java - 我们必须导入一些东西才能使用draw()吗？

Question

我试图使用 eclipse 在 java 中绘制一些矩形，并且调用 draw() 方法给我一个错误。我在这里缺少什么吗？

import java.awt.Rectangle;

public class UsingRectangle {
    public static void main(String[] args) {
        Rectangle box1 = new Rectangle(0, 0, 20, 30);

        //error "The method draw() is undefined for the type Rectangle"
        box1.draw();
    }
}

任何帮助将不胜感激。谢谢。

Answer 1

首先通读:

• JavaDocs for Rectangle
• Creating a GUI With JFC/Swing
• Performing Custom Painting
• 2D Graphics

矩形是形状的表示，它本身没有如何绘制的概念，但可以通过适当的API进行绘制

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class PaintRectangle {

    public static void main(String[] args) {
        new PaintRectangle();
    }

    public PaintRectangle() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private Rectangle box1;

        public TestPane() {
            box1 = new Rectangle(0, 0, 20, 30);
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            g2d.setColor(Color.RED);
            g2d.fill(box1);
            g2d.setColor(Color.BLUE);
            g2d.draw(box1);
            g2d.dispose();
        }
    }

}