[newbie] java.lang.NullPointerException

**jon80** · 05-27-2009, 05:09 PM

Any ideas? Program breaks at the point in bold.

:confused:

Java Code:

[B]FontFrame.java[/B]
package homenetwork.bkr.training;

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

@SuppressWarnings("serial")
public class FontFrame extends JFrame {
	
	public FontFrame() {
		setTitle("GridBagLayout Test");
		setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);
		
		GridBagLayout layout = new GridBagLayout();
		setLayout(layout);
		
		ActionListener listener = new FontAction();
		
		//construct components
		@SuppressWarnings("unused")
		JLabel faceLabel = new JLabel("Face :");
		face = new JComboBox(new String[] {"Serif", "SansSerif", "Monospaced", "Dialog", "DialogInput"});
		face.addActionListener(listener);
		
		@SuppressWarnings("unused")
		JLabel sizeLabel = new JLabel("Size: ");
		size = new JComboBox(new String[] {"8","10","12","15", "18", "24", "36", "48"});
		
		size.addActionListener(listener);
		
		bold = new JCheckBox("Bold");
		bold.addActionListener(listener);
		sample = new JTextArea();
		sample.setText("The quick brown fox jumps over the lazy dog.");
		sample.setEditable(false);
		sample.setLineWrap(true);
		sample.setBorder(BorderFactory.createEtchedBorder());
		
		//add components to grid, using GBC convenience class 
		add(faceLabel, new GBC(0,0).setAnchor(GBC.EAST));
		add(face, new GBC(1,0).setAnchor(GBC.HORIZONTAL));
		add(sizeLabel, new GBC(0,1).setAnchor(GBC.EAST));
		add(size, new GBC(1,1).setFill(GBC.HORIZONTAL).setWeight(100,0).setInsets(1,1,100,100)); //assumed (1,1) to (100,100)
		add(bold, new GBC(0,2,2,1).setAnchor(GBC.CENTER).setWeight(100,0).setInsets(1,1,100,100)); 
		add(italic, new [B]GBC(0,3,2,1).setAnchor(GBC.CENTER).setWeight(100,100)); [/B] 
		add(sample, new GBC(2,0,1,4).setAnchor(GBC.BOTH).setWeight(100,100));
		
	}
	
	public static final int DEFAULT_WIDTH = 300;
	public static final int DEFAULT_HEIGHT = 200;
	
	private JComboBox face;
	private JComboBox size;
	private JCheckBox bold;
	private JCheckBox italic;
	private JTextArea sample;
	
	/**
	 * An action listener that changes the font of the sample text
	 */
	private class FontAction implements ActionListener
	{
		public void actionPerformed(ActionEvent event)
		{
			String fontFace = (String) face.getSelectedItem();
			int fontStyle = (bold.isSelected() ? Font.BOLD : 0) +
			(italic.isSelected() ? Font.ITALIC : 0);
			int fontSize = Integer.parseInt((String) size.getSelectedItem());
			Font font = new Font(fontFace, fontStyle, fontSize);
			sample.setFont(font);
			sample.repaint();
		}
	}
}

[B]GBC.java[/B]
package homenetwork.bkr.training;

import java.awt.*;

@SuppressWarnings("serial")
/** Convenience class GBC which abbreviates java.awt.GridBagConstraints.
 */
public class GBC extends GridBagConstraints {
	/** 
	 * Constructs a GBC with a given gridx and gridy position and all other grid
	 * bag constraint values set to the default.
	 * @param gridx: the gridx position
	 * @param gridy: the gridy position
	 */
	public GBC (int gridx, int gridy)
	{
		this.gridx = gridx;
		this.gridy = gridy;
	}
	
	/** Constructs a GBC with given gridx, gridy, gridwidth, gridheight and all
	 * other grid bag constraint values set to the default.
	 * @param gridx: the gridx position
	 * @param gridy: the gridy position
	 * @param gridwidth: the cell span in x-direction
	 * @param gridheight: the cell span in y-direction
	 */
	public GBC (int gridx, int gridy, int gridwidth, int gridheight)
	{
		this.gridx = gridx;
		this.gridy = gridy;
		this.gridwidth = gridwidth;
		this.gridheight = gridheight;
	}
	
	/** Sets the anchor.
	 * @param anchor: the anchor value
	 * @param return: this object for further modification
	 */
	public GBC setAnchor(int anchor)
	{
		this.anchor = anchor;
		return this;
	}
	
