java - WindowEvent.WINDOW_CLOSING 提前终止程序

Question

我正在尝试使用 GUI 写入文本文件。我在执行此操作时遇到了问题，并且能够弄清楚 WindowEvent 出于某种原因以某种方式提前终止了程序。

最初我在 WindowEvent 行之后有 outFile.close();，因此 JTextArea 中的文本不会传输到文本文件。切换几行代码后，我意识到当尝试使用 WindowEvent 自动关闭 JFrame 时，之后的代码都没有执行。

我该如何解决这个问题？

import ...

public class TxtManager {
    static Input input;

    public static void overwriteCurrentFile() throws IOException {
        TxtManager txt = new TxtManager();
        input = new Input(txt);
    }

    public synchronized void sendData() throws IOException {
        try {
            BufferedWriter outFile = new BufferedWriter(new FileWriter(file1));
            String data = input.textArea.getText();
            outFile.write(data);
            outFile.close();
            input.frame.dispatchEvent(new WindowEvent(input.frame,WindowEvent.WINDOW_CLOSING));
            // Code from this point on in the try block does not execute.
            System.out.println("Finished with the write out..."); // Used for pinpointing the problem
            JOptionPane.showMessageDialog(null,"Data in " + TxtManager.file1 + " has been overwritten successfully.");
            TxtManager.showData = true;
            TxtManager.menu2();
        } catch (Exception ex) {
            JOptionPane.showMessageDialog(null,"Error: " + ex.getMessage(),"Error",JOptionPane.ERROR_MESSAGE);
        }
    }
}

class Input extends Thread {
    TxtManager txt;
    public JTextArea textArea;
    public JFrame frame;
    private JButton button;

    public Input(TxtManager txt) throws IOException {
        this.txt = txt;
        JOptionPane.showMessageDialog(null,"Enter desired data into the GUI screen.\n" +
            "Press the <Done> button once you are finished.");
        frame = new JFrame("Prompt");
        JPanel panel = new JPanel(new BorderLayout());
        frame.add(panel);
        JLabel label = new JLabel("Enter desired data.");
        panel.add(label,BorderLayout.NORTH);
        textArea = new JTextArea(15,80);
        panel.add(textArea,BorderLayout.CENTER);
        panel.add(new JScrollPane(textArea));
        button = new JButton("Done");
        panel.add(button,BorderLayout.SOUTH);

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.setVisible(true);

        start();
    }

    public void run() {
        button.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                try {
                    txt.sendData();
                } catch (IOException ex) {
                    JOptionPane.showMessageDialog(null,"Error: " + ex.getMessage(),"Error",JOptionPane.ERROR_MESSAGE);
                }
            }
        });
    }
}

Answer 1

我相信你的问题源于这一行(假设 input.frame 等同于你在这里创建的框架)

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

来自API

EXIT_ON_CLOSE (defined in JFrame): Exit the application using the System exit method. Use this only in applications.

这一切意味着当您抛出 WindowClosing 事件时，框架(理所当然地)会尝试自行关闭。这又会调用默认的关闭操作，恰好是 EXIT_ON_CLOSE，它会在那里调用 System.exit()。这将结束您的程序而不执行任何更多代码行。您可能正在寻找的是 WindowConstants.DISPOSE_ON_CLOSE 而不是 Frame.EXIT_ON_CLOSE，它应该关闭窗口并释放其资源而不退出您的程序。

老实说，通过 Frame.setVisible(false); 隐藏窗口可能更有意义。启动它的开销。