如何在 Java 中创建带有子菜单的弹出菜单
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时间：2020-10-30 20:53:07 来源:igfitidea点击:
How To Create a Pop Up Menu with Sub Menu in Java
提问by CanCeylan
I would like to add right click menu for my program. I added basit menu with the following code:
我想为我的程序添加右键菜单。我使用以下代码添加了基本菜单：
Pmenu = new JPopupMenu("Menu");
menuItem = new JMenuItem("Sections");
Pmenu.add(menuItem);
menuItem = new JMenuItem("Numbers");
Pmenu.add(menuItem);
However I want to add submenu to these menus, such as user hover the Sections menu, submenu will open and sections are shown.
但是我想向这些菜单添加子菜单，例如用户将鼠标悬停在“部分”菜单中，子菜单将打开并显示部分。
回答by Adi Mor
First Object name usually start with a small letter, caps letter usually used for class/interface names.
第一个对象名称通常以小写字母开头，大写字母通常用于类/接口名称。
for your question, there is the code for submenu
对于您的问题，有子菜单的代码
//parent menu
JPopupMenu pmenu = new JPopupMenu("Menu");
//sub menu
JMenu sectionsMenu = new JMenu("Sections");
JMenuItem menuItem1 = new JMenuItem("Item1");
sectionsMenu .add(menuItem1 );
JMenuItem menuItem2 = new JMenuItem("Item2");
sectionsMenu .add(menuItem2 );
pmenu.add(sectionsMenu);
//regular menu item
menuItem = new JMenuItem("Numbers");
Pmenu.add(menuItem);
回答by JB Nizet
Add a JMenuinstance to your JPopupMenu. The JMenushould of course contain JMenuIteminstances.
将JMenu实例添加到您的JPopupMenu. 的JMenu当然应该包含JMenuItem实例。
See http://download.oracle.com/javase/tutorial/uiswing/components/menu.htmlfor a tutorial over menus in Swing.
有关Swing 中菜单的教程，请参见http://download.oracle.com/javase/tutorial/uiswing/components/menu.html。
回答by Solmer_Ethiopia
public JMenuBar createMenuBar() {
JMenuBar menuBar;
JMenu menu, submenu;
JMenuItem menuItem;
JRadioButtonMenuItem rbMenuItem;
JCheckBoxMenuItem cbMenuItem;
//Create the menu bar.
menuBar = new JMenuBar();
//Build the first menu.
menu = new JMenu("A Menu");
menu.setMnemonic(KeyEvent.VK_A);
menu.getAccessibleContext().setAccessibleDescription(
"The only menu in this program that has menu items");
menuBar.add(menu);
//a group of JMenuItems
menuItem = new JMenuItem("A text-only menu item",
KeyEvent.VK_T);
//menuItem.setMnemonic(KeyEvent.VK_T); //used constructor instead
menuItem.setAccelerator(KeyStroke.getKeyStroke(
KeyEvent.VK_1, ActionEvent.ALT_MASK));
menuItem.getAccessibleContext().setAccessibleDescription(
"This doesn't really do anything");
menuItem.addActionListener(this);
menu.add(menuItem);
ImageIcon icon = createImageIcon("images/middle.gif");
menuItem = new JMenuItem("Both text and icon", icon);
menuItem.setMnemonic(KeyEvent.VK_B);
menuItem.addActionListener(this);
menu.add(menuItem);
menuItem = new JMenuItem(icon);
menuItem.setMnemonic(KeyEvent.VK_D);
menuItem.addActionListener(this);
menu.add(menuItem);
//a group of radio button menu items
menu.addSeparator();
ButtonGroup group = new ButtonGroup();
rbMenuItem = new JRadioButtonMenuItem("A radio button menu item");
rbMenuItem.setSelected(true);
rbMenuItem.setMnemonic(KeyEvent.VK_R);
group.add(rbMenuItem);
rbMenuItem.addActionListener(this);
menu.add(rbMenuItem);
rbMenuItem = new JRadioButtonMenuItem("Another one");
rbMenuItem.setMnemonic(KeyEvent.VK_O);
group.add(rbMenuItem);
rbMenuItem.addActionListener(this);
menu.add(rbMenuItem);
//a group of check box menu items
menu.addSeparator();
cbMenuItem = new JCheckBoxMenuItem("A check box menu item");
cbMenuItem.setMnemonic(KeyEvent.VK_C);
cbMenuItem.addItemListener(this);
menu.add(cbMenuItem);
cbMenuItem = new JCheckBoxMenuItem("Another one");
cbMenuItem.setMnemonic(KeyEvent.VK_H);
cbMenuItem.addItemListener(this);
menu.add(cbMenuItem);
//a submenu
menu.addSeparator();
submenu = new JMenu("A submenu");
submenu.setMnemonic(KeyEvent.VK_S);
menuItem = new JMenuItem("An item in the submenu");
menuItem.setAccelerator(KeyStroke.getKeyStroke(
KeyEvent.VK_2, ActionEvent.ALT_MASK));
menuItem.addActionListener(this);
submenu.add(menuItem);
menuItem = new JMenuItem("Another item");
menuItem.addActionListener(this);
submenu.add(menuItem);
menu.add(submenu);
//Build second menu in the menu bar.
