java JFrame graphics

graphics, java, jframe, paint, swing

Solution

Dont override`paint(..)` in `JFrame`

Rather add custom `JPanel` with overridden `paintComponent(Graphics g)` to `JFrame`

Dont use `Null`/`AbsoluteLayout` use an appropriate `LayoutManager`

Dont call `setBounds(..)` on `JFrame` instance (not that its not allowed but cant see it being relevant in this application)

Dont forget to use EDT for creating and changing GUI components:

javax.swing.SwingUtilities.invokeLater(new Runnable() {
            @Override
           public void run() {
                Test test = new Test();
           }
});

you would then do something like this:

public class Test {

    /**
     * Default constructor for Test.class
     */
    public Test() {
        initComponents();
    }

    public static void main(String[] args) {

        /**
         * Create GUI and components on Event-Dispatch-Thread
         */
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                Test test = new Test();
            }
        });
    }

    /**
     * Initialize GUI and components (including ActionListeners etc)
     */
    private void initComponents() {
        JFrame jFrame = new JFrame();
        jFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        jFrame.add(new MyPanel());

        //pack frame (size JFrame to match preferred sizes of added components and set visible
        jFrame.pack();
        jFrame.setVisible(true);
    }
}

class MyPanel extends JPanel {

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        int[] x = new int[]{65, 122, 77, 20};
        int[] y = new int[]{226, 258, 341, 310};
        g.setColor(Color.RED);
        g.drawPolygon(x, y, x.length);
    }

    //so our panel is the corerct size when pack() is called on Jframe
    @Override
    public Dimension getPreferredSize() {
        return new Dimension(400, 400);
    }
}

which produces:

Problem

Original source