Java 无法使用setSize或setPreferredSize更改JFrame的大小

我一直在研究Java的JFileChooser。我使用Oracles FileChooserDemo作为基本模板。我对Oracles演示做了一些轻微的修改。我的问题是，当我运行程序时，JFrame非常小。即使使用setSize或setPreferredSize，JFrame也保持不变。演示使用pack方法。我以为这会限制帧的大小，但通过删除该行，当我运行程序时，窗口会出现，但顶部只有最小化、最大化和关闭按钮。这是我的完整代码：

import javax.swing.*;
import java.awt.event.*;
import java.io.File;
import java.io.IOException;
import java.util.List;
import java.util.ArrayList;
import java.awt.*;

import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.PDDocumentCatalog;
import org.apache.pdfbox.pdmodel.interactive.form.*;

public class Swing_Main_Menu extends JFrame implements ActionListener
{
public static final  int WIDTH=900;
public static final  int HEIGHT=600;

public static void main(String[] args)
{
    Swing_Main_Menu gui = new Swing_Main_Menu();
    gui.setVisible(true);       
}

public Swing_Main_Menu()
{
    super();
    setSize(WIDTH, HEIGHT);
    setLayout(new GridLayout(2,2));
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    JButton readPDF = new JButton("Read PDF");
    readPDF.setFont(new Font("Arial",Font.PLAIN, 30));
    readPDF.setBackground(Color.LIGHT_GRAY);
    readPDF.addActionListener(new PDFExtraction());

    JButton view = new JButton("View");
    view.setFont(new Font("Arial",Font.PLAIN, 30));
    view.setBackground(Color.LIGHT_GRAY);
    view.addActionListener(this);

    JButton dashboard = new JButton("Dashboard");
    dashboard.setFont(new Font("Arial",Font.PLAIN, 30));
    dashboard.setBackground(Color.LIGHT_GRAY);
    dashboard.addActionListener(this);

    JButton upload = new JButton("Batch Upload");
    upload.setFont(new Font("Arial",Font.PLAIN, 30));
    upload.setBackground(Color.LIGHT_GRAY);
    upload.addActionListener(this);

    add(readPDF);
    add(view);
    add(dashboard);
    add(upload);
}

private class PDFExtraction implements ActionListener
{
    private void readFields(PDDocument doc) throws Exception
    {
        PDDocumentCatalog catalog = doc.getDocumentCatalog();
        PDAcroForm form = catalog.getAcroForm();
        List<PDField> fields = form.getFields();
        ArrayList <String> allFields= new ArrayList<>(1);
        for(PDField field: fields)
        {
            String name = field.getFullyQualifiedName();
            if (field instanceof PDTextField || field instanceof PDComboBox)
            {
                 String value = field.getValueAsString();
                 allFields.add(value);
            }
            else if (field instanceof PDPushButton)
                ;
            else
            {
                if (field instanceof PDRadioButton)
                {
                    PDRadioButton radioButton = (PDRadioButton)form.getField(name);
                    String value=radioButton.getValue();
                    allFields.add(value);
                }
                else if (field instanceof PDCheckBox)
                {
                    PDButton box = (PDButton)field;
                    String value = box.getValue();
                    allFields.add(value);
                }

            }
        }
        int count = 1;
        for (String element : allFields)
        {
            System.out.println(count + ": " + element );
            count++;
        }
    }

    private void readFile() throws Exception {
        FileChooserForRead fc = new FileChooserForRead();
        fc.chooseFile();
    }

    public void actionPerformed (ActionEvent e)
    {
            try
            {
                readFile();
            }

            catch (Exception except)
            {
                System.exit(0);
            }
    }
}

public void actionPerformed (ActionEvent e)
{
    String buttonString = e.getActionCommand();
    if (buttonString.equals("View"))
    {
        //JFrame newMenu = new JFrame();
        //newMenu.setSize(WIDTH, HEIGHT);
        //newMenu.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);           
        FileChooser pickFile = new FileChooser();
        pickFile.chooseFile();      
    }
    else if (buttonString.equals("Dashboard"))
    {
        System.exit(0);
    }
    else if(buttonString.equals("Batch Upload"))
    {
        System.exit(0);
    }
    else
    {
        System.exit(0);
    }

}

public class FileChooser extends JPanel
implements ActionListener 
{
static private final String newline = "\n";
JButton openButton;
JTextArea log;
JFileChooser fc;

public FileChooser() {
    super(new BorderLayout());
    log = new JTextArea(5,20);
    log.setMargin(new Insets(5,5,5,5));
    log.setEditable(false);
    JScrollPane logScrollPane = new JScrollPane(log);

    fc = new JFileChooser();
    //fc.setFileSelectionMode(JFileChooser.DIRECTORIES_ONLY);
    //fc.setFileSelectionMode(JFileChooser.FILES_AND_DIRECTORIES);

    openButton = new JButton("Open a File...");
    //openButton.setPreferredSize(new Dimension(100, 50));
    //openButton.setFont(new Font("Arial",Font.PLAIN, 30));
    openButton.addActionListener(this);

