2

我只研究了直到方法，没有足够的耐心等到我的 UNI 教我剩下的东西，所以我发现这很有趣......我想创建一个中间有一个圆圈的 GUI，它会根据你用 java 按下的按钮移动。经过大量阅读后，我设法以这种方式完成了它。因此，在我遇到问题中提到的错误之前，我有 19 个错误，只有当我弄清楚所有错误时，这个错误才突然出现。我希望我不会激怒任何人，因为我确信这个错误是由于缺乏编程基础造成的。任何帮助将不胜感激。我指出错误发生在“<---” 

import java.awt.*;
import java.awt.event.*;
public class Move_the_ball extends Frame {

public static void main(String[] args) {
    Move_the_ball me = new Move_the_ball();
    me.setVisible(true);
}
public Move_the_ball(){
    setSize(700,700);
    setLocation(100,100);
    setTitle("Moving the ball");
    setLayout(new BorderLayout());
    Panel buttonPanel = new Panel();
    buttonPanel.setBackground(Color.blue);
    buttonPanel.setLayout(new FlowLayout());

    Button goUp = new Button("Go up");
    goUp.addActionListener(this); <-----------------
    buttonPanel.add(goUp);

    Button goDown = new Button("Go down");
    goDown.addActionListener(this); <--------------
    buttonPanel.add(goDown);


    Button turnRight = new Button("Turn right");
    turnRight.addActionListener(this);  <-------------
    buttonPanel.add(turnRight);


    Button turnLeft = new Button("Turn left");
    turnLeft.addActionListener(this); <---------------
    buttonPanel.add(turnLeft);
}
    public void paint(Graphics g)
        {
        g.fillOval(x,y,h,d);
}
    private int x=200;
    private int y=100;
    private int h=50;
    private int d=50;

    public void actionPerformed (ActionEvent e){
        String actionCommand = e.getActionCommand();
        if(actionCommand.equals("Go up"))
        {
            y=y-5;
            repaint();
        } else if (actionCommand.equals("Go down"))
        {
            y=y+5;
            repaint();
        } else if (actionCommand.equals("Turn right"))
        {
            x=x+5;
            repaint();
        } else if (actionCommand.equals("Turn left"));
        {
            x=x-5;
            repaint();
        }
    } 
 }
4

1 回答 1

4

您的Move_the_ball类必须实现java.awt.event.ActionListener接口才能使其工作。

import java.awt.*;
import java.awt.event.*;
public class Move_the_ball extends Frame implements ActionListener {

   public void actionPerformed(ActionEvent e) {
      // handle the e event
   }
于 2012-05-25T15:03:29.930 回答