如何使用java.awt.图形绘制圆？

Question

我只是试图用DrawOval（）方法画圆，当我运行程序时，它只显示小正方形。我试图将构造函数添加到Surface类，但它不起作用。这是我制作的代码：

    package swing22;

    import java.awt.BorderLayout;
    import java.awt.Color;
    import javax.swing.*;
    import java.awt.EventQueue;
    import java.awt.Graphics;
    import java.awt.Graphics2D;
    import java.awt.event.ActionEvent;
    import java.awt.event.ActionListener;


    public class MyFrame {

        JFrame frame = new JFrame(" Test Frame ");
        JPanel panel = new JPanel();

        JButton button = new JButton("CLICK");
        JLabel label = new JLabel(" 33 ");

        public MyFrame(){

            gui();

        }

        public void gui(){

            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);    

            panel.setBackground(Color.GREEN);
            panel.add(button);
            panel.add(label);
            panel.add(new Surface());

            frame.add(panel, BorderLayout.CENTER);

            button.addActionListener(new Action());

            frame.pack();
            frame.setSize(300,300);
            frame.setVisible(true);
            frame.setResizable(false);

        }


        class Action implements ActionListener{
            @Override
            public void actionPerformed(ActionEvent arg0) {
                label.setText("new value");
            }
        }

    }


    class Surface extends JPanel {


            private void doDrawing(Graphics g) {

                Graphics2D g2d = (Graphics2D) g;

                    g.setColor(Color.red);
                    g.drawOval(80, 80, 30, 30);
                    g.fillArc(140, 140, 30, 30, 0, 90);
            }

            @Override
            public void paintComponent(Graphics g) {

                super.paintComponent(g);
                doDrawing(g);
            }
        }

Answer 1

use this class (Graphiic) and it's method (Draw_Circle)

import java.awt.Color;
import java.awt.Graphics2D;
import java.awt.Graphics;
import javax.swing.JFrame;

public class Graphiic
{   
    public Graphics GClass;
    public Graphics2D G2D;
    public  void Draw_Circle(JFrame jf,int radius , int  xLocation, int             yLocation)
    {
        GClass = jf.getGraphics();
        GClass.setPaintMode();
        GClass.setColor(Color.MAGENTA);
        GClass.fillArc(xLocation, yLocation, radius, radius, 0, 360);           
    }

Answer 2

您没有设置组件大小，因此组件太小，无法显示圆圈。

调整部件尺寸，圆圈将正确显示

public void gui(){
    ....
    Surface s = new Surface();
    s.setPreferredSize(new Dimension(200, 200));
    panel.add(new Surface());
    ...
}

您可以通过设置或覆盖其getPreferedSize（）-methode来调整组件的抓取