JAVA drawString问题

Posted 2023-03-18

我想做一个这样的程序：
监听键盘按键，除了按上、下、左、右方向键外，按其他键，窗口上就显示其他键值。按方向键，就移动窗口上的字符
比如我打开程序，按了一个Z，然后窗口上就显示Z，我再按方向键，就可以移动这个Z
可是我现在发现，X、Y的坐标值是可以根据我按方向键而变化的，就是按了屏幕上没反应，总是显示程序一开始时默认的画面
程序代码如下
import java.awt.event.*;import javax.swing.*;import java.awt.*;public class Test extends JFrame public static void main(String[] args) JFrame frame=new JFrame("title"); frame.setDefaultCloseOperation(frame.EXIT_ON_CLOSE); frame.setSize(300,300); frame.setVisible(true); frame.addKeyListener(new KeyboardPanel()); frame.getContentPane().add(new KeyboardPanel()); class KeyboardPanel extends JPanel implements KeyListener private int x = 100; private int y = 100; private char keyChar='A'; public void keyRelessed(KeyEvent e) public void keyPressed(KeyEvent e) switch(e.getKeyCode()) case KeyEvent.VK_DOWN: y+=10;break; case KeyEvent.VK_UP: y-=10;break; case KeyEvent.VK_LEFT:x-=10;break; case KeyEvent.VK_RIGHT: x+=10;break; default:keyChar=e.getKeyChar(); protected void paintComponent(Graphics g) super.paintComponent(g); g.setFont(new Font("TimesRoman",Font.PLAIN,24)); g.setColor(Color.black); g.drawString(String.valueOf(keyChar), x, y); System.out.println("x="+x+" y="+y);//输出测试一下 @Override public void keyReleased(KeyEvent arg0) @Override public void keyTyped(KeyEvent arg0)

你的程序我帮你改好了,你看看吧.完整的程序如下:

import java.awt.event.*;

import javax.swing.*;

import java.awt.*;

public class Test extends JFrame



    public static void main(String[] args)

    

        JFrame frame=new JFrame("title");

        KeyboardPanel kp=new KeyboardPanel();

        frame.getContentPane().add(kp);

        frame.setDefaultCloseOperation(frame.EXIT_ON_CLOSE);

        frame.setSize(300,300);

        frame.setVisible(true);

        kp.requestFocus();//把焦点移到KeyboardPanel上

        //frame.addKeyListener(new KeyboardPanel());//这里去掉,把监听加到KeyboardPanel上

    



class KeyboardPanel extends JPanel implements KeyListener



    private int x = 100;

    private int y = 100;

    private char keyChar='A';

    KeyboardPanel()

     addKeyListener(this);//把监听加到KeyboardPanel上

    

    public void keyRelessed(KeyEvent e)

    

    public void keyPressed(KeyEvent e)

    

        switch(e.getKeyCode())

        

            case KeyEvent.VK_DOWN: y+=10;break;

            case KeyEvent.VK_UP: y-=10;break;

            case KeyEvent.VK_LEFT:x-=10;break;

            case KeyEvent.VK_RIGHT: x+=10;break;

            default:keyChar=e.getKeyChar();

        

        repaint();//这里刷新KeyboardPanel

    

    protected void paintComponent(Graphics g)

    

        super.paintComponent(g);

        g.setFont(new Font("TimesRoman",Font.PLAIN,24));

        g.setColor(Color.black);

        g.drawString(String.valueOf(keyChar), x, y);

        System.out.println("x="+x+" y="+y);//输出测试一下

    

    @Override

    public void keyReleased(KeyEvent arg0) 

    

    @Override

    public void keyTyped(KeyEvent arg0) 

    

参考技术A case KeyEvent.VK_DOWN: y+=10;break;
case KeyEvent.VK_UP: y-=10;break;
case KeyEvent.VK_LEFT:x-=10;break;
case KeyEvent.VK_RIGHT: x+=10;break;
default:keyChar=e.getKeyChar();
坐标改变之后应该要调用一下repaint()方法
比如case KeyEvent.VK_DOWN: y+=10;repaint();break;
调用repaint方法之前可能还要擦除原图像。。