Java - 我需要更新 Swing GUI 程序中的 JTextFields

Question

我有一个程序可以查看单个记事本文件，其中包含类似于以下内容的信息:

Cardiff : 3245658

Bristol : 4726485

Manchester : 4728945

这些地点和数字来自自动系统，并且数字每 20 秒左右更改一次。 我需要创建一个循环(我猜)，以便当数字发生变化时，我的程序将回顾记事本文件并更新 JTextField 中的数字

P.s 我已经创建了该程序，以便它使用 ArrayList 查找文件，获取所需信息并将其放在正确的位置，

我需要的帮助是如何在文件发生更改时使代码自动更新，并且我需要在不使用任何类型的 Jbuttons 的情况下执行此操作，它只需要自己完成即可。

我的整个代码:

package window;

import java.awt.Color;
import java.awt.EventQueue;
import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class MapTest {

    private JFrame frame;
    static JTextField txtCardiff;
    static JTextField txtBristol;
    static JTextField txtSheffield;
    static JTextField txtDerby;
    static JTextField txtGlasgow;
    static JTextField txtFalkirk;
    static JTextField txtNewcastle;
    static JTextField txtLeeds;
    static JTextField txtPreston;
    static JTextField txtManchester;
    static JTextField txtWolverhampton;
    static JTextField txtBirmingham;
    static JTextField txtMiltonKeynes;
    static JTextField txtPeterborough;
    static JTextField txtColindale;
    static JTextField txtStepneyGreen;
    static JTextField txtSlough;
    static JTextField txtFaraday;
    static JTextField txtGuildford;
    static JTextField txtSouthbank;

    static BufferedReader CSVFile = new BufferedReader(new FileReader
        ("C:/Users/606854007/workspace/NetworkAppTest/jar/window/Cardiff.txt"));
// putting static infront of this Br ' CSVFile' gives: 
//Unhandled exception type FileNotFoundException. 
//but when i take away the 'static' it causes a problem in the 'FileCheckerWorker' class.
// (Will comment where and what)

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

    /**
    private String output = "";
    private String output1 = "";
    private String output2 = "";
    private String output3 = "";
    private String output4 = "";
    private String output5 = "";
    private String output6 = "";
    private String output7 = "";
    private String output8 = "";
    private String output9 = "";
    private String output10 = "";
    private String output11 = "";
    private String output12 = "";
    private String output13 = "";
    private String output14 = "";
    private String output15 = "";
    private String output16 = "";
    private String output17 = "";
    private String output18 = "";
    private String output19 = "";
    **/
    /** * Launch the application. */
    public static void main(String[] args) {
         try {
                UIManager.setLookAndFeel(
                            UIManager.getSystemLookAndFeelClassName());

            } catch (ClassNotFoundException e1) {
                e1.printStackTrace();

            } catch (InstantiationException e1) {
                e1.printStackTrace();

            } catch (IllegalAccessException e1) {
                e1.printStackTrace();

            } catch (UnsupportedLookAndFeelException e1) {
                e1.printStackTrace();
            }
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    MapTest window = new MapTest();
                    window.frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });

    }

    /**
     * Create the application.
     * 
     * @throws IOException
     */
    public MapTest() throws IOException {
        try {
            initialize();

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
    }

    /**
     * Initialise the contents of the frame.
     * 
     * @param output
     * @throws IOException
     */

    private void initialize() throws IOException {

                csv.add(CSVFile.readLine());
                csv.add(CSVFile.readLine());
                csv.add(CSVFile.readLine());
                csv.add(CSVFile.readLine());
                csv.add(CSVFile.readLine());
                csv.add(CSVFile.readLine());
                csv.add(CSVFile.readLine());
                csv.add(CSVFile.readLine());
                csv.add(CSVFile.readLine());
                csv.add(CSVFile.readLine());
                csv.add(CSVFile.readLine());
                csv.add(CSVFile.readLine());
                csv.add(CSVFile.readLine());
                csv.add(CSVFile.readLine());
                csv.add(CSVFile.readLine());
                csv.add(CSVFile.readLine());
                csv.add(CSVFile.readLine());
                csv.add(CSVFile.readLine());
                csv.add(CSVFile.readLine());
                csv.add(CSVFile.readLine());

