我正在编写用于合并pdf文件的GUI实用程序,但是JFileChooser的showOpenDialog()方法不会打开用于打开文件的对话框。单击“文件”菜单中的“打开”项时,没有任何响应。为方便起见,Apache pdfbox库的下载链接为:https://pdfbox.apache.org/download.cgi
我试图将openFiles()方法的胆量移到actionPerformed()方法中的相应位置,但仍然无法正常工作。但是,在出于不同目的的其他人的代码中,showOpenDialog()方法可在actionPerformed方法内调用的方法中工作。代码如下:
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import javax.swing.*;
import javax.swing.filechooser.FileFilter;
import org.apache.pdfbox.multipdf.PDFMergerUtility;
public class PDFMerger extends JFrame implements ActionListener {
private static final int DEFAULT_WIDTH = 500;
private static final int DEFAULT_HEIGHT = 500;
private JMenuItem openItem;
private JMenuItem saveItem;
private JMenuItem exitItem;
private JTextArea textArea;
private JTextField textField;
private JButton bindButton;
private File[] files;
private File mergedFile;
public static void main(String[] args) {
PDFMerger pdfMerger = new PDFMerger();
pdfMerger.setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);
pdfMerger.setDefaultCloseOperation(EXIT_ON_CLOSE);
pdfMerger.setVisible(true);
}
public PDFMerger () {
JMenu menu = new JMenu("File");
JMenuItem openItem = new JMenuItem("Open");
openItem.addActionListener(this);
saveItem = new JMenuItem("Save");
saveItem.setEnabled(false);
saveItem.addActionListener(this);
exitItem = new JMenuItem("Exit");
exitItem.addActionListener(this);
menu.add(openItem);
menu.add(saveItem);
menu.add(exitItem);
JMenuBar menuBar = new JMenuBar();
menuBar.add(menu);
setJMenuBar(menuBar);
textArea = new JTextArea(40, 50);
JScrollPane scrollPane = new JScrollPane(textArea);
add(scrollPane, BorderLayout.CENTER);
JPanel operationPanel = new JPanel();
BoxLayout layout = new BoxLayout(operationPanel, BoxLayout.LINE_AXIS);
operationPanel.setLayout(layout);
JLabel label = new JLabel("Result: ");
textField = new JTextField(30);
textField.setEditable(false);
bindButton = new JButton("Bind");
bindButton.addActionListener(this);
bindButton.setEnabled(false);
operationPanel.add(label);
operationPanel.add(textField);
operationPanel.add(bindButton);
add(operationPanel, BorderLayout.NORTH);
}
public void actionPerformed (ActionEvent event) {
if (event.getSource() == exitItem)
System.exit(0);
else if (event.getSource() == openItem) {
files = openFiles();
bindButton.setEnabled(false);
}
else if (event.getSource() == bindButton) {
mergedFile = mergeFiles();
saveItem.setEnabled(true);
}
else if (event.getSource() == saveItem)
saveFile();
}
public File[] openFiles () {
File[] selectedFiles = null;
JFileChooser chooser = new JFileChooser();
chooser.setCurrentDirectory(new File("."));
chooser.setMultiSelectionEnabled(true);
int option = chooser.showOpenDialog(PDFMerger.this);
if (option == JFileChooser.APPROVE_OPTION)
selectedFiles = chooser.getSelectedFiles();
return selectedFiles;
}
public File mergeFiles () {
File merged = null;
// TODO
return merged;
}
public void saveFile () {
//TODO
}
}
谢谢您的帮助。
我修复了您的代码,并打开了JFileChooser。
我进行的主要更改是:
我通过调用SwingUtilities invokeLater方法启动了Swing GUI。该方法确保在Event Dispatch Thread上创建并执行Swing组件。
我使用了JFrame。我没有扩展JFrame。仅当您打算覆盖一个或多个类方法时,才扩展Swing组件。
您的代码令人困惑。我将代码分为逻辑方法。我只留下了令人困惑的代码,但是当您创建Swing布局时,您确实应该按行,列顺序创建组件。您还应该将对特定组件的所有方法调用组合在一起。它使查找和解决问题变得更加容易。
您不应该只有一个动作监听器来处理所有事情。每个按钮或菜单项都应具有单独的动作侦听器。
无论如何,这是您的代码。一旦我按照逻辑分离了事物,就更容易发现导致您的JFileChooser无法显示的错误。
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import javax.swing.*;
public class PDFMerger implements ActionListener {
private JFrame frame;
private JMenuItem openItem;
private JMenuItem saveItem;
private JMenuItem exitItem;
private JTextArea textArea;
private JTextField textField;
private JButton bindButton;
private File[] files;
private File mergedFile;
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
new PDFMerger();
}
});
}
public PDFMerger() {
frame = new JFrame("PDF Merger");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JMenuBar menuBar = createJMenuBar();
frame.setJMenuBar(menuBar);
JPanel operationPanel = createOperationPanel();
frame.add(operationPanel, BorderLayout.NORTH);
JPanel textPanel = createTextPanel();
frame.add(textPanel, BorderLayout.CENTER);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
private JPanel createOperationPanel() {
JPanel operationPanel = new JPanel();
BoxLayout layout = new BoxLayout(operationPanel, BoxLayout.LINE_AXIS);
operationPanel.setLayout(layout);
JLabel label = new JLabel("Result: ");
textField = new JTextField(30);
textField.setEditable(false);
bindButton = new JButton("Bind");
bindButton.addActionListener(this);
bindButton.setEnabled(false);
operationPanel.add(label);
operationPanel.add(textField);
operationPanel.add(bindButton);
return operationPanel;
}
private JPanel createTextPanel() {
JPanel panel = new JPanel();
panel.setLayout(new BorderLayout());
textArea = new JTextArea(40, 50);
JScrollPane scrollPane = new JScrollPane(textArea);
panel.add(scrollPane, BorderLayout.CENTER);
return panel;
}
private JMenuBar createJMenuBar() {
JMenu menu = new JMenu("File");
openItem = new JMenuItem("Open");
openItem.addActionListener(this);
saveItem = new JMenuItem("Save");
saveItem.setEnabled(false);
saveItem.addActionListener(this);
exitItem = new JMenuItem("Exit");
exitItem.addActionListener(this);
menu.add(openItem);
menu.add(saveItem);
menu.add(exitItem);
JMenuBar menuBar = new JMenuBar();
menuBar.add(menu);
return menuBar;
}
@Override
public void actionPerformed (ActionEvent event) {
if (event.getSource() == exitItem) {
frame.dispose();
System.exit(0);
} else if (event.getSource() == openItem) {
files = openFiles();
bindButton.setEnabled(false);
} else if (event.getSource() == bindButton) {
mergedFile = mergeFiles();
saveItem.setEnabled(true);
} else if (event.getSource() == saveItem)
saveFile();
}
public File[] openFiles () {
File[] selectedFiles = null;
JFileChooser chooser = new JFileChooser();
chooser.setCurrentDirectory(new File("."));
chooser.setMultiSelectionEnabled(true);
int option = chooser.showOpenDialog(frame);
if (option == JFileChooser.APPROVE_OPTION)
selectedFiles = chooser.getSelectedFiles();
return selectedFiles;
}
public File mergeFiles () {
File merged = null;
// TODO
return merged;
}
public void saveFile () {
//TODO
}
}