这个GUI在设置了BoxLayout之后没有显示任何内容。

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go评论64阅读模式
英文:

This GUI is displaying nothing after setting BoxLayout

问题

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class GUI_Borrower extends JFrame implements ActionListener {

    JPanel panel = new JPanel();

    JLabel lblName = new JLabel("Name:");
    JLabel lblProg = new JLabel("Program:");
    JLabel lblId = new JLabel("Library ID: ");
    JLabel lblTitle = new JLabel("Add Borrower");
    JTextField txtName = new JTextField(10);
    JTextField txtProg = new JTextField(10);
    JTextField txtId = new JTextField(10);
    static int counter = 19000;
    JButton btnSubmit = new JButton("Submit");

    public GUI_Borrower() {
        super("Add Borrower");
        makeFrame();
        showFrame();
    }

    public void makeFrame() {
        lblTitle.setFont(new Font("Forte", Font.PLAIN, 40));
        lblTitle.setForeground(Color.BLUE);
        add(lblTitle);
        add(lblName);
        add(txtName);
        
        JPanel progPanel = new JPanel(); // Create a panel for program components
        progPanel.add(lblProg);
        progPanel.add(txtProg);
        panel.add(progPanel); // Add the program panel to the main panel
        
        JPanel idPanel = new JPanel(); // Create a panel for ID components
        idPanel.add(lblId);
        idPanel.add(txtId);
        panel.add(idPanel); // Add the ID panel to the main panel
        
        panel.setLayout(new BoxLayout(panel, BoxLayout.PAGE_AXIS));
        panel.add(btnSubmit);
        btnSubmit.addActionListener(this);
    }

    public void showFrame() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setSize(400, 200);
        setLocationRelativeTo(null);
        setVisible(true);
    }

    public void actionPerformed(ActionEvent ae) {
        Object source = ae.getSource();

        if (ae.getActionCommand().equals("Confirm")) {
            txtName.setText("");
            txtProg.setText("");
            btnSubmit.setText("Submit");
        } else if (source == btnSubmit) {
            if (txtName.getText().equals("") && txtProg.getText().equals("")) {
                txtId.setText("No entry of both");
            } else if (txtName.getText().equals("")) {
                txtId.setText("No entry of Name");
            } else if (txtProg.getText().equals("")) {
                txtId.setText("No entry of Program");
            } else {
                counter++;
                txtId.setText("" + counter);

                btnSubmit.setText("Confirm");
            }
        }
    }

    public static void main(String[] args) {
        new GUI_Borrower();
    }
}
英文: 
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class GUI_Borrower extends JFrame implements ActionListener {
JPanel panel = new JPanel();
JLabel lblName = new JLabel("Name:");
JLabel lblProg = new JLabel("Program:");
JLabel lblId = new JLabel("Library ID: ");
JLabel lblTitle = new JLabel("Add Borrower");
JTextField txtName = new JTextField(10);
JTextField txtProg = new JTextField(10);
JTextField txtId = new JTextField(10);
static int counter = 19000;
JButton btnSubmit = new JButton("Submit");
public GUI_Borrower() {
super("Add Borrower");
makeFrame();
showFrame();
}
public void makeFrame() {
lblTitle.setFont(new Font("Forte", Font.PLAIN, 40));
lblTitle.setForeground(Color.BLUE);
add(lblTitle);
add(lblName);
add(txtName);
add(lblProg);
add(txtProg);
add(lblId);
add(txtId);
panel.setLayout(new BoxLayout(panel, BoxLayout.PAGE_AXIS));
panel.add(btnSubmit);
btnSubmit.addActionListener(this);
}
public void showFrame() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setSize(400, 200);
setLocationRelativeTo(null);
setVisible(true);
}
public void actionPerformed(ActionEvent ae) {
Object source = ae.getSource();
if (ae.getActionCommand().equals("Confirm")) {
txtName.setText("");
txtProg.setText("");
btnSubmit.setText("Submit");
} else if (source == btnSubmit) {
if (txtName.getText().equals("") && txtProg.getText().equals("")) {
txtId.setText("No entry of both");
} else if (txtName.getText().equals("")) {
txtId.setText("No entry of Name");
} else if (txtProg.getText().equals("")) {
txtId.setText("No entry of Program");
} else {
counter++;
txtId.setText("" + counter);
btnSubmit.setText("Confirm");
}
}
}
public static void main(String[] args) {
new GUI_Borrower();
}
}

I tried adding BoxLayout because all the text fields and labels are on one line. So I tried box Layout and failed.

