java - JProgressBar 不更新

Question

我在这里做了一个非常简单的代码来展示它，我有一个按钮应该显示一个 JDialog 来检查进度状态，我正在使用延迟调用来通过 EDT 并且我的循环不在运行方法中，为什么我的栏没有更新？这是代码

import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JProgressBar;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class JBarEx extends JFrame {
private JTextField progStatus = new JTextField("Undefined");
private JButton dialogBtn = new JButton("Show Progression dialog");
final JDialog dlg = new JDialog((JFrame) null, "prog Title", false);
final JProgressBar dpb = new JProgressBar(0, 100);

public JBarEx() {
    JPanel pan = new JPanel();
    dialogBtn.addActionListener(new ActionListener() {

        @Override
        public void actionPerformed(ActionEvent e) {
            // TODO Auto-generated method stub
            showProgress();
        }
    });
    progStatus.setEditable(false);
    pan.add(progStatus);
    pan.add(dialogBtn);
    setContentPane(pan);
    this.setSize(200, 100);
    setVisible(true);
}

public void showProgress() {
    dlg.add(BorderLayout.CENTER, dpb);
    dlg.add(BorderLayout.NORTH, new JLabel("prog message"));
    dlg.setDefaultCloseOperation(JDialog.DISPOSE_ON_CLOSE);
    dlg.setSize(300, 75);
    dlg.setLocationRelativeTo(null);
    dlg.setVisible(true);

    for (int i = 0; i < 100; i++) {
        final int ii = i;
        try {
            Thread.sleep(25);
            SwingUtilities.invokeLater(new Runnable() {

                @Override
                public void run() {
                    updateBar(ii);

                }
            });
        }
        catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

}

public void updateBar(int newValue) {
    dpb.setValue(newValue);
}

public static void main(String[] args) {
    JBarEx jbx = new JBarEx();
}

Answer 1

您的showProgress 方法正在事件调度线程的上下文中执行。 EDT 负责处理油漆请求等。这意味着只要您的 for-loop 正在执行，EDT 就无法处理任何新的绘制请求(或处理 invokeLater 事件)，因为它正在阻止 EDT .

虽然有许多可能的方法可以解决问题，但根据您的代码示例，最简单的方法是使用 SwingWorker .

它有能力让你在后台线程中执行长时间运行的任务(释放 EDT)，但也允许你发布更新(如果需要)，这样他们就可以在 EDT 中进行处理，还提供方便的 progress 通知。

例如……

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JProgressBar;
import javax.swing.SwingWorker;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.border.EmptyBorder;

public class SwingWorkerProgress {

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

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

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

    public class TestPane extends JPanel {

        private JProgressBar pbProgress;
        private JButton start;

        public TestPane() {

            setBorder(new EmptyBorder(10, 10, 10, 10));
            pbProgress = new JProgressBar();
            setLayout(new GridBagLayout());
            GridBagConstraints gbc = new GridBagConstraints();
            gbc.insets = new Insets(4, 4, 4, 4);
            gbc.gridx = 0;
            gbc.gridy = 0;
            add(pbProgress, gbc);

            start = new JButton("Start");
            gbc.gridy++;
            add(start, gbc);

            start.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    start.setEnabled(false);
                    ProgressWorker pw = new ProgressWorker();
                    pw.addPropertyChangeListener(new PropertyChangeListener() {

                        @Override
                        public void propertyChange(PropertyChangeEvent evt) {
                            String name = evt.getPropertyName();
                            if (name.equals("progress")) {
                                int progress = (int) evt.getNewValue();
                                pbProgress.setValue(progress);
                                repaint();
                            } else if (name.equals("state")) {
                                SwingWorker.StateValue state = (SwingWorker.StateValue) evt.getNewValue();
                                switch (state) {
                                    case DONE:
                                        start.setEnabled(true);
                                        break;
                                }
                            }
                        }

                    });
                    pw.execute();
                }
            });

        }
    }

    public class ProgressWorker extends SwingWorker<Object, Object> {

        @Override
        protected Object doInBackground() throws Exception {

            for (int i = 0; i < 100; i++) {        
                setProgress(i);
                try {
                    Thread.sleep(25);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }

            return null;
        }
    }
}

查看 Concurrency in Swing了解更多详情