在buffrered圖像上使用鼠標在JPanel上繪製不重疊的n邊多邊形，圓形和橢圓

Question

我想讓Java swing程序使用鼠標繪製不重疊的n邊多邊形，圓形和橢圓形。

多邊形不應該添加最後一個點，並且首先指向自己，直到用戶創建它。

Answer 1

這是一個非常基本的例子

public class DrawPolygon { 

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

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

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

      }); 
     } 

     public static class PolyPane extends JPanel { 

      private MouseHandler mouseHandler; 
      private Path2D currentShape; 
      private List<Path2D> lstPloys; 
      private Point lastPoint; 
      private Point currentPoint; 

      public PolyPane() { 
       lstPloys = new ArrayList<>(); 
      } 

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

      @Override 
      public void addNotify() { 
       super.addNotify(); 
       addMouseListener(getMouseHandler()); 
       addMouseMotionListener(getMouseHandler()); 
      } 

      @Override 
      public void removeNotify() { 
       removeMouseListener(getMouseHandler()); 
       removeMouseMotionListener(getMouseHandler()); 
       super.removeNotify(); 
      } 

      public MouseHandler getMouseHandler() { 
       if (mouseHandler == null) { 
        mouseHandler = new MouseHandler(); 
       } 
       return mouseHandler; 
      } 

      @Override 
      protected void paintComponent(Graphics g) { 
       super.paintComponent(g); 
       Graphics2D g2d = (Graphics2D) g.create(); 
       if (lastPoint != null) { 
        g2d.setColor(Color.RED); 
        g2d.fillOval(lastPoint.x - 2, lastPoint.y - 2, 4, 4); 
       } 
       if (currentShape != null) { 
        g2d.setColor(Color.RED); 
        g2d.draw(currentShape); 
        if (lastPoint != null && currentPoint != null) { 
          System.out.println(lastPoint + " - " + currentPoint); 
          g2d.setColor(new Color(255, 0, 0, 64)); 
          g2d.draw(new Line2D.Float(lastPoint, currentPoint)); 
        } 
       } 
       g2d.setColor(Color.BLACK); 
       for (Shape shape : lstPloys) { 
        g2d.draw(shape); 
       } 
       g2d.dispose(); 
      } 

      public class MouseHandler extends MouseAdapter { 

       @Override 
       public void mouseClicked(MouseEvent e) { 
        if (e.getButton() == MouseEvent.BUTTON1) { 
          if (e.getClickCount() == 1) { 
           Point p = e.getPoint(); 
           lastPoint = p; 
           if (currentShape == null) { 
            currentShape = new Path2D.Float(); 
            currentShape.moveTo(p.x, p.y); 
           } else { 
            currentShape.lineTo(p.x, p.y); 
           } 
           repaint(); 
          } else if (e.getClickCount() == 2) { 
           currentShape.closePath(); 
           lstPloys.add(currentShape); 
           currentShape = null; 
           lastPoint = null; 
           repaint(); 
          } 
        } 
       } 

       @Override 
       public void mouseMoved(MouseEvent e) { 
        if (currentShape != null) { 
          currentPoint = e.getPoint(); 
          repaint(); 
        } else { 
          currentPoint = null; 
        } 
       } 

      } 

     } 

} 

你會希望時間通過

• Performing Custom Painting
• 2D Graphics

012閱讀

由於這些將涵蓋你需要知道的基本知識，以實現你正在嘗試做的事情。

更新

我已經更新的例子，包括表示利用線下一個點MosueMotionListener