java - 从 main 方法传递一个字符串以在同一类文件中进行绘制

Question

我最近开始学习java编程，并且开始做一些图形。我正在为图形制作 GUI，但在传递使用 JOptionPane.showInputDialog 从数组中选择的形状时遇到了一些麻烦。是否建议为我想要绘制的每个 2D 形状创建方法，然后将 Paint 方法放在另一个类文件中并重载它？请给我一些帮助。我的代码如下所示。

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridLayout;
import java.awt.Rectangle;
import java.awt.geom.Ellipse2D;
import java.awt.geom.Line2D;

import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;

public class test extends JFrame {

    String x1; // starting x co-ordinate
    String y1; // starting y co-ordinate
    String r1; // radius for circle
    String l1; // length for shape
    String h1; // height for shape
    String draw;

    int x = 0;
    int y = 0;
    int l = 0;
    int h = 0;
    int r = 0;

    /**
     * Launch the application.
     */
    public static void main(String[] args) {

        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    test frame = new test();
                    JPanel panel = new JPanel() {
                        @Override
                        public Dimension getPreferredSize() {
                            return new Dimension(2000, 2000);
                        }
                    };
                    // frame.getContentPane().add(new JScrollPane(panel),
                    // BorderLayout.CENTER);
                    frame.setVisible(true);
                    frame.setSize(1200, 600);

                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Create the frame.
     */
    public test() {

        String[] shapes = { "Circle", "Ellipse", "Line", "Rectangle" };

        String drawShape = (String) JOptionPane.showInputDialog(null,
                "Select a shape to be drawn: ", "Drawing 2D Shapes",
                JOptionPane.QUESTION_MESSAGE, null, shapes, shapes[0]);

        if (drawShape == "Circle") {
            System.out.println("Shape selected is: " + drawShape);

            x1 = JOptionPane.showInputDialog(null,
                    "Input center (x value): ");
            y1 = JOptionPane.showInputDialog(null,
                    "Input center (y value): ");
            r1 = JOptionPane.showInputDialog(null, "Input radius: ");

            // parsing the variables from String to Integer
            x = Integer.parseInt(x1);
            y = Integer.parseInt(y1);
            r = Integer.parseInt(r1);
        }

        if (drawShape == "Ellipse") {
            System.out.println("Shape selected is: " + drawShape);

            x1 = JOptionPane.showInputDialog(null,
                    "Input x starting point: ");
            y1 = JOptionPane.showInputDialog(null,
                    "Input y starting point: ");
            l1 = JOptionPane.showInputDialog(null, "Please enter Width: ");
            h1 = JOptionPane
                    .showInputDialog(null, "Please enter Height: ");

            // parsing the variables from String to Integer
            x = Integer.parseInt(x1);
            y = Integer.parseInt(y1);
            l = Integer.parseInt(l1);
            h = Integer.parseInt(h1);
        }

        if (drawShape == "Line") {
            System.out.println("Shape selected is: " + drawShape);

            x1 = JOptionPane.showInputDialog(null, "Input point 1: ");
            y1 = JOptionPane.showInputDialog(null, "Input point 2: ");
            l1 = JOptionPane.showInputDialog(null, "Input point 3: ");
            h1 = JOptionPane.showInputDialog(null, "Input point 4: ");

            // parsing the variables from String to Integer
            x = Integer.parseInt(x1);
            y = Integer.parseInt(y1);
            l = Integer.parseInt(l1);
            h = Integer.parseInt(h1);
        }

        if (drawShape == "Rectangle") {
            x1 = JOptionPane.showInputDialog(null,
                    "Input x starting point: ");
            y1 = JOptionPane.showInputDialog(null,
                    "Input y starting point: ");
            l1 = JOptionPane.showInputDialog(null, "Please enter Width: ");
            h1 = JOptionPane
                    .showInputDialog(null, "Please enter Height: ");

            // parsing the variables from String to Integer
            x = Integer.parseInt(x1);
            y = Integer.parseInt(y1);
            l = Integer.parseInt(l1);
            h = Integer.parseInt(h1);
        }

    }

    public void paint(Graphics g) {
        super.paint(g);

        // drawing the shape
        Graphics2D g2 = (Graphics2D) g;

        Rectangle r = new Rectangle(x, y, l, h);
        g2.draw(r);


        /*
         * Ellipse2D.Double circle = new Ellipse2D.Double(x, y, r, r);
         * g2.draw(circle); g2.drawString("This is a Circle", (x + (r / 2)), y);
         * 
         * g2.setColor(new Color(0, 0, 255));
         * System.out.println("Shape selected is: " + type);
         * 
         * Ellipse2D.Double ellipse = new Ellipse2D.Double(x, y, l, h); //
         * defining // the // object // graphically g2.draw(ellipse);
         * g2.drawString("This is a ellipse", x, y);
         * 
         * g2.setColor(new Color(0, 0, 255));
         * System.out.println("Shape selected is: " + type);
         * 
         * Line2D.Double line1 = new Line2D.Double(x, y, l, h); g2.draw(line1);
         * g2.drawString("Point 1", x, y); g2.drawString("Point 2", l, h);
         */

    }

}

Answer 1

有几种不同的选择。就像你有 x,y 等作为类变量一样，让你的drawShape成为一个类变量。然后在你的绘制方法中，你就会知道要画什么。

有时您可能想要绘制多个形状。

我会为您想要绘制的每个形状创建一个类。它们都应该实现一个接口(interface)，该接口(interface)具有一个“draw”方法，该方法将 Graphics 作为参数。

假设您的界面名为 MyShapeI。您的类将具有 MyShapeI 对象的集合。

然后，您无需设置类变量，而是创建 MyCircle 的新实例，并设置其 x、y、r 字段，并将其添加到您的集合中。

最后在绘制中，您将循环遍历集合，并调用每个对象的绘制方法。

这给了你无限的可能性。您可以有一个 MyElephant 类，它知道如何在指定的 x,y 点绘制大象。