JMenuBar で [編集] を押すと、アプリで受け取ります
スレッド「AWT-EventQueue-0」での例外 java.lang.NullPointerException
sun.swing.SwingUtilities2.getLeftSideBearing(SwingUtilities2.java:241) で
sun.swing.MenuItemLayoutHelper.getLeftExtraWidth(MenuItemLayoutHelper.java:162) で
sun.swing.MenuItemLayoutHelper.calcExtraWidths(MenuItemLayoutHelper.java:158) で
sun.swing.MenuItemLayoutHelper.reset(MenuItemLayoutHelper.java:148) で
sun.swing.MenuItemLayoutHelper.(MenuItemLayoutHelper.java:107) で
javax.swing.plaf.basic.BasicMenuItemUI.getPreferredMenuItemSize(BasicMenuItemUI.java:408)で
javax.swing.plaf.basic.BasicMenuItemUI.getPreferredSize(BasicMenuItemUI.java:363)で
javax.swing.JComponent.getPreferredSize (JComponent.java:1634) で
javax.swing.BoxLayout.checkRequests(BoxLayout.java:481)で
javax.swing.BoxLayout.preferredLayoutSize(BoxLayout.java:298) で
javax.swing.plaf.basic.DefaultMenuLayout.preferredLayoutSize(DefaultMenuLayout.java:60) で
java.awt.Container.preferredSize (Container.java:1605) で
java.awt.Container.getPreferredSize (Container.java:1590) で
javax.swing.JComponent.getPreferredSize (JComponent.java:1636) で
javax.swing.JMenu.getPopupMenuOrigin (JMenu.java:383) で
javax.swing.JMenu.setPopupMenuVisible(JMenu.java:349) で
javax.swing.JPopupMenu.menuSelectionChanged (JPopupMenu.java:1433) で
javax.swing.MenuSelectionManager.setSelectedPath(MenuSelectionManager.java:117) で
javax.swing.plaf.basic.BasicMenuUI.appendPath(BasicMenuUI.java:223)
javax.swing.plaf.basic.BasicMenuUI.access$200 (BasicMenuUI.java:49) で
javax.swing.plaf.basic.BasicMenuUI$Handler.mousePressed(BasicMenuUI.java:463)で
java.awt.Component.processMouseEvent(Component.java:6265)で
javax.swing.JComponent.processMouseEvent(JComponent.java:3267)で
java.awt.Component.processEvent(Component.java:6033)で
java.awt.Container.processEvent(Container.java:2045)で
java.awt.Component.dispatchEventImpl (Component.java:4629) で
java.awt.Container.dispatchEventImpl (Container.java:2103) で
java.awt.Component.dispatchEvent(Component.java:4455)で
java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4633) で
java.awt.LightweightDispatcher.processMouseEvent(Container.java:4294)で
java.awt.LightweightDispatcher.dispatchEvent(Container.java:4227)で
java.awt.Container.dispatchEventImpl (Container.java:2089) で
java.awt.Window.dispatchEventImpl (Window.java:2517) で
java.awt.Component.dispatchEvent(Component.java:4455)で
java.awt.EventQueue.dispatchEventImpl (EventQueue.java:649) で
java.awt.EventQueue.access$000 (EventQueue.java:96) で
java.awt.EventQueue$1.run(EventQueue.java:608) で
java.awt.EventQueue$1.run(EventQueue.java:606) で
java.security.AccessController.doPrivileged(ネイティブメソッド)で
java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:105) で
java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:116) で
java.awt.EventQueue$2.run(EventQueue.java:622) で
java.awt.EventQueue$2.run(EventQueue.java:620) で
java.security.AccessController.doPrivileged(ネイティブメソッド)で
java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:105) で
java.awt.EventQueue.dispatchEvent(EventQueue.java:619) で
java.awt.EventDispatchThread.pumpOneEventForFilters (EventDispatchThread.java:275) で
java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:200) で
java.awt.EventDispatchThread.pumpEventsForHierarchy (EventDispatchThread.java:190) で
java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:185) で
java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:177) で
java.awt.EventDispatchThread.run(EventDispatchThread.java:138) で
アプリの何が問題なのかわかりません。コードは次のとおりです。
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.event.*;
import javax.swing.undo.*;
public class Jaba extends JFrame {
public Jaba() {
super("Hello Swing");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setSize(640, 480);
setLayout(new FlowLayout());
txt.getDocument().addUndoableEditListener(undoListener);
add(txt);
setJMenuBar(menuBar);
menuBar.add(editMenu);
editMenu.add(undoAction);
editMenu.add(redoAction);
}
public static void main(String args[]) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
new Jaba().setVisible(true);
}
});
}
private UndoableEditListener undoListener = new UndoableEditListener() {
@Override
public void undoableEditHappened(UndoableEditEvent e) {
undo.addEdit(e.getEdit());
}
};
private AbstractAction undoAction = new AbstractAction() {
@Override
public void actionPerformed(ActionEvent e) {
try {
undo.undo();
} catch (CannotUndoException ex) {
System.err.println("Cannon undo");
ex.printStackTrace();
}
}
};
private AbstractAction redoAction = new AbstractAction() {
@Override
public void actionPerformed(ActionEvent e) {
try {
undo.redo();
} catch (CannotUndoException ex) {
System.err.println("Cannon undo");
ex.printStackTrace();
}
}
};
private UndoManager undo = new UndoManager();
private JTextArea txt = new JTextArea(40, 40);
private JMenuBar menuBar = new JMenuBar();
private JMenu editMenu = new JMenu("Edit");
}