Java Swing JTextArea滚动条未显示在内部

Question

I am trying to add scrollbars in JTextArea but scrollbars are not displaying in the textarea..

Here is my code,

import java.awt.Color;
import java.awt.Dimension;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;

public class Test {

    public static void main(String[] args) {
        JFrame frame = new JFrame("MySql Console");
        frame.setSize(400, 300);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JPanel panel = new JPanel();
        frame.add(panel);
        panel.setLayout(null);

        JTextArea txtQuery = new JTextArea ();
        txtQuery.setBounds(10, 10, 365, 45);        
        JScrollPane scroll = new JScrollPane (txtQuery, 
           JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
        //scroll.setPreferredSize(new Dimension(100, 50));
        panel.add(scroll);
        panel.add(txtQuery);

        frame.setVisible(true);
    }

}

tried some alternatives from internet but still not working.

Answer 1

   panel.setLayout(null);

    JTextArea txtQuery = new JTextArea ();
    txtQuery.setBounds(10, 10, 365, 45);        
    JScrollPane scroll = new JScrollPane (txtQuery, 
       JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
    //scroll.setPreferredSize(new Dimension(100, 50));
    panel.add(scroll);
    panel.add(txtQuery);

1. Don't use a null layout. The layout manager will determine the preferred size of a component and in turn the scrollpane can then determine when a scrollbar is required. The scrollbar will appear automatically as you add text to the text area.

2. Don't add the text area to the panel. A component can only have a single parent. You already added the text area to the scrollpane.

3. Give the text area a preferred size by specifying the row/column of the text area.

So your modified code should be something like:

   //panel.setLayout(null);

    JTextArea txtQuery = new JTextArea (5, 20);
    //txtQuery.setBounds(10, 10, 365, 45);        
    JScrollPane scroll = new JScrollPane (txtQuery);
    //scroll.setPreferredSize(new Dimension(100, 50));
    panel.add(scroll);
    //panel.add(txtQuery);

Answer 2

please remove them below line, then everything will work fine.

panel.setLayout(null);

to work your application more effectively consider points in @camickr answer also.

Answer 3

Would it help to add a viewport to your JTextArea?

Something along the lines of jScrollPane.setViewportView(jTextArea); ? If that doesn't work you may need to make a GroupLayout block. Which isn't necessarily hard all things considered. I have this :

javax.swing.GroupLayout layout = new 
javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
                .addContainerGap(118, Short.MAX_VALUE)
                .addComponent(jScrollPane, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addGap(116, 116, 116))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
                .addContainerGap(105, Short.MAX_VALUE)
                .addComponent(jScrollPane, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addGap(99, 99, 99))
        );

        pack();
    }

Hope this helps! Good luck :D