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我在使用我的swing GUI时遇到了一个奇怪的问题。我正在尝试刷新按钮清除组合框列表以刷新组件。它不工作,我可能只是犯了一个愚蠢的错误。这里是我的代码:Java Swing GUI组合框问题
public class GUI2 extends JFrame implements ActionListener {
/**
*
*/
private JPanel contentPane;
public JComboBox combobox;
public ReadJoystick stick;
private JButton refresh;
/**
* Launch the application.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
GUI2 frame = new GUI2();
frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the frame.
*/
public GUI2() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setBounds(100, 100, 450, 300);
contentPane = new JPanel();
contentPane.setLayout(new BorderLayout(0, 0));
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
setContentPane(contentPane);
StickWidget Left = new StickWidget();
Left.setName("Left Stick");
contentPane.add(Left.draw(), BorderLayout.WEST);
StickWidget Right = new StickWidget();
Right.setName("Right Stick");
contentPane.add(Right.draw(), BorderLayout.EAST);
JPanel panel = new JPanel();
contentPane.add(panel, BorderLayout.CENTER);
panel.setLayout(new BorderLayout(0, 0));
JPanel panel_1 = new JPanel();
panel.add(panel_1, BorderLayout.NORTH);
ReadJoystick stick = new ReadJoystick();
JComboBox combobox = new JComboBox<Object>(stick.read().toArray());
combobox.setPrototypeDisplayValue("XXXXXXX");
panel_1.add(combobox);
JButton btnRefresh = new JButton("Refresh");
btnRefresh.addActionListener(this);
panel_1.add(btnRefresh);
}
public void actionPerformed(ActionEvent e) {
combobox.removeAll();
}
}
此代码当前读取计算机可用的操纵杆并将它们显示在组合框列表中。下面是我目前的GUI的一个画面:
我每次按下刷新按钮,它抛出这个错误:
typeException in thread "AWT-EventQueue-0" java.lang.NullPointerException
at xxxxxxxx.xxxxxx.xxxxxx.GUI2.actionPerformed(GUI2.java:74)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
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:6516)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
at java.awt.Component.processEvent(Component.java:6281)
at java.awt.Container.processEvent(Container.java:2229)
at java.awt.Component.dispatchEventImpl(Component.java:4872)
at java.awt.Container.dispatchEventImpl(Container.java:2287)
at java.awt.Component.dispatchEvent(Component.java:4698)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
at java.awt.Container.dispatchEventImpl(Container.java:2273)
at java.awt.Window.dispatchEventImpl(Window.java:2719)
at java.awt.Component.dispatchEvent(Component.java:4698)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:747)
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.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:720)
at java.awt.EventQueue$4.run(EventQueue.java:718)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:717)
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)
[请尝试搜索(http://stackoverflow.com/questions/12249336 /删除,所有的项目,从-A-组合框式的Java) – alex2410