我想檢測(cè)選擇內(nèi)容何時(shí)發(fā)生變化JPopupMenu。不是單擊菜單項(xiàng)時(shí)，而是選擇（武裝）菜單項(xiàng)時(shí)。用更簡(jiǎn)單的話來(lái)說(shuō)，我想檢測(cè)到這一點(diǎn)：https://i.stack.imgur.com/gSUvP.gif 應(yīng)該起作用的事情是將 a 添加ChangeListener到其SelectionModel，但它似乎沒(méi)有響應(yīng)選擇事件：public class PopupSelection extends JFrame { private static final long serialVersionUID = 363879723515243543L; public PopupSelection() { super("something"); setDefaultCloseOperation(EXIT_ON_CLOSE); setLayout(new FlowLayout()); JLabel label = new JLabel("right click me"); JPopupMenu menu = new JPopupMenu(); menu.getSelectionModel().addChangeListener(System.out::println); JMenuItem menuItem1 = new JMenuItem("Item1"); JMenuItem menuItem2 = new JMenuItem("Item2"); JMenuItem menuItem3 = new JMenuItem("Item3"); menu.add(menuItem1); menu.add(menuItem2); menu.add(menuItem3); label.setComponentPopupMenu(menu); getContentPane().add(label); setSize(400, 400); setLocationRelativeTo(null); } public static void main(String[] args) { SwingUtilities.invokeLater(() -> new PopupSelection().setVisible(true)); }}我嘗試的第二件事是使用 a PropertyChangeListener，但它不起作用（不檢測(cè)此特定事件）：menu.addPropertyChangeListener(System.out::println);我知道有另一種選擇，ChangeListener即JMenuItem每次迭代 的所有組件時(shí)都添加 a JPopupMenu，以便找到選擇的組件，但這不是我想要遵循的解決方案，因?yàn)樗鼤?huì)在我的代碼中增加不必要的復(fù)雜性。那么，有沒(méi)有辦法檢測(cè)選擇呢？如果出現(xiàn)XY 問(wèn)題，我的最終目標(biāo)是當(dāng)用戶(hù)使用箭頭按鈕更改菜單選擇時(shí)正確增加/減少此滾動(dòng)條：↑ ↓
2 回答
MM們
TA貢獻(xiàn)1886條經(jīng)驗(yàn) 獲得超2個(gè)贊
在項(xiàng)目的按鈕模型上使用更改偵聽(tīng)器。這是解決方案：
import java.awt.Component;
import java.awt.FlowLayout;
import java.util.stream.Stream;
import javax.swing.AbstractButton;
import javax.swing.ButtonModel;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JMenuItem;
import javax.swing.JPopupMenu;
import javax.swing.SwingUtilities;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
/**
* <code>PopupSelection</code>.
*/
public class PopupSelection extends JFrame {
private static final long serialVersionUID = 363879723515243543L;
public PopupSelection() {
super("something");
setDefaultCloseOperation(EXIT_ON_CLOSE);
setLayout(new FlowLayout());
JLabel label = new JLabel("right click me");
JPopupMenu menu = new MyPopupMenu();
menu.getSelectionModel().addChangeListener(System.out::println);
JMenuItem menuItem1 = new JMenuItem("Item1");
JMenuItem menuItem2 = new JMenuItem("Item2");
JMenuItem menuItem3 = new JMenuItem("Item3");
menu.add(menuItem1);
menu.add(menuItem2);
menu.add(menuItem3);
label.setComponentPopupMenu(menu);
getContentPane().add(label);
setSize(400, 400);
setLocationRelativeTo(null);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> new PopupSelection().setVisible(true));
}
private static class MyPopupMenu extends JPopupMenu {
private final ChangeListener listener = this::changed;
@Override
protected void addImpl(Component comp, Object constraints, int index) {
super.addImpl(comp, constraints, index);
if (comp instanceof AbstractButton) {
((AbstractButton) comp).getModel().addChangeListener(listener);
}
}
@Override
public void remove(int index) {
Component comp = getComponent(index);
if (comp instanceof AbstractButton) {
((AbstractButton) comp).getModel().removeChangeListener(listener);
}
super.remove(index);
}
private void changed(ChangeEvent e) {
ButtonModel model = (ButtonModel) e.getSource();
AbstractButton selected = Stream.of(getComponents()).filter(AbstractButton.class::isInstance)
.map(AbstractButton.class::cast)
.filter(b -> b.getModel().isArmed() && b.getModel() == model).findAny().orElse(null);
setSelected(selected);
}
}
}
溫溫醬
TA貢獻(xiàn)1752條經(jīng)驗(yàn) 獲得超4個(gè)贊
您可以將a添加到 MenuSelectionManager，而不是向ChangeListener每個(gè)添加 a 。JMenuItemChangeListener
MenuSelectionManager.defaultManager().addChangeListener(e -> {
Object o = e.getSource();
if (o instanceof MenuSelectionManager) {
MenuSelectionManager m = (MenuSelectionManager) o;
printMenuElementArray(m.getSelectedPath());
}
});
PopupSelection2.java
import java.awt.*;
import javax.swing.*;
public class PopupSelection2 extends JFrame {
public PopupSelection2() {
super("something");
setDefaultCloseOperation(EXIT_ON_CLOSE);
setLayout(new FlowLayout());
JLabel label = new JLabel("right click me");
JPopupMenu menu = new JPopupMenu();
menu.getSelectionModel().addChangeListener(System.out::println);
JMenuItem menuItem1 = new JMenuItem("Item1");
JMenuItem menuItem2 = new JMenuItem("Item2");
JMenuItem menuItem3 = new JMenuItem("Item3");
menu.add(menuItem1);
menu.add(menuItem2);
menu.add(menuItem3);
label.setComponentPopupMenu(menu);
MenuSelectionManager.defaultManager().addChangeListener(e -> {
Object o = e.getSource();
if (o instanceof MenuSelectionManager) {
MenuSelectionManager m = (MenuSelectionManager) o;
printMenuElementArray(m.getSelectedPath());
}
});
getContentPane().add(label);
setSize(400, 400);
setLocationRelativeTo(null);
}
// @see javax/swing/MenuSelectionManager.java
private static void printMenuElementArray(MenuElement[] path) {
System.out.println("Path is(");
for (int i = 0, j = path.length; i < j ; i++) {
for (int k = 0; k <= i; k++) {
System.out.print(" ");
}
MenuElement me = path[i];
if (me instanceof JMenuItem) {
System.out.println(((JMenuItem)me).getText() + ", ");
} else if (me instanceof JMenuBar) {
System.out.println("JMenuBar, ");
} else if (me instanceof JPopupMenu) {
System.out.println("JPopupMenu, ");
} else if (me == null) {
System.out.println("NULL , ");
} else {
System.out.println("" + me + ", ");
}
}
System.out.println(")");
}
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> new PopupSelection2().setVisible(true));
}
}
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