Bottom of JScrollPane is cut off

问题

I am trying to create a simple email client and the bottom of the body is being cut-off. If I add a horizontal scroll bar, it does not appear, and the bottom of the Vertical scroll bar does not appear either.

Here is my code:

   import java.awt.BorderLayout;
   import java.awt.Container;
   import java.awt.FlowLayout;
   import java.awt.Font;

   import javax.swing.JFrame;
   import javax.swing.JLabel;
   import javax.swing.JPanel;
   import javax.swing.JScrollBar;
   import javax.swing.JScrollPane;
   import javax.swing.JTextArea;
   import javax.swing.JTextField;
   import javax.swing.UIManager;


   @SuppressWarnings("serial")
   public class gui extends JFrame{

gui(String title, int x, int y){

    super(title);
    setSize(x,y);
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    setResizable(false);

}

public void addElements(){

    Font size30 = new Font(null, Font.PLAIN, 30);

    JPanel pnl = new JPanel();

    Container contentPane = getContentPane();

    //--- User Info ---//

    JPanel userInfo = new JPanel();

    JLabel userLabel = new JLabel("Username: ");
    JTextField userField = new JTextField(12);
    userInfo.add(userLabel);
    userInfo.add(userField);

    JLabel passLabel = new JLabel("Password: ");
    JTextField passField = new JTextField(10);
    userInfo.add(passLabel);
    userInfo.add(passField);

    JLabel serverLabel = new JLabel("Mail Server: ");
    JTextField serverField = new JTextField(10);
    userInfo.add(serverLabel);
    userInfo.add(serverField);

    JLabel portLabel = new JLabel("Server Port: ");
    JTextField portField = new JTextField(3);
    userInfo.add(portLabel);
    userInfo.add(portField);

    //--- To: CC: and Subject Fields ---//

    JPanel msgInfo = new JPanel();

    JLabel toLabel = new JLabel("To: ");
    JTextField toField = new JTextField(30);
    msgInfo.add(toLabel);
    msgInfo.add(toField);

    JLabel subLabel = new JLabel("Subject: ");
    JTextField subField = new JTextField(30);
    msgInfo.add(subLabel);
    msgInfo.add(subField);

    //--- Body ---//

    JPanel bodyPnl = new JPanel(new BorderLayout(10,10));

    JLabel bodyLabel = new JLabel("Body");
    bodyLabel.setFont(size30);

    JTextArea bodyField = new JTextArea(30,70);
    bodyField.setLineWrap(true);
    bodyField.setWrapStyleWord(true);

    JScrollPane bodyScroll = new JScrollPane(bodyField);

    bodyScroll.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED);
    bodyScroll.setBounds(getX(), getY(), bodyField.getWidth(), bodyField.getHeight());

    bodyPnl.add("South",bodyScroll);

    pnl.add(userInfo);
    pnl.add(msgInfo);
    pnl.add(bodyLabel);
    pnl.add(bodyScroll);

    contentPane.add("North", pnl);

    setVisible(true);

}

}

In my main class I am just creating a new gui and then calling the addElements() function.

回答1:

FlowLayout doesn't "wrap" well. Consider a different layout, GridBagLayout for example...

Also, stop "trying" to force a size onto your UI, you don't have enough control over the factors which affect sizing to do this.

Instead, rely on the layout managers and API functionality. For example, instead of calling setSize on your frame, call pack...I would have posted soon, but it took me this long to find that call...I was scratching my head wondering why the UI wouldn't layout the way I expected...

import java.awt.Color;
import java.awt.EventQueue;
import java.awt.Font;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import javax.swing.JFrame;
import static javax.swing.JFrame.EXIT_ON_CLOSE;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.border.LineBorder;

public class Test extends JFrame {

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                Test frame = new Test("Testing", 400, 400);
            }
        });
    }

    Test(String title, int x, int y) {

        super(title);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        addElements();
        pack();
        setVisible(true);
//        setResizable(false);

    }

    public void addElements() {

        Font size30 = new Font(null, Font.PLAIN, 30);

        //--- User Info ---//
        JPanel userInfo = new JPanel(new GridBagLayout());

        GridBagConstraints gbc = new GridBagConstraints();
        gbc.insets = new Insets(2, 2, 4, 2);
        gbc.gridx = 0;
        gbc.gridy = 0;
        JLabel userLabel = new JLabel("Username: ");
        JTextField userField = new JTextField(12);
        userInfo.add(userLabel, gbc);
        gbc.gridx++;
        userInfo.add(userField, gbc);

        JLabel passLabel = new JLabel("Password: ");
        JTextField passField = new JTextField(10);
        gbc.gridx++;
        userInfo.add(passLabel, gbc);
        gbc.gridx++;
        userInfo.add(passField, gbc);

        JLabel serverLabel = new JLabel("Mail Server: ");
        JTextField serverField = new JTextField(10);
        gbc.gridx++;
        userInfo.add(serverLabel, gbc);
        gbc.gridx++;
        userInfo.add(serverField, gbc);

