java - java中如何保留以前绘制的形状？

Question

在此程序中，我尝试通过从 ComboBox 中选择形状来在面板上绘制形状。但是当我从 ComboBox 中选择新项目(或形状)时，先前绘制的形状会消失。我想一次在面板上显示许多形状 那么我应该怎么做才能保留以前的形状 我正在考虑将所有形状存储在 Arraylist 中，但不知道该怎么做 所以请帮助我

import java.awt.*;
import java.awt.event.*;
import java.util.*;
import java.awt.geom.*;
import javax.swing.*;


 class ShapeTest
{
  public static void main(String args[])
   {
     EventQueue.invokeLater(new Runnable()
      {
        public void run()
         {
           JFrame frame = new ShapeTestFrame();
           frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
           frame.setVisible(true);
         }
      });
    }
}


class ShapeTestFrame extends JFrame
{
  public ShapeTestFrame()
  {
      setTitle("Shape Test");
      setSize(WD,HT);

      Container contentPane = getContentPane();

      final ShapePanel panel = new ShapePanel();
      contentPane.add(panel,BorderLayout.CENTER);
      final JComboBox comboBox = new JComboBox();
      comboBox.addItem(new LineMaker());
      comboBox.addItem(new RectangleMaker());
      comboBox.addItem(new RoundRectangleMaker());
      comboBox.addItem(new EllipseMaker());
      comboBox.addItem(new PolygonMaker());
      comboBox.addItem(new QuadCurveMaker());
      comboBox.addItem(new CubicCurveMaker());

      comboBox.addActionListener(new ActionListener()
      {
         public void actionPerformed(ActionEvent event)
          {
             ShapeMaker shapeMaker = (ShapeMaker)comboBox.getSelectedItem();
             panel.setShapeMaker(shapeMaker);
          }
       });

      contentPane.add(comboBox,BorderLayout.NORTH);
    }

    private static final int WD = 300;
    private static final int HT = 300;
}


class ShapePanel extends JPanel 
{
  private Point2D[] points ;
  private static Random generator = new Random();
  private static int SIZE = 10;
  private int current;
  private ShapeMaker shapeMaker;

  public ShapePanel()
  {
    addMouseListener(new MouseAdapter()
      {
         public void mousePressed(MouseEvent event)
          {
             Point p = event.getPoint();
             for(int i = 0; i<points.length;i++)
             {
               //System.out.println("points = "+points);
               double x = points[i].getX() - SIZE/2;
               double y = points[i].getY() - SIZE/2;
               Rectangle2D r = new Rectangle2D.Double(x,y,SIZE,SIZE);
               if (r.contains(p))
               {
                  current = i;
                  return;
               }
            }
         }

         public void mouseReleased(MouseEvent event)
         {
             current = -1;
         }
      });

  addMouseMotionListener(new MouseMotionAdapter()
  {
     public void mouseDragged(MouseEvent event) 
     {
       if(current == -1)     return;
       points[current]  = event.getPoint();
       repaint();
     }
   });
  current = -1;
  }

  public void setShapeMaker(ShapeMaker aShapeMaker)
   {
      shapeMaker = aShapeMaker;
      int n = shapeMaker.getPointCount();
      points = new Point2D[n];
      for(int i = 0; i<n; i++)
      {
         double x = generator.nextDouble()*getWidth();
         double y = generator.nextDouble()*getHeight();
         points[i] = new Point2D.Double(x,y);
       }  
       repaint();
     }

    public void paintComponent(Graphics g)
    {
      super.paintComponent(g);
      if(points ==null)   return;
      Graphics2D g2 = (Graphics2D) g;
      for(int i = 0; i < points.length ; i++)
       {
          double x = points[i].getX() - SIZE/2;
          double y = points[i].getY() - SIZE/2;
          g2.fill(new Rectangle2D.Double(x,y,SIZE,SIZE));
        }

       g2.draw(shapeMaker.makeShape(points));
     }


}


abstract class ShapeMaker
{
  private int pointCount;

  public ShapeMaker(int aPointCount)
  {
     pointCount = aPointCount;
  }

  public int getPointCount()
   {
      return pointCount;
    }

  public abstract Shape makeShape(Point2D[] p);

  public String toString()
  {
     return getClass().getName();
   }

}


class LineMaker extends ShapeMaker
{
  public LineMaker(){    super(2);     }

  public Shape makeShape(Point2D[] p)
   {
      return new Line2D.Double(p[0],p[1]);
   }
}

class RectangleMaker extends ShapeMaker
{
  public RectangleMaker()  {    super(2);     }