                System.out.println(csv.get(0));
                System.out.println(csv.get(1));
                System.out.println(csv.get(2));
                System.out.println(csv.get(3));
                System.out.println(csv.get(4));
                System.out.println(csv.get(5));
                System.out.println(csv.get(6));
                System.out.println(csv.get(7));
                System.out.println(csv.get(8));
                System.out.println(csv.get(9));
                System.out.println(csv.get(10));
                System.out.println(csv.get(11));
                System.out.println(csv.get(12));
                System.out.println(csv.get(13));
                System.out.println(csv.get(14));
                System.out.println(csv.get(15));
                System.out.println(csv.get(16));
                System.out.println(csv.get(17));
                System.out.println(csv.get(18));
                System.out.println(csv.get(19));


        /**
         * JPanel container = new JPanel(); container.add(txtBirmingham);
         * container.add(txtBristol); container.add(txtCardiff);
         * container.add(txtColindale); container.add(txtDerby);
         * container.add(txtFalkirk); container.add(txtGlasgow);
         * container.add(txtGuildford); container.add(txtLeeds);
         * container.add(txtManchester); container.add(txtMiltonKeynes);
         * container.add(txtNewcastle); container.add(txtPeterborough);
         * container.add(txtPreston); container.add(txtSheffield);
         * container.add(txtSlough); container.add(txtSouthbank);
         * container.add(txtStepneyGreen); container.add(txtWolverhampton);
         * //container.add(); JScrollPane jsp = new JScrollPane(container);
         * frame.add(jsp);
         **/

        frame = new JFrame();
        frame.setBounds(0, 0, 1000, 1086);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().setLayout(null);
        frame.setBackground(Color.CYAN);

        txtCardiff = new JTextField();
        txtCardiff.setText(csv.get(0));
        txtCardiff.setBackground(Color.GREEN);
        txtCardiff.setBounds(305, 699, 102, 20);
        frame.getContentPane().add(txtCardiff);
        txtCardiff.setColumns(10);

        txtBristol = new JTextField();
        txtBristol.setText(csv.get(1));
        txtBristol.setBackground(Color.GREEN);
        txtBristol.setBounds(416, 780, 102, 20);
        frame.getContentPane().add(txtBristol);
        txtBristol.setColumns(10);

        txtSheffield = new JTextField();
        txtSheffield.setText(csv.get(2));
        txtSheffield.setBackground(Color.GREEN);
        txtSheffield.setBounds(517, 356, 110, 20);
        frame.getContentPane().add(txtSheffield);
        txtSheffield.setColumns(10);

        txtDerby = new JTextField();
        txtDerby.setText(csv.get(3));
        txtDerby.setBackground(Color.GREEN);
        txtDerby.setBounds(582, 451, 90, 20);
        frame.getContentPane().add(txtDerby);
        txtDerby.setColumns(10);

        txtGlasgow = new JTextField();
        txtGlasgow.setText(csv.get(4));
        txtGlasgow.setBackground(Color.GREEN);
        txtGlasgow.setBounds(250, 94, 102, 20);
        frame.getContentPane().add(txtGlasgow);
        txtGlasgow.setColumns(10);

        txtFalkirk = new JTextField();
        txtFalkirk.setText(csv.get(5));
        txtFalkirk.setColumns(10);
        txtFalkirk.setBackground(Color.GREEN);
        txtFalkirk.setBounds(331, 41, 102, 20);
        frame.getContentPane().add(txtFalkirk);

        txtNewcastle = new JTextField();
        txtNewcastle.setText(csv.get(6));
        txtNewcastle.setColumns(10);
        txtNewcastle.setBackground(Color.GREEN);
        txtNewcastle.setBounds(424, 141, 111, 20);
        frame.getContentPane().add(txtNewcastle);