    JPanel buttonPanel = new JPanel(); //use FlowLayout
    buttonPanel.add(openButton);

    add(buttonPanel, BorderLayout.PAGE_START);
    add(logScrollPane, BorderLayout.CENTER);
}

public void actionPerformed(ActionEvent e)
{
    if (e.getSource() == openButton) {
        int returnVal = fc.showOpenDialog(FileChooser.this);

    if (returnVal == JFileChooser.APPROVE_OPTION) 
    {
        File file = fc.getSelectedFile();
        log.append("Opening: " + file.getName() + "." + newline);
        try
        {
            Desktop.getDesktop().open(file);
        }
        catch (IOException ex)
        {
            System.exit(0);
        }
    }
    else {
        log.append("Open command cancelled by user." + newline);
    }
    log.setCaretPosition(log.getDocument().getLength());
    }
}

/**
* Create the GUI and show it.  For thread safety,
* this method should be invoked from the
* event dispatch thread.
*/
private void createAndShowGUI() {
//Create and set up the window.
JFrame frame = new JFrame("FileChooser");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

//Add content to the window.
frame.add(new FileChooser());

//Display the window.
//frame.setPreferredSize(new Dimension(WIDTH, HEIGHT));
frame.setSize(WIDTH,HEIGHT);
frame.pack();
frame.setVisible(true);
}

public void chooseFile () {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
  UIManager.put("swing.boldMetal", Boolean.FALSE); 
  createAndShowGUI();
}
});
}
}

public class FileChooserForRead extends JPanel implements ActionListener 
{
    static private final String newline = "\n";
    JButton openButton;
    JTextArea log;
    JFileChooser fc;

    public FileChooserForRead() {
        super(new BorderLayout());
        log = new JTextArea(5,20);
        log.setMargin(new Insets(5,5,5,5));
        log.setEditable(false);
        JScrollPane logScrollPane = new JScrollPane(log);

        fc = new JFileChooser();
        //fc.setFileSelectionMode(JFileChooser.DIRECTORIES_ONLY);
        //fc.setFileSelectionMode(JFileChooser.FILES_AND_DIRECTORIES);

        openButton = new JButton("Open a File...");
        //openButton.setPreferredSize(new Dimension(100, 50));
        //openButton.setFont(new Font("Arial",Font.PLAIN, 30));
        openButton.addActionListener(this);

        JPanel buttonPanel = new JPanel(); //use FlowLayout
        buttonPanel.add(openButton);

        add(buttonPanel, BorderLayout.PAGE_START);
        add(logScrollPane, BorderLayout.CENTER);
    }

    public void actionPerformed(ActionEvent e)
    {
        if (e.getSource() == openButton) {
            int returnVal = fc.showOpenDialog(FileChooserForRead.this);

        if (returnVal == JFileChooser.APPROVE_OPTION) 
        {
            File file = fc.getSelectedFile();
            log.append("Opening: " + file.getName() + "." + newline);
            try
            {
                PDDocument doc = PDDocument.load(file);
                PDFExtraction reader = new PDFExtraction();
                reader.readFields(doc);
            }
            catch (Exception ex)
            {
                System.exit(0);
            }
        }
        else {
            log.append("Open command cancelled by user." + newline);
        }
        log.setCaretPosition(log.getDocument().getLength());
        }           
    }

    private void createAndShowGUI() {
        //Create and set up the window.
        JFrame frame = new JFrame("FileChooser");
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

        //Add content to the window.
        frame.add(new FileChooserForRead());

        //Display the window.
        //frame.setPreferredSize(new Dimension(WIDTH, HEIGHT));
        frame.pack();
        frame.setVisible(true);
        }

        public void chooseFile () 
        {
            SwingUtilities.invokeLater(new Runnable()
            {
                public void run() 
                {
                    UIManager.put("swing.boldMetal", Boolean.FALSE); 
                    createAndShowGUI();
                }
            });
        }
    }

}

---

这很简单。您可以使用setSize方法或pack，但决不能同时使用这两种方法

private static void createAndShowGUI() {
    //Create and set up the window.
    JFrame frame = new JFrame("FileChooser");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    //Add content to the window.
    frame.add(new FileChooser());

    //Display the window.

    //frame.setPreferredSize(new Dimension(WIDTH, HEIGHT));
    frame.setSize(1024, 768);
    //frame.pack();
    frame.setVisible(true);
}

---

即使添加了导入，发布的代码也不会编译。为了更快地获得更好的帮助，请发布一个or。您能解释为什么不使用pack&setSize或提供一个参考吗？@PaulEdison，因为它们做的是相同的事情：更改帧大小。pack根据LayoutManager确定的内容窗格大小设置窗口大小。setSize设置窗口的固定大小。@SergiyMedvynskyy我知道我不应该同时使用这两个按钮，但如果我取出包装，窗口将消失，除了窗口的关闭、最小化和最大化按钮。当我取出包装并设置尺寸宽度、高度时，窗口仍然不存在，除了三个窗口按钮。@Sergiymedvynsky我已经添加了我的所有代码以及Oracle示例，该示例没有无法更改JFrame窗口大小的问题。@PaulEdison我仍然无法理解您的问题。我已经运行了您发布的代码，至少在我的方法createAndShowGUI版本中，这些代码对我来说都很好。

private static void createAndShowGUI() {
    //Create and set up the window.
    JFrame frame = new JFrame("FileChooser");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    //Add content to the window.
    frame.add(new FileChooser());

    //Display the window.

    //frame.setPreferredSize(new Dimension(WIDTH, HEIGHT));
    frame.setSize(1024, 768);
    //frame.pack();
    frame.setVisible(true);
}