Card Layout button glitch

[dd2308]

Hi,
I reacently tried using card layout, and i got it to work ,but when i try to add buttons i get these errors;

public class CardLayoutExample {
	JFrame guiFrame;
	CardLayout cards;
	JPanel cardPanel;

	public static void main(String[] args) {

		// Use the event dispatch thread for Swing components
		EventQueue.invokeLater(new Runnable() {

			@Override
			public void run() {

				try {
					new CardLayoutExample();
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
		});

	}

	public CardLayoutExample() throws IOException {
		guiFrame = new JFrame();

		// make sure the program exits when the frame closes
		guiFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		guiFrame.setTitle("CardLayout Example");
		guiFrame.setSize(800, 600);

		// This will center the JFrame in the middle of the screen
		guiFrame.setLocationRelativeTo(null);
		guiFrame.setLayout(new BorderLayout());

		// creating a border to highlight the JPanel areas
		Border outline = BorderFactory.createLineBorder(Color.black);

		JPanel tabsPanel = new JPanel();
		tabsPanel.setBorder(outline);
		JButton switchCards = new JButton("Switch Card");
		switchCards.setActionCommand("Switch Card");
		switchCards.addActionListener(new ActionListener() {
			@Override
			public void actionPerformed(ActionEvent event) {
				cards.next(cardPanel);
				
			}
		});
		tabsPanel.add(switchCards);

		guiFrame.add(tabsPanel, BorderLayout.NORTH);// add tabs panel at top

		cards = new CardLayout();
		cardPanel = new JPanel();
		cardPanel.setLayout(cards);
		cards.show(cardPanel, "Fruits");
		final BufferedImage img = ImageIO.read(new File(
				"C:/dq5-orc-king.jpg"));
		final BufferedImage img2 = ImageIO.read(new File(
				"C:/drak slime.png"));
		
		final BufferedImage img3 = ImageIO.read(new File(
				"C:/king slime.jpg"));
		JPanel firstCard = null;
		JButton button = new JButton();
		//firstCard.add(button);
		//ImageIcon slimeIcon = new ImageIcon("C:/Users/Denys/workspace/HelloWorld/Dragon quest  game/slime.png");
		//button.setIcon();
		
		firstCard = new JPanel() {
				
			@Override
			public void paint(Graphics g) {
				 Graphics2D g2d = (Graphics2D) g;
				    int x = (this.getWidth() - img2.getWidth(null)) / 2;// get width of image and then utalize window frame 
				    int y = (this.getHeight() - img2.getHeight(null)) / 2;// get height
				g.drawImage(img2, x, y, null);
				
				 repaint();
				 
			}
		};
		JPanel thirdCard = null;
		thirdCard = new JPanel() {

			@Override
			public void paint(Graphics g) {
				 Graphics2D g2d = (Graphics2D) g;
				    int x = (this.getWidth() - img3.getWidth(null)) / 2;
				    int y = (this.getHeight() - img3.getHeight(null)) / 2;
				g.drawImage(img3, x, y, null);
				 repaint();
				 
			}
		};
		
		JPanel secondCard = null;
		secondCard = new JPanel() {

			@Override
			public void paint(Graphics g) {
				g.drawImage(img, 0, 0, null);
				 Graphics2D g2d = (Graphics2D) g;
				    int x = (this.getWidth() - img.getWidth(null)) / 2;
				    int y = (this.getHeight() - img.getHeight(null)) / 2;
				
				repaint();

			}

		};

		cardPanel.add(firstCard);
		cardPanel.add(secondCard);
		cardPanel.add(thirdCard);

		guiFrame.add(tabsPanel, BorderLayout.NORTH);//at top
		guiFrame.add(cardPanel, BorderLayout.CENTER);// add to frame in center
		guiFrame.setVisible(true);
	}

	// All the buttons are following the same pattern
	// so create them all in one place.

}

Whats wrong with the buttons?

[Fubarable]

Hi,
I reacently tried using card layout, and i got it to work ,but when i try to add buttons i get these errors;
...

What errors are you getting?

[Fubarable]

Also, your JPanel's should draw in a paintComponent method override, not a paint method override, and more importantly never ever call repaint() from within a paint or paintComponent method.

[DarrylBurke]

Hi,
I reacently tried using card layout, and i got it to work ,but when i try to add buttons i get these errors;

What errors?

db

[dd2308]

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at CardLayoutExample.<init>(CardLayoutExample.java:87 )
at CardLayoutExample$1.run(CardLayoutExample.java:34)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$000(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPri vilege(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)

[dd2308]

...more importantly never ever call repaint() from within a paint or paintComponent method.

How would i call it then

[Fubarable]

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at CardLayoutExample.<init>(CardLayoutExample.java:87 )
at CardLayoutExample$1.run(CardLayoutExample.java:34)

Please show us which lines are 87 and 34.

How would I call it then

It depends on what you're trying to do. But calling it from inside of these methods risk a bad recursion.

[Fubarable]

Let me guess, one of the lines is this one:

cards.show(cardPanel, "Fruits");

You seem to be calling this before you've added any components to the cardPanel. Not only that, you don't appear to be using String literals much less one refering to fruits" when you do in fact get around to adding components to the cardPanel.

[dd2308]

My errors are gone now that i put the show command at the end. Thank you all.