当我的 JButton 很忙时，有没有办法显示正在加载的 JLabel？

Question

我已经上传了我的代码的特定部分，我希望这足以理解我的问题。我在具有多个按钮的框架中使用p6 面板，其中一个按钮显示此面板。

此面板p6 有两个按钮。单击check_api，程序需要一些时间来执行，对用户来说，好像应用程序已经挂起。因此，我尝试添加一个在按钮忙时显示等待消息的方法。但是这样做时，我的面板会失去用户定义的大小。

有没有办法在不影响面板尺寸的情况下显示等待消息？

public static void prepare_url(JPanel p6, JPanel content, int count) {
    InnerOperations.removeexcept(6, content);
    if (count != 1) {
        p6.removeAll();
        p6.revalidate();
        System.out.println("Count is greater than 1");
    }
    JPanel p_back = new JPanel();
    JTextField field = new JTextField(" Enter url(s) with delimiter ';'");
    JButton check_list = new JButton(" CHECK URL LIST STATUS");
    JButton check_api = new JButton(" CHECK  PREDEFINED API LIST");
    p_back.add(check_list);
    p_back.add(field);
    p_back.add(l_check);
    p_back.add(check_api);
    check_api.setBounds(200, 130, 400, 30);
    l_check.setBounds(50, 300, 600, 20);
    field.setBounds(200, 50, 400, 30);
    check_list.setBounds(200, 90, 400, 30);
    p6.add(p_back);
    p_back.setBounds(0, 0, 800, 600);
    check_list.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {

            String url_pref 
            String list[] = url_pref.split(";");
            int i = 0;
            while (i < list.length) {
                try {
                    // thread1.start();
                    prepareurl(p6, p_back, list, list.length);
                    // thread1.stop();
                } catch (IOException e1) {
                    // TODO Auto-generated catch block
                    e1.printStackTrace();
                }
                i++;

            }
        }
    });
    check_api.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            // thread2.start();
            // p_back.removeAll();
            //check_api.setText("Will load in a while");
            prepare_api(p6, content, p_back);
            // thread2.stop();

        }
    });

}
public static void userwait(JPanel ppanel)
{
    JLabel waiting = new JLabel();
    ppanel.add(waiting);
    waiting.setText("Please Wait......");
    waiting.setBounds(200, 200, 400, 30);
}   

Answer 1

在 EDT 中执行长时间运行的任务通常是个坏主意 - 请改用 SwingWorker，参见示例 Improve Application Performance With SwingWorker。 您可以在启动工作线程之前显示一些文本并禁用按钮以防止用户再次单击：

public class SwingworkerExample extends JFrame {

    private JButton startBtn = new JButton("Start");
    private JProgressBar progressBar = new JProgressBar(0, 100);
    private JLabel progressLbl = new JLabel("");
    private JLabel statusLbl = new JLabel("");

    public static void main(String... args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                SwingworkerExample swe = new SwingworkerExample("SwingWorker: progress");
                swe.setVisible(true);
            }
        });
    }

    public SwingworkerExample(String title) {
        super(title);
        setupUI();
        startBtn.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {
                startWorkerThread();
            }
        });
    }

    private void startWorkerThread() {
        // Disable JButton:
        startBtn.setEnabled(false);
        // Show info
        statusLbl.setText("running...");
        progressLbl.setText("...");

        /*
         * Create SwingWorker<Boolean, Integer> where
         * Boolean : type for thread result, use "Void" if no return value
         * Integer : type for published values
         */
        SwingWorker<Boolean, Integer> swingWorker = new SwingWorker<Boolean, Integer>() {

            @Override
            protected Boolean doInBackground() throws Exception {
                // WARN: do not update the GUI from within doInBackground(), use process() / done()!

                // Do something ... 
                // prepareurl(p6, p_back, list, list.length);
                // 
                for (int i = 0; i <= 100; i++) {
                    Thread.sleep((int) (Math.random() * 60));
                    // Use publish to send progress information to this.process() [optional]
                    publish(i);
                }
                return true;
            }

            @Override
            protected void process(List<Integer> chunks) {
                // handle published progress informations / update UI
                StringBuilder sb = new StringBuilder();
                chunks.forEach(val -> sb.append(" ").append(val));
                progressLbl.setText(String.format("processing: %s%n", sb));
                int progress = chunks.get(chunks.size() - 1);
                progressBar.setValue(progress);
            }

            @Override
            protected void done() {
                // Swingworker finished - update UI / handle result
                try {
                    Boolean result = get();
                    statusLbl.setText("DONE. Result= " + result);
                } catch (InterruptedException | ExecutionException e) {
                    e.printStackTrace();
                    statusLbl.setText("Error: " + e.getMessage());
                }
                // Enable JButton
                startBtn.setEnabled(true);
            }
        };
        swingWorker.execute();
    } // end: startWorkerThread

    private void setupUI() {
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setSize(240, 160);
        setLayout(new GridBagLayout());
        GridBagConstraints gc = new GridBagConstraints();
        gc.fill = GridBagConstraints.BOTH;
        gc.weightx = 1;
        gc.weighty = 1;
        gc.gridx = 0;
        gc.weighty = 1;

        gc.gridy = 0;
        add(startBtn, gc);

        gc.gridy = 1;
        add(progressBar, gc);

        gc.gridy = 2;
        add(statusLbl, gc);

        gc.gridy = 3;
        add(progressLbl, gc);
    }
}

Answer 2

几个选项：

1. 您可以使用不确定的JProgressBar。有关更多信息和工作示例，请参阅 How to Use Progress Bars 上的 Swing 教程部分。

2. 您可以使用GlassPane 在面板顶部显示消息。有关此方法的示例，请参阅 Disabled Glass Pane。