我想了解为什么当KeyPressedListener触发上下按键事件时,此JLIST对象的打印列表索引与突出显示的行不同步,以及我如何解决问题
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import javax.swing.JFrame;
import javax.swing.JList;
import java.awt.BorderLayout;
public class ListTest
{
private JFrame frame;
private String[] values = new String[] {"Line 0", "Line 1", "Line 2", "Line 3"};
public static void main(String[] args)
{
ListTest window = new ListTest();
window.frame.setVisible(true);
}
public ListTest()
{
frame = new JFrame();
frame.setBounds(100, 100, 136, 153);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JList<String> list = new JList<String>(values);
frame.getContentPane().add(list, BorderLayout.CENTER);
list.setSelectedIndex(0);
list.addKeyListener(new KeyListener()
{
@Override
public void keyReleased(KeyEvent arg0){}
@Override
public void keyTyped(KeyEvent arg0){}
@Override
public void keyPressed(KeyEvent e)
{
int code = e.getKeyCode();
switch( code )
{
case KeyEvent.VK_UP:
System.out.println("UP " + list.getSelectedIndex());
break;
case KeyEvent.VK_DOWN:
System.out.println("DOWN " + list.getSelectedIndex());
break;
}
}
});
}
}
答案 0 :(得分:3)
因为keyPressed
事件将返回上一个选择。
只需获取keyReleased
事件的输出即可。
public void keyReleased(KeyEvent arg0){
int code = arg0.getKeyCode();
switch( code )
{
case KeyEvent.VK_UP:
System.out.println("UP " + list.getSelectedIndex());
break;
case KeyEvent.VK_DOWN:
System.out.println("DOWN " + list.getSelectedIndex());
break;
}
}
以下是对关键事件的更好解释
keyPressed():当密钥关闭时
keyReleased():当键出现时
keyTyped():当发送此键表示的unicode字符时 通过键盘输入系统。
当键出现时,会发生JList中项目的选择。当keyReleased():
被触发时,JList中的下一个项目将被选中。但是keyPressed():
事件会在选择项目之前触发。