在更改JFrame的大小时，在GridLayout中添加ScrollPane不会在JPane中调整JTextarea的大小

Question

I want to add a grid to the current GridLayout with a filled JTextArea component. It works fine, but as mentioned in the title the JTextArea won't resizes itself after changing the size of frame.

I have already localized the error:

text.setLineWrap(true); //<--- here is the problem!!enter code here

in the method createGui.

Here is my Code:

import java.awt.*;
import java.awt.event.*;

import javax.swing.*;
class GridLayoutExample {

    private JFrame frame = new JFrame();
    private JPanel panel = new JPanel();
    private JScrollPane pane;
    final JTextArea text = new JTextArea("Click me!\nClick me!\nClick me!\nClick me!\nClick me!");

    GridLayoutExample() { createGui(); } //constrcutor

    private JPanel createGui () {
        panel.setLayout(new GridLayout(0, 2,0,0));          
        panel.add( new JLabel("Hello"));        
        //set style of first row, second column
        text.setLineWrap(true); //<--- here is the problem!!
        text.setEditable(true);
        //enable mouse listening and allow mouse action 
        doMouseActions();
        panel.add(text);
        return panel;
    }

    void addNewRow() {
        panel.add(new JLabel("Test1"));
        panel.add(new JTextField("Test"));
    }//addNewRow

    void showFrame() {
        pane = new JScrollPane(panel);
        frame.add(pane);
        frame.pack();
        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }//showframe

    void doMouseActions() {
        text.addMouseListener(new MouseListener() {

            @Override
            public void mouseClicked(MouseEvent arg0) {
                addNewRow();
            }

            @Override
            public void mouseEntered(MouseEvent arg0) {
                text.setBackground(Color.YELLOW);               
            }

            @Override
            public void mouseExited(MouseEvent arg0) {
                text.setBackground(Color.WHITE);                
            }

            @Override
            public void mousePressed(MouseEvent arg0) {}

            @Override
            public void mouseReleased(MouseEvent arg0) {}           
        });
    } // end of mouse action    

    public static void main(String[] args) {
        GridLayoutExample test = new GridLayoutExample();
        test.showFrame();
    }// end of main
}// class GridLayoutExampleenter code here

On the one hand It works fine when I disable line wrapping, on the other hand I need it to get the line breaks.

So any suggestions to do it better?

Many thanks in advance!

Answer 1

You are adding components at run time. In such cases you need to ensure the container gets revalidated:

void addNewRow() {
    panel.add(new JLabel("Test1"));
    panel.add(new JTextField("Test"));
    panel.revalidate();
    panel.repaint();
}//addNewRow

Also, you should create and access swing components only in the event dispatch thread. See here for more.