Question

我有一个简单的Gui

public Gui(){
    ablak = new JFrame("Snake game");
    ablak.setVisible(true);
    ablak.setSize(new Dimension(600,600));
    ablak.setFocusable(true);
    ablak.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    ablak.add(new Grid());
    ablak.add(new Key());
}

列表到keyevents的关键类

package snake;

import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;

public class Key implements KeyListener {

    @Override
    public void keyPressed(KeyEvent e) {
        if(e.getKeyCode() == KeyEvent.VK_UP){
            System.out.println("Hi");
        }
    }

    @Override
    public void keyTyped(KeyEvent e) {
        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }

    @Override
    public void keyReleased(KeyEvent e) {
        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }


}

正如你所看到的那样按下向上箭头键应该说像Hi，但没有任何反应。如果我尝试在Gui类中添加（new Key（）），则会出错。我做错了什么？

谢谢

Answer 1

您需要先阅读教程。您不会使用add(...)添加KeyListeners，而是使用addKeyListener(...)添加add(...)，因为import java.awt.*; import java.awt.event.*; import javax.swing.*; public class Test2 { public static void main(String[] args) { JFrame ablak = new JFrame("Snake game"); ablak.setVisible(true); ablak.setSize(new Dimension(600, 600)); ablak.setFocusable(true); ablak.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); ablak.addKeyListener(new KeyAdapter() { @Override public void keyPressed(KeyEvent e) { if (e.getKeyCode() == KeyEvent.VK_UP) { System.out.println("Hi from KeyListener"); } } }); ablak.setVisible(true); JPanel contentPane = (JPanel) ablak.getContentPane(); int condition = JComponent.WHEN_IN_FOCUSED_WINDOW; InputMap inputMap = contentPane.getInputMap(condition); ActionMap actionMap = contentPane.getActionMap(); String down = "down"; inputMap.put(KeyStroke.getKeyStroke(KeyEvent.VK_DOWN, 0), down); actionMap.put(down, new AbstractAction() { @Override public void actionPerformed(ActionEvent arg0) { System.out.println("Hi from Key Binding"); } }); } }仅用于添加组件，但话虽如此，我甚至不会使用一个KeyListener，而不是Key Bindings，这将有助于解决焦点阻止KeyListener工作时将来会遇到的问题。

Key Bindings tutorial Link

例如，使用我的小键绑定添加编译并运行Kevin Bowersox的程序：

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Test2 {
   public static void main(String[] args) {
      JFrame ablak = new JFrame("Snake game");
      ablak.setVisible(true);
      ablak.setSize(new Dimension(600, 600));
      ablak.setFocusable(true);
      ablak.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      ablak.addKeyListener(new KeyAdapter() {
         @Override
         public void keyPressed(KeyEvent e) {
            if (e.getKeyCode() == KeyEvent.VK_UP) {
               System.out.println("Hi from KeyListener");
            }
         }
      });

      JPanel contentPane = (JPanel) ablak.getContentPane();
      int condition = JComponent.WHEN_IN_FOCUSED_WINDOW;
      InputMap inputMap = contentPane.getInputMap(condition);
      ActionMap actionMap = contentPane.getActionMap();

      String down = "down";
      inputMap.put(KeyStroke.getKeyStroke(KeyEvent.VK_DOWN, 0), down);
      actionMap.put(down, new AbstractAction() {

         @Override
         public void actionPerformed(ActionEvent arg0) {
            System.out.println("Hi from Key Binding");
         }
      });

      JButton fooButton = new JButton("Foo");
      contentPane.setLayout(new FlowLayout());
      contentPane.add(fooButton);

      ablak.setVisible(true);
   }
}

如果你运行它并按向上和向下箭头，你会看到来自正常运行的KeyListener和Key Bindings的响应。

但是，如果你像这样添加一个JButton：

{{1}}

然后按下按钮后会发生什么？告诉我哪个关键处理程序有效？

Answer 2

您需要使用addKeyListener()方法：

public class Test2 {
    public static void main(String[] args) {
        JFrame ablak = new JFrame("Snake game");
        ablak.setVisible(true);
        ablak.setSize(new Dimension(600,600));
        ablak.setFocusable(true);
        ablak.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        ablak.addKeyListener(new KeyListener(){
             @Override
                public void keyPressed(KeyEvent e) {
                    if(e.getKeyCode() == KeyEvent.VK_UP){
                        System.out.println("Hi");
                    }
                }

                @Override
                public void keyTyped(KeyEvent e) {
                    throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
                }

                @Override
                public void keyReleased(KeyEvent e) {
                    throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
                }
        });
        ablak.setVisible(true);
    }
}

如何在java中为我的Gui添加一个keylistener

2 个答案: