使用GridBagLayout实现的计算器UI

GridBagLayout相对于GridLayout来说更灵活，功能也更强大，用它实现的计算器的布局效果图如下：

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

/**
 * Calculator类，实现计算器界面
 * @author Ares
 */
public class Calculator{
	final String[] KEYS = { "CE", "C", "←", "÷", "7", "8", "9", "×", "4","5", "6", "-", "1", "2", "3", "+", "0", ".", "=" };
	JButton[] keys = new JButton[KEYS.length];
	JTextField resultText = new JTextField("0");

	public void addComponentsToPane(Container pane) {
		GridBagLayout layout = new GridBagLayout();
		pane.setLayout(layout);
		resultText.setFont(new Font("Century Schoolbook", Font.PLAIN, 14));
		resultText.setEditable(false);
		resultText.setHorizontalAlignment(SwingConstants.RIGHT);
		pane.add(resultText,new GBC(0, 0, 4, 1).setIpad(400, 50).setWeight(0.5, 0.5).setFill(GridBagConstraints.BOTH));
		for (int i = 0; i < keys.length; i++) {
			keys[i] = new JButton(KEYS[i]);
			if(i == keys.length-3){
				pane.add(keys[i],new GBC(i % 4, i / 4 + 1,2,1).setIpad(0, 12).setInsets(1).setFill(GridBagConstraints.BOTH).setWeight(0.5, 0.5));
			}else if (i == keys.length-2 || i == keys.length-1) {
				pane.add(keys[i],new GBC(i % 4+1, i / 4 + 1).setIpad(0, 12).setInsets(1).setFill(GridBagConstraints.BOTH).setWeight(0.5, 0.5));
			}else {
				pane.add(keys[i], new GBC(i % 4, i / 4 + 1).setIpad(0, 12).setInsets(1).setFill(GridBagConstraints.BOTH).setWeight(0.5, 0.5));
			}
		}
	}

	public void createAndShowGUI() {
		JFrame frame = new JFrame("Calculator");
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		addComponentsToPane(frame.getContentPane());
		frame.pack();
		frame.setVisible(true);
	}

	public static void main(String[] args) {
		EventQueue.invokeLater(new Runnable() {
			public void run() {
				new Calculator().createAndShowGUI();
			}
		});
	}
}

用来设置GridBagConstraints的类如下：

import java.awt.GridBagConstraints;
import java.awt.Insets;

public class GBC extends GridBagConstraints {
	/**
	 * 构造函数，用来设置组件所占单元格的坐标
	 *
	 * @param gridx 横向坐标
	 * @param gridy 纵向坐标
	 */
	public GBC(int gridx, int gridy) {
		this.gridx = gridx;
		this.gridy = gridy;
	}

	/**
	 * 构造函数，用来设置组件所占单元格的坐标，同时指定宽度和高度
	 * @param gridx 横向坐标
	 * @param gridy 纵向坐标
	 * @param gridwidth 组件宽度
	 * @param gridheight 组件高度
	 */
	public GBC(int gridx, int gridy, int gridwidth, int gridheight) {
		this.gridx = gridx;
		this.gridy = gridy;
		this.gridwidth = gridwidth;
		this.gridheight = gridheight;
	}

	/**
	 * 当组件没有空间大时，设置组件的位置
	 * @param anchor 组建位置
	 * @return 当前对象
	 */
	public GBC setAnchor(int anchor) {
		this.anchor = anchor;
		return this;
	}

	/**
	 * 设置填充
	 * @param fill 设置填充方式
	 * @return 当前对象
	 */
	public GBC setFill(int fill) {
		this.fill = fill;
		return this;
	}

	/**
	 * 设置组件随窗口延伸的幅度
	 * @param weightx 横向延伸大小
	 * @param weighty 纵向延伸大小
	 * @return 当前对象
	 */
	public GBC setWeight(double weightx, double weighty) {
		this.weightx = weightx;
		this.weighty = weighty;
		return this;
	}

	/**
	 * 设置组件之间的间距
	 * @param distance 上下左右间距一样
	 * @return 当前对象
	 */
	public GBC setInsets(int distance) {
		this.insets = new Insets(distance, distance, distance, distance);
		return this;
	}

	/**
	 * 设置组件之间的间距
	 * @param top 上间距
	 * @param left 左间距
	 * @param bottom 底间距
	 * @param right 右间距
	 * @return 当前对象
	 */
	public GBC setInsets(int top, int left, int bottom, int right) {
		this.insets = new Insets(top, left, bottom, right);
		return this;
	}

	/**
	 * 设置组件内部填充空间，即给组件的最小高度或宽度添加多大的空间
	 * @param ipadx 横向填充
	 * @param ipady 纵向填充
	 * @return 当前对象
	 */
	public GBC setIpad(int ipadx, int ipady) {
		this.ipadx = ipadx;
		this.ipady = ipady;
		return this;
	}
}