单击按钮时显示叠加层，并在使用 Swing 执行操作后再次消失

Question

我想在单击按钮时在我的 JFrame 顶部显示带有加载说明或微调器的不透明叠加层，并在执行操作后再次消失。我已经阅读了 Glass Pane，但我无法理解在使用按钮执行的操作功能下执行此操作的正确方法。有没有办法使用 Java 和 Swing 来做到这一点？顺便说一句，这是我现在的 JFrame...

public class Frame {

private JButton btnH;

/** Main Panel */
private static final Dimension PANEL_SIZE = new Dimension(500, 500);
private static JPanel panel = new JPanel();

public Frame() {
   init();
   panel.setLayout(null);
   panel.setPreferredSize(PANEL_SIZE);
}

public void init() {
   btnH = new JButton("HELP");
   btnH.setBounds(50, 50, 100, 25);

   panel.add(btnH);

   // Action listener to listen to button click and display pop-up when received.
   btnH.addActionListener(new ActionListener() {
       public void actionPerformed(ActionEvent event) {
            // Message box to display.
            JOptionPane.showMessageDialog(null, "Helpful info...", JOptionPane.INFORMATION_MESSAGE);
       }
   });
} 

public JComponent getComponent() {
    return panel;
}

private static void createAndDisplay() {
    JFrame frame = new JFrame("Frame");
    frame.getContentPane().add(new Frame().getComponent());
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.pack();
    frame.setLocationRelativeTo(null);
    frame.setVisible(true);
} 

public static void main(String[] args) {
    java.awt.EventQueue.invokeLater(new Runnable() {
        public void run() {
            createAndDisplay();
        }
    });
}

Answer 1

如果我没理解错的话，您需要显示某种正在进行的进度，直到按钮完成其工作。

如果是这样，您可以使用 CardLayout 和不确定的 JProgressBar。

CardLayout 是一个 LayoutManager（例如 BorderLayout、FlowLayout 等...），它允许您定义 cards.每个卡片是一个 Component（例如 Container 和其他 Component，例如 JPanel）。任何时候都只能看到一张卡片。每个 card 都与一个字符串相关联以识别它并能够 select 它比其他卡片可见。您可以阅读有关 CardLayout in the corresponding Java tutorial.

的更多信息

A JProgressBar 是进度条，即 JComponent 显示正在进行的任务的进度。有两种模式：确定和不确定。在确定模式下，您指定问题的大小，并通过代码自行推进进度条。在不确定模式下，指示器旋钮不断旋转（这让用户知道正在进行的任务正在进行中，并且程序不知道需要多长时间）。 JProgressBar 可以用作用户的简单视觉指示器。您可以阅读有关 JProgressBar in the corresponding Java tutorial.

的更多信息

因此，在您的情况下，您可以将 CardLayout 与两张卡片一起使用，其中一张卡片包含 "Help" 按钮，另一张包含不确定的 JProgressBar。当用户单击 "Help" 时，您会显示进度条卡片，当进度完成后，您会切换回 "Help" 按钮卡片。

现在，如果您在按钮 "Help" 的 ActionListener 内执行进度，那将在事件调度线程（或简称 EDT）上运行。所以你的卡将无法切换，因为切换也在 EDT 内部完成。在这种情况下，我们将创建一个单独的 SwingWorker 来处理进度。所以 ActionListener 唯一要做的就是创建并启动这样一个 SwingWorker。这样就会让ActionListener在进度结束之前结束，所以牌会被切换。

考虑以下示例代码：

import java.awt.CardLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.FlowLayout;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JProgressBar;
import javax.swing.SwingWorker;

public class MyPanel extends JPanel {

    private static final Dimension PANEL_SIZE = new Dimension(500, 500);

    public MyPanel() {
        //Always prefer a layout instead of setting it to null.
        super(new CardLayout()); //Set the layout of the main panel to CardLayout, so we can add the cards...

        //Obtain the CardLayout we just created for this panel:
        final CardLayout cardLayout = (CardLayout) super.getLayout();

        //String names of each card:
        final String nameForCardWithButton = "BUTTON",
                     nameForCardWithProgress = "PROGRESS";

        //Creating first card...
        final JPanel cardWithButton = new JPanel(new GridBagLayout());
        /*Using a GridBagLayout in a panel which contains a single component (such as the
        cardWithButton panel, containing a single JButton) will layout the component in
        the center of the panel.*/
        final JButton btnH = new JButton("HELP");
        cardWithButton.add(btnH);

        // Action listener to listen to button click and display pop-up when received.
        btnH.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent event) {

                cardLayout.show(MyPanel.this, nameForCardWithProgress); //Switch to progress bar card...

                //Create and start worker Thread:
                new SwingWorker() {
                    @Override
                    protected Object doInBackground() throws Exception {
                        /*Simulate a long ongoing process without blocking the EDT...
                        Well, actually, the JOptionPane will block the EDT I think, so I will leave
                        it here for demonstration puprposes only.*/
                        JOptionPane.showMessageDialog(null, "Helpful info...", "info", JOptionPane.INFORMATION_MESSAGE);
                        return null; //Not sure if returning null here is a good practice or not.
                    }

                    @Override
                    protected void done() {
                        cardLayout.show(MyPanel.this, nameForCardWithButton); //Switch back to button card, when the job has finished.
                    }
                }.execute();
            }
        });