  public Shape makeShape(Point2D[] p)
  {
    Rectangle2D s = new Rectangle2D.Double();
    s.setFrameFromDiagonal(p[0],p[1]);
    return s;
   }
}

class RoundRectangleMaker extends ShapeMaker
{
  public RoundRectangleMaker()  {  super(2);    }

  public Shape makeShape(Point2D[] p)
  {
    RoundRectangle2D s = new RoundRectangle2D.Double(0,0,0,0,20,20);
    s.setFrameFromDiagonal(p[0],p[1]);
    return s;
  }
}


class EllipseMaker extends ShapeMaker
{
  public EllipseMaker()   {   super(2);     }

  public Shape makeShape(Point2D[] p)
   {
     Ellipse2D s = new Ellipse2D.Double();
     s.setFrameFromDiagonal(p[0],p[1]);
     return s;
    }
}


class PolygonMaker extends ShapeMaker
{
   public PolygonMaker()    {   super(6);    }

   public Shape makeShape(Point2D[] p)
   {
     GeneralPath s = new GeneralPath();
     s.moveTo((float)p[0].getX(),(float)p[0].getY());
     for(int i = 1; i< p.length; i++)

           s.lineTo((float)p[i].getX(),(float)p[i].getY());
           s.closePath();
           return s;
   }
}


class QuadCurveMaker extends ShapeMaker
{
  public QuadCurveMaker()  {   super(3);     }

  public Shape makeShape(Point2D[] p)
   {
      return new QuadCurve2D.Double(p[0].getX(),p[0].getY(),p[1].getX(),p[1].getY(),p[2].getX(),p[2].getY());
   }
}


class CubicCurveMaker extends ShapeMaker
{
  public CubicCurveMaker()  {   super(4);      }  

  public Shape makeShape(Point2D[] p)
  {
     return new CubicCurve2D.Double(p[0].getX(),p[0].getY(),p[1].getX(),p[1].getY(),p[2].getX(),p[2].getY(),p[3].getX(),p[3].getY());
  }
}

Answer 1

将形状保存到 List<Shape> 。为此，请考虑添加形状 Shape 字段。例如，

import java.awt.*;
import java.awt.event.*;
import java.util.*;
import java.util.List;
import java.awt.geom.*;

import javax.swing.*;

class ShapeTest {
   public static void main(String args[]) {
      EventQueue.invokeLater(new Runnable() {
         public void run() {
            JFrame frame = new ShapeTestFrame();
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            frame.setVisible(true);
         }
      });
   }
}

class ShapeTestFrame extends JFrame {
   public ShapeTestFrame() {
      setTitle("Shape Test");

      Container contentPane = getContentPane();

      final ShapePanel panel = new ShapePanel();
      contentPane.add(panel, BorderLayout.CENTER);
      final JComboBox comboBox = new JComboBox();
      comboBox.addItem(new LineMaker());
      comboBox.addItem(new RectangleMaker());
      comboBox.addItem(new RoundRectangleMaker());
      comboBox.addItem(new EllipseMaker());
      comboBox.addItem(new PolygonMaker());
      comboBox.addItem(new QuadCurveMaker());
      comboBox.addItem(new CubicCurveMaker());

      comboBox.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent event) {
            ShapeMaker shapeMaker = (ShapeMaker) comboBox.getSelectedItem();
            panel.setShapeMaker(shapeMaker);
         }
      });

      contentPane.add(comboBox, BorderLayout.NORTH);
      pack();
   }

}

class ShapePanel extends JPanel {

   private static final int WD = 600;
   private static final int HT = WD;
   private static final Color SHAPES_COLOR = Color.RED;
   private static final Color SHAPE_COLOR = Color.black;
   private List<Shape> shapes = new ArrayList<>();
   private Point2D[] points;
   private static Random generator = new Random();
   private static int SIZE = 10;
   private int current;
   private ShapeMaker shapeMaker;
   private Shape shape;

   public ShapePanel() {

      addMouseListener(new MouseAdapter() {
         public void mousePressed(MouseEvent event) {
            Point p = event.getPoint();
            for (int i = 0; i < points.length; i++) {
               // System.out.println("points = "+points);
               double x = points[i].getX() - SIZE / 2;
               double y = points[i].getY() - SIZE / 2;
               Rectangle2D r = new Rectangle2D.Double(x, y, SIZE, SIZE);
               if (r.contains(p)) {
                  current = i;
                  return;
               }
            }
         }

         public void mouseReleased(MouseEvent event) {
            current = -1;
         }
      });

      addMouseMotionListener(new MouseMotionAdapter() {
         public void mouseDragged(MouseEvent event) {
            if (current == -1)
               return;
            points[current] = event.getPoint();
            shape = shapeMaker.makeShape(points);
            repaint();
         }
      });
      current = -1;

