在java中绘制一个圆的切片？

Question

我想表示一个定时器，它具有一个填充的圆，它在段定时器的过程中完全绘制。即如果在4秒内每隔1秒钟填充圆圈，则第一个将显示四分之一圆圈，然后是一半，然后是四分之三，最后是一整圈。

有没有办法在java中绘制这些圆的切片？我研究过图形API中的任意形状，但不知道这是否是正确的方式，或者是否有写入语言的东西可以轻松生成这些类型的形状？

任何帮助非常感谢。

Answer 1

是的，这是可能的。是的，Graphics2D有能力为你做这件事

看看Drawing Geometric Primitives（查找Arc2D部分）。

要使进度“动画化”，使用javax.swing.Timer可能是最容易的，但是您的要求可能需要使用SwingWorker来代替。有关更多信息，请参阅Currency in Swing和How to use Swing Timers。

下面的例子比较简单。它假定0-100％的进展并根据需要生成一个弧。这将是一个简单的问题，改变Graphics2D上下文的颜色，并使用draw(Shape)绘制一个你想要圈出的圆圈。

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(); 
     } 
    } 
}