Java Actionlisteners错误
我已经试了很长一段时间了,我不知道问题出在哪里。我在我的JmenuItems上使用actionlisteners,但是当我启动程序并单击按钮时,我会出现错误,我不明白为什么?感谢您的帮助 im使用的按钮代码:Java Actionlisteners错误,java,swing,nullpointerexception,jmenuitem,Java,Swing,Nullpointerexception,Jmenuitem,我已经试了很长一段时间了,我不知道问题出在哪里。我在我的JmenuItems上使用actionlisteners,但是当我启动程序并单击按钮时,我会出现错误,我不明白为什么?感谢您的帮助 im使用的按钮代码: final JMenuItem Start = new JMenuItem("Start"); Start.addActionListener(new ActionListener() { public void actionPerformed(ActionEve
final JMenuItem Start = new JMenuItem("Start");
Start.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
if(e.getSource() == Start) {
pane.GuessBox.setEditable(true);
}
}
});
我收到的错误是:
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at Main$1.actionPerformed(Main.java:37)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.AbstractButton.doClick(Unknown Source)
at javax.swing.plaf.basic.BasicMenuItemUI.doClick(Unknown Source)
at javax.swing.plaf.basic.BasicMenuItemUI$Handler.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$200(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.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
猜框:
JTextField GuessBox = new JTextField(1);
GuessBox.setEditable(false);
GuessBox.addActionListener(new Command());
GuessPanel.add(GuessBox);
看来你的问题可能就在这里
pane.GuessBox.setEditable(true)代码>
如果未实例化GuessBox
(或pane
)或未将其设置为null,则无法在null上调用setEditable。看起来您的问题可能就在这里
pane.GuessBox.setEditable(true)代码>
如果未实例化GuessBox
(或pane
)或未将其设置为null,则无法在null上调用setEditable。看起来您的问题可能就在这里
pane.GuessBox.setEditable(true)代码>
如果未实例化GuessBox
(或pane
)或未将其设置为null,则无法在null上调用setEditable。看起来您的问题可能就在这里
pane.GuessBox.setEditable(true)代码>
如果GuessBox
(或pane
)未实例化(或设置为null),则不能对null调用setEditable。这是Main.java?pane.GuessBox.setEditable(true)中的第37行;什么是窗格
?什么是窗格.猜测框
?我可以向你们保证其中一个是空的,我想窗格是空的,请阅读Main.java?pane.Guessbox.setEditable(true)中的第37行;什么是窗格
?什么是窗格.猜测框
?我可以向你们保证其中一个是空的,我想窗格是空的,请阅读Main.java?pane.Guessbox.setEditable(true)中的第37行;什么是窗格
?什么是窗格.猜测框
?我可以向你们保证其中一个是空的,我想窗格是空的,请阅读Main.java?pane.Guessbox.setEditable(true)中的第37行;什么是窗格
?什么是窗格.猜测框
?我可以向你们保证其中一个是空的,我认为窗格是空的。请阅读关于未实例化和空是两个不同的东西。否则你是对的。@SimonAndréForsberg-是的,这是真的。我会把“ie”改成“eg”之类的。谢谢:)未实例化和为null是两件不同的事情。否则你是对的。@SimonAndréForsberg-是的,这是真的。我会把“ie”改成“eg”之类的。谢谢:)未实例化和为null是两件不同的事情。否则你是对的。@SimonAndréForsberg-是的,这是真的。我会把“ie”改成“eg”之类的。谢谢:)未实例化和为null是两件不同的事情。否则你是对的。@SimonAndréForsberg-是的,这是真的。我会把“ie”改成“eg”之类的。谢谢:)