我正在尝试让进度条准确反射(reflect)我的 SwingWorker。但我真的不知道该怎么做。在操作完成之前，我得到了只做静态动画的栏，但我想要一个真正的 Activity 栏。

/*
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 */
package frglauncher;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.RandomAccessFile;
import java.net.MalformedURLException;
import java.net.URL;
import java.nio.channels.Channels;
import java.nio.channels.ReadableByteChannel;
import java.util.Enumeration;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JLabel;
import javax.swing.JProgressBar;
import javax.swing.SwingWorker;

/**
 *
 * @author KYLE-LAPTOP
 */
class DownloadWorker extends SwingWorker<String, Object> {

    private String game;
    private JProgressBar bar;
    private JLabel label;

    public DownloadWorker(JProgressBar bar, String game, JLabel label) {
        this.game = game;
        this.bar = bar;
        this.label = label;
    }

    @Override
    public String doInBackground() {

        // Download here
        label.setText("test");
        try {
            // ProgressBar/Install
            System.out.println("FILELOCATION:\n----------");
            String URL_LOCATION = "http://www.futureretrogaming.tk/gamefiles/ProfessorPhys.jar";
            String LOCAL_FILE = ("\\" + game + "\\");
            File localfile = new File(LOCAL_FILE);
            if (localfile.exists()) {
                System.out.println("Directory exists!");
            }
            else {
                System.out.println("Directory doesn't exist! Creating...");
                localfile.mkdir();
                if (localfile.exists()) {
                    System.out.println("Directory created!");
                }
            }
            System.out.println("LOCALFILE:\n-------");
            System.out.println(LOCAL_FILE);
            URL website = new URL(URL_LOCATION);
            ReadableByteChannel rbc = Channels.newChannel(website.openStream());
            FileOutputStream fos = new FileOutputStream(LOCAL_FILE + "\\ProfessorPhys.jar\\");
            fos.getChannel().transferFrom(rbc, 0, Long.MAX_VALUE);
            System.out.println("--------\nDone Downloading\n---------");

            RandomAccessFile randomAccessFile = null;

            File file = new File(LOCAL_FILE + "ProfessorPhys.jar\\");
            JarFile jar = new JarFile(file);
            Enumeration enum1 = jar.entries();
            while (enum1.hasMoreElements()) {
                JarEntry file1 = (JarEntry) enum1.nextElement();
                System.out.println("Directory to extract: " + LOCAL_FILE);
                System.out.println("\n" + file1.getName() + "\n");
                File f = new File(file1.getName());
                if (file1.isDirectory()) { // If it's a directory, create it
                    f.mkdir();
                    continue;
                }
                try (InputStream is1 = jar.getInputStream(file1)) {
                    FileOutputStream fos1 = new FileOutputStream(f);
                    while (is1.available() > 0) {  // Write contents of 'is' to 'fos'
                        fos1.write(is1.read());
                    }
                    fos1.close();
                }
            }
        }
        catch (FileNotFoundException ex) {
            Logger.getLogger(DownloadWorker.class.getName()).log(Level.SEVERE, null, ex);
        }
        catch (MalformedURLException ex) {
            Logger.getLogger(DownloadWorker.class.getName()).log(Level.SEVERE, null, ex);
        }
        catch (IOException ex) {
            Logger.getLogger(DownloadWorker.class.getName()).log(Level.SEVERE, null, ex);
        }
        return "done";
    }

    @Override
    protected void done() {

        // Done
        label.setText("Download of " + game + "is done.");
        System.exit(0);
    }
}

最佳答案

几件事:

1. SwingWorker 有四个规则要遵循。可以引用这张图: .

所以，这段代码:

@Override
public String doInBackground() {
    //download here
    label.setText("test");

