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在这个程序中，我试图通过从ComboBox中选择形状来绘制面板上的形状。但是当我从comboBox中选择新项目（或形状）时，以前绘制的形状消失。我想有面板上许多形状一次 所以我应该怎么办保留我以前的形状 我想在ArrayList的各种形状的存储，但DONOT知道该怎么做 所以，请帮我如何在java中保留以前绘制的形状？
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());
}
}
或者1.创建一个形状集合或者2.绘制不会更改为BufferedImage的图像，该图像显示在您的JPanel的paintComponent方法中。 –
我应该在我的程序中添加集合（意味着在哪个类中）。 – Puneet
以答案为例。 –