        txtLeeds = new JTextField();
        txtLeeds.setText(csv.get(7));
        txtLeeds.setColumns(10);
        txtLeeds.setBackground(Color.GREEN);
        txtLeeds.setBounds(481, 244, 102, 20);
        frame.getContentPane().add(txtLeeds);

        txtPreston = new JTextField();
        txtPreston.setText(csv.get(8));
        txtPreston.setColumns(10);
        txtPreston.setBackground(Color.GREEN);
        txtPreston.setBounds(356, 221, 102, 20);
        frame.getContentPane().add(txtPreston);

        txtManchester = new JTextField();
        txtManchester.setText(csv.get(9));
        txtManchester.setColumns(10);
        txtManchester.setBackground(Color.GREEN);
        txtManchester.setBounds(394, 394, 124, 20);
        frame.getContentPane().add(txtManchester);

        txtWolverhampton = new JTextField();
        txtWolverhampton.setText(csv.get(10));
        txtWolverhampton.setColumns(10);
        txtWolverhampton.setBackground(Color.GREEN);
        txtWolverhampton.setBounds(360, 486, 153, 20);
        frame.getContentPane().add(txtWolverhampton);

        txtBirmingham = new JTextField();
        txtBirmingham.setText(csv.get(11));
        txtBirmingham.setColumns(10);
        txtBirmingham.setBackground(Color.GREEN);
        txtBirmingham.setBounds(424, 553, 128, 20);
        frame.getContentPane().add(txtBirmingham);

        txtMiltonKeynes = new JTextField();
        txtMiltonKeynes.setText(csv.get(12));
        txtMiltonKeynes.setColumns(10);
        txtMiltonKeynes.setBackground(Color.GREEN);
        txtMiltonKeynes.setBounds(474, 604, 135, 20);
        frame.getContentPane().add(txtMiltonKeynes);

        txtPeterborough = new JTextField();
        txtPeterborough.setText(csv.get(13));
        txtPeterborough.setColumns(10);
        txtPeterborough.setBackground(Color.GREEN);
        txtPeterborough.setBounds(655, 576, 135, 20);
        frame.getContentPane().add(txtPeterborough);

        txtColindale = new JTextField();
        txtColindale.setText(csv.get(14));
        txtColindale.setColumns(10);
        txtColindale.setBackground(Color.GREEN);
        txtColindale.setBounds(541, 699, 107, 20);
        frame.getContentPane().add(txtColindale);

        txtStepneyGreen = new JTextField();
        txtStepneyGreen.setText(csv.get(15));
        txtStepneyGreen.setColumns(10);
        txtStepneyGreen.setBackground(Color.GREEN);
        txtStepneyGreen.setBounds(667, 699, 137, 20);
        frame.getContentPane().add(txtStepneyGreen);

        txtSlough = new JTextField();
        txtSlough.setText(csv.get(16));
        txtSlough.setColumns(10);
        txtSlough.setBackground(Color.GREEN);
        txtSlough.setBounds(525, 756, 102, 20);
        frame.getContentPane().add(txtSlough);

        txtFaraday = new JTextField();
        txtFaraday.setText(csv.get(17));
        txtFaraday.setColumns(10);
        txtFaraday.setBackground(Color.GREEN);
        txtFaraday.setBounds(650, 756, 102, 20);
        frame.getContentPane().add(txtFaraday);

        txtGuildford = new JTextField();
        txtGuildford.setText(csv.get(18));
        txtGuildford.setColumns(10);
        txtGuildford.setBackground(Color.GREEN);
        txtGuildford.setBounds(525, 822, 102, 20);
        frame.getContentPane().add(txtGuildford);

        txtSouthbank = new JTextField();
        txtSouthbank.setText(csv.get(19));
        txtSouthbank.setColumns(10);
        txtSouthbank.setBackground(Color.GREEN);
        txtSouthbank.setBounds(655, 807, 115, 20);
        frame.getContentPane().add(txtSouthbank);

        JLabel lblNewLabel = new JLabel("New label");
        lblNewLabel.setForeground(Color.BLACK);
        lblNewLabel.setBackground(Color.BLACK);
        lblNewLabel
                .setIcon(new ImageIcon(
                        "C:\\Users\\606854007\\workspace\\NetworkAppTest\\Test\\window\\England_Wales.gif"));
        lblNewLabel.setBounds(33, 11, 890, 1086);
        frame.getContentPane().add(lblNewLabel);

        new FileCheckerWorker(null).execute();
\\ if i dont but null in the '()' then it comes up with an error, 
\\and this just makes it execute:
    /**
public FileCheckerWorker(MapTest mapTest) {
        this.mapTest = mapTest;
    }
**/
\\ which is not what I want, I have tried to add commands 
\\to run the methods from within:
\\ ' public FileCheckerWorker(MapTest mapTest)' method
\\ but it gives me a null pointer exception,


}

    }

下面是“FileCheckerWorker”类，希望我做得正确:p

package window;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.util.ArrayList;
import java.util.List;
import javax.swing.SwingWorker;


public class FileCheckerWorker extends SwingWorker<Object, List<String>> {

    private MapTest mapTest;

    public FileCheckerWorker(MapTest mapTest) {
        this.mapTest = mapTest;
    }


        @Override
        protected void process(List<List<String>> chunks) {
           List<String> values = chunks.get(chunks.size() - 1);

           mapTest.txtCardiff.setText(values.get(0));
           mapTest.txtBristol.setText(values.get(1));
           mapTest.txtSheffield.setText(values.get(2));
           mapTest.txtDerby.setText(values.get(3));
           mapTest.txtGlasgow.setText(values.get(4));
           mapTest.txtFalkirk.setText(values.get(5));
           mapTest.txtNewcastle.setText(values.get(6));
           mapTest.txtLeeds.setText(values.get(7));
           mapTest.txtPreston.setText(values.get(8));
           mapTest.txtManchester.setText(values.get(9));
           mapTest.txtWolverhampton.setText(values.get(10));
           mapTest.txtBirmingham.setText(values.get(11));
           mapTest.txtMiltonKeynes.setText(values.get(12));
           mapTest.txtPeterborough.setText(values.get(13));
           mapTest.txtColindale.setText(values.get(14));
           mapTest.txtStepneyGreen.setText(values.get(15));
           mapTest.txtSlough.setText(values.get(16));
           mapTest.txtFaraday.setText(values.get(17));
           mapTest.txtGuildford.setText(values.get(18));
           mapTest.txtSouthbank.setText(values.get(19));
        }

        @Override
        protected Object doInBackground() throws Exception {
            long lastUpdated = -1;
            File csvFile = new File("C:/Users/606854007/workspace/NetworkAppTest/Jar/window/Cardiff.txt");
            while (true) {
                if (csvFile.lastModified() != lastUpdated) {
                    BufferedReader csvReader = null;
                    List<String> values = new ArrayList<String>(20);
                    try {
                        csvReader = new BufferedReader(new FileReader("C:/Users/606854007/workspace/NetworkAppTest/Jar/window/Cardiff.txt"));
                        for (int index = 0; index < 20; index++) {
                            values.add(mapTest.CSVFile.readLine());
                        }
                        publish(values);
                        lastUpdated = csvFile.lastModified();
                    } finally {
                        try {
                            csvReader.close();
                        } catch (Exception e) {
                        }
                    }

                    Thread.sleep(5000);
                    System.out.println("Check For Change");
                }
            }
        }

}

将这两个代码更新为现在的样子。

此外，当我认为“doInBackground”正常工作时，如果在线给了我一个 NullPointerException value.add(mapTest.CSVFile.readLine());

Answer 1

看看ScheduledExecutorService 。使用它您可以安排一些定期任务。 (在您的情况下，每 20 秒就会从文件中读取一次)。