Question

我知道关于动作监听器等存在很多问题。但是，对于我的特定问题，没有任何人可以帮助我...无论我尝试采用哪种方式，我总是会出错。这是我简单的弹跳球程序：

public class ControlledBall extends JPanel implements Runnable {

    int diameter;
    long delay;
    private int x;
    private int y;
    private int vx;
    private int vy;

    public ControlledBall(int xvelocity, int yvelocity) {


        diameter = 30;
        delay = 40;
        x = 1;
        y = 1;
        vx = xvelocity;
        vy = yvelocity;
    }

    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D)g;
        g.setColor(Color.blue);
        g.fillOval(x,y,30,30);
        g.setColor(Color.black);
        g2.drawOval(x,y,30,30); //draw
    }

    public void run() {
        while(isVisible()) {
            try {
                Thread.sleep(delay);
            } catch(InterruptedException e) {
                System.out.println("Something Went Wrong!");
            }
            move();
            repaint();
        }
    }

    public void move() {
        if(x + vx < 0 || x + diameter + vx > getWidth()) {
            vx *= -1;
        }
        if(y + vy < 0 || y + diameter + vy > getHeight()) {
            vy *= -1;
        }
        x += vx;
        y += vy;

    }

    public void stop(){
        x=0;
        y=0;
    }

    public class Action implements ActionListener{
        public void actionPerformed(ActionEvent e){
            stop();
        }
    }



    public static void main(String[] args) {
        ControlledBall ball2 = new ControlledBall(12,2);
        JFrame window = new JFrame("Controlled Ball");
        window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        window.setLayout(new GridBagLayout());
        GridBagConstraints c = new GridBagConstraints();
        JButton stop = new JButton("Stop");
        stop.setSize(4,400);
        stop.setVisible(true);
        stop.setText("Stop");
 //       stop.addActionListener(new Action());

        stop.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {

           }
        });

        window.add(stop);
        JButton start = new JButton("Start");
        start.setSize(100,100);
        start.setVisible(true);
        start.setText("Start");
        window.add(start);
        start.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {

            }
        });


        c.ipadx = 400;
        c.ipady = 400;
        c.gridx = 10;
        c.gridy = 10;
        window.add(ball2,c);
       c.ipadx = 50;
      c.ipady = 20;
       c.gridx = 10;
       c.gridy = 10;

        window.pack();
        window.setSize(600,600);
        window.setLocation(250,200);
        window.setVisible(true);


        new Thread(ball2).start();
    }
}

正如您所看到的，我已经尝试了几种不同的技术，但都没有奏效。任何建议将不胜感激。谢谢

我得到的主要错误是：

non static field cannot be referenced from a static context

我认为那是因为我正在从main方法运行它。

Answer 1

您真正想做的第一件事是摆脱run方法（以及对Runnable的依赖）。这确实是在Swing中执行定期更新的不适当方法。

Swing是单线程的，并且不是线程安全的，您当前的方法面临跨线程边界进行脏读/写操作的风险。

相反，您想使用Swing Timer，有关更多详细信息，请参见How to Use Swing Timers。

接下来要做的是添加一个start方法并更新stop方法以支持使用Swing Timer ...

public class ControlledBall extends JPanel {

    //...

    private Timer timer;

    public void stop() {
        if (timer == null) {
            return;
        }
        timer.stop();
        timer = null;
        x = 0;
        y = 0;
    }

    public void start() {
        if (timer != null) {
            return;
        }
        timer = new Timer(delay, new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                move();
                repaint();
            }
        });
        timer.start();
    }

然后，只需更新您的开始和停止按钮即可调用这些方法...

    stop.addActionListener(new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent e) {
            ball2.stop();
        }
    });
    //...
    start.addActionListener(new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent e) {
            ball2.start();
        }
    });

我如何使我的按钮工作？ Java

1 个答案: