I have a JFrame with two panels. And I am setting the UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName()) in a class which extends JFrame.So It works fine for both panels If I dont've JTable in it. But If I add JTable to any panel then going to that panel gives me NullPointerException like below.
So what is the problem here, am I need to set anything for JTable also
EDIT: I figured it out that the problem is not with JTable but with tableCellRenderer. I am adding a tableRenderer like below
public class Frame extends JFrame
{
public void initialize()
{
try
{
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
}
catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException e)
{
e.printStackTrace();
}
JPanel panel1 = new JPanel();
panel1.add(new JLabel("Panel1"));
JPanel panel2 = new JPanel();
JTable table = new JTable(2,2);
table.getColumnModel().getColumn(1).setCellRenderer(new CheckBoxRenderer()); // Adding this renderer creates me problem
JScrollPane jScrollPane = new JScrollPane(table);
jScrollPane.setSize(100, 100);
panel2.add(jScrollPane);
JTabbedPane tabbedPane = new JTabbedPane();
tabbedPane.addTab("Panel1", panel1);
tabbedPane.addTab("Panel2", panel2);
add(tabbedPane);
setSize(400, 400);
setVisible(true);
}
class CheckBoxRenderer implements TableCellRenderer
{
JCheckBox check = new JCheckBox();
public Component getTableCellRendererComponent(JTable table, Object obj, boolean isSelected, boolean hasFocus, int row, int column)
{
if (row != 0 && obj instanceof Boolean)
{
check.setSelected((Boolean) obj);
return check;
}
return null;
}
}
public static void main(String[] args)
{
Frame frame = new Frame();
frame.initialize();
}
}
So this gives me NullPointerException. And If I remove the setCellRenderer line it works fine. Can someone help me out
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at javax.swing.plaf.synth.SynthTableUI.paintCell(SynthTableUI.java:685)
at javax.swing.plaf.synth.SynthTableUI.paintCells(SynthTableUI.java:581)
at javax.swing.plaf.synth.SynthTableUI.paint(SynthTableUI.java:365)
at javax.swing.plaf.synth.SynthTableUI.update(SynthTableUI.java:276)
at javax.swing.JComponent.paintComponent(JComponent.java:779)
at javax.swing.JComponent.paint(JComponent.java:1055)
at javax.swing.JComponent.paintChildren(JComponent.java:888)
at javax.swing.JComponent.paint(JComponent.java:1064)
at javax.swing.JViewport.paint(JViewport.java:731)
at javax.swing.JComponent.paintChildren(JComponent.java:888)
at javax.swing.JComponent.paint(JComponent.java:1064)
at javax.swing.JComponent.paintChildren(JComponent.java:888)
at javax.swing.JComponent.paint(JComponent.java:1064)
at javax.swing.JComponent.paintChildren(JComponent.java:888)
at javax.swing.JComponent.paint(JComponent.java:1064)
at javax.swing.JComponent.paintChildren(JComponent.java:888)
at javax.swing.JComponent.paint(JComponent.java:1064)
at javax.swing.JComponent.paintToOffscreen(JComponent.java:5232)
at javax.swing.BufferStrategyPaintManager.paint(BufferStrategyPaintManager.java:295)
at javax.swing.RepaintManager.paint(RepaintManager.java:1249)
at javax.swing.JComponent._paintImmediately(JComponent.java:5180)
at javax.swing.JComponent.paintImmediately(JComponent.java:4991)
at javax.swing.RepaintManager$3.run(RepaintManager.java:808)
at javax.swing.RepaintManager$3.run(RepaintManager.java:796)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:796)
at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:769)
at javax.swing.RepaintManager.prePaintDirtyRegions(RepaintManager.java:718)
at javax.swing.RepaintManager.access$1100(RepaintManager.java:62)
at javax.swing.RepaintManager$ProcessingRunnable.run(RepaintManager.java:1677)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:312)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:745)
at java.awt.EventQueue.access$300(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:706)
at java.awt.EventQueue$3.run(EventQueue.java:704)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:715)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)
EDIT2: On googling I found this NullPointerException at javax.swing.plaf.synth.SynthContext.getPainter.
And If I do UIManager.setLookAndFeel("com.sun.java.swing.plaf.motif.MotifLookAndFeel"); which works fine. But I am using Ubuntu OS so I need GTK look. So I did UIManager.setLookAndFeel("ccom.sun.java.swing.plaf.gtk.GTKLookAndFeel"); but this again gives me the exception. I can't figure it out what is wrong here. I came to know about these packages from the actual implementation of getSystemLookAndFeelClassName()
This code works fine for me now
class CheckBoxRenderer implements TableCellRenderer
{
JCheckBox check = new JCheckBox();
@Override
public Component getTableCellRendererComponent(JTable table, Object obj, boolean isSelected, boolean hasFocus, int row, int column)
{
if (row != 0 && obj instanceof Boolean)
{
check.setSelected((Boolean) obj);
}
// return null; this line gives NullPointerException
return check;
}
}
Finally, I figured out the problem. The problem is with the above line return null. Returning null is giving the NullPointerException. Because if we see the implementation of
private void paintCell(SynthContext context, Graphics g, Rectangle cellRect, int row, int column) of SynthTableUI.class it has a line as
Color b = component.getBackground(); but because I am returning null, it is trying to get the background of null. That is what the actual problem is. Thanks for all your help