JPanels并没有完全伸展以占据可用空间

Question

我有一个面板,我可以并排放置几个不同尺寸和颜色的迷你面板,它们应该占据整个父面板(​​水平).

为此我使用BorderLayout(用于父面板),BoxLayout用于子面板,我放置所有迷你面板(参见下面的代码).它可以正常工作,并且可以正常调整大小和一切.但是,随着迷你面板数量的增加,会出现奇怪的行为:父面板末端出现空白区域.

我想我发现这是布局管理器中的拉伸错误,因为为了拉伸面板,布局管理器尝试向每个迷你面板添加一个像素.但是,当迷你面板的数量很大时,向每个面板添加一个像素将导致添加许多像素并超出父级的大小.因此,布局管理器最终不会向任何迷你面板添加任何像素,从而导致空白空间.

这是我的SSCCE :(尝试运行,拉伸窗口,以了解问题)

package com.myPackage;

import java.awt.*;
import java.util.Vector;
import javax.swing.BorderFactory;
import javax.swing.BoxLayout;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class ColoredPanels extends JPanel
{
    /* Content information. */
    private Vector<Integer> partitions;
    private Vector<Color> colors;

    /* Panel where the content panels will go. */
    private JPanel contentHolder;

    private final int defaultHeight = 20;

    public ColoredPanels(Vector<Integer> partitions, Vector<Color> colors)
    {
        assert partitions != null;
        assert !partitions.isEmpty();
        assert colors != null;
        assert !colors.isEmpty();
        assert colors.size() == partitions.size();

        this.partitions = partitions;
        this.colors = colors;

        /* Set layout manager. */
        setLayout(new BorderLayout());

        /* Create the content holder. */
        contentHolder = new JPanel();
        contentHolder.setLayout(new BoxLayout(contentHolder, BoxLayout.X_AXIS));
        this.add(contentHolder, BorderLayout.NORTH);

        /* Fill content holder with colored panels. */
        createPanels();
    }

    private void createPanels()
    {
        assert partitions != null;
        assert !partitions.isEmpty();
        assert colors != null;
        assert !colors.isEmpty();
        assert colors.size() == partitions.size();

        for (int i = 0; i < partitions.size(); i++)
        {
            JPanel newPanel = new JPanel();
            newPanel.setBackground(colors.get(i));
            newPanel.setPreferredSize(new Dimension(partitions.get(i), defaultHeight));
            newPanel.setMinimumSize(new Dimension(1, defaultHeight));
            contentHolder.add(newPanel);
        }
    }

    public static void main(String[] in)
    {
        Vector<Integer> sizes = new Vector<Integer>();
        Vector<Color> cols = new Vector<Color>();

        /* Make 100 random sizes, and use two colors. */
        for (int i = 0; i < 100; i++)
        {
            int size = (int)Math.round(1 + Math.random() * 10);
            sizes.add(size);
            cols.add((i%2 == 0)? Color.red : Color.green);
        }

        ColoredPanels panels = new ColoredPanels(sizes, cols);
        panels.setBorder(BorderFactory.createLineBorder(Color.yellow, 1));

        JFrame newFrame = new JFrame();
        newFrame.getContentPane().add(panels);
        newFrame.pack();
        newFrame.setVisible(true);
    }
}

我该如何避免这种行为？我希望我的面板占据整个容器.

编辑: 迷你面板旨在(一旦解决)鼠标听众.因此,涂料解决方案是不幸的.

Answer 1

布局问题可以通过... LayoutManagers 解决:-) 如果没有达到您想要的效果，请实现您想要的行为。

因此，如果核心 BoxLayout 只是由于舍入错误而忽略像素，请子类化并使其根据需要分配这些像素。一个非常原始的快速示例：

public static class XBoxLayout extends BoxLayout {

    enum Strategy {
        NONE,
        STRETCH_LAST,
        DISTRUBUTE
    }

    private Strategy strategy;

    public XBoxLayout(Container target, int axis, Strategy strategy) {
        super(target, axis);
        this.strategy = strategy;
    }


    @Override
    public void layoutContainer(Container target) {
        super.layoutContainer(target);
        if (Strategy.NONE == strategy) return;
        Insets targetInsets = target.getInsets();
        int targetSize = target.getWidth() - targetInsets.left - targetInsets.right;
        int childSum = 0;
        for (Component child : target.getComponents()) {
            childSum += child.getWidth();
        }
        if (targetSize > childSum) {
            int excess = targetSize - childSum;
            distribute(target, excess);
        }
    }


    private void distribute(Container target, int excess) {
        System.out.println("childCount/rounding excess " + target.getComponentCount() + "/" + excess);
        if (Strategy.STRETCH_LAST == strategy) {
            Component lastChild = target.getComponent(target
                    .getComponentCount() - 1);
            lastChild.setSize(lastChild.getWidth() + excess,
                    lastChild.getHeight());
        } else {
            int firstToDistribute = target.getComponentCount() - excess;
            int summedOffset = 0;
            for(int index = firstToDistribute; index < target.getComponentCount(); index++) {
                Component child = target.getComponent(index);
                Rectangle bounds = child.getBounds();
                bounds.x += summedOffset++;
                bounds.width += 1;
                child.setBounds(bounds);
            }
        }
    }

}