Question

我尝试使用Swing编写一个简单的测试程序，我想要做的就是加载一个文本文件并在文本区域中显示所选文本文件的路径。我一直收到关于“从不在本地使用”的处理方法的警告，并且它没有在文本框中附加任何文本。也许我误解了一些事情，希望有人能帮助我。

代码：

import java.awt.Color;
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.File;
import javax.swing.BorderFactory;
import javax.swing.BoxLayout;
import javax.swing.JButton;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextArea;
import javax.swing.SwingWorker;
import javax.swing.filechooser.FileNameExtensionFilter;



public class MyPanel3 extends JPanel{ 

    /**
     * 
     */
    private static final long serialVersionUID = 1L;
    private JTextArea jcomp;
    private JButton btn;
    private String testfile;

    public MyPanel3() {


        //construct components
        jcomp = new JTextArea (1, 1);
        jcomp.setBorder(BorderFactory.createDashedBorder(Color.BLACK)); 
        btn = new JButton ("open");

        //adjust size and set layout
        setPreferredSize (new Dimension (944, 575));
        BoxLayout layout = new BoxLayout (this, BoxLayout.Y_AXIS);
        setLayout(layout);


        //add main components
        add (jcomp);
        add (btn);


        new SwingWorker<Void, String>(){


            protected Void doInBackground(){

                //do processes...       
                btn.addActionListener(new ActionListener() {

                    public void actionPerformed(ActionEvent ae) {

                        final JFileChooser chooseFile = new JFileChooser();
                        FileNameExtensionFilter filter = new FileNameExtensionFilter(".txt","txt");
                        chooseFile.setFileFilter(filter);
                        chooseFile.setAcceptAllFileFilterUsed(false);
                        chooseFile.setMultiSelectionEnabled(true);

                        if(ae.getSource().equals(btn))  
                        {  
                            System.out.println("do in background running");

                            int returnVal = chooseFile.showOpenDialog(MyPanel3.this);

                            if(returnVal == JFileChooser.APPROVE_OPTION) 
                            {                                                                   
                                File[] files = chooseFile.getSelectedFiles();


                                 testfile = files[0].getPath();

                                 publish(testfile);
                            }
                        }
                    }
                });

                return null;
            }


            protected void process(String s) {
                        jcomp.append(s);

            }


        protected void done() {

            try 
            {
                //System.out.println("The operation was completed");
            } 
            catch (Exception e)
            {
                e.printStackTrace();
            }
        }


        }.execute();    
    }


    public static void main(String[] args){

        JFrame frame = new JFrame ("MyTest");
        frame.getContentPane();     
        frame.add(new MyPanel3());      
        frame.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);  
        frame.pack();
        frame.setVisible (true);               
    }
}

警告说：

new类型的方法进程（String） SwingWorker（）{}从不在本地使用

编辑：在MadProgrammer的帮助下，程序正在运行（选择3个文件并在文本框中将路径打印为字符串）

import java.awt.Color;
import java.awt.Dimension;
import java.util.ArrayList;
import java.util.List;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.File;
import javax.swing.BorderFactory;
import javax.swing.BoxLayout;
import javax.swing.JButton;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextArea;
import javax.swing.SwingWorker;
import javax.swing.filechooser.FileNameExtensionFilter;

public class MyPanel4 extends JPanel {

    /**
     *
     */
    private static final long serialVersionUID = 1L;
    private JTextArea jcomp;
    private JButton btn;


    public MyPanel4() {
        //construct components
        jcomp = new JTextArea(1, 1);
        jcomp.setBorder(BorderFactory.createDashedBorder(Color.BLACK));
        btn = new JButton("open");

        btn.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent ae) {

                final JFileChooser chooseFile = new JFileChooser();
                FileNameExtensionFilter filter = new FileNameExtensionFilter(".txt", "txt");
                chooseFile.setFileFilter(filter);
                chooseFile.setAcceptAllFileFilterUsed(false);
                chooseFile.setMultiSelectionEnabled(true);

                int returnVal = chooseFile.showOpenDialog(MyPanel4.this);
                if (returnVal == JFileChooser.APPROVE_OPTION) {
                    final File[] files = chooseFile.getSelectedFiles();


                    new SwingWorker<Void, String>() {

                        private String testfile1 = files[0].getPath();
                        private String testfile2 = files[1].getPath();
                        private String testfile3 = files[2].getPath();



