JFrame 程序和运行另一个 class in Java

Question

所以目前我想使用一个 jframe 程序，它将运行另一个 class 在 window.

一个工作示例：
Jframe:

import javax.swing.JFrame;

public class FaceJFrame
{
    public static void main(String[] args)
    {
        JFrame frame = new JFrame();
        frame.setSize(300,400);
        frame.setTitle("A Rectangle Object in a JFrame");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        Face aRectangle = new Face();

        frame.add(aRectangle);
        frame.setVisible(true);
    }
}

程序：

import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.awt.geom.Line2D;
import javax.swing.JComponent;

public class Face extends JComponent
{
    public void paintComponent(Graphics g)
    {
        Graphics2D g2 = (Graphics2D) g;

        // Construct face and eyes
        Rectangle face = new Rectangle(0, 0, 50, 50); 
        Rectangle eye = new Rectangle(5, 5, 15, 15);
        Rectangle eye2 = new Rectangle(25, 5, 15, 15);

        //make some lines for the mouth
        Line2D mouth1 = new Line2D.Double(15, 30, 15, 35);
        Line2D mouth2 = new Line2D.Double(15, 35, 35, 35);
        Line2D mouth3 = new Line2D.Double(35, 35, 35, 30); 

        // draw the rectangle
        g2.draw(face); 
        g2.draw(eye);
        g2.draw(eye2);
        g2.draw(mouth1);
        g2.draw(mouth2);
        g2.draw(mouth3);
    }

}

使用这两个代码片段，运行在 cmd 中使用 Jframe 会弹出一个window，上面有一张小脸。

我想用下面的代码做同样的事情：
Jframe:

import javax.swing.JFrame;


public class Car_JFrame
{
    public static void main(String[] args)
    {
        JFrame frame = new JFrame();
        frame.setSize(300,400);
        frame.setTitle("a car");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        Car aRectangle = new Car();

        frame.add(aRectangle);
        frame.setVisible(true);
    }
}

和主要 class:

import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.awt.geom.Line2D;
import java.awt.geom.Ellipse2D;
import javax.swing.JComponent;
public class Car
{
    public void paintComponent(Graphics g)
    {
        Graphics2D g2 = (Graphics2D) g;

        Rectangle body = new Rectangle(0, 10, 60, 20); 

        Line2D roof1 = new Line2D.Double(10, 10, 20, 0);
        Line2D roof2 = new Line2D.Double(20, 0, 40, 0);
        Line2D roof3 = new Line2D.Double(40, 0, 50, 10); 
        Ellipse2D.Double wheel1 = new Ellipse2D.Double(15, 25, 10,10);
        Ellipse2D.Double wheel2 = new Ellipse2D.Double(45, 25, 10,10);
        // draw the rectangle
        g2.draw(body);
        g2.draw(roof1);
        g2.draw(roof2);
        g2.draw(roof3);
        g2.draw(wheel1);
        g2.draw(wheel2);

    }
}

它不会产生相同的结果。其实cmd中运行ning car_jframe会输出人脸程序。（他们在同一个 blueJ 项目中）

我该怎么办？

Answer 1

您的主要问题是您的 Car class 没有扩展 JPanel 或 JComponent 或任何派生自它们的 class，因此无法将其添加到您的 JFrame 中，并且任何尝试这样做所以会导致编译错误。您有两个主要可能的解决方案：

通过扩展 JPanel（或 JComponent，但我推荐 JPanel）使 Car 成为真正的组件。
或者，如果您希望 Car 是逻辑 class 而不是组件 class，则创建一个包含 Car 对象的 JPanel 并通过直接调用该对象的 paintComponent 来绘制 Car 对象JPanel 自己的 paintComponent 方法中的方法。

其他说明：

您几乎总是想在覆盖中调用 super.paintComponent(g) 方法，以便 JPanel 可以进行内务处理。
您总是希望在您认为是带有@Override注解的重写方法的任何方法前加上这样的方法，如果您的假设不正确，编译器会警告您.