        //Creating second card...
        final JPanel cardWithProgress = new JPanel(new FlowLayout());
        final JProgressBar bar = new JProgressBar();
        bar.setIndeterminate(true); //Here we initialize the progress bar to indeterminate mode...
        cardWithProgress.add(bar);

        super.add(cardWithButton, nameForCardWithButton);
        super.add(cardWithProgress, nameForCardWithProgress);
        super.setPreferredSize(PANEL_SIZE);
    }

    private static void createAndDisplay() {
        JFrame frame = new JFrame("Frame");
        frame.getContentPane().add(new MyPanel());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    } 

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

你可以在这里看到 MyPanel 的创建和初始化，它是 CardLayout 的容器。在其中，我们添加了两张卡片。一个带按钮，一个带进度条。

Answer 2

这方面的难点不是玻璃面板，而是 UI 和 SwingWorker 之间的互操作性。

您可以通过多种方式执行此操作，这只是其中一种。

您应该从通读 How to Use Root Panes which goes into how to use glass panes and Worker Threads and SwingWorker 开始，因为在您了解它之前，它会把您搞得一团糟。

这里需要注意的重要事项是：

Swing 是单线程的，你不应该阻塞事件调度线程，这就是 SwingWorker 的目的
Swing 不是线程安全的。这意味着你不应该直接或间接地从事件调度线程

因此，SwingWorker

的重要性

import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.FocusAdapter;
import java.awt.event.FocusEvent;
import java.awt.event.KeyAdapter;
import java.awt.event.MouseAdapter;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JProgressBar;
import javax.swing.SwingUtilities;
import javax.swing.SwingWorker;

public class Test {

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

    public Test() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame frame = new JFrame();
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        public TestPane() {
            setLayout(new GridBagLayout());

            JButton workButton = new JButton("Do some work already");
            add(workButton);

            workButton.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    workButton.setEnabled(false);
                    ProgressPane progressPane = new ProgressPane();
                    // This is a dangrous kind of thing to do and you should
                    // check that the result is a JFrame or JDialog first
                    JFrame parent = (JFrame) SwingUtilities.windowForComponent(TestPane.this);
                    parent.setGlassPane(progressPane);
                    progressPane.setVisible(true);
                    // This is a little bit of overkill, but it allows time
                    // for the component to become realised before we try and
                    // steal focus...
                    SwingUtilities.invokeLater(new Runnable() {
                        @Override
                        public void run() {
                            progressPane.requestFocusInWindow();
                        }
                    });
                    Worker worker = new Worker();
                    worker.addPropertyChangeListener(new PropertyChangeListener() {
                        @Override
                        public void propertyChange(PropertyChangeEvent evt) {
                            if ("state".equals(evt.getPropertyName())) {
                                if (worker.getState() == SwingWorker.StateValue.DONE) {
                                    progressPane.setVisible(false);
                                    workButton.setEnabled(true);
                                }
                            } else if ("progress".equals(evt.getPropertyName())) {
                                double value = (int) evt.getNewValue() / 100.0;
                                progressPane.progressChanged(value);
                            }
                        }
                    });
                    worker.execute();
                }
            });
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }

    }

    public class Worker extends SwingWorker<Object, Object> {

        @Override
        protected Object doInBackground() throws Exception {
            for (int value = 0; value < 100; value++) {
                Thread.sleep(100);
                value++;
                setProgress(value);
            }
            return this;
        }

    }

    public interface ProgressListener {

        public void progressChanged(double progress);
    }

    public class ProgressPane extends JPanel implements ProgressListener {

        private JProgressBar pb;
        private JLabel label;

        private MouseAdapter mouseHandler = new MouseAdapter() {
        };
        private KeyAdapter keyHandler = new KeyAdapter() {
        };
        private FocusAdapter focusHandler = new FocusAdapter() {
            @Override
            public void focusLost(FocusEvent e) {
                if (isVisible()) {
                    requestFocusInWindow();
                }
            }
        };

        public ProgressPane() {
            pb = new JProgressBar(0, 100);
            label = new JLabel("Doing important work here...");

            setLayout(new GridBagLayout());
            GridBagConstraints gbc = new GridBagConstraints();
            gbc.gridwidth = GridBagConstraints.REMAINDER;
            gbc.insets = new Insets(8, 8, 8, 8);
            add(pb, gbc);
            add(label, gbc);

            setOpaque(false);
        }

        @Override
        public void addNotify() {
            super.addNotify();

            addMouseListener(mouseHandler);
            addMouseMotionListener(mouseHandler);
            addMouseWheelListener(mouseHandler);

            addKeyListener(keyHandler);

            addFocusListener(focusHandler);
        }

        @Override
        public void removeNotify() {
            super.removeNotify();

            removeMouseListener(mouseHandler);
            removeMouseMotionListener(mouseHandler);
            removeMouseWheelListener(mouseHandler);

            removeKeyListener(keyHandler);

            removeFocusListener(focusHandler);
        }

        @Override
        public void progressChanged(double progress) {
            pb.setValue((int) (progress * 100));
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            g2d.setColor(new Color(128, 128, 128, 224));
            g2d.fillRect(0, 0, getWidth(), getHeight());
            g2d.dispose();
        }

    }

}

作为旁注，我已验证 SwingWorker 使用的 PropertyChangeListener 已在 EDT

的上下文中更新

您还应该看看 JLayer（正式名称为 JXLayer）

For example, example

就像是打了兴奋剂的玻璃板

现在，如果你真的想做一些花哨的事情，你可以做类似 this for example

单击按钮时显示叠加层，并在使用 Swing 执行操作后再次消失

Display an overlay when a button is click and disappear again when the action has been performed using Swing

java

swing

jframe

glasspane