gpt4 book ai didi

java - 线程 "AWT-EventQueue-1"中的异常

转载 作者:行者123 更新时间:2023-11-29 07:20:51 25 4
gpt4 key购买 nike

我会让这一切变得又快又容易。

我收到 NPE 错误...

Row: 0
You pressed on Item 1
Removed cancel for Item 1
Exception in thread "AWT-EventQueue-1" java.lang.NullPointerException
at inv$MousePopupListener.checkPopup(inv.java:118)
at inv$MousePopupListener.mouseReleased(inv.java:104)
at java.awt.AWTEventMulticaster.mouseReleased(AWTEventMulticaster.java:2
73)
at java.awt.Component.processMouseEvent(Component.java:6267)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3267)
at java.awt.Component.processEvent(Component.java:6032)
at java.awt.Container.processEvent(Container.java:2041)
at java.awt.Component.dispatchEventImpl(Component.java:4630)
at java.awt.Container.dispatchEventImpl(Container.java:2099)
at java.awt.Component.dispatchEvent(Component.java:4460)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4577
)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4238)

at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4168)
at java.awt.Container.dispatchEventImpl(Container.java:2085)
at java.awt.Component.dispatchEvent(Component.java:4460)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThre
ad.java:269)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.
java:184)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThre
ad.java:174)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)

at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)

at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)

我到处搜索,但我不知道如何解决:

import java.awt.*;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseAdapter;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
import javax.swing.border.*;
import javax.swing.event.*;

public class inv extends JApplet implements MouseListener
{
public JList listbox;
public JPopupMenu popup;
public JMenuItem item;

public JPopupMenu useDropPopup;
public JPopupMenu useCancelPopup;



public void init() {
ActionListener menuListener = new ActionListener()
{
public void actionPerformed(ActionEvent event)
{
String invAction = event.getActionCommand();


int itemSelect = listbox.getSelectedIndex();
Object actItem = listbox.getModel().getElementAt(itemSelect);

System.out.println("Popup menu item [" + invAction + "] [ " + actItem + " ] was pressed.");
}
};

useDropPopup = new JPopupMenu();
useCancelPopup = new JPopupMenu();

JMenuItem useMenuItem = new JMenuItem("Use");
useMenuItem.addActionListener(menuListener);
JMenuItem dropMenuItem = new JMenuItem("Drop");
dropMenuItem.addActionListener(menuListener);
JMenuItem cancelMenuItem = new JMenuItem("Cancel");
cancelMenuItem.addActionListener(menuListener);

useDropPopup.add(useMenuItem);
useDropPopup.add(dropMenuItem);

useCancelPopup.add(useMenuItem);
useCancelPopup.add(cancelMenuItem);


String listData[] =
{
"Item 1","Item 2","Item 3","Item 4"
};

listbox = new JList( listData );
listbox.addMouseListener( new MouseAdapter()
{
public void mousePressed(MouseEvent e)
{
if ( SwingUtilities.isRightMouseButton(e) )
{
System.out.println("Row: " + getRow(e.getPoint()));
listbox.setSelectedIndex(getRow(e.getPoint()));
}
}
}
);

listbox.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
add(listbox);
listbox.setVisible(true);
listbox.setFocusable(false);


listbox.addMouseListener(new MousePopupListener());

useMenuItem.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent event) {
useMenuAction(event);
}
};

// ... after the init method

public void useMenuAction(ActionEvent evt) {
// Add specific use menu code here.
}
}



class MousePopupListener extends MouseAdapter
{
public void mousePressed(MouseEvent e)
{
checkPopup(e);
}

public void mouseClicked(MouseEvent e)
{
checkPopup(e);
}

public void mouseReleased(MouseEvent e)
{
checkPopup(e);
}

private void checkPopup(MouseEvent e)
{
if (e.isPopupTrigger())
{

int itemSelectx = listbox.getSelectedIndex();
Object actItemx = listbox.getModel().getElementAt(itemSelectx);
System.out.println("You pressed on " + actItemx);

if (actItemx == "Item 1") {
System.out.println("Removed cancel for " + actItemx);
popup.remove(itemSelectx); // So upon right-click on Item 1, you won't see "Cancel" menu.
}

popup.show(inv.this, e.getX(), e.getY());
popup.revalidate();
}
}
}

private int getRow(Point point)
{
return listbox.locationToIndex(point);
}

public void mouseEntered(MouseEvent e)
{
}

public void mouseReleased(MouseEvent e)
{
}

public void mousePressed(MouseEvent e)
{
}

public void mouseClicked(MouseEvent e)
{
}

public void mouseExited(MouseEvent e)
{
}
}

最佳答案

学习阅读堆栈跟踪:

Exception in thread "AWT-EventQueue-1" java.lang.NullPointerException
at inv$MousePopupListener.checkPopup(inv.java:118)
at inv$MousePopupListener.mouseReleased(inv.java:104)
at java.awt.AWTEventMulticaster.mouseReleased(AWTEventMulticaster.java:2
73)

它说,第118行有一个NullPointerException

...checkPopup(inv.java:118)....

第 104 行又调用了它:

... useReleased(inv.java:104).. 

如果您看到这些行,您将拥有:

this

如您所见,在那一行中您正在调用:

popup.remove(itemSelectx);

该行可能抛出 NullPointerException 的唯一方法是 popup 为 null,因为 null.remove.. 抛出 NullPointerException。

因此,将您的弹出窗口初始化为有意义的内容。

我希望这对您将来的异常有帮助。

关于java - 线程 "AWT-EventQueue-1"中的异常,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/4879756/

25 4 0
Copyright 2021 - 2024 cfsdn All Rights Reserved 蜀ICP备2022000587号
广告合作:1813099741@qq.com 6ren.com