TableCellRenderer Java的异常行为

Question

I'm trying to implement a custom TableCellRenderer on a jtable. the table is set to 100 rows and 100 columns. This table should contain all the glyphs for a specified font. My problem is that when the table is not fully complete with values, on the first column it puts the last value until it reaches the bottom of the table. Below i have the code for my custom renderer and a screenshot with the strange behaviour. Any help would be apreciated.

public class FontRenderer extends JLabel implements TableCellRenderer
{
Font desired_font;
Object prec_value;

public FontRenderer(Font f)
{
    desired_font = f;
}

public Component getTableCellRendererComponent(JTable table, Object value,
        boolean isSelected, boolean hasFocus, int rowIndex, int vColIndex)
{


    setOpaque(true);
    setHorizontalAlignment(SwingConstants.CENTER);
    setBackground(new Color(255, 255, 255));
    if (isSelected)
    {
        if (value == null)
        {
            setText("");
        }
        else
        {
            setText(value.toString());
        }
        setFont(desired_font);
        setBackground(new Color(56, 195, 254));
    }
    if (value == null)
    {
        setText("");
    }
    else
    {
        if(value==null)
            table.setValueAt(null, rowIndex, vColIndex);
        else
        setText(value.toString());
            //table.setValueAt(value.toString(), rowIndex, vColIndex);

    }
    setFont(desired_font);

    return this;
}
}

Edit: Here is the code where I populate the table.

while (cnt_i < 100) {
    while (cnt_j < 100) {
        if (my_fnt.canDisplay((char) unicode_char) && glyph_count <= total_glyphs) {
            jTable1.setValueAt((char) unicode_char, cnt_i, cnt_j);
            cnt_j++;
            if (glyph_count == total_glyphs) {
                break;
            }
            glyph_count++;
        }
        unicode_char++;
    }
    cnt_i++;
    cnt_j = 0;
}

Solved it. Ty all. it was how i populated the table. the following code has the changes:

while (cnt_i < 100) {
    while (cnt_j < 100) {
        if (my_fnt.canDisplay((char) unicode_char) && glyph_count <= total_glyphs) {
            if (glyph_count == total_glyphs) {
                break;
            }
            else {
                jTable1.setValueAt((char) unicode_char, cnt_i, cnt_j);
                cnt_j++;
                glyph_count++;
            }
        }
        unicode_char++;
    }
    cnt_i++;
    cnt_j = 0;
}

Answer 1

1) there are about Unicode Chars, I think that is not job for Renderer

2) set JTable#Font for JTable rather that passing parameters for Renderer

3) use prepareRenderer if you want to change bunch of data on Runtime

4) most important would be to see how did you populate JTable's data and define/set for Font(s)

Answer 2

I dont think that your problem is the CellRenderer ..

But I cleaned it up a bit for you

public class FontRenderer extends JLabel implements TableCellRenderer
{
    Font desired_font;
    Object prec_value;

    public FontRenderer(Font f)
    {
        desired_font = f;
    }

    public Component getTableCellRendererComponent(JTable table, Object value,
            boolean isSelected, boolean hasFocus, int rowIndex, int vColIndex)
    {
        setOpaque(true);
        setHorizontalAlignment(SwingConstants.CENTER);
        setBackground(new Color(255, 255, 255));
        setFont(desired_font);

        if (value == null)
        {
            setText("");
        }
        else
        {
            setText(value.toString());
        }

        if (isSelected)
        {
            setBackground(new Color(56, 195, 254));
        }

        //what was that for?
        //table.setValueAt(null, rowIndex, vColIndex);

        return this;
    }
}

Answer 3

As an aside, canDisplay(int) may help determine if a particular code point has a glyph in a given Font . REPLACEMENT CHARACTER is a convenient placeholder, and GlyphSet is a related example.