(m_pHSB2);
        int iSpeed = p.getSpeed();
        int iDir = p.getDir();

        // Adjust position.
        JScrollBar pBar;
        if(bIsHoriz)
            pBar = horizontalScrollBar;
        else
            pBar = verticalScrollBar;

        int iInc = pBar.getUnitIncrement(iDir);
        iInc *= iSpeed;
        int iValue = pBar.getValue();
        iValue += iDir*iInc;
        pBar.setValue(iValue);

        if(!e.getValueIsAdjusting())
        {
            // move back to center
            p.moveToMid();
        }
    }
}