Can anyone show me how to make it like the title one line, label Different line, button different line?

Like this:

这个GUI在设置了BoxLayout之后没有显示任何内容。

答案1

得分: 3

正如camickr在他的评论中所说，通常使用GridBagLayout来创建一个表单。

我重新修改了你的代码，因为我希望展示一种更好的编写GUI面板的方法。

这是GUI界面。

这个GUI在设置了BoxLayout之后没有显示任何内容。

我所做的主要更改包括：

  1. 所有的Swing应用程序都必须以对SwingUtilities的invokeLater方法的调用开始。这个方法确保所有的Swing组件都在事件分派线程上创建和执行。

  2. 我将GUI代码组织成了三个方法，这样我可以一次专注于GUI的一个部分。在run方法中创建了JFrame，在createTitlePanel方法中创建了标题JPanel，在createFormPanel方法中创建了表单JPanel。JFrame的代码在不同的Swing应用程序之间很少会改变。

  3. 我使用了Swing组件。我没有扩展Swing组件，或者任何Java类，除非我打算重写类的某个方法。

  4. createFormPanel类使用了GridBagLayout来组织标签和文本字段以形成列。你可以将GridBagLayout想象成一个灵活的网格。网格的单元格大小不必相同。Oracle的教程，如何使用GridBagLayout，有另一个示例。

  5. 我将ActionListener放在了一个单独的类中。在这个示例中，我将它设置为内部类，这样我可以将代码粘贴成一个文件。通常，你应该将不同的类放在不同的文件中。这使得每个类都更短，更容易理解。

这是可运行的示例代码。

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.FlowLayout;
import java.awt.Font;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;

public class BorrowerGUI implements Runnable {

    private static int ID_COUNTER = 19000;

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new BorrowerGUI());
    }

    private JButton btnSubmit;

    private JTextField txtName;
    private JTextField txtProg;
    private JTextField txtId;

    @Override
    public void run() {
        JFrame frame = new JFrame("Add Borrower");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        frame.add(createTitlePanel(), BorderLayout.BEFORE_FIRST_LINE);
        frame.add(createFormPanel(), BorderLayout.CENTER);

        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    private JPanel createTitlePanel() {
        JPanel panel = new JPanel(new FlowLayout());

        JLabel lblTitle = new JLabel("Add Borrower");
        lblTitle.setFont(new Font("Forte", Font.PLAIN, 40));
        lblTitle.setForeground(Color.BLUE);
        panel.add(lblTitle);

        return panel;
    }

    private JPanel createFormPanel() {
        JPanel panel = new JPanel(new GridBagLayout());
        panel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));

        GridBagConstraints gbc = new GridBagConstraints();
        gbc.anchor = GridBagConstraints.LINE_START;
        gbc.fill = GridBagConstraints.HORIZONTAL;
        gbc.insets = new Insets(5, 5, 5, 5);
        gbc.gridx = 0;
        gbc.gridy = 0;

