Java 控制台键盘 - 自动接受输入

Question

我正在创建一个简单的控制台应用程序，在其中我可以使用键盘箭头键作为输入，就像典型的玩具 Remote 一样。当我按向上箭头时，控制台将打印输出文本“UP”，或者如果我按向下箭头，它将打印“向下”。

我只想按箭头键一次，即我不需要随后按 Enter 来接受我的输入。我希望按下箭头键时自动接受输入。

我已经尝试了一些代码，但这仍然没有发生，我仍然需要按 Enter 来接受我的输入。如果您知道我如何尽可能简单地实现这一目标，我将非常感激。

Answer 1

此示例代码将帮助您获取左箭头键事件。你可以引用这个，

import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;

import javax.swing.*;

public class Test2 extends JPanel {
   private static final int PREF_W = 400;
   private static final int PREF_H = PREF_W;
   private static final int TIMER_DELAY = 50;
   private Timer leftKeyTimer = new Timer(TIMER_DELAY , new TimerListener());


   public Test2() {
      int condition = JComponent.WHEN_IN_FOCUSED_WINDOW;
      InputMap inputMap = getInputMap(condition );
      ActionMap actionMap = getActionMap();

      String leftDownKey = "Left Down";
      String leftUpKey = "Left Up";
      KeyStroke leftDown = KeyStroke.getKeyStroke(KeyEvent.VK_LEFT , 0, false);
      KeyStroke leftUp = KeyStroke.getKeyStroke(KeyEvent.VK_LEFT , 0, true);
      inputMap.put(leftDown, leftDownKey);
      inputMap.put(leftUp, leftUpKey);

      actionMap.put(leftDownKey, new LeftKeyAction(false));
      actionMap.put(leftUpKey, new LeftKeyAction(true));
      leftKeyTimer.setActionCommand("Left Key");
   }

   @Override
   public Dimension getPreferredSize() {
      return new Dimension(PREF_W, PREF_H);
   }

   private class LeftKeyAction extends AbstractAction {
      private boolean onKeyRelease;

      public LeftKeyAction(boolean onKeyRelease) {
         this.onKeyRelease = onKeyRelease;
      }

      @Override
      public void actionPerformed(ActionEvent e) {
         if (onKeyRelease) {
            if (leftKeyTimer != null && leftKeyTimer.isRunning()) {
               leftKeyTimer.stop();
            }
         } else {
            if (leftKeyTimer != null && !leftKeyTimer.isRunning()) {
               leftKeyTimer.start();
            }

         }
      }
   }

   private class TimerListener implements ActionListener {
      public void actionPerformed(ActionEvent actEvt) {
         System.out.println(actEvt.getActionCommand());
      }
   }

   private static void createAndShowGui() {
      Test2 mainPanel = new Test2();

      JFrame frame = new JFrame("Test2");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.getContentPane().add(mainPanel);
      frame.pack();
      frame.setLocationByPlatform(true);
      frame.setVisible(true);
   }

   public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {
         public void run() {
            createAndShowGui();
         }
      });
   }
}