在ActionListener中連續設置JTextArea文本

Question

我試圖創建一個按鈕，當按下該按鈕時，它將在JTextArea顯示文本，每次在等待時間后運行循環中的某個步驟時，該按鈕都會不斷更新。 現在，我所擁有的代碼將在循環的第一步中顯示其外觀，然后停止。 我所指的動作位於//Actions的底部。

public class MainWindow {

    private JFrame frmMcakennaAntivirus;

    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    MainWindow window = new MainWindow();
                    window.frmMcakennaAntivirus.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Create the application.
     */
    public MainWindow() {
        initialize();
    }

    /**
     * Initialize the contents of the frame.
     */
    private void initialize() {
        frmMcakennaAntivirus = new JFrame();
        frmMcakennaAntivirus.setResizable(false);
        frmMcakennaAntivirus.setTitle("McAkenna Anti-Virus");
        frmMcakennaAntivirus.setAlwaysOnTop(true);
        frmMcakennaAntivirus.setBounds(100, 100, 303, 197);
        frmMcakennaAntivirus.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        GridBagLayout gridBagLayout = new GridBagLayout();
        gridBagLayout.columnWidths = new int[]{0, 149, 135, 0, 0};
        gridBagLayout.rowHeights = new int[]{0, 14, 0, 24, 45, 0, 0};
        gridBagLayout.columnWeights = new double[]{0.0, 0.0, 0.0, 0.0, Double.MIN_VALUE};
        gridBagLayout.rowWeights = new double[]{0.0, 0.0, 0.0, 0.0, 0.0, 0.0, Double.MIN_VALUE};
        frmMcakennaAntivirus.getContentPane().setLayout(gridBagLayout);

        JSeparator separator = new JSeparator();
        GridBagConstraints gbc_separator = new GridBagConstraints();
        gbc_separator.insets = new Insets(0, 0, 5, 5);
        gbc_separator.gridx = 1;
        gbc_separator.gridy = 0;
        frmMcakennaAntivirus.getContentPane().add(separator, gbc_separator);

        JSeparator separator_1 = new JSeparator();
        GridBagConstraints gbc_separator_1 = new GridBagConstraints();
        gbc_separator_1.insets = new Insets(0, 0, 5, 5);
        gbc_separator_1.gridx = 0;
        gbc_separator_1.gridy = 1;
        frmMcakennaAntivirus.getContentPane().add(separator_1, gbc_separator_1);

        JButton btnBeginScan = new JButton("Begin Scan");
        btnBeginScan.setFont(new Font("Tahoma", Font.BOLD, 11));
        btnBeginScan.setForeground(new Color(0, 0, 0));
        btnBeginScan.setBackground(new Color(124, 252, 0));
        GridBagConstraints gbc_btnBeginScan = new GridBagConstraints();
        gbc_btnBeginScan.insets = new Insets(0, 0, 5, 5);
        gbc_btnBeginScan.gridx = 1;
        gbc_btnBeginScan.gridy = 1;
        frmMcakennaAntivirus.getContentPane().add(btnBeginScan, gbc_btnBeginScan);

        JButton btnFixProblems = new JButton("Fix Problems");
        btnFixProblems.setBackground(new Color(127, 255, 0));
        GridBagConstraints gbc_btnFixProblems = new GridBagConstraints();
        gbc_btnFixProblems.insets = new Insets(0, 0, 5, 5);
        gbc_btnFixProblems.gridx = 2;
        gbc_btnFixProblems.gridy = 1;
        frmMcakennaAntivirus.getContentPane().add(btnFixProblems, gbc_btnFixProblems);

        JSeparator separator_2 = new JSeparator();
        GridBagConstraints gbc_separator_2 = new GridBagConstraints();
        gbc_separator_2.insets = new Insets(0, 0, 5, 0);
        gbc_separator_2.gridx = 3;
        gbc_separator_2.gridy = 1;
        frmMcakennaAntivirus.getContentPane().add(separator_2, gbc_separator_2);

        Choice choice = new Choice();
        choice.setBackground(SystemColor.scrollbar);
        GridBagConstraints gbc_choice = new GridBagConstraints();
        gbc_choice.insets = new Insets(0, 0, 5, 5);
        gbc_choice.fill = GridBagConstraints.HORIZONTAL;
        gbc_choice.gridx = 1;
        gbc_choice.gridy = 2;
        frmMcakennaAntivirus.getContentPane().add(choice, gbc_choice);
        choice.add("Full System Scan");
        choice.add("Quick Scan");

        JProgressBar progressBar = new JProgressBar();
        GridBagConstraints gbc_progressBar = new GridBagConstraints();
        gbc_progressBar.fill = GridBagConstraints.BOTH;
        gbc_progressBar.insets = new Insets(0, 0, 5, 5);
        gbc_progressBar.gridx = 1;
        gbc_progressBar.gridy = 3;
        frmMcakennaAntivirus.getContentPane().add(progressBar, gbc_progressBar);

        final JTextArea textArea = new JTextArea();
        textArea.setLineWrap(true);
        textArea.setFont(new Font("Source Sans Pro Light", Font.PLAIN, 12));
        textArea.setEditable(false);
        textArea.setBackground(SystemColor.inactiveCaption);
        GridBagConstraints gbc_textArea = new GridBagConstraints();
        gbc_textArea.insets = new Insets(0, 0, 5, 5);
        gbc_textArea.fill = GridBagConstraints.BOTH;
        gbc_textArea.gridx = 1;
        gbc_textArea.gridy = 4;
        frmMcakennaAntivirus.getContentPane().add(textArea, gbc_textArea);

        JButton btnCancelScan = new JButton("Cancel Scan");
        btnCancelScan.setBackground(new Color(255, 0, 0));
        GridBagConstraints gbc_btnCancelScan = new GridBagConstraints();
        gbc_btnCancelScan.insets = new Insets(0, 0, 0, 5);
        gbc_btnCancelScan.gridx = 1;
        gbc_btnCancelScan.gridy = 5;
        frmMcakennaAntivirus.getContentPane().add(btnCancelScan, gbc_btnCancelScan);



        //Actions

        btnBeginScan.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {

                for (int x= 1; x < 6735; x++){
                    textArea.setText("Files scanned: " + x + "\nViruses found: " + x/350);
                    try {
                        Thread.sleep(randInt(90, 200));
                    } catch (InterruptedException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }

            }
        });

    }

    public static int randInt(int min, int max) {

        Random rand = null;

        int randomNum = rand.nextInt((max - min) + 1) + min;

        return randomNum;
    }

}

Answer 1

您正在阻止事件調度線程，該線程負責處理重繪請求。

Swing是一個單線程框架，切勿在EDT上下文中長時間運行或阻止操作。

有關更多詳細信息，請參見Swing中的並發。

請改用SwingWorker或Swing Timer 。

有關更多詳細信息，請參見工作線程和SwingWorker以及如何使用Swing計時器 。

附帶說明，您還將遇到NullPointerException ...

Random rand = null;
int randomNum = rand.nextInt((max - min) + 1) + min;

使用Random ，您應該創建一個實例並在需要時重復使用。 這將確保您從中獲得的值正確（盡其所能）是隨機的，否則最終可能會在很短的時間內重復出現這些值