        JLabel lblName = new JLabel("Name:");
        panel.add(lblName, gbc);

        gbc.gridx++;
        txtName = new JTextField(20);
        panel.add(txtName, gbc);

        gbc.gridx = 0;
        gbc.gridy++;
        JLabel lblProg = new JLabel("Program:");
        panel.add(lblProg, gbc);

        gbc.gridx++;
        txtProg = new JTextField(20);
        panel.add(txtProg, gbc);

        gbc.gridx = 0;
        gbc.gridy++;
        JLabel lblId = new JLabel("Library ID:");
        panel.add(lblId, gbc);

        gbc.gridx++;
        txtId = new JTextField(20);
        txtId.setEditable(false);
        panel.add(txtId, gbc);

        gbc.gridx = 0;
        gbc.gridy++;
        gbc.gridwidth = 2;
        btnSubmit = new JButton("Submit");
        btnSubmit.addActionListener(new SubmitListener());
        panel.add(btnSubmit, gbc);

        return panel;
    }

    public class SubmitListener implements ActionListener {

        @Override
        public void actionPerformed(ActionEvent ae) {
            Object source = ae.getSource();

            if (ae.getActionCommand().equals("Confirm")) {
                txtName.setText("");
                txtName.requestFocus();
                txtProg.setText("");
                txtId.setText("");
                btnSubmit.setText("Submit");
            } else if (source == btnSubmit) {
                if (txtName.getText().equals("") &&
                        txtProg.getText().equals("")) {
                    txtId.setText("No entry of both");
                } else if (txtName.getText().equals("")) {
                    txtId.setText("No entry of Name");
                } else if (txtProg.getText().equals("")) {
                    txtId.setText("No entry of Program");
                } else {
                    ID_COUNTER++;
                    txtId.setText("" + ID_COUNTER);
                    btnSubmit.setText("Confirm");
                }
            }
        }
    }
}

编辑以补充：如果你想让标题JLabel右对齐，你需要切换到BorderLayout。我添加了一个空边框，这样文本就不会出现在JFrame的右边缘。

这是修改后的方法。

private JPanel createTitlePanel(String title) {
    JPanel panel = new JPanel(new BorderLayout());
    panel.setBorder(BorderFactory.createEmptyBorder(10, 10, 0, 10));

    JLabel lblTitle = new JLabel(title);
    lblTitle.setFont(new Font("Forte", Font.PLAIN, 40));
    lblTitle.setForeground(Color.BLUE);
    panel.add(lblTitle, BorderLayout.AFTER_LINE_ENDS);

