使用滑块处理程序用弧填充椭圆

Question

我想知道如何在用户调整滑块值时用度数填充椭圆内部的弧。滑块侦听器位于与弧和椭圆不同的文件中。

Answer 1

1. 在进行任何自定义绘制之前，先调用super.paintComponent，这样可以防止生成任何可能的绘制工件，虽然时髦，但并不是很好。有关详细信息，请参阅Painting in AWT and Swing和Performing Custom Painting
2. 当滑块状态发生变化时，将当前值传递给用于绘制圆弧的组件并在其上调用reapint
3. 小心地将组件与自定义绘画与其他组件（弧形窗格上的滑块）混合，因为如果您不希望它被其他组件覆盖，则很难确定如何执行自定义绘画...



import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JSlider;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;

public class FillEllipse {

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

    public FillEllipse() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                final ArcPane arcPane = new ArcPane();
                final JSlider slider = new JSlider(0, 360);
                slider.addChangeListener(new ChangeListener() {
                    @Override
                    public void stateChanged(ChangeEvent e) {
                        int value = slider.getValue();
                        arcPane.setAngle(value);
                    }
                });
                slider.setValue(0);

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(arcPane);
                frame.add(slider, BorderLayout.SOUTH);
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class ArcPane extends JPanel {

        private int angel;

        public ArcPane() {
        }

        public void setAngle(int angel) {

            this.angel = angel;
            repaint();

        }

        public int getAngel() {
            return angel;
        }

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

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();

            int diameter = Math.min(getWidth(), getHeight());
            int x = (getWidth() - diameter) / 2;
            int y = (getHeight() - diameter) / 2;

            g2d.setColor(Color.RED);
            g2d.fillArc(x, y, diameter, diameter, 0, getAngel());
            g2d.dispose();
        }

    }

}