如果JPanel填满整个屏幕，它将不会移动

Question

First of all, sorry for the vague title I don't know how to word the question in a sentence.

I have a simple programme that slides one JPanel into view as another gets pushed out, when a button is clicked.

If the first JPanel's width is set as getWidth() then the JPanel will not move when the button is clicked, however if I change the width to getWidth() - 1 it works perfectly fine!?!

A simple example is shown below

public class SlidingJPanel extends JFrame{

    public JPanel panel = new JPanel();
    public JPanel panel2 = new JPanel();
    public JLabel label = new JLabel(" SUCCESS!!!!!!!");
    public JButton button = new JButton("TESTING"); 

    public class MyJPanel extends JPanel implements ActionListener{
        public int x = 0;
        public int delay = 70;
        final Timer timer = new Timer(delay,this);

        public MyJPanel(){};

        public void paintComponent(Graphics g)
        {
            super.paintComponent(g);

            button.setBounds(10, 20, 100, 50);
            button.addActionListener(this);
            panel.setBorder(BorderFactory.createLineBorder(Color.black));
            panel.setBounds(x, 0, getWidth(), getHeight());
            panel.add(button);
            panel2.setBorder(BorderFactory.createLineBorder(Color.blue));
            panel2.setBounds(x - getWidth(), 0, getWidth(), getHeight());
            panel2.add(label);
            add(panel);
            add(panel2);
        }

        @Override
        public void actionPerformed(ActionEvent arg0) {
            timer.addActionListener(move);
            timer.start();
        }

        ActionListener move = new ActionListener(){
            public void actionPerformed(ActionEvent e){
                repaint();
                x++;
            }
        };

    }

    public static void main(String args [])
    {         
        new SlidingJPanel();        
    }

    SlidingJPanel()
    {
        Container container = getContentPane();
        MyJPanel panel = new MyJPanel();
        container.add(panel);           
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setSize(500,500);
        setTitle("JPanel Draw Rect Animation");
        setVisible(true);
    }       
}

ignore any coding conventions I may have ignored or missed this is just a rough draft.

Hope someone can help :)

Answer 1

The paintComponent() method is for painting only! There is no need for you to override this method.

You should NOT be:

1. updating the property of components (ie. bounds, border)
2. adding components to a container

If you want to animate a component then when the timer fires you can use setLocation(...) or setSize() or setBounds(). The component will automatically be repainted.

I don't know if fixing this will solve your problem, but the current approach is wrong.