带有 JDialog 的 Java SwingWorker 在 JDBC 网络操作期间显示 JProgressBar

Question

我有一个带有按钮的框架，当按下它时会显示带有进度条的JDialog，并且正在使用 jdbc 驱动程序获取一些数据（正在更新进度条）。我需要一个取消按钮，所以我花了一些时间弄清楚如何连接所有东西。它似乎有效，但我真的不确定这种方式是否有好处。如果有人有空闲时间，请检查此代码并告诉我它是否有任何问题 - 主要是整个 SwingWorker 和取消的东西。

在我的电脑 (linux) 上，不成功的网络连接尝试（someNetworkDataFetching 方法）需要一整分钟才能超时，当我尝试创建时，我是否必须担心仍在工作的 SwingWorkers（尽管被取消但仍在等待连接）新的？

注意：你需要mysql jdbc驱动库来运行这段代码。

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.CancellationException;
import java.util.concurrent.ExecutionException;
import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JProgressBar;
import javax.swing.SwingConstants;
import javax.swing.SwingUtilities;
import javax.swing.SwingWorker;

public class Test extends JFrame {

    private JProgressBar progressBar = new JProgressBar();
    private JLabel label = new JLabel();
    private DataFetcherProgress dfp;

    /**
     * This class holds retrieved data.
     */
    class ImportantData {

        ArrayList<String> chunks = new ArrayList<>();

        void addChunk(String chunk) {
            // Add this data 
            chunks.add(chunk);
        }
    }

    /**
     * This is the JDialog which shows data retrieval progress.
     */
    class DataFetcherProgress extends JDialog {

        JButton cancelButton = new JButton("Cancel");
        DataFetcher df;

        /**
         * Sets up data fetcher dialog.
         */
        public DataFetcherProgress(Test owner) {
            super(owner, true);
            getContentPane().add(progressBar, BorderLayout.CENTER);
            // This button  cancels the data fetching worker.
            cancelButton.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    df.cancel(true);

                }
            });
            getContentPane().add(cancelButton, BorderLayout.EAST);
            setLocationRelativeTo(owner);
            setSize(200, 50);
            df = new DataFetcher(this);
        }

        /**
         * This executes data fetching worker.
         */
        public void fetchData() {
            df.execute();
        }
    }

    class DataFetcher extends SwingWorker<ImportantData, Integer> {

        DataFetcherProgress progressDialog;

        public DataFetcher(DataFetcherProgress progressDialog) {
            this.progressDialog = progressDialog;
        }

        /**
         * Update the progress bar.
         */
        @Override
        protected void process(List<Integer> chunks) {
            if (chunks.size() > 0) {
                int step = chunks.get(chunks.size() - 1);
                progressBar.setValue(step);
            }
        }

        /**
         * Called when worker finishes (or is cancelled).
         */
        @Override
        protected void done() {
            System.out.println("done()");
            ImportantData data = null;
            try {
                data = get();
            } catch (InterruptedException | ExecutionException | CancellationException ex) {
                System.err.println("done() exception: " + ex);
            }
            label.setText(data != null ? "Retrieved data!" : "Did not retrieve data.");
            progressDialog.setVisible(false);
        }

        /**
         * This pretends to do some data fetching.
         */
        private String someNetworkDataFetching() throws SQLException {
            DriverManager.getConnection("jdbc:mysql://1.1.1.1/db", "user", "pass");
            // Retrieve data...
            return "data chunk";
        }

        /**
         * This tries to create ImportantData object.
         */
        @Override
        protected ImportantData doInBackground() throws Exception {
            // Show the progress bar dialog.
            SwingUtilities.invokeLater(new Runnable() {
                @Override
                public void run() {
                    dfp.setVisible(true);
                }
            });

            ImportantData data = new ImportantData();
            try {
                int i = 0;
                // There is a network operation here (JDBC data retrieval)
                String chunk1 = someNetworkDataFetching();
                if (isCancelled()) {
                    System.out.println("DataFetcher cancelled.");
                    return null;
                }
                data.addChunk(chunk1);
                publish(++i);

                // And another jdbc data operation....
                String chunk2 = someNetworkDataFetching();
                if (isCancelled()) {
                    System.out.println("DataFetcher cancelled.");
                    return null;
                }
                data.addChunk(chunk2);
                publish(++i);
            } catch (Exception ex) {
                System.err.println("doInBackground() exception: " + ex);
                return null;
            }
            System.out.println("doInBackground() finished");
            return data;
        }
    }

    /**
     * Set up the main window.
     */
    public Test() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        label.setHorizontalAlignment(SwingConstants.CENTER);
        getContentPane().add(label, BorderLayout.CENTER);
        // Add a button starting data fetch.
        JButton retrieveButton = new JButton("Do it!");
        retrieveButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                fetchData();
            }
        });
        getContentPane().add(retrieveButton, BorderLayout.EAST);
        setSize(400, 75);
        setLocationRelativeTo(null);
        progressBar.setMaximum(2);
    }

    // Shows new JDialog with a JProgressBar and calls its fetchData()
    public void fetchData() {
        label.setText("Retrieving data...");
        dfp = new DataFetcherProgress(this);
        dfp.fetchData();
    }

    public static void main(String[] args) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    // Use jdbc mysql driver
                    Class.forName("com.mysql.jdbc.Driver");
                } catch (ClassNotFoundException ex) {
                    ex.printStackTrace();
                    return;
                }

                // Show the Frame
                new Test().setVisible(true);
            }
        });

    }
}

Answer 1

关于我唯一可能做的不同的事情是不要在 doInBackground 方法中使用 SwingUtilities.invokeLater 来显示对话框，但可能会使用 PropertyChangeListener 来监视对 state 属性工作者的更改。

我还将使用PropertyChangeListener 来监视对worker 的progress 属性的更改。我将使用setProgress 方法（以及PropertyChangeListener 中的getProgress）而不是使用publish 来指示进度变化

例如...java swingworker thread to update main Gui

我还可以考虑在 JPanel 上创建 UI 并将其添加到 JDialog 而不是从 JDialog 扩展目录，因为如果您愿意，它会给以其他方式重用面板的机会...