                        protected Void doInBackground() {

                            List<String> b = new ArrayList<String>();

                            b.add(testfile1);
                            b.add(testfile2);
                            b.add(testfile3);   

                            publish(b.get(0));
                            publish(b.get(1));
                            publish(b.get(2));

                            return null;
                        }

                        @Override
                        protected void process(List<String> chunks) {

                            for (String pathname : chunks) 
                            {
                                jcomp.append(pathname + "\n");
                            }
                        }

                        protected void done() {
                            try 
                            {
                                System.out.println("Opration Completed");

                            } catch (Exception e) {
                                e.printStackTrace();
                            }
                        }
                    }.execute();
                }
            }
        });

        //adjust size and set layout
        setPreferredSize(new Dimension(944, 575));
        BoxLayout layout = new BoxLayout(this, BoxLayout.Y_AXIS);
        setLayout(layout);

        //add main components
        add(jcomp);
        add(btn);
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame("MyTest");
        frame.getContentPane();
        frame.add(new MyPanel4());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.setVisible(true);
    }
}

Answer 1

应在按钮SwingWorker方法内创建actionPerformed，这样当您点击该按钮时，它将会运行SwingWorker

您还应该确保在事件调度线程的上下文中与用户界面的所有交互都很好。这意味着您应该要求用户在actionPerformed方法的上下文中选择文件，并将结果传递给SwingWorked

<强>更新

另外两件事......

您实际上并未阅读该文件，只是将文件名称传递给publish方法
SwingWorker将process定义为protected void process(List<V> chunks)，但您已将其定义为protected void process(String s) ...意味着您实际上并未覆盖SwingWorker process方法，但创建自己的...

查看this example，了解如何使用SwingWorker阅读文件......

并且，更新您的process以获得更正的方法签名......

@Override
protected void process(List<String> chunks) {
    for (String line : chunks) {
        output.append(line);
    }
}

请记住，当你认为你重写一个方法时，你应该尽可能地使用@Override注释，编译器会在你弄错的时候告诉你，为你节省很多麻烦......

Answer 2

应该是这样的：

import java.awt.Color;
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.File;
import javax.swing.BorderFactory;
import javax.swing.BoxLayout;
import javax.swing.JButton;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextArea;
import javax.swing.SwingWorker;
import javax.swing.filechooser.FileNameExtensionFilter;

public class MyPanel3 extends JPanel {

    /**
     *
     */
    private static final long serialVersionUID = 1L;
    private JTextArea jcomp;
    private JButton btn;
    private String testfile;

    public MyPanel3() {
        //construct components
        jcomp = new JTextArea(1, 1);
        jcomp.setBorder(BorderFactory.createDashedBorder(Color.BLACK));
        btn = new JButton("open");

        btn.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent ae) {
                final JFileChooser chooseFile = new JFileChooser();
                FileNameExtensionFilter filter = new FileNameExtensionFilter(".txt", "txt");
                chooseFile.setFileFilter(filter);
                chooseFile.setAcceptAllFileFilterUsed(false);
                chooseFile.setMultiSelectionEnabled(true);

                int returnVal = chooseFile.showOpenDialog(MyPanel3.this);
                if (returnVal == JFileChooser.APPROVE_OPTION) {
                    File[] files = chooseFile.getSelectedFiles();

                    testfile = files[0].getPath();

                    new SwingWorker<Void, String>() {
                        protected Void doInBackground() {
                            publish(testfile);
                            return null;
                        }

                        protected void process(String s) {
                            jcomp.append(s);
                        }

                        protected void done() {
                            try {
                                //System.out.println("The operation was completed");
                            } catch (Exception e) {
                                e.printStackTrace();
                            }
                        }
                    }.execute();
                }
            }
        });

        //adjust size and set layout
        setPreferredSize(new Dimension(944, 575));
        BoxLayout layout = new BoxLayout(this, BoxLayout.Y_AXIS);
        setLayout(layout);

        //add main components
        add(jcomp);
        add(btn);
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame("MyTest");
        frame.getContentPane();
        frame.add(new MyPanel3());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.setVisible(true);
    }
}

在创建面板时，您正在运行worker。但是你应该在点击按钮时运行它。

SwingWorker Process（）警告

2 个答案: