Java 多边形调整大小

Question

我正在尝试制作一个程序，该程序有一个显示多边形和两个按钮的窗口。多边形从 3 个点(一个三角形)开始，并允许用户按“+”和“-”按钮来添加或减去多边形的边。这是我的代码:

在测试多边形框中:

package testpolygonbox
import javax.swing.*;
import java.awt.*;
public class TestPolygonBox extends JFrame {


public TestPolygonBox(){
    setLayout(new BorderLayout(5,5));
    add(new PolygonBox ());
}
public static void main(String[] args) {
    TestPolygonBox frame = new TestPolygonBox();
    frame.setTitle("Polygon Box");
    frame.setSize(400,420);
    frame.setLocationRelativeTo(null);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setVisible(true);

}
}

接下来是控制类:

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

public class PolygonBox extends JPanel {
private JButton jbtEnlarge = new JButton("+");
private JButton jbtShrink = new JButton("-");
private PolygonPanel polygonPanel = new PolygonPanel();

public PolygonBox(){
    JPanel panel = new JPanel();
    panel.add(jbtEnlarge);
    panel.add(jbtShrink);
     setLayout(new BorderLayout());
    this.add(polygonPanel,BorderLayout.CENTER);
    this.add(panel, BorderLayout.SOUTH);

    jbtEnlarge.addActionListener(new EnlargeListener());
    jbtShrink.addActionListener(new ShrinkListener());
}


class EnlargeListener implements ActionListener{
@Override
public void actionPerformed(ActionEvent e){
    polygonPanel.enlarge();
   }
}
class ShrinkListener implements ActionListener{
@Override
public void actionPerformed(ActionEvent e){
    polygonPanel.shrink();
}
}
}

class PolygonPanel extends JPanel{
private int polygonSides = 3;

/** Add side to the polygon*/
public void enlarge(){
    polygonSides++;
    repaint();
}
public void shrink(){
    polygonSides--;
    repaint();
}
  @Override /** Draw requested Shape*/
protected void paintComponent(Graphics g){

    int frameWidth = getWidth() / 2;
    int frameHeight = getHeight() / 2;
    int radius = (int)(Math.min(getWidth(),getHeight())* 0.4);
    int xCenter = getWidth() / 2;
    int yCenter = getHeight() / 2;


    g.setColor(Color.BLUE);
    Polygon polygon = new Polygon();

    polygon.addPoint(xCenter + radius, yCenter);
                polygon.addPoint((int)(xCenter + radius * Math.cos(2 * Math.PI/polygonSides)),
                        (int)(yCenter - radius * Math.sin(2 * Math.PI / polygonSides)));
                for (int polygonPoint = 2; polygonPoint <= polygonSides; polygonPoint++){
                    polygon.addPoint((int)(xCenter + radius * Math.cos(polygonPoint * 2 * Math.PI/polygonSides)),
                        (int)(yCenter - radius * Math.sin(polygonPoint * 2 * Math.PI / polygonSides)));
                }

    g.fillPolygon(polygon);
}


}

当我尝试运行该程序时，出现错误:线程“main”中的异常 java.lang.IllegalArgumentException:向容器添加窗口 在 java.awt.Container.checkNotAWindow(Container.java:483) 在 java.awt.Container.addImpl(Container.java:1084) 在 java.awt.Container.add(Container.java:998) 在 javax.swing.JFrame.addImpl(JFrame.java:562) 在 java.awt.Container.add(Container.java:410) 在 testpolygonbox.TestPolygonBox.(TestPolygonBox.java:21) 在 testpolygonbox.TestPolygonBox.main(TestPolygonBox.java:24)Java 结果:1

如果有人能告诉我在哪里向容器添加窗口？我不确定我做错了什么。

Answer 1

PolygonBox 是一个 JFrame 窗口，但您要将其添加到另一个 JFrame 中。更改该类，使其扩展 JPanel。

public class PolygonBox extends JPanel {