        JLabel portLabel = new JLabel("Server Port: ");
        JTextField portField = new JTextField(3);
        gbc.gridx++;
        userInfo.add(portLabel, gbc);
        gbc.gridx++;
        userInfo.add(portField, gbc);

        gbc = new GridBagConstraints();
        gbc.insets = new Insets(2, 2, 4, 2);
        gbc.gridx = 0;
        gbc.gridy = 0;
        //--- To: CC: and Subject Fields ---//
        JPanel msgInfo = new JPanel(new GridBagLayout());

        JLabel toLabel = new JLabel("To: ");
        JTextField toField = new JTextField(30);
        msgInfo.add(toLabel, gbc);
        gbc.gridx++;
        msgInfo.add(toField, gbc);

        JLabel subLabel = new JLabel("Subject: ");
        JTextField subField = new JTextField(30);
        gbc.gridx++;
        msgInfo.add(subLabel, gbc);
        gbc.gridx++;
        msgInfo.add(subField, gbc);

        //--- Body ---//
//        JPanel bodyPnl = new JPanel(new GridBagLayout());
//        gbc = new GridBagConstraints();
//        gbc.insets = new Insets(2, 2, 4, 2);
//        gbc.gridx = 0;
//        gbc.gridy = 0;

        JLabel bodyLabel = new JLabel("Body");
        bodyLabel.setHorizontalAlignment(JLabel.CENTER);
        bodyLabel.setFont(size30);

        JTextArea bodyField = new JTextArea(30, 70);
        bodyField.setLineWrap(true);
        bodyField.setWrapStyleWord(true);

        JScrollPane bodyScroll = new JScrollPane(bodyField);

        bodyScroll.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED);
//        bodyScroll.setBounds(getX(), getY(), bodyField.getWidth(), bodyField.getHeight());

        setLayout(new GridBagLayout());
        gbc = new GridBagConstraints();
        gbc.gridx = 0;
        gbc.gridy = 0;
        gbc.weightx = 1;
        gbc.fill = GridBagConstraints.HORIZONTAL;

        add(userInfo, gbc);
        gbc.gridy++;
        add(msgInfo, gbc);
        gbc.gridy++;
        gbc.insets = new Insets(10, 10, 4, 10);
        add(bodyLabel, gbc);
        gbc.gridy++;
        gbc.insets = new Insets(4, 10, 10, 10);
        gbc.weighty = 1;
        gbc.fill = GridBagConstraints.BOTH;
        add(bodyScroll, gbc);

    }

}

回答2:

The problem is because of FlowLayout Manager is being used. I have solved your problem with a different layout manager.
Before posting the solution here are some tips that you should follow

Change your class name. It should be in camel-case

Try to call pack() instead of setSize() as it will handle it automatically. When I replaced your setSize() with pack(), it was showing a awkward looking GUI which proves your layout and adding elements were not proper.

    Font size30 = new Font(null, Font.PLAIN, 30);

    JPanel pnl = new JPanel();
    pnl.setLayout(new BoxLayout(pnl,BoxLayout.Y_AXIS));

    Container contentPane = getContentPane();

    //--- User Info ---//

    JPanel userInfo = new JPanel();

    JLabel userLabel = new JLabel("Username: ");
    JTextField userField = new JTextField(12);
    userInfo.add(userLabel);
    userInfo.add(userField);

    JLabel passLabel = new JLabel("Password: ");
    JTextField passField = new JTextField(10);
    userInfo.add(passLabel);
    userInfo.add(passField);

    JLabel serverLabel = new JLabel("Mail Server: ");
    JTextField serverField = new JTextField(10);
    userInfo.add(serverLabel);
    userInfo.add(serverField);

    JLabel portLabel = new JLabel("Server Port: ");
    JTextField portField = new JTextField(3);
    userInfo.add(portLabel);
    userInfo.add(portField);

    //--- To: CC: and Subject Fields ---//

    JPanel msgInfo = new JPanel();

    JLabel toLabel = new JLabel("To: ");
    JTextField toField = new JTextField(30);
    msgInfo.add(toLabel);
    msgInfo.add(toField);

    JLabel subLabel = new JLabel("Subject: ");
    JTextField subField = new JTextField(30);
    msgInfo.add(subLabel);
    msgInfo.add(subField);

    //--- Body ---//

    JLabel bodyLabel = new JLabel("Body");
    bodyLabel.setFont(size30);

    JTextArea bodyField = new JTextArea(30,70);
    bodyField.setLineWrap(true);
    bodyField.setWrapStyleWord(true);

    JScrollPane bodyScroll = new JScrollPane(bodyField);

    bodyScroll.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED);
    bodyScroll.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);


    pnl.add(userInfo);
    pnl.add(msgInfo);
    pnl.add(bodyLabel);
    pnl.add(bodyScroll);

    contentPane.add(pnl);

    setVisible(true);
    pack();

来源：https://stackoverflow.com/questions/25256052/bottom-of-jscrollpane-is-cut-off

标签

java

swing

user-interface

jscrollpane

jtextarea