Question

这是我第一次使用KeyListener，如果我犯了一个明显的错误，请原谅我。我的问题是每当我按下箭头键或WASD键时，省略号都没有反应。我知道我的代码中还有其他缺陷，但我只想关注KeyListener问题。

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.geom.Ellipse2D;
import javax.swing.JPanel;
import javax.swing.Timer;
import java.awt.event.KeyListener;

public class idkdude extends JPanel implements ActionListener, KeyListener {

    Timer t = new Timer(5, this);
     int rx = 395, ry = 395, rvelx = 0, rvely = -2, bx = 195, by = 195, bvelx =     0, bvely = 2;
     boolean redWins = false;
     boolean blueWins = false;

     public void paint(Graphics g)
        {
            super.paint(g);
             drawSurface(g);
            Graphics2D g2 = (Graphics2D) g;             
            g.setColor(Color.red);
            Ellipse2D rcircle = new Ellipse2D.Double(rx, ry, 10, 10);
            g2.fill(rcircle);
            g2.drawLine(400, 400, rx+5, ry+5);
            g.setColor(Color.blue);
            Ellipse2D bcircle = new Ellipse2D.Double(bx, by, 10, 10);
            g2.fill(bcircle);
            g2.drawLine(200, 200, bx+5, by+5);
            if (redWins == true)
            {
                redWins(g);
            }
            if (blueWins == true)
            {
                blueWins(g);
            }
            t.start();
        }

     public void init()
     {
         addKeyListener(this);
     }
     public void keyReleased(KeyEvent e){}
        public void keyTyped(KeyEvent e) {}
        public void keyPressed(KeyEvent e)
        { //make sure to put
            //rx+=rvelx;
            //ry+=rvely;
            // and draw a new line
            int key = e.getKeyCode();
            if (key == KeyEvent.VK_LEFT) 
            {rvelx = -2;rvely = 0;}
            if (key == KeyEvent.VK_RIGHT)
            {rvelx = 2; rvely = 0;}
            if (key == KeyEvent.VK_UP)
            {rvelx = 0; rvely = -2;}
            if (key == KeyEvent.VK_DOWN)
            {rvelx = 0; rvely = 2;}
            if (key == KeyEvent.VK_W)
            {bvelx = 0; rvely = -2;}
            if (key == KeyEvent.VK_A)
            {bvelx = -2; rvely = 0;}
            if (key == KeyEvent.VK_S)
            {bvelx = 0; rvely = 2;}
            if (key == KeyEvent.VK_D)
            {bvelx = 2; rvely = 0;}
        }
     public void actionPerformed(ActionEvent e)
        {
            rx+=rvelx;
            ry+=rvely;
            bx+=bvelx;
            by+=bvely;
            if (rx> 600 || rx <0)
            {
                blueWins = true;
            }

            if (ry<0 || ry>600)
            {
                blueWins = true;
            }
            if (bx>600 || bx<0)
            {
                redWins = true;
            }
            if (by>600 || by<0)
            {
                redWins = true;             
            }                
            repaint();              
        }

     public void redWins(Graphics g)
     {
         g.setColor(Color.black);
            g.fillRect(0,0,600,600);
            g.setColor(Color.white);
            g.drawString("RED HAS WON!!!!!", 250, 250);
            g.drawString("Click Anywhere to Start Another Game", 250, 350);  
     }
     public void blueWins(Graphics g)
     {
         g.setColor(Color.black);
            g.fillRect(0,0,600,600);
            g.setColor(Color.white);
            g.drawString("BLUE HAS WON!!!!!", 250, 250);
            g.drawString("Click Anywhere to Start Another Game", 250, 350);
     }
     public void drawSurface(Graphics g)
     {
        g.setColor(Color.black);
        g.fillRect(0,0,600,600);
        g.setColor(Color.white);
        for (int x = 0; x <= 600; x+=25)
            g.drawLine(x,0,x,600);
        for (int y= 0; y <=600; y+=25)
            g.drawLine(0,y,600,y);
     }
}

Answer 1

KeyListener

上的键绑定

使用Key bindings的恕我直言是一种更灵活，更可靠的方法，带来了这些好处：

将动作本身与击键分开。
触发这些操作有不同的条件：WHEN_FOCUSED，WHEN_IN_FOCUSED_WINDOW，WHEN_ANCESTOR_OF_FOCUSED_COMPONENT
我们可以利用这些条件将不同的操作附加到依赖于基于优先级的策略的不同组件上（请参阅示例here）。

话虽如此，您可以创建KeyStrokes，如下所示：

KeyStroke upKeyStroke = KeyStroke.getKeyStroke(KeyEvent.VK_UP, 0);
KeyStroke leftKeyStroke = KeyStroke.getKeyStroke(KeyEvent.VK_LEFT, 0);
KeyStroke downKeyStroke = KeyStroke.getKeyStroke(KeyEvent.VK_DOWN, 0);
KeyStroke rightKeyStroke = KeyStroke.getKeyStroke(KeyEvent.VK_RIGHT, 0);

您还可以指定在键释放事件上触发击键：

KeyStroke upReleasedKeyStroke = KeyStroke.getKeyStroke(KeyEvent.VK_UP, 0, true);

注意： 0表示没有修饰符，true是一个标志，表示键击表示键释放事件。有关详细信息，请参阅the API。

最后，您应该使用WHEN_IN_FOCUSED_WINDOW条件将不同的操作附加到面板的输入映射（面板不可聚焦）。

另请参阅此主题：Key bindings vs. key listeners in Java和How to Use Key Bindings教程

进行自定义绘画

请注意，您不应该覆盖paint(...)方法，而应覆盖paintComponent(...)。见A Closer Look at the Paint Mechanism

KeyListener出现问题

1 个答案:

KeyListener

进行自定义绘画