Draggable circle in swing blinks when I drag it

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I'm implementing a Swing program that draws shapes to the screen and then lets the user drag them around. I can draw a shape just fine, but once I click on a shape to drag it, that shape starts to blink as it is dragged.

This is my GUI class and my MouseAdapter class:

public class GUI extends JFrame {
    private JMenu addShapeMenu = new JMenu("Add Shape");
    private JLabel statusBar = new JLabel();
    private List<Shape> _shapes;
    private Shape chosenShape;
    private boolean isShapeClicked = false;
    private List<String> shapeSubclasses = new ArrayList<>();

    public GUI() throws IOException, ClassNotFoundException, IllegalAccessException, InstantiationException {
        super("DrawingBoard");
        setSize(500, 500);
        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

        JMenuBar menuBar = new JMenuBar();
        setJMenuBar(menuBar);
        menuBar.add(addShapeMenu);

        getContentPane().setLayout(new BorderLayout());

        getLoadedShapes();
        for(String shape : shapeSubclasses)
        {
            Class drawableShape = Class.forName("gui.Drawable" + shape);
            addShapeMenu.add(((DrawableShape)drawableShape.newInstance()).getInstance().getMenuItem());
        }

        add(statusBar, BorderLayout.SOUTH);
        statusBar.setText("Add a shape.");

        MouseHandler mouseHandler = new MouseHandler();
        addMouseListener(mouseHandler);
        addMouseMotionListener(mouseHandler);

        setVisible(true);
    }

    private void getLoadedShapes() throws ClassNotFoundException, NullPointerException {
        String classPath = Shape.class.getResource("").getPath();
        classPath = classPath.replaceAll("%20", " ");

        File root = new File(classPath);
        for (File file : root.listFiles()) {
            if (!file.isDirectory()) {
                if (file.getName().endsWith(".class")) {
                    String className = file.getName().substring(0, file.getName().length() - 6);
                    Class<?>[] interfaces = Class.forName("draw." + className).getInterfaces();
                    for(Class<?> classInterface : interfaces)
                    {
                        if(classInterface.getName().compareTo("draw.Shape") == 0)
                            shapeSubclasses.add(className);
                    }
                }
            }
        }
    }

    public void setDrawing(Drawing drawing)
    {
        _shapes = drawing.getShapes();
        AddShapeListener.getInstance().setDrawing(drawing);
        AddShapeListener.getInstance().setGUI(this);
        for (Component component : addShapeMenu.getMenuComponents()) {
            ((JMenuItem)component).addActionListener(AddShapeListener.getInstance());
        }
    }

    public void paint(Graphics graphics)
    {
        super.paint(graphics);
        for(Shape shape : _shapes)
        try
        {
            Class painter = Class.forName("gui.Drawable" + shape.getClass().getSimpleName());
            ((DrawableShape)painter.newInstance()).getInstance().paint(getGraphics(), shape);
        }

        catch(Exception e)
        {
            JOptionPane.showMessageDialog(this, "Failed to load Drawable" + shape);
        }
    }

    public void setStatusBar(String message)
    {
        statusBar.setText(message);
    }

    private class MouseHandler extends MouseAdapter implements MouseMotionListener {
        public void mousePressed(MouseEvent event) {
            _shapes.forEach(shape -> {
                if(shape.isPointInside(event.getX(), event.getY()))
                    chosenShape = shape;
                isShapeClicked = true;
            });
        }

        public void mouseDragged(MouseEvent event) {
            if (isShapeClicked) {
                chosenShape.moveTo(event.getX(), event.getY());
                repaint();
            }
        }

        public void mouseReleased(MouseEvent event) {
            isShapeClicked = false;
                chosenShape = null;
        }
    }
}

where my DrawableCircle class has a method paint:

public void paint(Graphics graphics, Shape shape)
    {
        int radius = ((Circle)shape).getRadius();
        graphics.fillOval(shape.getX() - radius, shape.getY() - radius, radius * 2, radius * 2);
    }

the DrawRectangle class is similar.

asked 17 secs ago

ThomYorkkke

79

Draggable circle in swing blinks when I drag it