	/**
	 * Sets the fill direction.
	 * @param fill: the fill direction.
	 * @return: this object for further modification
	 */
	public GBC setFill(int fill)
	{
		this.fill = fill;
		return this;
	}
	
	/**
	 * Sets the cell weights
	 * @param weightx: the cell weight in x-direction
	 * @param weighty: the cell height in y-direction
	 * @return: this object for further modification
	 */
	public GBC setWeight(double weightx, double weighty)
	{
		this.weightx = weightx;
		this.weighty = weighty;
		return this;
	}
	
	/**
	 * Sets the insets of this cell.
	 * @param top: the spacing to use on top
	 * @param left: the spacing to use to the left
	 * @param bottom: the spacing to use to the bottom
	 * @param right: the spacing to use to the right
	 * @return: this object for further modification
	 */
	public GBC setInsets(int top, int left, int bottom, int right)
	{
		this.insets = new Insets(top, left, bottom, right);
		return this;
	}
	
	/** Sets the internal padding.
	 * @param: ipadx: the internal padding in x-direction
	 * @param: ipady: the internal padding in y-direction
	 */
	public GBC setIpad(int ipadx, int ipady)
	{
		this.ipadx = ipadx;
		this.ipady = ipady;
		return this;
	}
}

Error:
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at java.awt.Container.addImpl(Unknown Source)
at java.awt.Container.add(Unknown Source)
at javax.swing.JFrame.addImpl(Unknown Source)
at java.awt.Container.add(Unknown Source)
at homenetwork.bkr.training.FontFrame.<init>(FontFram e.java:46)
at homenetwork.bkr.training.GridBagLayoutTest$1.run(G ridBagLayoutTest.java:14)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilter s(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(U nknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarch y(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

**hardwired** · 05-27-2009, 08:08 PM

The JCheckBox "italic" has not been instantiated and is therefore null.

**jon80** · 05-27-2009, 08:23 PM

Thanks that was it.

Now I'm getting another error:

Exception in thread "AWT-EventQueue-0" java.lang.IllegalArgumentException: illegal anchor value
at java.awt.GridBagLayout.AdjustForGravity(Unknown Source)
at java.awt.GridBagLayout.adjustForGravity(Unknown Source)
at java.awt.GridBagLayout.ArrangeGrid(Unknown Source)
at java.awt.GridBagLayout.arrangeGrid(Unknown Source)
at java.awt.GridBagLayout.layoutContainer(Unknown Source)
at java.awt.Container.layout(Unknown Source)
at java.awt.Container.doLayout(Unknown Source)
at java.awt.Container.validateTree(Unknown Source)
at java.awt.Container.validateTree(Unknown Source)
at java.awt.Container.validateTree(Unknown Source)
at java.awt.Container.validateTree(Unknown Source)
at java.awt.Container.validate(Unknown Source)
at java.awt.Window.show(Unknown Source)
at java.awt.Component.show(Unknown Source)
at java.awt.Component.setVisible(Unknown Source)
at java.awt.Window.setVisible(Unknown Source)
at homenetwork.bkr.training.GridBagLayoutTest$1.run(G ridBagLayoutTest.java:16)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilter s(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(U nknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarch y(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
Exception in thread "AWT-EventQueue-0" java.lang.IllegalArgumentException: illegal anchor value
at java.awt.GridBagLayout.AdjustForGravity(Unknown Source)
at java.awt.GridBagLayout.adjustForGravity(Unknown Source)
at java.awt.GridBagLayout.ArrangeGrid(Unknown Source)
at java.awt.GridBagLayout.arrangeGrid(Unknown Source)
at java.awt.GridBagLayout.layoutContainer(Unknown Source)
at java.awt.Container.layout(Unknown Source)
at java.awt.Container.doLayout(Unknown Source)
at java.awt.Container.validateTree(Unknown Source)
at java.awt.Container.validateTree(Unknown Source)
at java.awt.Container.validateTree(Unknown Source)
at java.awt.Container.validateTree(Unknown Source)
at java.awt.Container.validate(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilter s(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(U nknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarch y(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

Updated code:

Project GridBagLayoutTest

Java Code:

[B]FontFrame.java[/B]
package homenetwork.bkr.training;

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

@SuppressWarnings("serial")
public class FontFrame extends JFrame {
	
	public FontFrame() {
		setTitle("GridBagLayout Test");
		setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);
		
		GridBagLayout layout = new GridBagLayout();
		setLayout(layout);
		
		ActionListener listener = new FontAction();
		
		//construct components
		@SuppressWarnings("unused")
		JLabel faceLabel = new JLabel("Face :");
		face = new JComboBox(new String[] {"Serif", "SansSerif", "Monospaced", "Dialog", "DialogInput"});
		face.addActionListener(listener);
		
		@SuppressWarnings("unused")
		JLabel sizeLabel = new JLabel("Size: ");
		size = new JComboBox(new String[] {"8","10","12","15", "18", "24", "36", "48"});
		
		size.addActionListener(listener);
		
		bold = new JCheckBox("Bold");
		bold.addActionListener(listener);
		
		italic = new JCheckBox("Italic");
		italic.addActionListener(listener);

		sample = new JTextArea();
		sample.setText("The quick brown fox jumps over the lazy dog.");
		sample.setEditable(false);
		sample.setLineWrap(true);
		sample.setBorder(BorderFactory.createEtchedBorder());
		
		//add components to grid, using GBC convenience class 
		add(faceLabel, new GBC(0,0).setAnchor(GBC.EAST));
		add(face, new GBC(1,0).setAnchor(GBC.HORIZONTAL));
		add(sizeLabel, new GBC(0,1).setAnchor(GBC.EAST));
		add(size, new GBC(1,1).setFill(GBC.HORIZONTAL).setWeight(100,0).setInsets(1,1,100,100)); //assumed (1,1) to (100,100)
		add(bold, new GBC(0,2,2,1).setAnchor(GBC.CENTER).setWeight(100,0).setInsets(1,1,100,100)); 
		add(italic, new GBC(0,3,2,1).setAnchor(GBC.CENTER).setWeight(100,100)); //ERROR:java.lang.NullPointerException
		add(sample, new GBC(2,0,1,4).setAnchor(GBC.BOTH).setWeight(100,100));
		
	}
	
	public static final int DEFAULT_WIDTH = 300;
	public static final int DEFAULT_HEIGHT = 200;
	
	private JComboBox face;
	private JComboBox size;
	private JCheckBox bold;
	private JCheckBox italic;
	private JTextArea sample;
	
	/**
	 * An action listener that changes the font of the sample text
	 */
	private class FontAction implements ActionListener
	{
		public void actionPerformed(ActionEvent event)
		{
			String fontFace = (String) face.getSelectedItem();
			int fontStyle = (bold.isSelected() ? Font.BOLD : 0) +
			(italic.isSelected() ? Font.ITALIC : 0);
			int fontSize = Integer.parseInt((String) size.getSelectedItem());
			Font font = new Font(fontFace, fontStyle, fontSize);
			sample.setFont(font);
			sample.repaint();
		}
	}
}


[B]GridBagLayoutTest.java[/B]
package homenetwork.bkr.training;

import java.awt.*;
import javax.swing.*;

public class GridBagLayoutTest {

	public static void main (String[] args)
	{
		EventQueue.invokeLater(new Runnable()
		{
			public void run()
			{
				FontFrame frame = new FontFrame();
				frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
				frame.setVisible(true);
			}
		});
	}
}

**hardwired** · 05-27-2009, 08:32 PM

Java Code:

        //add components to grid, using GBC convenience class
        add(faceLabel,
                new GBC(0,0).setAnchor(GBC.EAST));
        add(face,
                new GBC(1,0)[b]//.setAnchor(GBC.HORIZONTAL));[/b]
                            .setFill(GBC.HORIZONTAL));
        add(sizeLabel, new GBC(0,1).setAnchor(GBC.EAST));
        //assumed (1,1) to (100,100)
        add(size,
                new GBC(1,1).setFill(GBC.HORIZONTAL)
                            .setWeight(100,0)
                            .setInsets(1,1,100,100));
        add(bold,
                new GBC(0,2,2,1).setAnchor(GBC.CENTER)
                                .setWeight(100,0)
                                .setInsets(1,1,100,100));
        add(italic,
                new GBC(0,3,2,1).setAnchor(GBC.CENTER)
                                .setWeight(100,100));
        add(sample,
                new GBC(2,0,1,4)[b]//.setAnchor(GBC.BOTH)[/b]
                                .setFill(GBC.BOTH)
                                .setWeight(100,100));

**jon80** · 05-27-2009, 08:42 PM

hmm...nope, still the same error

**xierangh** · 09-25-2009, 08:43 AM

//add components to grid, using GBC convenience class
add(faceLabel, new GBC(0,0).setAnchor(GBC.EAST));
add(face, new GBC(1,0).setAnchor(GBC.HORIZONTAL));
add(sizeLabel, new GBC(0,1).setAnchor(GBC.EAST));

the code whick underline is wrong.

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