    return panel;
}


<details>
<summary>英文:</summary>
As camickr says in his comment, you generally use a `GridBagLayout` to create a form.
I reworked your code because I hope to show a better way to code a GUI panel.
Here&#39;s the GUI.
[![Add Borrower GUI][1]][1]
The major changes I made include:
1.  All Swing applications must start with a call to the `SwingUtilities` `invokeLater` method.  This method ensures that all Swing components are created and executed on the [Event Dispatch Thread][2].
2.  I organized the GUI code into three methods so I could focus on one part of the GUI at a time.  The `JFrame` is created in the `run` method.  The title `JPanel` is created in the `createTitlePanel` method.  The form `JPanel` is created in the `createFormPanel` method. The code for the `JFrame` will rarely change from Swing application to Swing application.
3.  I use Swing components.  I don&#39;t extend Swing components, or any Java class, unless I intend to override one of the class methods.
4.  The `createFormPanel` class uses the `GridBagLayout` to organize the labels and text fields in columns.  You can think of the `GridBagLayout` as a flexible grid.  The cells of the grid don&#39;t have to be the same size.  The Oracle tutorial, [How to Use GridBagLayout][3], has another example.
5.  I put the `ActionListener` in a separate class.  I made it an inner class in this example so I could paste the code as one file.  Generally, you should put separate classes in separate files.  It makes each class shorter and easier to understand.
Here&#39;s the runnable, example code.  
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.FlowLayout;
import java.awt.Font;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
public class BorrowerGUI implements Runnable {
private static int ID_COUNTER = 19000;
public static void main(String[] args) {
SwingUtilities.invokeLater(new BorrowerGUI());
}
private JButton btnSubmit;
private JTextField txtName;
private JTextField txtProg;
private JTextField txtId;
@Override
public void run() {
JFrame frame = new JFrame(&quot;Add Borrower&quot;);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(createTitlePanel(), BorderLayout.BEFORE_FIRST_LINE);
frame.add(createFormPanel(), BorderLayout.CENTER);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
private JPanel createTitlePanel() {
JPanel panel = new JPanel(new FlowLayout());
JLabel lblTitle = new JLabel(&quot;Add Borrower&quot;);
lblTitle.setFont(new Font(&quot;Forte&quot;, Font.PLAIN, 40));
lblTitle.setForeground(Color.BLUE);
panel.add(lblTitle);
return panel;
}
private JPanel createFormPanel() {
JPanel panel = new JPanel(new GridBagLayout());
panel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
GridBagConstraints gbc = new GridBagConstraints();
gbc.anchor = GridBagConstraints.LINE_START;
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.insets = new Insets(5, 5, 5, 5);
gbc.gridx = 0;
gbc.gridy = 0;
JLabel lblName = new JLabel(&quot;Name:&quot;);
panel.add(lblName, gbc);
gbc.gridx++;
txtName = new JTextField(20);
panel.add(txtName, gbc);
gbc.gridx = 0;
gbc.gridy++;
JLabel lblProg = new JLabel(&quot;Program:&quot;);
panel.add(lblProg, gbc);
gbc.gridx++;
txtProg = new JTextField(20);
panel.add(txtProg, gbc);
gbc.gridx = 0;
gbc.gridy++;
JLabel lblId = new JLabel(&quot;Library ID:&quot;);
panel.add(lblId, gbc);
gbc.gridx++;
txtId = new JTextField(20);
txtId.setEditable(false);
panel.add(txtId, gbc);
gbc.gridx = 0;
gbc.gridy++;
gbc.gridwidth = 2;
btnSubmit = new JButton(&quot;Submit&quot;);
btnSubmit.addActionListener(new SubmitListener());
panel.add(btnSubmit, gbc);
return panel;
}
public class SubmitListener implements ActionListener {
@Override
public void actionPerformed(ActionEvent ae) {
Object source = ae.getSource();
if (ae.getActionCommand().equals(&quot;Confirm&quot;)) {
txtName.setText(&quot;&quot;);
txtName.requestFocus();
txtProg.setText(&quot;&quot;);
txtId.setText(&quot;&quot;);
btnSubmit.setText(&quot;Submit&quot;);
} else if (source == btnSubmit) {
if (txtName.getText().equals(&quot;&quot;) &amp;&amp;
txtProg.getText().equals(&quot;&quot;)) {
txtId.setText(&quot;No entry of both&quot;);
} else if (txtName.getText().equals(&quot;&quot;)) {
txtId.setText(&quot;No entry of Name&quot;);
} else if (txtProg.getText().equals(&quot;&quot;)) {
txtId.setText(&quot;No entry of Program&quot;);
} else {
ID_COUNTER++;
txtId.setText(&quot;&quot; + ID_COUNTER);
btnSubmit.setText(&quot;Confirm&quot;);
}
}
}
}
}
Edited to add:  If you want the title `JLabel` to be right-justified, you&#39;ll have to switch to a `BorderLayout`.  I added an empty border so the text wouldn&#39;t be on the right edge of the `JFrame`.
Here&#39;s the changed method.
private JPanel createTitlePanel(String title) {
JPanel panel = new JPanel(new BorderLayout());
panel.setBorder(BorderFactory.createEmptyBorder(10, 10, 0, 10));
JLabel lblTitle = new JLabel(title);
lblTitle.setFont(new Font(&quot;Forte&quot;, Font.PLAIN, 40));
lblTitle.setForeground(Color.BLUE);
panel.add(lblTitle, BorderLayout.AFTER_LINE_ENDS);
return panel;
}
[1]: https://i.stack.imgur.com/gmvKr.png
[2]: https://docs.oracle.com/javase/tutorial/uiswing/concurrency/dispatch.html
[3]: https://docs.oracle.com/javase/tutorial/uiswing/layout/gridbag.html
</details>

huangapple
  • 本文由 发表于 2020年8月29日 02:10:55
  • 转载请务必保留本文链接：https://go.coder-hub.com/63638937.html
  • boxlayout
  • java
  • layout-manager
  • swing
  • user-interface
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