在Mac上无法绘图 [英] Swing not drawing on Mac

问题描述

我正在尝试使用Java中的swing绘制令人难以置信的基本形状，但是由于某些原因，它似乎无法正常工作.这是我从讲师那里下载的代码，他在一次演讲中向我们展示了该代码，但是当我运行该代码时，窗口会打开，但什么都没画，我也不知道为什么.

I am trying to draw an incredibly basic shape using swing in Java, however for some reason it does not seem to be working. This is code that I downloaded from my lecturer that he showed us in a lecture, but when I run it the window opens but nothing is drawn and I have no idea why.

package graphicsEx;

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

public class Lecture1Example extends JPanel{
    // This is where the JPanel gets (re-)painted when the screen is refreshed.
    public void paintComponent(Graphics g) {
        // Cast to Graphics2D for more features.        
        Graphics2D g2D = (Graphics2D) g;

        Rectangle2D rect = new Rectangle2D.Double(20,30,40,50);
        g2D.setColor(Color.red);
        g2D.draw(rect);
        g2D.fill(rect); 
    }

    public static void main(String args[]) {
        JFrame frame = new JFrame("Playing with Graphics");
        frame.setSize(500, 400);
        frame.setVisible(true);
        frame.setContentPane(new Lecture1Example());        
    }
}

我正在使用Eclipse IDE.

I am using the Eclipse IDE.

推荐答案

尊敬的user1821475的讲师:

Dear user1821475's lecturer:

• 仅在"具有UI委托的Swing组件的子类(相对于JComponent的直接子类)应调用

  "Subclasses of Swing components which have a UI delegate (vs. direct subclasses of JComponent), should invoke super.paintComponent() within their paintComponent override.

  "为方便起见，add及其变体将remove和setLayout覆盖为

  "As a convenience add and its variants, remove and setLayout have been overridden to forward to the contentPane as necessary."

  在调用pack()和其他影响几何的方法之后，最外面的Container应该仅是 .

  The outermost Container should be setVisible() only after invoking pack() and other methods affecting geometry.

  这篇关于在Mac上无法绘图的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！