java - 等待在循环内按下一个键

Question

我有一个 Java 应用程序，我想等待按下一个键来执行另一个操作。直到现在我发现:

public void keyPressed(KeyEvent e) {
  if (e.getKeyCode() == KeyEvent.VK_RIGHT ) {
        //Right arrow key code
  }
}

但我希望它在循环内或等待键匹配的东西。

请帮忙。

更新:

我希望程序一直等到按键被按下，当它被按下时我想触发另一个 Action 。例如:

public void something(){
  //do something
  wait until a key is pressed
  if( key pressed is a arrow key){
    something();
  }else{
    wait for the key to be pressed
  }
}

public void dootherthing(){
 //do other thing
}

我在 swing 工作，我不希望 GUI 不负责任。即当我通过单击按钮调用 dootherthing 时。它应该这样做，等待应该结束。

Answer 1

Swing(和大多数 GUI)是事件驱动的环境。也就是说，某些事情发生了，您对此做出了 react 。

让循环等待某种 Action 有点违反直觉(恕我直言)。

一般来说，您应该尽可能避免使用 KeyListener。他们在重点方面存在问题。 key bindings API 有办法克服这个限制。

它允许您针对 Action 注册一个 KeyStroke 并允许您的程序坐下来等待事情发生...

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import javax.swing.AbstractAction;
import javax.swing.ActionMap;
import javax.swing.InputMap;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.KeyStroke;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.border.LineBorder;

public class KeyBindings {

    public static void main(String[] args) {
        new KeyBindings();
    }

    public KeyBindings() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        public TestPane() {

            setLayout(new GridBagLayout());
            GridBagConstraints gbc = new GridBagConstraints();
            gbc.gridx = 1;
            gbc.gridy = 0;

            add(new KeyPane(KeyEvent.VK_UP, 0), gbc);

            gbc.gridy = 2;
            add(new KeyPane(KeyEvent.VK_DOWN, 0), gbc);

            gbc.gridx = 0;
            gbc.gridy = 1;
            add(new KeyPane(KeyEvent.VK_LEFT, 0), gbc);

            gbc.gridx = 2;
            add(new KeyPane(KeyEvent.VK_RIGHT, 0), gbc);

        }
    }

    public class KeyPane extends JPanel {

        public KeyPane(int keyCode, int modifier) {

            setBorder(new LineBorder(Color.DARK_GRAY));

            InputMap im = getInputMap(WHEN_IN_FOCUSED_WINDOW);
            ActionMap am = getActionMap();

            im.put(KeyStroke.getKeyStroke(keyCode, modifier, false), "keyPressed");
            im.put(KeyStroke.getKeyStroke(keyCode, modifier, true), "keyReleased");

            am.put("keyPressed", new AbstractAction() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    setBackground(Color.RED);
                }
            });

            am.put("keyReleased", new AbstractAction() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    setBackground(UIManager.getColor("Panel.background"));
                }
            });

        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(20, 20);
        }
    }

}