Why setPreferredSize does not change the size of the button?

Question

Here is the code:

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

public class TestGrid {

    public static void main(String[] args) {
        JFrame frame = new JFrame("Colored Trails");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

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

        JPanel panel = new JPanel();
        panel.setLayout(new GridLayout(4, 9));
        panel.setMaximumSize(new Dimension(9*30-20,4*30));

        JButton btn;
        for (int i=1; i<=4; i++) {
            for (int j=1; j<=4; j++) {
                btn = new JButton();
                btn.setPreferredSize(new Dimension(30, 30));
                panel.add(btn);
            }

            btn = new JButton();
            btn.setPreferredSize(new Dimension(30, 10));
            panel.add(btn);

            for (int j=1; j<=4; j++) {
                btn = new JButton();
                btn.setPreferredSize(new Dimension(30, 30));
                panel.add(btn);
            }

        }
        mainPanel.add(panel);
        frame.add(mainPanel);

        frame.setSize(450,950);
        frame.setVisible(true);
    }
}

I suppose to have a table of buttons with 4 rows and 9 columns. And the middle column should be narrower that other columns. I tried Dimension(30, 10) and Dimension(30, 10) both have no effect on the width of the middle column. Why?

Answer 1

Layout managers are free to ignore the preferred size. Specifically, GridLayout will always make each cell in the grid exactly the same size (it's a pretty useless layout manager for that reason).

You'll have to use a different layout manager, such as nested BoxLayout or a GroupLayout.

Answer 2

호스트 웹의 색상을 사용하려면 일부 JavaScript로 호스트 웹 스타일 시트를 동적으로로드해야합니다.페이지에서 jQuery를 사용하는 경우 다음 JavaScript 블록을 사용하여 호스트 웹 스타일 시트를 페이지에 주입 할 수 있습니다.

(function () {
    // Retrieve the host web's URL from the query string
    var scriptbase = $.queryString('SPHostUrl') + '/_layouts/15/';

    // Create a <link> tag for the style sheet
    var $doclink = $('link').attr('rel', 'stylesheet');
    // The style sheet is loaded through an ASP.NET HTTP handler (defaultcss.ashx)
    $doclink.attr('href', scriptbase + 'defaultcss.ashx');

    // Add the style sheet link to the 
    $('head').append($doclink);
})();

.

이 작동하지 않으면 Microsoft의 기사 방법 : jQuery가 필요하지 않은 예는 SharePoint 앱에서 SharePoint 웹 사이트의 스타일 시트를 사용합니다.

Answer 3

setPreferredSize will not change the size of the button until dimension is set by using Dimension.

Example:-

Dimension dim = new Dimension(20,20), then use setPerferredSize(dim).

Answer 4

I found this method version, that fits perfect to your solution:

.addComponent(<<a jButton instance>>, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, <<put here an integer to set you max width button size>>)