我正在尝试自定义 LayoutManager，但我不了解在本身具有上层布局管理器的组件中使用它的微妙之处。
下面是一个测试程序，它用一对 JPanel 制作两个框架。两个 JPanel 中的每一个都有一个细黑色边框，并使用我的 WeirdGridLayout 将其子组件强制为网格中的正方形，JPanel 的高度是根据宽度计算的。两个 JPanel 都位于另一个 JPanel 中，该 JPanel 具有使用 BorderLayout 的细红色边框。
在一帧中，具有 WeirdGridLayout 的 JPanel 排列为 EAST 和 WEST，另一个排列为 NORTH 和 SOUTH。
问题是，在北/南情况下，如果我更改框架的宽度/高度，则具有 WeirdGridLayout 的两个 JPanel 具有正确的大小，但不是正确的位置（它们要么有间隙，要么垂直重叠）。
在东/西的情况下，它最终是错误的。
我必须做些什么才能让我的布局管理器与外部布局管理器配合得很好？
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Component;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.LayoutManager2;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
/**
*/
public class WeirdGridLayout implements LayoutManager2
{
static final private int GRIDGAP = 10;
static final private int COMPONENT_SIZE = 30;
static final private int GRIDSPACING = COMPONENT_SIZE + GRIDGAP;
final private List<Component> components
= new ArrayList<Component>();
@Override public void addLayoutComponent(Component comp, Object constraints) {
this.components.add(comp);
}
@Override public void addLayoutComponent(String name, Component comp) {
this.components.add(comp);
}
@Override public void removeLayoutComponent(Component comp) {
this.components.remove(comp);
}
@Override public float getLayoutAlignmentX(Container target) {
return Component.LEFT_ALIGNMENT;
}
@Override public float getLayoutAlignmentY(Container target) {
return Component.TOP_ALIGNMENT;
}
@Override public void invalidateLayout(Container target) {}
@Override public Dimension maximumLayoutSize(Container target) {
return new Dimension(Integer.MAX_VALUE, Integer.MAX_VALUE);
}
@Override public Dimension minimumLayoutSize(Container parent) {
return new Dimension(0,0);
}
@Override public void layoutContainer(Container parent) {
int x = GRIDGAP;
int y = GRIDGAP;
Dimension d = preferredLayoutSize(parent);
parent.setSize(d);
for (Component component : this.components)
{
component.setBounds(x, y, COMPONENT_SIZE, COMPONENT_SIZE);
x += GRIDSPACING;
if (x >= d.getWidth())
{
x = GRIDGAP;
y += GRIDSPACING;
}
}
}
@Override public Dimension preferredLayoutSize(Container parent) {
// how many blocks wide can we fit?
int n = this.components.size();
int nblockwidth = (parent.getWidth() - GRIDGAP) / GRIDSPACING;
int nblockheight = (nblockwidth == 0) ? 0
: ((n-1)/nblockwidth) + 1;
return new Dimension(
nblockwidth*GRIDSPACING+GRIDGAP,
nblockheight*GRIDSPACING+GRIDGAP);
}
/* ---- test methods ---- */
static public class ColorPanel extends JPanel {
final private Color color;
final private String label;
public ColorPanel(String label, Color color) {
this.label = label;
this.color = color;
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(this.color);
g.fillRect(0,0,getWidth(),getHeight());
g.setColor(Color.WHITE);
FontMetrics fm = g.getFontMetrics();
int w = fm.stringWidth(this.label);
g.drawString(this.label, (getWidth()-w)/2,
(getHeight()+fm.getAscent())/2);
}
}
public static void main(String[] args) {
showFrame(true);
showFrame(false);
}
private static void showFrame(boolean eastWest) {
JFrame frame = new JFrame("WeirdGridLayout test: eastWest="+eastWest);
JPanel framePanel = new JPanel(new BorderLayout());
framePanel.setPreferredSize(new Dimension(400,200));
JPanel panel[] = new JPanel[2];
for (int i = 0; i < 2; ++i)
{
panel[i] = new JPanel(new WeirdGridLayout());
panel[i].setBorder(BorderFactory.createLineBorder(Color.BLACK));
final Random r = new Random();
for (int j = 0; j < 24; ++j)
{
Color c = new Color(
r.nextFloat(),
r.nextFloat(),
r.nextFloat());
JPanel subpanel = new ColorPanel(Integer.toString(j), c);
panel[i].add(subpanel);
}
}
framePanel.add(new JButton("test"), BorderLayout.NORTH);
JPanel bottomPanel = new JPanel(new BorderLayout());
framePanel.add(bottomPanel, BorderLayout.SOUTH);
if (eastWest)
{
bottomPanel.add(panel[0], BorderLayout.WEST);
bottomPanel.add(panel[1], BorderLayout.EAST);
}
else
{
bottomPanel.add(panel[0], BorderLayout.NORTH);
bottomPanel.add(panel[1], BorderLayout.SOUTH);
}
bottomPanel.setBorder(BorderFactory.createLineBorder(Color.RED));
frame.setContentPane(framePanel);
frame.pack();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
}