比较两个字符串并根据结果显示图像

Question

所需的功能：侦听行划定的条形码扫描（一串字符）。对于每一对（总是以相同的顺序扫描，一个比另一个长），比较两者是否相等。如果它们相同，则显示图像。如果它们不同，则显示另一幅图像。无限重复，直到 window 关闭。

在我看来，这个程序有两个模块。一个是不断循环，接收字符串，比较，然后发送结果（== 或 !=）。另一个只是等待结果，显示合适的图像，等待下一次比较结果。

下面是我的代码，我想不通如何让 repaint() 在每个循环结束时正常工作（一旦比较结果已知）。我尝试将结果推送到 MyFrame Class 并在那里重绘 () 并且我尝试在循环中调用 repaint() ，但这也不起作用。

ScannerCompare Class 在控制台中自行运行，但这对我的预期实现不是很有用。要是System.out.println("OK")和("NG")是图片就好了！

非常感谢！

package BarcodeVerification;

import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Image;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.WindowConstants;


public class MyFrame extends JFrame {

private Image ngImage = null;
private Image okImage = null;

public MyFrame(String ngFilename, String okFilename) {
    setTitle("MyWindow");
    setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
    setSize(800, 600);

    this.ngImage = new ImageIcon(ngFilename).getImage();
    this.okImage = new ImageIcon(okFilename).getImage();

    Container container = getContentPane();
    container.setLayout(new BorderLayout());

}

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

    if (m.getResult()) {
        g.drawImage(okImage, 0, 0, okImage.getWidth(null), okImage.getHeight(null), null);
    }
    else {
        g.drawImage(ngImage, 0, 0, ngImage.getWidth(null), ngImage.getHeight(null), null);
    }
}

public static void main(String[] args) {
    EventQueue.invokeLater(new Runnable() {

        @Override
        public void run() {
            MyFrame frame = new MyFrame("src/NG.png","src/OK/png");
            ScannerCompare m = new ScannerCompare();
            frame.setVisible(true);
        }

    });
}
}



package BarcodeVerification;

import java.util.Scanner;


public class ScannerCompare {

public Boolean ok;
public String scan1, scan2, injectorExtract;

public ScannerCompare (){
Scanner in = new Scanner(System.in);

    while (true) {
        System.out.println("Scan the paper");
        scan1 = in.nextLine();

        System.out.println("Scan the Injector QR Code");
        scan2 = in.nextLine();

        injectorExtract = scan2.substring(19);

        if (scan1.compareTo(injectorExtract) != 0) {
            System.out.println("NG");
            ok = false;
            repaint();
        } else {
            System.out.println("OK");
            ok = true;
            repaint()
        }
    }
}
public boolean getResult(){
    return ok;
}
}

Answer 1

你的基本问题可以用 Observer Pattern 来解决。

"scanner" 检查扫描结果并生成某种 event/notification 到 registered/interested observers/listeners

Swing 是一个单线程框架，因此您不能简单地在您的代码中放置一个 while (true)，因为它可能会阻塞事件调度线程，阻止它处理任何事件，包括绘画事件。有关详细信息，请参阅 Concurrency in Swing。

您可以使用 SwingWorker 来克服此限制，允许 doInBackground 方法处理扫描，并允许 publish/process 方法触发通知在 EDT 的上下文中安全地查看 Worker Threads and SwingWorker 了解更多详细信息

作为概念证明...

import java.awt.BorderLayout;
import javax.swing.ImageIcon;
import java.awt.EventQueue;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.List;
import java.util.Scanner;
import javax.imageio.ImageIO;
import javax.swing.Icon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingWorker;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class Scanny {

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

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

                try {
                    BufferedImage empty = ImageIO.read(...);
                    BufferedImage good = ImageIO.read(...);
                    BufferedImage bad = ImageIO.read(...);

                    JFrame frame = new JFrame("Testing");
                    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                    frame.add(new ScannerPane(new ImageIcon(empty), new ImageIcon(good), new ImageIcon(bad)));
                    frame.pack();
                    frame.setLocationRelativeTo(null);
                    frame.setVisible(true);
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        });
    }

    public class ScannerPane extends JPanel {

        private JLabel label;
        private Icon empty;
        private Icon good;
        private Icon bad;

        public ScannerPane(Icon empty, Icon good, Icon bad) {
            setLayout(new BorderLayout());
            this.empty = empty;
            this.good = good;
            this.bad = bad;

            label = new JLabel(empty, JLabel.CENTER);
            add(label);

            ScannerWorker worker = new ScannerWorker(new ScannerObserver() {
                @Override
                public void scanWasGood() {
                    label.setIcon(good);
                }

                @Override
                public void scanWasBad() {
                    label.setIcon(bad);
                }
            });
            worker.execute();
        }

    }

    public interface ScannerObserver {
        public void scanWasGood();
        public void scanWasBad();
    }

    public class ScannerWorker extends SwingWorker<Void, Boolean> {

        private ScannerObserver observer;

        public ScannerWorker(ScannerObserver observer) {
            this.observer = observer;
        }

        @Override
        protected Void doInBackground() throws Exception {
            Scanner in = new Scanner(System.in);

            while (true) {
                String scan1 = in.nextLine();
                String scan2 = in.nextLine();

                String injectorExtract = scan2.substring(19);

                if (scan1.compareTo(injectorExtract) != 0) {
                    publish(Boolean.TRUE);
                } else {
                    publish(Boolean.FALSE);
                }
            }
        }

        @Override
        protected void process(List<Boolean> chunks) {
            boolean last = chunks.get(chunks.size() - 1);
            if (last) {
                observer.scanWasGood();
            } else {
                observer.scanWasBad();
            }
        }

    }

}

有关 ImageIO

的更多详细信息，请参阅 Reading/Loading an Image

比较两个字符串并根据结果显示图像

Comparing Two Strings and Displaying an Image Based on Result

java

graphics

swing

overriding

repaint