java - SwingWorker Process() 警告

Question

我尝试使用 Swing 编写一个简单的测试程序，我想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。我不断收到有关处理方法“从未在本地使用”的警告，并且它没有将任何文本附加到文本框。可能是我理解有误，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);               
    }
}

警告内容为:

The method process(String) from the type new SwingWorker(){} is never used locally

编辑:在 MadProgrammer 的帮助下，程序现在可以运行(选择 3 个文件并将路径作为字符串打印在文本框中)

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

SwingWorker应该在按钮 actionPerformed 内创建方法，这样当您单击按钮时，它将运行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正常。这意味着您应该要求用户在 actionPerformed 的上下文中选择文件。方法并将结果传递给SwingWorked

已更新

另外两件事...

1. 您实际上并未读取该文件，而只是将文件名传递给 publish方法
2. SwingWorker定义process如protected void process(List<V> chunks)但您已将其定义为 protected void process(String s) ...意味着您实际上并没有覆盖 SwingWorker的process方法，但要创建自己的...

看看this example了解如何使用 SwingWorker读取文件...

并且，更新您的 process拥有更正的方法签名...

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

请记住，您应该尽可能使用 @Override当你认为你正在重写一个方法时，编译器会在你错误时告诉你，这样你就省去了很多麻烦......