      JPanel bottomPanel = new JPanel();
      bottomPanel.add(new JButton(new SaveShapeAction("Save Shape")));
      setLayout(new BorderLayout());
      add(bottomPanel, BorderLayout.PAGE_END);
   }

   public void setShapeMaker(ShapeMaker aShapeMaker) {
      shapeMaker = aShapeMaker;
      int n = shapeMaker.getPointCount();
      points = new Point2D[n];
      for (int i = 0; i < n; i++) {
         double x = generator.nextDouble() * getWidth();
         double y = generator.nextDouble() * getHeight();
         points[i] = new Point2D.Double(x, y);
      }
      shape = shapeMaker.makeShape(points);
      repaint();
   }

   public Dimension getPreferredSize() {
      return new Dimension(WD, HT);
   }

   public void paintComponent(Graphics g) {
      super.paintComponent(g);
      if (points == null)
         return;
      Graphics2D g2 = (Graphics2D) g;
      g2.setColor(SHAPES_COLOR);
      for (Shape shape : shapes) {
         g2.draw(shape);
      }
      g2.setColor(SHAPE_COLOR);
      for (int i = 0; i < points.length; i++) {
         double x = points[i].getX() - SIZE / 2;
         double y = points[i].getY() - SIZE / 2;
         g2.fill(new Rectangle2D.Double(x, y, SIZE, SIZE));
      }

      if (shape != null) {
         g2.draw(shape);
      }
   }

   private class SaveShapeAction extends AbstractAction {
      public SaveShapeAction(String name) {
         super(name);
         int mnemonic = (int) name.charAt(0);
      }

      @Override
      public void actionPerformed(ActionEvent e) {
         shapes.add(shape);
         repaint();
      }
   }

}

abstract class ShapeMaker {
   private int pointCount;

   public ShapeMaker(int aPointCount) {
      pointCount = aPointCount;
   }

   public int getPointCount() {
      return pointCount;
   }

   public abstract Shape makeShape(Point2D[] p);

   public String toString() {
      return getClass().getName();
   }

}

class LineMaker extends ShapeMaker {
   public LineMaker() {
      super(2);
   }

   public Shape makeShape(Point2D[] p) {
      return new Line2D.Double(p[0], p[1]);
   }
}

class RectangleMaker extends ShapeMaker {
   public RectangleMaker() {
      super(2);
   }

   public Shape makeShape(Point2D[] p) {
      Rectangle2D s = new Rectangle2D.Double();
      s.setFrameFromDiagonal(p[0], p[1]);
      return s;
   }
}

class RoundRectangleMaker extends ShapeMaker {
   public RoundRectangleMaker() {
      super(2);
   }

   public Shape makeShape(Point2D[] p) {
      RoundRectangle2D s = new RoundRectangle2D.Double(0, 0, 0, 0, 20, 20);
      s.setFrameFromDiagonal(p[0], p[1]);
      return s;
   }
}

class EllipseMaker extends ShapeMaker {
   public EllipseMaker() {
      super(2);
   }

   public Shape makeShape(Point2D[] p) {
      Ellipse2D s = new Ellipse2D.Double();
      s.setFrameFromDiagonal(p[0], p[1]);
      return s;
   }
}

class PolygonMaker extends ShapeMaker {
   public PolygonMaker() {
      super(6);
   }

   public Shape makeShape(Point2D[] p) {
      GeneralPath s = new GeneralPath();
      s.moveTo((float) p[0].getX(), (float) p[0].getY());
      for (int i = 1; i < p.length; i++)

         s.lineTo((float) p[i].getX(), (float) p[i].getY());
      s.closePath();
      return s;
   }
}

class QuadCurveMaker extends ShapeMaker {
   public QuadCurveMaker() {
      super(3);
   }

   public Shape makeShape(Point2D[] p) {
      return new QuadCurve2D.Double(p[0].getX(), p[0].getY(), p[1].getX(),
            p[1].getY(), p[2].getX(), p[2].getY());
   }
}

class CubicCurveMaker extends ShapeMaker {
   public CubicCurveMaker() {
      super(4);
   }

   public Shape makeShape(Point2D[] p) {
      return new CubicCurve2D.Double(p[0].getX(), p[0].getY(), p[1].getX(),
            p[1].getY(), p[2].getX(), p[2].getY(), p[3].getX(), p[3].getY());
   }
}