JCombobox focusLost没有解雇 – 为什么会这样？

我的代码中有一个JCombobox 。 我添加了FocusLost event 。 但无论如何它并没有被解雇。 我已经尝试了很多时间，但没有找到解决方案。

 jcbItemType.addFocusListener(new java.awt.event.FocusAdapter() { public void focusLost(java.awt.event.FocusEvent evt) { jcbItemTypeFocusLost(evt); } }); private void jcbItemTypeFocusLost(java.awt.event.FocusEvent evt) { // TODO add your handling code here: System.out.println("name=" + ((Component) evt.getSource()).getName()); System.out.println("index=" + jcbItemType.getSelectedIndex()); } 

但是在控制台中没有打印出来 请告诉我我做错了什么。

Answer 1

• FocusListener不是JComboBox的正确监听器，与另一个监听器一起可以创建无限循环（尤其是可编辑的JComboBox），

• FocusListener是异步的，有时很难捕获事件是正确的命令，尤其是在JComponents也添加了另一个Listener的情况下

示例如何从派生的JTextField / JFormattedTextField侦听Focus

 import java.awt.*; import java.awt.event.*; import javax.swing.*; public class ComboBoxTwo extends JFrame implements ItemListener { private static final long serialVersionUID = 1L; private JComboBox mainComboBox; private JComboBox subComboBox; public ComboBoxTwo() { String[] items = {"Select Item", "Color", "Shape", "Fruit"}; String[] subItems1 = {"Select Color", "Red", "Blue", "Green"}; mainComboBox = new JComboBox(items); mainComboBox.addItemListener(this); mainComboBox.addFocusListener(fcsListener); add(mainComboBox, BorderLayout.WEST); subComboBox = new JComboBox(subItems1); subComboBox.setPrototypeDisplayValue("XXXXXXXXXXXXXXXXXXX"); subComboBox.addItemListener(this); add(subComboBox, BorderLayout.EAST); } @Override public void itemStateChanged(ItemEvent e) { if (e.getStateChange() == ItemEvent.SELECTED) { if (e.getSource() == mainComboBox) { System.out.println("Source : mainComboBox"); } else if (e.getSource() == subComboBox) { System.out.println("Source : subComboBox"); } } } public static void main(String[] args) { SwingUtilities.invokeLater(new Runnable() { @Override public void run() { JFrame frame = new ComboBoxTwo(); frame.setDefaultCloseOperation(EXIT_ON_CLOSE); frame.pack(); frame.setLocationRelativeTo(null); frame.setVisible(true); } }); } // private FocusListener fcsListener = new FocusListener() { @Override public void focusGained(FocusEvent e) { dumpInfo(e); } @Override public void focusLost(FocusEvent e) { dumpInfo(e); } private void dumpInfo(FocusEvent e) { System.out.println("Source : " + name(e.getComponent())); System.out.println("Opposite : " + name(e.getOppositeComponent())); System.out.println("Temporary: " + e.isTemporary()); final Component c = e.getComponent();//works for editable JComboBox too if (c instanceof JFormattedTextField) { SwingUtilities.invokeLater(new Runnable() { @Override public void run() { ((JFormattedTextField) c).selectAll(); } }); } else if (c instanceof JTextField) { SwingUtilities.invokeLater(new Runnable() { @Override public void run() { ((JTextField) c).selectAll(); } }); } } private String name(Component c) { return (c == null) ? null : c.getName(); } }; } 

Answer 2

我找到了一种解决这个问题的简单方法。

JComboBox默认编辑器有一个内部类BasicComboBoxEditor $ BorderlessTextField，它是获取和失去焦点的组件。

它可以简单地访问

 Component component = comboBox.getEditor().getEditorComponent(); if (component instanceof JTextField) JTextField borderlesstextfield = (JTextField) borderless; 

然后像对待任何JTextField一样添加焦点侦听器

 borderlesstextfield.addFocusListener(new FocusListener() { public void focusGained(FocusEvent e) { } public void focusLost(FocusEvent e) { } }}); 

现在你有了一个FocusListener，它将按预期响应ComboBox的获取和失去焦点