如何在JFrame中使用KeyListener？

如何在JFrame中使用KeyListener？

矩形没有移动，因为使用不

Jframe

正确。您必须分配

frame

给

new mainframe()

而不是忽略实例化的

mainframe

对象。

@MadProgrammer指出了其他一些问题。

这是修复某些问题的代码：

mainframe.java

import java.awt.*;import java.awt.event.KeyEvent;import java.awt.event.KeyListener;import javax.swing.Jframe;public class mainframe extends Jframe implements KeyListener{    private mainDraw draw;    public void keyPressed(KeyEvent e) {        System.out.println("keyPressed");    }    public void keyReleased(KeyEvent e) {        if(e.getKeyCode()== KeyEvent.VK_RIGHT) draw.moveRight();        else if(e.getKeyCode()== KeyEvent.VK_LEFT) draw.moveLeft();        else if(e.getKeyCode()== KeyEvent.VK_DOWN) draw.moveDown();        else if(e.getKeyCode()== KeyEvent.VK_UP) draw.moveUp();    }    public void keyTyped(KeyEvent e) {        System.out.println("keyTyped");    }    public mainframe(){        this.draw=new mainDraw();        addKeyListener(this);        setFocusable(true);        setFocusTraversalKeysEnabled(false);    }    public static void main(String[] args) {        javax.swing.SwingUtilities.invokeLater(new Runnable() { public void run() {     mainframe frame = new mainframe();     frame.setTitle("Square Move Practice");     frame.setResizable(false);     frame.setSize(600, 600);     frame.setMinimumSize(new Dimension(600, 600));     frame.setDefaultCloseOperation(Jframe.EXIT_ON_CLOSE);     frame.getContentPane().add(frame.draw);     frame.pack();     frame.setVisible(true); }        });    }}

mainDraw.java

import java.awt.Color;import java.awt.Graphics;import javax.swing.JComponent;public class mainDraw extends JComponent {    public int x = 50;    public int y = 50;    public void paintComponent(Graphics g) {        super.paintComponent(g);        g.drawRect(x, y, 50, 50);        g.fillRect(x, y, 50, 50);        g.setColor(Color.BLACK);    }    public void moveRight() {        x = x + 5;        repaint();    }    public void moveLeft() {        x = x - 5;        repaint();    }    public void moveDown() {        y = y + 5;        repaint();    }    public void moveUp() {        y = y - 5;        repaint();    }}

顺便说一句，用于

SwingUtilities

放置gui更新代码，因为swing对象不是线程安全的。