JButton-放置图片不起作用

Question

I'm just a freshman for this swing stuff so I've encountered this problem:

I'm trying to put an image to my button but whenever I try to add, it returns this

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at javax.swing.ImageIcon.<init>(ImageIcon.java:217)
at gui.MainPanel.<init>(MainPanel.java:45)
at gui.IntroPanel$2.actionPerformed(IntroPanel.java:62)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2346)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6527)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
at java.awt.Component.processEvent(Component.java:6292)
at java.awt.Container.processEvent(Container.java:2234)
at java.awt.Component.dispatchEventImpl(Component.java:4883)
at java.awt.Container.dispatchEventImpl(Container.java:2292)
at java.awt.Component.dispatchEvent(Component.java:4705)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4898)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4533)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4462)
at java.awt.Container.dispatchEventImpl(Container.java:2278)
at java.awt.Window.dispatchEventImpl(Window.java:2739)
at java.awt.Component.dispatchEvent(Component.java:4705)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:746)
at java.awt.EventQueue.access$400(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:697)
at java.awt.EventQueue$3.run(EventQueue.java:691)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:86)
at java.awt.EventQueue$4.run(EventQueue.java:719)
at java.awt.EventQueue$4.run(EventQueue.java:717)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:716)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)

I'm a little bit confused because in other entries people say that It works fine, however, it became a challenging duty for me to overcome. You should know in advance that MainPanel class represents a panel in the frame, inside the MainPanel , I have input panel which I'm trying to place my JButton . Here's my code:

 public class MainPanel extends JPanel {
   private JPanel inputPanel;
   private JButton inputButton;

   public MainPanel() {

    setBackground( new Color( 250, 250, 250));
    setPreferredSize( new Dimension( 1400, 800) );
    setLayout(new BorderLayout());

    inputPanel = new JPanel();

    inputButton = new JButton( new ImageIcon(getClass().getResource("images/input.png")));

    inputPanel.add( inputButton );

    add( inputPanel);
    }
  }

Edit: My folder structure is simple in

• Project → gui (package) → images (folder) this is for images.
• Project → gui (package) → MainPanel.java (and all other source code).

SOLUTION: The file directory should have been like ../images/input.png .

Answer 1

Obviously the problem is the code new ImageIcon(getClass().getResource("images/input.png"))

It can't dine the image there. Check the path "images/input.png". It could be "/images/input.png". Are you sure it exists together with classes?

Answer 2

Icon iconInput;
ClassLoader classLoader;
InputStream inputStreamIcon;

try {
    classLoader = Thread.currentThread().getContextClassLoader();

    inputStreamIcon = classLoader.getResourceAsStream("images/input.png");
    iconInput = new ImageIcon(ImageIO.read(inputStreamIcon));
}
catch (IOException e) {
    System.err.println(ioe);
}

JButton inputButton = new JButton(iconInput);