网格组布局是Java较为复杂的布局，虽然这又背于Java简单的初衷。网格组布局十分优雅，组件可以随着窗口的调整自动放大或缩小。
要有效地使用网格组布局，必须自定义GridBagConstraints与其组件关联的一个或多个对象。您可以GridBagConstraints 通过设置一个或多个实例变量来自定义对象：
GridBagConstraints.gridx， GridBagConstraints.gridy
每个格子都有自己的单元格坐标（gridx,gridy），并不以长度为单位，左上角的原点单元格，坐标为（0,0)。右边格子的坐标为（1，0），一次类推。
GridBagConstraints.gridwidth， GridBagConstraints.gridheight
指跨过的单元格数，网格坐标为（0，0）的单元格网格长度为（2，2）,表明其占据了2*2的方格
GridBagConstraints.fill
指窗口拉伸时的填充的方向
GridBagConstraints.insets
指定组件的外部填充，即组件与其显示区域的边缘之间的最小间距。
GridBagConstraints.anchor
指对齐方式
GridBagConstraints.NORTH
GridBagConstraints.SOUTH
GridBagConstraints.WEST
GridBagConstraints.EAST
GridBagConstraints.NORTHWEST
GridBagConstraints.NORTHEAST
GridBagConstraints.SOUTHWEST
GridBagConstraints.SOUTHEAST
GridBagConstraints.CENTER （默认）
方向相对值：
GridBagConstraints.PAGE_START
GridBagConstraints.PAGE_END
GridBagConstraints.LINE_START
GridBagConstraints.LINE_END
GridBagConstraints.FIRST_LINE_START
GridBagConstraints.FIRST_LINE_END
GridBagConstraints.LAST_LINE_START
GridBagConstraints.LAST_LINE_END
基准相对值：
GridBagConstraints.BASELINE
GridBagConstraints.BASELINE_LEADING
GridBagConstraints.BASELINE_TRAILING
GridBagConstraints.ABOVE_BASELINE
GridBagConstraints.ABOVE_BASELINE_LEADING
GridBagConstraints.ABOVE_BASELINE_TRAILING
GridBagConstraints.BELOW_BASELINE
GridBagConstraints.BELOW_BASELINE_LEADING
GridBagConstraints.BELOW_BASELINE_TRAILING
GridBagConstraints.weightx， GridBagConstraints.weighty
指最大拉伸宽度或高度
要想更加方便地使用GridBagLayout，一般我们重写GridBagConstraints，改名为GBC。这样我们可以采用流式写法，快速定义GBC的参数。代码如下：
import java.awt.*;
public class GBC extends GridBagConstraints
{
public GBC(int gridx,int gridy)
{
this.gridx=gridx;
this.gridy=gridy;
}
public GBC(int gridx,int gridy,int gridwidth,int gridheight)
{
this.gridx=gridx;
this.gridy=gridy;
this.gridwidth=gridwidth;
this.gridheight=gridheight;
}
public GBC setAnchor(int anchor)
{
this.anchor=anchor;
return this;
}
public GBC setFill(int fill)
{
this.fill=fill;
return this;
}
public GBC setWeight(double weightx,int weighty)
{
this.weightx=weightx;
this.weighty=weighty;
return this;
}
public GBC setInsets(int distance)
{
this.insets=new Insets(distance,distance,distance,distance);
return this;
}
public GBC setIpad(int ipadx,int ipady)
{
this.ipadx=ipadx;
this.ipady=ipady;
return this;
}
}
下面给一个例子，如何使用GBC构建网格组布局,来自《Java核心技术》：
package GridBag;
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class FontFrame extends JFrame
{
private final int TEXT_ROWS=10;
private final int TEXT_COLUMNS=20;
private JComboBox<String> face;
private JComboBox<Integer> size;
private JTextArea sample;
private JCheckBox italic;
private JCheckBox bold;
public FontFrame()
{
setDefaultCloseOperation(EXIT_ON_CLOSE);
GridBagLayout layout=new GridBagLayout();
setLayout(layout);
ActionListener lisenter=event->{
upsample();
};
JLabel faceLabel=new JLabel("Face:");
JLabel sizeLabel=new JLabel("Size:");
face=new JComboBox<>(new String[] {
"Serif", "SansSerif", "Monospaced", "Dialog", "Dialoglnput"});
face.addActionListener(lisenter);
size=new JComboBox<>(new Integer[] {
8, 10, 12, 15, 18, 24, 36, 48});
size.addActionListener(lisenter);
bold=new JCheckBox("bold");
italic=new JCheckBox("italic");
bold.addActionListener(lisenter);
italic.addActionListener(lisenter);
sample=new JTextArea(TEXT_ROWS,TEXT_COLUMNS);
sample.setText("The quick brown fox jumps over the lazy dog");
sample.setEditable(false);
sample.setLineWrap(true);
sample.setBorder(BorderFactory.createEtchedBorder());
add(faceLabel, new GBC(0, 0).setFill(GBC.EAST).setWeight(100, 100));
add(sizeLabel, new GBC(0,1).setFill(GBC.EAST).setWeight(100, 100));
add(face,new GBC(1,0).setFill(GBC.HORIZONTAL).setWeight(100, 100));
add(size,new GBC(1,1).setFill(GBC.HORIZONTAL).setWeight(100, 100));
add(bold,new GBC(0,2,2,1).setFill(GBC.CENTER).setWeight(100, 100));
add(italic,new GBC(0,3,2,1).setFill(GBC.CENTER).setWeight(100, 100));
add(sample,new GBC(2,0,1,4).setFill(GBC.BOTH).setWeight(100, 100));
pack();
upsample();
}
private void upsample()
{
String fontFace=(String)face.getSelectedItem();
int fontStyle=(bold.isSelected()? Font.BOLD:0)+(italic.isSelected()? Font.ITALIC:0);
int fontSize=(Integer)size.getSelectedItem();
Font font=new Font(fontFace,fontStyle,fontSize);
sample.setFont(font);
sample.repaint();
}
}
测试类：
package GridBag;
import java.awt.EventQueue;
import java.awt.Font;
public class FontTest {
public static void main(String[] args) {
EventQueue.invokeLater(()->{
;
FontFrame frame=new FontFrame();
frame.setVisible(true);
});
}
}