I am trying to use a JLabel
for column headers in a JTable
, and override paintComponent
to color a percentage of non-null values for each column, kind of like a background visualization of a fill rate. It seems to be quite straightforward, but for some reason visualization is always applied to the first (left) column only, like in the picture below:
The "fill rate" is just random in the example, but only applied for the first column although looping through all columns.
Edit: Using Java 8 and MacOS
The full source code is:
import javax.swing.*;
import javax.swing.table.TableCellRenderer;
import javax.swing.table.TableColumnModel;
import java.awt.*;
import java.util.Random;
public class CustomTable extends JFrame {
private static class CustomLabel extends JLabel {
public CustomLabel(String text) {
super(text);
}
@Override
protected void paintComponent(Graphics g) {
Random random = new Random(System.currentTimeMillis());
int w = random.nextInt(getWidth());
int h = getHeight();
int x = getX();
int y = getY();
Graphics2D g2 = (Graphics2D) g.create();
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2.setColor(Color.green);
g2.fillRect(x, y, w, h);
super.paintComponent(g2);
g2.dispose();
}
}
private static class CustomTableCellRenderer implements TableCellRenderer {
@Override
public Component getTableCellRendererComponent(JTable table, Object value, boolean isSelected, boolean hasFocus, int row, int column) {
return ((CustomLabel) value);
}
}
public CustomTable() {
setTitle("CustomTable");
setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
setSize(320, 240);
setLayout(new GridLayout(1, 1));
String[] columns = {"id", "fname", "lname"};
String[][] data = {{"1", "John", "Doe"}, {"2", "Jane", "Doe"}};
JTable jt = new JTable(data, columns);
TableColumnModel model = jt.getColumnModel();
for (int i = 0; i < columns.length; i++) {
CustomLabel cl = new CustomLabel(columns[i]);
model.getColumn(i).setHeaderValue(cl);
model.getColumn(i).setHeaderRenderer(new CustomTableCellRenderer());
}
add(new JScrollPane(jt));
setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getCrossPlatformLookAndFeelClassName());
} catch (Exception e) {
}
new CustomTable();
}
});
}
}
Painting of a Swing component should always be done relative the to component, not the location of the component.
So custom painting should always have an x/y location of (0, 0), if you want to paint from the top/left of the component.
int x = getX();
int y = getY();
Graphics2D g2 = (Graphics2D) g.create();
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2.setColor(Color.green);
g2.fillRect(x, y, w, h);
Should be:
//int x = getX();
//int y = getY();
Graphics2D g2 = (Graphics2D) g.create();
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2.setColor(Color.green);
//g2.fillRect(x, y, w, h);
g2.fillRect(0, 0, w, h);
Also, I assume you are just using the "random" method for the simplicity of the example code. As suggested above in the comment you should not be using random in a painting method since the paintComponent method is called every time a cell needs to be repainted. For example, resize the width of the frame to see the random results.