在JTextArea中显示后台进程状态 [英] Show background process status in JTextArea

问题描述

有什么办法可以在JTextArea中编写有关后台进程的文本.屏幕上有一个按钮.当用户单击该按钮时，将启动某些过程.我想在屏幕上的文本"区域中显示该进程的正在进行状态.在执行textArea.append("Some status")之后，我会打电话给textArea.repaint()，但这对我来说不起作用.

Is there any way to write text in JTextArea about background process. I have one button on screen. When user click on that button, some process is started. I want to show ongoing status of that process on screen which is in Text area. After doing textArea.append("Some status") I use to call textArea.repaint() but this not work for me.

我是否需要为此实现自己的线程?

Should I need to implement my own Thread for this?

推荐答案

您只需使用 SwingWorker ，您实际上不必担心在Event Dispatcher Thread上执行定期任务.您只需在doInBackground()方法内调用publish()将指定的文本附加到JTextArea，这将调用process()并自动在Event Dispatcher Thread上执行整个任务.

You simply can use a SwingWorker, where you really doesn't have to worry about performing the periodic task on the Event Dispatcher Thread. You simply will call publish() inside doInBackground() method to append the specified text to JTextArea, which will invoke process() and perform the whole task on Event Dispatcher Thread automatically.

看看这个工作示例:

import java.awt.*;
import java.awt.event.*;
import java.net.URL;
import javax.imageio.ImageIO;
import javax.swing.*;

public class LoadingImage {

    private JPanel contentPane;
    private JTextArea logArea;
    private JLabel imageLabel;
    private ImageIcon[] images;
    private JButton startStopButton;
    private String[] path;
    private int counter;

    private Timer timer;

    private ActionListener timerAction = 
                            new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent ae) {
            counter %= path.length;
            imageLabel.setIcon(images[counter++]);
        }
    };

    private ActionListener buttonAction = 
                            new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent ae) {
            if (timer.isRunning()) {
                startStopButton.setText("Start");
                timer.stop();
            }
            else {
                startStopButton.setText("Stop");
                timer.start();
            }
        }
    };

    public LoadingImage() {
        imageLabel = new JLabel("Nothing to display yet...", JLabel.CENTER);
        images = new ImageIcon[5];
        path = new String[] {
            "http://i.imgur.com/922oehL.gif",
            "http://i.imgur.com/2Fim5t4.gif",
            "http://i.imgur.com/jJKlCiI.gif",
            "http://i.imgur.com/0KuZuGl.gif",
            "http://i.imgur.com/evuKoI5.gif"
        };
        counter = 0;
    }

    private void displayGUI() {
        JFrame frame = new JFrame("Loading Image Example");
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

        contentPane = new JPanel(new BorderLayout(5, 5));
        JPanel centerPanel = new JPanel(new GridLayout(1, 2, 5, 5));
        logArea = new JTextArea(10, 10);
        JScrollPane logScroller = new JScrollPane();
        logScroller.setViewportView(logArea);

        centerPanel.add(logScroller);
        centerPanel.add(imageLabel);
        contentPane.add(centerPanel, BorderLayout.CENTER);

        startStopButton = new JButton("Stop");
        startStopButton.addActionListener(buttonAction);
        contentPane.add(startStopButton, BorderLayout.PAGE_END);

        frame.setContentPane(contentPane);
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);

        new BackgroundTask().execute();
        timer = new Timer(1000, timerAction);
        timer.start();
    }

    private class BackgroundTask extends SwingWorker<ImageIcon[], String> {
        @Override
        protected ImageIcon[] doInBackground() {
            ImageIcon[] images = new ImageIcon[path.length];
            for (int i = 0; i < path.length; i++)
            {
                try {
                images[i] = new ImageIcon(ImageIO.read(new URL(path[i])));
                }catch(Exception e) {e.printStackTrace();}
                publish(String.format("Loaded : %s%n", path[i]));
            }

            return images;
        }

        @Override
        protected void process(java.util.List<String> messages) {
            for (String message : messages)
                logArea.append(message);
        }

        @Override
        protected void done() {
            try {
                images = get();             
            } catch(Exception e) {e.printStackTrace();}
        }
    }

    public static void main(String[] args) {
        Runnable runnable = new Runnable() {
            @Override
            public void run() {
                new LoadingImage().displayGUI();
            }
        };
        EventQueue.invokeLater(runnable);
    }
}

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