java - 需要帮助理解 swing 代码中的意外输出

Question

我开发了一个应用程序来产生以下输出：-

我覆盖了 JPanel 的 getPrefferredSize，但为什么我在更改大小时没有观察到输出的任何变化。即使我将大小设置为 0,0，图表也根本没有翻译，我得到的输出与上图相同。

这是我的完整代码：-

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.geom.AffineTransform;
import java.awt.geom.Ellipse2D;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;


public class Skeleton extends JFrame{
Skeleton()
{
super("Donut");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setSize(400,400);

add(new Board());
setVisible(true);
}
public static void main(String args[])
{
SwingUtilities.invokeLater(new Runnable(){public void run(){new Skeleton();}});
}
}

class Board extends JPanel
{
public void paintComponent(Graphics g)
{
    super.paintComponent(g);
    Graphics2D g2=(Graphics2D)g;
    RenderingHints rh=new RenderingHints(RenderingHints.KEY_ANTIALIASING,RenderingHints.VALUE_ANTIALIAS_ON);
    //the following statement has no noticeable effect.
    rh.put(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
    g2.setRenderingHints(rh);
    Ellipse2D e=new Ellipse2D.Double(0, 0, 80, 130);
    g2.setStroke(new BasicStroke(1));
    g2.setColor(Color.RED);
    for(int deg=0;deg<360;deg+=5)
    {
        AffineTransform at=AffineTransform.getTranslateInstance(getWidth()/2,getHeight()/2);
        at.rotate(Math.toRadians(deg));
        //returns a new Shape object after it has been undergone the 'at' transformation.
        g2.draw(at.createTransformedShape(e));
    }
}
public Dimension getPreferredSize()
{
    return new Dimension(100,100);
}
}

Answer 1

因为你的布局管理器。默认情况下BorderLayout会忽略首选大小，但会填充所有可用空间。使用 egFlowLayout和 yu 会看到区别。