例如，

import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.awt.geom.*;
import javax.swing.*;

public class TestCar {
    private static void createAndShowGui() {
        Car mainPanel = new Car();

        JFrame frame = new JFrame("A Car");
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        frame.getContentPane().add(mainPanel);
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        // start all code on the Swing event thread
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGui();
            }
        });
    }
}

class Car extends JPanel {
    private static final int PREF_W = 400;
    private static final int PREF_H = 300;
    private static final Rectangle BODY = new Rectangle(0, 10, 60, 20); 
    private static final Line2D ROOF_1 = new Line2D.Double(10, 10, 20, 0);
    private static final Line2D ROOF_2 = new Line2D.Double(20, 0, 40, 0);
    private static final Line2D ROOF_3 = new Line2D.Double(40, 0, 50, 10); 
    private static final Ellipse2D WHEEL_1 = new Ellipse2D.Double(15, 25, 10,10);
    private static final Ellipse2D WHEEL_2 = new Ellipse2D.Double(45, 25, 10,10);

    public Car() {

    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D) g;

        // draw the rectangle
        g2.draw(BODY);
        g2.draw(ROOF_1);
        g2.draw(ROOF_2);
        g2.draw(ROOF_3);
        g2.draw(WHEEL_1);
        g2.draw(WHEEL_2);
    }

    @Override
    public Dimension getPreferredSize() {
        if (isPreferredSizeSet()) {
            return super.getPreferredSize();
        }
        return new Dimension(PREF_W, PREF_H);
    }
}

如果你想要真正的花哨，使用 Path2D 对象、AffineTransform 和 Swing Timer 并给你的 GUI 一点动画：

import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.geom.AffineTransform;
import java.awt.geom.Ellipse2D;
import java.awt.geom.Line2D;
import java.awt.geom.Path2D;
import javax.swing.JPanel;
import javax.swing.Timer;

public class Car2 extends JPanel {
    private static final int PREF_W = 400;
    private static final int PREF_H = 300;
    private static final Rectangle BODY = new Rectangle(0, 10, 60, 20);
    private static final Line2D ROOF_1 = new Line2D.Double(10, 10, 20, 0);
    private static final Line2D ROOF_2 = new Line2D.Double(20, 0, 40, 0);
    private static final Line2D ROOF_3 = new Line2D.Double(40, 0, 50, 10);
    private static final Ellipse2D WHEEL_1 = new Ellipse2D.Double(15, 25, 10,
            10);
    private static final Ellipse2D WHEEL_2 = new Ellipse2D.Double(45, 25, 10,
            10);
    private static final int TIMER_DELAY = 30;
    private static final int CAR_DELTA_X = 1;
    private static final int CAR_DELTA_Y = CAR_DELTA_X;
    private Path2D path2D = new Path2D.Double();

    public Car2() {
        path2D.append(BODY, false);
        path2D.append(ROOF_1, false);
        path2D.append(ROOF_2, false);
        path2D.append(ROOF_3, false);
        path2D.append(WHEEL_1, false);
        path2D.append(WHEEL_2, false);

        new Timer(TIMER_DELAY, new CarTimerListener()).start();;
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D) g;
        g2.draw(path2D);
    }

    @Override
    public Dimension getPreferredSize() {
        if (isPreferredSizeSet()) {
            return super.getPreferredSize();
        }
        return new Dimension(PREF_W, PREF_H);
    }

    class CarTimerListener implements ActionListener {
        @Override
        public void actionPerformed(ActionEvent e) {
            path2D.transform(AffineTransform.getTranslateInstance(CAR_DELTA_X, CAR_DELTA_Y));
            repaint();
        }
    }
}

Answer 2

您的应用程序中应该只有一个主要方法。我会像下面这样更改它，让用户 select 在运行应用程序时打印哪个形状。

import javax.swing.JFrame;

public class DrawFrame {
    public static void main(String[] args) {

        if(args[0].equals("face") {

            paintFace()
        }
        else if(args[0].equals("car") {

            paintCar();
        }
        else {
            System.out.println("No Shape Selected to Print");
        }
    }

    private static paintFace() {

        JFrame frame = new JFrame();
        frame.setSize(300,400);
        frame.setTitle("A Rectangle Object in a JFrame");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        Face face = new Face();
        frame.add(face);
        frame.setVisible(true);
    }

    private static paintCar() {

        JFrame frame = new JFrame();
        frame.setSize(300,400);
        frame.setTitle("a car");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        Car car = new Car();
        frame.add(car);
        frame.setVisible(true);
    }
}

你的车也没有扩展组件。不行。

更正为

public class Car extends JComponent { ... }

JFrame 程序和运行另一个 class in Java

JFrame program and running another class in Java

java

swing

jframe

paintcomponent

JFrame 程序和 运行 另一个 class in Java

JFrame program and running another class in Java

java

swing

jframe

paintcomponent

JFrame 程序和运行另一个 class in Java