绘图没有出现java

Question

我在让特定对象出现在我的框架/面板中时遇到问题。在下面的代码中，我有“绘图”类型的对象，如浅色，红色，黄色和绿色。该程序应该创建一个红绿灯，但另一个绘图没有出现，我不知道为什么。 light与其他人分开，因此如果背景覆盖它就不会受到影响，但这不是问题。圆圈/灯光不画画，我不知道我错过了什么，或者我做错了什么。

What the frame should look like

package lab8;

import oracle.jvm.hotspot.jfr.JFR;

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

enum shape{
    circle,square;
}

public class TrafficLight2 extends JFrame {
JPanel panel = new JPanel();
JFrame frame = new JFrame();
TrafficLight2(){
    frame.setPreferredSize(new Dimension(500, 500));
    frame.setLayout(new FlowLayout());
    panel.setLayout(new FlowLayout());
    TrafficLight t = new TrafficLight();
    t.setPreferredSize(new Dimension(500,500));
    panel.setPreferredSize(new Dimension(500,500));
    panel.add(t,BorderLayout.CENTER);
    Drawing light = new Drawing();
    light.colour=Color.RED;
    light.s=shape.circle;
    repaint();
    panel.add(light);
    frame.add(light);
    frame.add(panel);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.pack();
    frame.setVisible(true);
}
public static void main(String[] args){
    new TrafficLight2();
}
class ButtonListener implements ActionListener{
    @Override
    public void actionPerformed(ActionEvent e) {
        repaint();
    }
    ButtonListener(){

    }
}
class Drawing extends JPanel{
    int width=50;
    int height=50;
    shape s;
    Color colour;
    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        int verticalCenter = getParent().getHeight()/2;
        int horizontalCenter = getParent().getWidth()/2;
        int topLeftSquareCornerY = verticalCenter - (height/2);
        int topLeftSquareCornerX = horizontalCenter - (width/2);
        g.setColor(colour);
        if (s==shape.square) {
            g.fillRect(topLeftSquareCornerX, topLeftSquareCornerY, width, height);
        }
        else{
            g.fillOval(topLeftSquareCornerX,topLeftSquareCornerY,width,height);
        }
    }
}

class TrafficLight extends Drawing{
    Drawing red = new Drawing();
    Drawing yellow = new Drawing();
    Drawing green = new Drawing();
    Drawing background = new Drawing();
    TrafficLight(){
        this.red.s=shape.circle;
        this.red.colour=Color.RED;
        this.yellow.s=shape.circle;
        this.yellow.colour=Color.YELLOW;
        this.green.s=shape.circle;
        this.green.colour=Color.GREEN;
        this.background.s=shape.square;
        this.background.colour=Color.BLACK;
        this.background.width=100;
        this.background.height=300;
        this.s=shape.square;
        this.colour=Color.BLACK;
        this.width=100;
        this.height=300;
        background.add(red,BorderLayout.NORTH);
        background.add(yellow,BorderLayout.CENTER);
        background.add(green,BorderLayout.SOUTH);
        this.add(background)
        repaint();
    }
  }
}

Answer 1

您忘了向TrafficLight添加背景。

TrafficLight(){
   .... other stuff
   this.add(background);
}

此外，我发现TrafficLight2扩展JFrame很奇怪，但实际上并未使用...