使用计时器在 JLabel 中刷新图像

Refresh Image in JLabel with Timer

我目前正在开发一个小程序 在一个小 Swing GUI 中显示来自网站的图片。问题是,每次图片更改时都会弹出一个新框架而不是刷新 JLable。

用不同的方法尝试了几次后,我不知道如何实现这一点。

如果你能给我一点提示就太好了。

import java.awt.BorderLayout;
import java.awt.Image;
import java.io.*;
import java.net.MalformedURLException;
import java.net.URL;

import javax.imageio.ImageIO;
import javax.swing.*;


public class PageReader extends JFrame {

    JLabel picture;
    static String[] viewable;
    int counter;
    static String urlString;
    Image image;
    URL url;

    public PageReader(int pos) throws IOException
    {
        urlString = "http:"+viewable[pos];

        url = new URL(urlString);
        image = ImageIO.read(url);

        ImageIcon icon = new ImageIcon(image); 

        picture = new JLabel();
        picture.setIcon(icon);


        int breite = icon.getImage().getWidth(this);
        int hoehe = icon.getImage().getHeight(this);


        do
        {
            if(hoehe>400)
            {
                breite *= 0.75;
                hoehe *= 0.75;
                icon.setImage(icon.getImage().getScaledInstance(breite, hoehe, image.SCALE_DEFAULT));
            }

            if(hoehe<400)
            {
                hoehe *= 1.2;
                breite *=1.2;
                icon.setImage(icon.getImage().getScaledInstance(breite, hoehe, image.SCALE_DEFAULT));
            }
        }while(hoehe>400&&hoehe<300);


        icon.setImage(icon.getImage().getScaledInstance(breite, hoehe, image.SCALE_DEFAULT));


        JPanel anzeige = new JPanel();
        anzeige.add(picture, BorderLayout.CENTER);

        setContentPane(anzeige);


        pack();
        setResizable(false);
        setVisible(true);
    }



    public static void main(String[] args) throws IOException, InterruptedException {
        // TODO Auto-generated method stub

        String meineURL = "http://www.pr0gramm.com/static/";

         URL url = new URL(meineURL);

         InputStreamReader isr = new InputStreamReader(url.openConnection().getInputStream());
         BufferedReader br = new BufferedReader(isr);

         // Kompletten Seiteninhalt auslesen
         String line ="";
         String quelltext ="";

         while((line = br.readLine()) != null)
         {
         quelltext += line + "\r\n";
         }

         // Reader Schließen
         br.close();
         isr.close();

         String test = quelltext.substring(1708);
         String[] parts = test.split("<a href=");


         for(int i=1; i<parts.length; i++)
         {
             parts[i]=parts[i].substring(1,15);
         }

         viewable = new String[parts.length];

         for(int i = 1; i<(parts.length-1); i++)
         {
             String sitePath = "http://pr0gramm.com"+parts[i];

             meineURL = sitePath;

             url = new URL(meineURL);

             isr = new InputStreamReader(url.openConnection().getInputStream());
             br = new BufferedReader(isr);

             // Kompletten Seiteninhalt auslesen
             line ="";
             quelltext ="";

             while((line = br.readLine()) != null)
             {
             quelltext += line + "\r\n";
             }

             CharSequence picPath = quelltext.subSequence(quelltext.indexOf("//img.pr0gramm.com/"), quelltext.indexOf("//img.pr0gramm.com/")+50);

             viewable[i] = picPath.toString();

             // Seiteninhalt ausgeben
             //System.out.println(quelltext);
             System.out.println(viewable[i]);
         }

         System.out.println("\nLink-Counter: "+viewable.length);
         //System.out.println("//img.pr0gramm.com/2015/06/25/87fd872bde0ab593.jpg");

         new PageReader(4);
         //System.out.println("\n \n \n Sub \n \n"+test);
         for(int i = 1; i<viewable.length; i++)
         {
             if(!(viewable[i].contains(".web")))
             {
                url = new URL("http:"+viewable[i]);

                new PageReader(i);

                System.out.println("test"+i);
                urlString = "http:"+viewable[i];
                Thread.sleep(5000);
             }
         }


    }

}

这是我当前的代码。

由于language.But不同,我无法理解变量命名约定,据我所知,我认为你不应该在每次更新时调用new PageReader()

相反,你应该调用 update(int pos)

public void update(int pos)
{
    //The Code that went into your constructor
}

这将确保重复使用相同的 JFrame 而不是创建新的。

另外我认为你不应该每次都初始化一个新的 JLabelJPanel,相反你应该在构造函数中将 JLabel 添加到 JPanel 并且在 update 函数中,调用 picture.setIcon(icon); 而不创建新的 JLabel.

您的构造函数应如下所示:

public PageReader()
{
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    picture=new JLabel();
    JPanel anzeige = new JPanel();
    anzeige.add(picture, BorderLayout.CENTER);

    setContentPane(anzeige);


    pack();
    setResizable(false);
    setVisible(true);
}

构造函数中剩余的代码部分应该转到 update

编辑:

public void update(int pos) throws IOException
{
    urlString = "http:"+viewable[pos];

    url = new URL(urlString);
    image = ImageIO.read(url);

    ImageIcon icon = new ImageIcon(image); 

    picture.setIcon(icon);


    int breite = icon.getImage().getWidth(this);
    int hoehe = icon.getImage().getHeight(this);


    do
    {
        if(hoehe>400)
        {
            breite *= 0.75;
            hoehe *= 0.75;
            icon.setImage(icon.getImage().getScaledInstance(breite, hoehe, image.SCALE_DEFAULT));
        }

        if(hoehe<400)
        {
            hoehe *= 1.2;
            breite *=1.2;
            icon.setImage(icon.getImage().getScaledInstance(breite, hoehe, image.SCALE_DEFAULT));
        }
    }while(hoehe>400&&hoehe<300);


    icon.setImage(icon.getImage().getScaledInstance(breite, hoehe, image.SCALE_DEFAULT));

}

现在在主class中,你应该声明类似

的东西
PageReader pr=new PageReader

无论你在哪里使用 new PageReader(4),你都应该使用 pr.update(4)

@MegaCleptomaniac,我不是图像方面的专家,所以我认为你应该听听@MadProgrammer 关于不使用 getScaledInstance

的说法

先看看 Concurrency in Swing and Worker Threads and SwingWorker

您可能还想看看 jsoup,因为使用 String#substring 等来解析 html 是一个非常糟糕的主意

Swing 是单线程的,这意味着您不能使用阻塞或长 运行 进程(如 Thread.sleep)来阻塞事件调度线程,但它也不是线程安全的,这意味着您应该' 从 EDT 外部修改它。

为此,SwingWorker 提出了一个合理的解决方案,因为它可以在 EDT 之外处理 html 和图像下载,但提供了多种方法可以将更新重新同步到 EDT .

首先,您需要更新 JLabelicon 属性 而不是创建 PageReader 的新实例,这是 (许多)我们通常不鼓励人们从 JFrame.

扩展的原因
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Image;
import java.awt.image.BufferedImage;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.URL;
import java.util.List;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
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 Test {

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

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

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

    public class TestPane extends JPanel {

        private JLabel label;

        public TestPane() {
            setLayout(new BorderLayout());
            label = new JLabel("Loading...");
            label.setHorizontalAlignment(JLabel.CENTER);
            label.setVerticalAlignment(JLabel.CENTER);
            add(label);
            ImageWorker worker = new ImageWorker(label);
            worker.execute();
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(400, 400);
        }

        public class ImageWorker extends SwingWorker<Object, Image> {

            private JLabel output;

            public ImageWorker(JLabel output) {
                this.output = output;
            }

            @Override
            protected void process(List<Image> chunks) {
                output.setText(null);
                output.setIcon(new ImageIcon(chunks.get(chunks.size() - 1)));
            }

            @Override
            protected Object doInBackground() throws Exception {
                String meineURL = "http://www.pr0gramm.com/static/";

                URL url = new URL(meineURL);

                String quelltext = "";
                try (InputStreamReader isr = new InputStreamReader(url.openConnection().getInputStream()); BufferedReader br = new BufferedReader(isr)) {

                    // Kompletten Seiteninhalt auslesen
                    String line = "";

                    while ((line = br.readLine()) != null) {
                        quelltext += line + "\r\n";
                    }

                }

                String test = quelltext.substring(1708);
                String[] parts = test.split("<a href=");

                for (int i = 1; i < parts.length; i++) {
                    parts[i] = parts[i].substring(1, 15);
                }

                String[] viewable = new String[parts.length];

                for (int i = 1; i < (parts.length - 1); i++) {
                    String sitePath = "http://pr0gramm.com" + parts[i];

                    meineURL = sitePath;

                    url = new URL(meineURL);

                    try (InputStreamReader isr = new InputStreamReader(url.openConnection().getInputStream()); BufferedReader br = new BufferedReader(isr)) {

                        // Kompletten Seiteninhalt auslesen
                        String line = "";
                        quelltext = "";

                        while ((line = br.readLine()) != null) {
                            quelltext += line + "\r\n";
                        }

                        CharSequence picPath = quelltext.subSequence(quelltext.indexOf("//img.pr0gramm.com/"), quelltext.indexOf("//img.pr0gramm.com/") + 50);

                        viewable[i] = picPath.toString();

                    }
                }

                System.out.println("\nLink-Counter: " + viewable.length);

                for (int i = 1; i < viewable.length; i++) {
                    if (!(viewable[i].contains(".web"))) {
                        url = new URL("http:" + viewable[i]);

                        System.out.println("Reading " + url);
                        BufferedImage original = ImageIO.read(url);
                        Image image = original;

                        if (original.getWidth() > original.getHeight()) {
                            image = original.getScaledInstance(400, -1, Image.SCALE_SMOOTH);
                        } else {
                            image = original.getScaledInstance(-1, 400, Image.SCALE_SMOOTH);
                        }

                        publish(image);

                        System.out.println("test" + i);
                        Thread.sleep(5000);
                    }
                }

                return null;

            }

        }

    }

}

还应该查看 The try-with-resources Statement 以获得有关如何管理资源的更好想法

我不想在示例中引入更多代码,但您应该尽可能避免使用 getScaledInstance,有关详细信息,请参阅 The Perils of Image.getScaledInstance()

您可以查看 Java: maintaining aspect ratio of JPanel background image and Quality of Image after resize very low -- Java 的替代方案