在Java中绘制圆的切片？

Question

我想用填充的圆表示计时器，通过小段时间内的绘制来完整绘制整个圆。例如，如果在四秒钟的计时器中，每一秒钟都填满圆，则第一个圆将显示四分之一的圆形，然后是半圆、三分之三和最后是一个完整的圆形。

有没有一种方法可以在Java中绘制这些圆的部分？我已经研究了图形API中的任意形状，但不确定是否应该这样做，或是是否有内置到语言中的东西可以轻松生成这些类型的形状？

非常感谢任何帮助。

- John Smith

---

可以的，是的，Graphics2D是正确的API，看一下Graphics2D，特别是Arc2D类。你还需要研究javax.swing.Timer。 - MadProgrammer

Answer 1

是的，这是可能的。是的，Graphics2D有能力为您完成此操作。

看一下绘制几何图形（查找Arc2D部分）。

要“动画”进度，最简单的方法可能是使用javax.swing.Timer，但您的要求可能需要您改用SwingWorker。请查看Swing中的货币和如何使用Swing计时器以获取更多信息。

以下示例相对简单。它假设进度为0-100％并根据需要生成弧形。如果您想要一个圆形轮廓线，只需更改Graphics2D上下文的颜色并使用draw(Shape)进行绘制即可。

import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.FlowLayout;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Insets;
import java.awt.RenderingHints;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.geom.Arc2D;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class ArcProgress {

    public static void main(String[] args) {
        new ArcProgress();
    }
    private float progress;

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

                final ArcProgressPane p1 = new ArcProgressPane();
                p1.setForeground(Color.RED);
                final ArcProgressPane p2 = new ArcProgressPane();
                p2.setForeground(Color.BLUE);
                p2.setFillProgress(true);

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new FlowLayout());
                frame.add(p1);
                frame.add(p2);
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);

                Timer timer = new Timer(40, new ActionListener() {
                    @Override
                    public void actionPerformed(ActionEvent e) {
                        progress += 0.01f;
                        if (progress >= 1f) {
                            progress = 1f;
                            ((Timer) e.getSource()).stop();
                        }
                        p1.setProgress(progress);
                        p2.setProgress(progress);
                    }
                });
                timer.setRepeats(true);
                timer.setCoalesce(true);
                timer.start();

            }
        });
    }

    public class ArcProgressPane extends JPanel {

        private boolean fillProgress = false;
        private float progress;

        public ArcProgressPane() {
        }

        public void setFillProgress(boolean value) {
            if (fillProgress != value) {
                this.fillProgress = value;
                firePropertyChange("fillProgress", !fillProgress, fillProgress);
            }
        }

        public boolean isFillProgress() {
            return fillProgress;
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(100, 100);
        }

        public void setProgress(float value) {
            if (progress != value) {
                float old = progress;
                this.progress = value;
                firePropertyChange("progress", old, progress);
                repaint();
            }
        }

        public float getProgress() {
            return progress;
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);

            Graphics2D g2d = (Graphics2D) g.create();
            g2d.setRenderingHint(RenderingHints.KEY_ALPHA_INTERPOLATION, RenderingHints.VALUE_ALPHA_INTERPOLATION_QUALITY);
            g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
            g2d.setRenderingHint(RenderingHints.KEY_COLOR_RENDERING, RenderingHints.VALUE_COLOR_RENDER_QUALITY);
            g2d.setRenderingHint(RenderingHints.KEY_DITHERING, RenderingHints.VALUE_DITHER_ENABLE);
            g2d.setRenderingHint(RenderingHints.KEY_FRACTIONALMETRICS, RenderingHints.VALUE_FRACTIONALMETRICS_ON);
            g2d.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
            g2d.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
            g2d.setRenderingHint(RenderingHints.KEY_STROKE_CONTROL, RenderingHints.VALUE_STROKE_PURE);

            Insets insets = getInsets();
            int width = getWidth() - (insets.left + insets.right);
            int height = getHeight() - (insets.bottom + insets.top);
            int raidus = Math.min(width, height);
            int x = insets.left + ((width - raidus) / 2);
            int y = insets.right + ((height - raidus) / 2);

            double extent = 360d * progress;

            g2d.setColor(getForeground());
            Arc2D arc = null;
            if (isFillProgress()) {
                arc = new Arc2D.Double(x, y, raidus, raidus, 90, -extent, Arc2D.PIE);
            } else {
                extent = 360 - extent;
                arc = new Arc2D.Double(x, y, raidus, raidus, 90, extent, Arc2D.PIE);
            }
            g2d.fill(arc);
            g2d.dispose();
        }
    }
}

- MadProgrammer