Java在gui中用箭头键移动圆圈

Question

我正试图用keyEvent移动一个圆圈。到目前为止，圆形画在窗口上，但它不会左移！我觉得问题是我将Window（）构造函数添加到容器的位置。控制台上没有输出来告诉我它正在工作。所以我不认为它甚至达到了KeyEvent类。这里是我的代码：

import java.awt.*; 
import java.awt.event.*; 
import java.awt.geom.Ellipse2D; 
import javax.swing.*; 


public class Window extends JPanel { 

    private static Ellipse2D.Double circle; 

    public Window() { 
     super(); 
     int width = 400; 
     int height = 400; 
     circle = new Ellipse2D.Double(0.5 * width, 0.9 * height, 
       0.1 * width, 0.05 * height); 
     addKeyListener(new MoveCircle()); 
    } 

    @Override 
    protected void paintComponent(Graphics g) { 
     super.paintComponents(g); 
     Graphics2D brush = (Graphics2D) g; 
     int width = getWidth(); 
     int height = getHeight(); 
     g.clearRect(0, 0, width, height); 
     brush.setRenderingHint(RenderingHints.KEY_ANTIALIASING, 
       RenderingHints.VALUE_ANTIALIAS_ON); 
     brush.draw(circle); 
    } 

    public class MoveCircle implements KeyListener { 

     @Override 
     public void keyPressed(KeyEvent e) { 
      System.out.println("Working on top!"); 
      if (e.getKeyCode() == KeyEvent.VK_LEFT) { 
       System.out.println("Working on bottom!"); 
       circle.x++; 
       repaint(); 
      } 
     } 

     @Override 
     public void keyReleased(KeyEvent e) { 
      // TODO Auto-generated method stub 
     } 

     @Override 
     public void keyTyped(KeyEvent e) { 
      // TODO Auto-generated method stub 
     } 
    } 

    public static void main(String[] args) { 
     Window window = new Window(); 
     JFrame frame = new JFrame(); 
     Container container = frame.getContentPane(); 
     container.add(new Window()); 
     frame.addKeyEvent(window.new MoveCircle()); 
     frame.setSize(800, 700); 
     frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE); 
     frame.setVisible(true); 
    } 
} 

Answer 1

实际上正在发生的事情是这样，要添加Window到JFrame，但重点在于与JFrame，所以当你在你的Keyboard那东西键入转到JFrame不是KeyListener连接到Window类。所以为了克服它，你只需在Window类的对象上调用requestFocusInWindow()即可。试试这个代码，我已经做了一些关于EDT和东西的修改。

import java.awt.*; 
import java.awt.event.*; 
import java.awt.geom.Ellipse2D; 
import javax.swing.*; 


public class Window extends JPanel { 

    private static Ellipse2D.Double circle; 
    private JFrame frame; 

    public Window() { 
     super(); 
     int width = 400; 
     int height = 400; 
     circle = new Ellipse2D.Double(0.5 * width, 0.9 * height, 
       0.1 * width, 0.05 * height);   
    } 

    public Dimension getPreferredSize() 
    { 
     return (new Dimension(frame.getWidth(), frame.getHeight())); 
    } 

    @Override 
    protected void paintComponent(Graphics g) { 
     super.paintComponents(g); 
     Graphics2D brush = (Graphics2D) g; 
     int width = getWidth(); 
     int height = getHeight(); 
     g.clearRect(0, 0, width, height); 
     brush.setRenderingHint(RenderingHints.KEY_ANTIALIASING, 
       RenderingHints.VALUE_ANTIALIAS_ON); 
     brush.draw(circle); 
    } 

    public class MoveCircle implements KeyListener { 

     @Override 
     public void keyPressed(KeyEvent e) { 
      System.out.println("Working on top!"); 
      if (e.getKeyCode() == Event.ENTER) { 
       System.out.println("Working on bottom!"); 
       double newX = circle.x - 1; 
       circle.x = newX; 
       repaint(); 
      } 
     } 

     @Override 
     public void keyReleased(KeyEvent e) { 
      // TODO Auto-generated method stub 
     } 

     @Override 
     public void keyTyped(KeyEvent e) { 
      // TODO Auto-generated method stub 
     } 
    } 

    private void createAndDisplayGUI(Window window) 
    { 
     frame = new JFrame(); 
     Container container = frame.getContentPane();  
     container.add(window); 
     window.addKeyListener(new MoveCircle());   
     frame.setSize(800, 700); 
     frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE); 
     frame.setVisible(true); 
     window.requestFocusInWindow(); 
    } 

    public static void main(String[] args) { 
     SwingUtilities.invokeLater(new Runnable() 
     { 
      public void run() 
      { 
       Window window = new Window(); 
       window.createAndDisplayGUI(window); 
      } 
     }); 
    } 
} 

Answer 2

只有焦点组件会得到关键事件。你需要在某个时候调用requestFocus（）。

Answer 3

解决方案是，将KeyListener添加到JFrame。通过这种方式，当JFrame拥有焦点时，所有关键笔画都将引发一个事件。