违反了这条规则。您的 label.setText() 应该移至构造函数。

1. 要向 Swing 组件(如进度条)发送“更新”，您需要使用 process() 方法，您可以使用 publish() 从内部调用该方法你的 doInBackground()。您的第二个 SwingWorker 参数反射(reflect)了您要传递的值的类型。我附上了两个 SSCCE。一个将 Integer 传递给 process() 方法，另一个传递一个 String。应该让您了解正在发生的事情。

使用 Integer 的 SSCCE:

import java.util.List;
import java.util.concurrent.ExecutionException;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JProgressBar;
import javax.swing.SwingUtilities;
import javax.swing.SwingWorker;

/**
 *
 * @author Ryan
 */
public class Test {

    public static void main(String args[]) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                go();
            }
        });
    }

    public static void go() {
        JFrame frame = new JFrame();
        JPanel panel = new JPanel();
        JLabel label = new JLabel("Loading...");
        JProgressBar jpb = new JProgressBar();
        jpb.setIndeterminate(false);
        int max = 1000;
        jpb.setMaximum(max);
        panel.add(label);
        panel.add(jpb);
        frame.add(panel);
        frame.pack();
        frame.setSize(200,90);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        new Task_IntegerUpdate(jpb, max, label).execute();

    }

    static class Task_IntegerUpdate extends SwingWorker<Void, Integer> {

        JProgressBar jpb;
        int max;
        JLabel label;
        public Task_IntegerUpdate(JProgressBar jpb, int max, JLabel label) {
            this.jpb = jpb;
            this.max = max;
            this.label = label;
        }

        @Override
        protected void process(List<Integer> chunks) {
            int i = chunks.get(chunks.size()-1);
            jpb.setValue(i); // The last value in this array is all we care about.
            System.out.println(i);
            label.setText("Loading " + i + " of " + max);
        }

        @Override
        protected Void doInBackground() throws Exception {
            for(int i = 0; i < max; i++) {
                Thread.sleep(10); // Illustrating long-running code.
                publish(i);
            }
            return null;
        }

        @Override
        protected void done() {
            try {
                get();
                JOptionPane.showMessageDialog(jpb.getParent(), "Success", "Success", JOptionPane.INFORMATION_MESSAGE);
            } catch (ExecutionException | InterruptedException e) {
                e.printStackTrace();
            }
        }
    }   
}

使用 String 的 SSCCE:

import java.util.List;
import java.util.concurrent.ExecutionException;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JProgressBar;
import javax.swing.SwingUtilities;
import javax.swing.SwingWorker;

/**
 *
 * @author Ryan
 */
public class Test2 {

    public static void main(String args[]) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                go();
            }
        });
    }

    public static void go() {
        JFrame frame = new JFrame();
        JPanel panel = new JPanel();
        JLabel label = new JLabel("Loading...");
        JProgressBar jpb = new JProgressBar();
        jpb.setIndeterminate(true);
        panel.add(label);
        panel.add(jpb);
        frame.add(panel);
        frame.pack();
        frame.setSize(200,90);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        new Task_StringUpdate(label).execute();
    }

    static class Task_StringUpdate extends SwingWorker<Void, String> {

        JLabel jlabel;
        public Task_StringUpdate(JLabel jlabel) {
            this.jlabel = jlabel;
        }

        @Override
        protected void process(List<String> chunks) {
            jlabel.setText(chunks.get(chunks.size()-1)); // The last value in this array is all we care about.
            System.out.println(chunks.get(chunks.size()-1));
        }

        @Override
        protected Void doInBackground() throws Exception {

            publish("Loading Step 1...");
            Thread.sleep(1000);
            publish("Loading Step 2...");
            Thread.sleep(1000);
            publish("Loading Step 3...");
            Thread.sleep(1000);
            publish("Loading Step 4...");
            Thread.sleep(1000);

            return null;
        }

        @Override
        protected void done() {
            try {
                get();
                JOptionPane.showMessageDialog(jlabel.getParent(), "Success", "Success", JOptionPane.INFORMATION_MESSAGE);
            } catch (ExecutionException | InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

关于java - SwingWorker 进度条，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/20260372/