Java更改JPanel的形状 [英] Java Change shape of JPanel

问题描述

我正在尝试做一些我认为很简单但找不到直接答案的事情.基本上，我想将JPanel的默认形状更改为圆形(或矩形以外的其他任何形状).

I'm trying to do something which I'd think would be fairly easy but can't find a straight forward answer to. Basically I want to change a JPanel's default shape to a circular shape (or any other shape other than a rectangle).

推荐答案

您将需要提供自己的自定义绘制例程.

You will need to provide your own custom painting routines.

您将遇到的另一个问题是让布局管理器使用它，但是您可以提供自己的插图以在面板中提供可以安全使用的区域

The other problem you will have is getting the layout managers to work with it, but you can supply your own insets to provided an area within the panel that can safely used

您还希望使组件透明，以使组件的圆形位置之外的区域透明.

You'll also want to make the component transparent, to allow the area outside the circle position of the component to be transparent.

退房

• 自定义绘画
• JCompnent#getInsets

您可能还需要操纵Graphics上下文的剪切矩形.这是棘手和危险的，如果可以避免的话，我会的.

You might need to also manipulate the clipping rectangle of the Graphics context. This is tricky and dangerous and if you can avoid it, I would.

已更新示例

public class CirclePaneTest {

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

    public CirclePaneTest() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (Exception ex) {
                }

                JFrame frame = new JFrame("Test");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        public TestPane() {
            setBackground(Color.RED);
            setLayout(new GridBagLayout());
            CirclePane circlePane = new CirclePane();
            JLabel label = new JLabel("This is a test");
            label.setHorizontalAlignment(JLabel.CENTER);
            label.setVerticalAlignment(JLabel.CENTER);
            // This is a test to show the usable bounds
            label.setBorder(new LineBorder(Color.RED));
            circlePane.setLayout(new BorderLayout());
            circlePane.add(label);
            add(circlePane);
        }

    }

    public class CirclePane extends JPanel {

        public CirclePane() {
            setOpaque(false);
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }

        protected int getRadius() {
            // Determines the radius based on the smaller of the width
            // or height, so we stay symmetrical
            return Math.min(getWidth(), getHeight());
        }

        @Override
        public Insets getInsets() {
            int radius = getRadius();
            int xOffset = (getWidth() - radius) / 2;
            int yOffset = (getHeight() - radius) / 2;
            // These are magic numbers, you might like to calculate
            // your own values based on your needs
            Insets insets = new Insets(
                    radius / 6,
                    radius / 6,
                    radius / 6,
                    radius / 6);
            return insets;
        }

        @Override
        protected void paintComponent(Graphics g) {

            super.paintComponent(g);

            int radius = getRadius();
            int xOffset = (getWidth() - radius) / 2;
            int yOffset = (getHeight() - radius) / 2;

            Graphics2D g2d = (Graphics2D) g.create();
            g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
            g2d.setColor(getBackground());
            g2d.fillOval(xOffset, yOffset, radius, radius);
            g2d.setColor(Color.GRAY);
            g2d.drawOval(xOffset, yOffset, radius, radius);
//            This is test code to test the insets/usable area bounds...
//            Insets insets = getInsets();
//            g2d.drawRect(xOffset + insets.left, 
//                    yOffset + insets.top,
//                    (xOffset + radius) - (insets.right + insets.left), 
//                    (yOffset + radius) - (insets.bottom + insets.top));
            g2d.dispose();

        }
    }
}

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