每当我用类名创建一个新对象时,都会收到以下错误消息:
"无法实例化类型Main"
这是代码:
import javax.swing.*;
import java.util.Scanner;
import java.applet.Applet;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.geom.Ellipse2D;
public abstract class Main extends JPanel implements ActionListener, KeyListener{
Timer t = new Timer(5, this);
double x = 0, y = 0, velX = 0, velY = 0;
public Main() {
t.start();
addKeyListener(this);
setFocusable(true);
setFocusTraversalKeysEnabled(false);
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
g2.fill(new Ellipse2D.Double(x, y, 40, 40));
}
public void actionPerformed(ActionEvent e) {
repaint();
x += velX;
y += velY;
}
public void up() {
velY = -1.5;
velX = 0;
}
public void down() {
velY = -1.5;
velX = 0;
}
public void left() {
velX = -1.5;
velY = 0;
}
public void right() {
velX = -1.5;
velY = 0;
}
public void keyPressed(KeyEvent e) {
int code = e.getKeyCode();
if (code == KeyEvent.VK_UP) {
up();
}
if (code == KeyEvent.VK_DOWN) {
down();
}
if (code == KeyEvent.VK_LEFT) {
left();
}
if (code == KeyEvent.VK_RIGHT) {
right();
}
Main m = new Main();
JFrame f = new JFrame();
f.add(m);
f.setVisible(true);;
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setSize(800,600);
}
public void keyTyped(KeyEvent e) {}
public void keyReleased(KeyEvent e) {}
}
这是一直出现“错误”的对象:
Main m = new Main();
我非常非常新手制作UI,事实上,这是我的第三个,所以我不知道为什么我无法实例化该类型。
abstract
限定符上也一样--把它去掉。同时,似乎需要将public void keyPressed(KeyEvent)
方法的最后一部分移动到public static void main(String[])
方法中。 - Ted Hopp