如何使用标准 Java 布局管理器更正/居中 GridLayout? [英] How to correct/center GridLayout using standard Java layout managers?

问题描述

下面的代码代表了问题.由于我设置了南北面板的高度，因此其余部分使用 GridLayout 转到中心面板.我认为因为它不能在其行之间平均共享剩余的像素，所以它只会留下它们.因此，在下面的代码中，我们在南面板上有难看的白线.

The below code represents the problem. Since I have heights of the north and south panels set the rest of it goes to the center panel using GridLayout. I think that since it cannot share the leftover pixels equally among its rows it just leaves them. Therefore in the below code we have ugly white line over south panel.

我的问题是:如何确保当 GridLayout 没有占据整个空间时，它至少是居中的?

My question here is: How to make sure that when the GridLayout is not taking the whole space it is at least centered?

通常我会使用 TableLayout 并对情况进行排序，但由于我正在编写答案，因此我只想使用标准管理器.提前知道这对我非常有用.

Normally I would use TableLayout and situation is sorted, but since I was writing an answer I wanted to use only standard managers. Knowing this would be very useful for me thanks in advance.

示例:

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.GridLayout;
import javax.swing.BorderFactory;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class AligningButonsTest
{
    public static void main(String[] args)
    {
        SwingUtilities.invokeLater(new Runnable()
        {
            @Override
            public void run()
            {                   
                JFrame f = new JFrame();
                f.setSize(800, 600);
                double CONSTANT_FACTOR = .1;
                int noOfRows = 5;
                JPanel centerP = new JPanel(new GridLayout(noOfRows,1));

                for(int i = 0; i < noOfRows; i++)
                {   
                    BoxPanel bP = new BoxPanel();
                    centerP.add(bP);
                }
                JPanel contentPane = new JPanel(new BorderLayout());                
                f.setContentPane(contentPane);
                contentPane.add(centerP, BorderLayout.CENTER);
                JPanel southP = new JPanel();
                southP.setBackground(Color.RED.darker());//southP.setOpaque(false);
                southP.setPreferredSize(new Dimension(1, (int)(CONSTANT_FACTOR* f.getHeight())));
                contentPane.add(southP, BorderLayout.SOUTH);
                JPanel northP = new JPanel();
                northP.setBackground(Color.RED.darker());//northP.setOpaque(false);
                northP.setPreferredSize(new Dimension(1, (int)(CONSTANT_FACTOR* f.getHeight())));
                contentPane.add(northP, BorderLayout.NORTH);            
                f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                f.setVisible(true);
            }
        });
    }   
}

class BoxPanel extends JPanel
{
    public BoxPanel()
    {
        setBorder(BorderFactory.createMatteBorder(1, 0, 1, 0, Color.RED));
        setBackground(Color.DARK_GRAY);
    }   
}

推荐答案

BoxLayout 在使用 Box.createVerticalGlue() 分配组件之间的空间方面做得非常好.此示例使用 Box.createVerticalStrut()，顶部和底部.How to Use BoxLayout: Using Invisible 中描述了间隔器组件作为填充物.

BoxLayout does a pretty good job of distributing the space between components using Box.createVerticalGlue(). This example uses Box.createVerticalStrut(), top and bottom. The spacers are described in How to Use BoxLayout: Using Invisible Components as Filler.

附录:BoxTest2 是使用 BoxLayout 创建固定尺寸的边缘面板和垂直胶水以更均匀地分布空间.Box.Filler 也可用于控制剩余"垂直空间.

Addendum: BoxTest2 is a variation that uses BoxLayout to create fixed-size edge panels and vertical glue to distribute the space more evenly. Box.Filler may also be used to control the "leftover" vertical space.

/** @see http://stackoverflow.com/questions/6072956 */
public class BoxTest2 {

    private static final int WIDE = 480;
    private static final int HIGH = WIDE / 8;
    private static final int ROWS = 5;
    private static final Box center = new Box(BoxLayout.Y_AXIS);

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {

            @Override
            public void run() {
                JFrame f = new JFrame();
                f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                center.setOpaque(true);
                center.setBackground(Color.lightGray);
                center.add(Box.createVerticalGlue());
                center.add(new EdgePanel());
                for (int i = 0; i < ROWS; i++) {
                    center.add(new BoxPanel());
                }
                center.add(new EdgePanel());
                center.add(Box.createVerticalGlue());
                f.add(center, BorderLayout.CENTER);
                f.pack();
                f.setVisible(true);
            }
        });
    }

    private static class EdgePanel extends JPanel {

        public EdgePanel() {
            Dimension d = new Dimension(WIDE, 2 * HIGH / 3);
            setPreferredSize(d);
            setBackground(Color.red.darker());
        }
    }

    private static class BoxPanel extends JPanel {

        public BoxPanel() {
            setPreferredSize(new Dimension(WIDE, HIGH));
            setBorder(BorderFactory.createMatteBorder(1, 0, 1, 0, Color.red));
            setBackground(Color.darkGray);
        }
    }
}

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