使用KeyListener使用箭头键在JPanel中移动矩形

Question

我一直试图JPanel用箭头键移动.它没有奏效.我相信这是我的内心阶级KeyAdapter.我也不确定ActionListener它是否实现了.我所做的另一课并不重要,因为它只是框架.

package jerryWorlds;

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

public class Jerry extends JPanel implements ActionListener{

int SizeX, SizeY, PosX, PosY, VelX, VelY;
Image img;
Timer time = new Timer(1, this);

public Jerry(){
    ImageIcon i = new ImageIcon();
    addKeyListener(new AL());
    time.start();
    img = i.getImage();
    PosX = 375;
    PosY = 250;
}

public void paint(Graphics g){
    Graphics2D g2d = (Graphics2D)g;
    g2d.fillRect(PosX, PosY, 50, 100);
}
public void actionPerformed(ActionEvent e) {
    PosX = PosX + VelX;
    repaint();
}

private class AL extends KeyAdapter{
    public void keyPressed(KeyEvent e) {
        int key = e.getKeyCode();
        System.out.println("YAY!");
        if(key == KeyEvent.VK_LEFT)
            VelX = -1;
        else if(key == KeyEvent.VK_RIGHT)
            VelX = 1;
    }

    public void keyReleased(KeyEvent e) {
        int key = e.getKeyCode();
        if(key == KeyEvent.VK_LEFT)
            VelX = 0;
        else if(key == KeyEvent.VK_RIGHT)
            VelX = 0;
    }
}

}

Answer 1

• 您将需要在此网站上搜索类似的问题,因为它们通常具有相同的问题和相同的答案.
• 他们会告诉你焦点是一个问题,因为除非它具有焦点,否则组件的KeyListener将无法工作.
• 他们会告诉你,不管你不应该使用KeyListener而不是Key Bindings.
• 他们会告诉你不要覆盖paint(...),而是paintComponent(...)除非你确定要覆盖组件边框和子项的绘制(你没有).
• 他们会告诉你一定要调用里面的super方法paintComponent(...).

另请查看此动画和键绑定示例.