menu = new JMenu("Another Menu");
menu.setMnemonic(KeyEvent.VK_N);
menu.getAccessibleContext().setAccessibleDescription(
"This menu does nothing");
menuBar.add(menu);
return menuBar;
}
public Container createContentPane() {
//Create the content-pane-to-be.
JPanel contentPane = new JPanel(new BorderLayout());
contentPane.setOpaque(true);
//Create a scrolled text area.
output = new JTextArea(5, 30);
output.setEditable(false);
scrollPane = new JScrollPane(output);
//Add the text area to the content pane.
contentPane.add(scrollPane, BorderLayout.CENTER);
return contentPane;
}
public void createPopupMenu() {
JMenuItem menuItem;
//Create the popup menu.
JPopupMenu popup = new JPopupMenu();
menuItem = new JMenuItem("A popup menu item");
menuItem.addActionListener(this);
popup.add(menuItem);
menuItem = new JMenuItem("Another popup menu item");
menuItem.addActionListener(this);
popup.add(menuItem);
//Add listener to the text area so the popup menu can come up.
MouseListener popupListener = new PopupListener(popup);
output.addMouseListener(popupListener);
}
public void actionPerformed(ActionEvent e) {
JMenuItem source = (JMenuItem)(e.getSource());
String s = "Action event detected."
+ newline
+ " Event source: " + source.getText()
+ " (an instance of " + getClassName(source) + ")";
output.append(s + newline);
output.setCaretPosition(output.getDocument().getLength());
}
public void itemStateChanged(ItemEvent e) {
JMenuItem source = (JMenuItem)(e.getSource());
String s = "Item event detected."
+ newline
+ " Event source: " + source.getText()
+ " (an instance of " + getClassName(source) + ")"
+ newline
+ " New state: "
+ ((e.getStateChange() == ItemEvent.SELECTED) ?
"selected":"unselected");
output.append(s + newline);
output.setCaretPosition(output.getDocument().getLength());
}
// Returns just the class name -- no package info.
protected String getClassName(Object o) {
String classString = o.getClass().getName();
int dotIndex = classString.lastIndexOf(".");
return classString.substring(dotIndex+1);
}
/** Returns an ImageIcon, or null if the path was invalid. */
protected static ImageIcon createImageIcon(String path) {
java.net.URL imgURL = PopupMenuDemo.class.getResource(path);
if (imgURL != null) {
return new ImageIcon(imgURL);
} else {
System.err.println("Couldn't find file: " + path);
return null;
}
}
/**
* Create the GUI and show it. For thread safety,
* this method should be invoked from the
* event-dispatching thread.
*/
private static void createAndShowGUI() {
//Create and set up the window.
JFrame frame = new JFrame("PopupMenuDemo");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//Create/set menu bar and content pane.
PopupMenuDemo demo = new PopupMenuDemo();
frame.setJMenuBar(demo.createMenuBar());
frame.setContentPane(demo.createContentPane());
//Create and set up the popup menu.
demo.createPopupMenu();
//Display the window.
frame.setSize(450, 260);
frame.setVisible(true);
}
public static void main(String[] args) {
//Schedule a job for the event-dispatching thread:
//creating and showing this application's GUI.
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}
class PopupListener extends MouseAdapter {
JPopupMenu popup;
PopupListener(JPopupMenu popupMenu) {
popup = popupMenu;
}
public void mousePressed(MouseEvent e) {
maybeShowPopup(e);
}
public void mouseReleased(MouseEvent e) {
maybeShowPopup(e);
}
private void maybeShowPopup(MouseEvent e) {
if (e.isPopupTrigger()) {
popup.show(e.getComponent(),
e.getX(), e.getY());
}
}
}
}
}
