jtable中表头换行显示

在jtable渲染表头时,由于有些表头字体较多,需要折行显示,但jtable没有自动折行的功能,所以自己实现表头的渲染器.

有两种方案实现表头的折行渲染:

1、渲染器继承自JTextArea,实现TableCellRenderer接口，具体代码如下：

import java.awt.Component;
import java.awt.Dimension;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

import javax.swing.JTable;
import javax.swing.JTextArea;
import javax.swing.UIManager;
import javax.swing.table.DefaultTableCellRenderer;
import javax.swing.table.JTableHeader;
import javax.swing.table.TableCellRenderer;
import javax.swing.table.TableColumn;
import javax.swing.table.TableColumnModel;

public class TextAreaHeaderRenderer extends JTextArea implements
		TableCellRenderer {
	private final DefaultTableCellRenderer adaptee = new DefaultTableCellRenderer();
	/** map from table to map of rows to map of column heights */
	private final Map cellSizes = new HashMap();

	public TextAreaHeaderRenderer() {
		setLineWrap(true);
		setWrapStyleWord(true);
		setHighlighter(null);
	}

	public Component getTableCellRendererComponent(
			//
			JTable table, Object obj, boolean isSelected, boolean hasFocus,
			int row, int column) {
		// 设置表头渲染时的一些属性参数
		JTableHeader header = table.getTableHeader();
		setForeground(header.getForeground());
		setBackground(header.getBackground());
		setFont(header.getFont());
		setText(obj.toString());
		setBorder(UIManager.getBorder("TableHeader.cellBorder"));
		// This line was very important to get it working with JDK1.4
		TableColumnModel columnModel = table.getColumnModel();
		int width = columnModel.getColumn(column).getWidth();
		setSize(width, 100000);
		int height_wanted = (int) getPreferredSize().getHeight();
		addSize(table, column, height_wanted);
		height_wanted = findTotalMaximumRowSize(table, column);
		if (height_wanted != header.getHeight()) {
			// 设置JTextArea的大小
			this.setSize(new Dimension(width, height_wanted));
		}
		return this;
	}

	private void addSize(JTable table, int column, int height) {
		Map cols = (Map) cellSizes.get(table);
		if (cols == null) {
			cellSizes.put(table, cols = new HashMap());
		}
		Map rowheights = (Map) cols.get(new Integer(column));
		if (rowheights == null) {
			cols.put(new Integer(column), rowheights = new HashMap());
		}
		rowheights.put(new Integer(column), new Integer(height));
	}

	/**
	 * Look through all columns and get the renderer. If it is also a
	 * TextAreaRenderer, we look at the maximum height in its hash table for
	 * this row.
	 */
	private int findTotalMaximumRowSize(JTable table, int column) {
		int maximum_height = 0;
		Enumeration columns = table.getColumnModel().getColumns();
		while (columns.hasMoreElements()) {
			TableColumn tc = (TableColumn) columns.nextElement();
			TableCellRenderer cellRenderer = tc.getHeaderRenderer();
			if (cellRenderer instanceof TextAreaHeaderRenderer) {
				TextAreaHeaderRenderer tar = (TextAreaHeaderRenderer) cellRenderer;
				maximum_height = Math.max(maximum_height, tar
						.findMaximumRowSize(table, column));
			}
			// System.out.println("aaa");
		}
		return maximum_height;
	}

	private int findMaximumRowSize(JTable table, int column) {
		Map rows = (Map) cellSizes.get(table);
		if (rows == null)
			return 0;
		Map rowheights = (Map) rows.get(new Integer(column));
		if (rowheights == null)
			return 0;
		int maximum_height = 0;
		for (Iterator it = rowheights.entrySet().iterator(); it.hasNext();) {
			Map.Entry entry = (Map.Entry) it.next();
			int cellHeight = ((Integer) entry.getValue()).intValue();
			maximum_height = Math.max(maximum_height, cellHeight);
		}
		return maximum_height;
	}
}

 此种渲染器的缺点是没有办法实现居中对齐。

2、因为JLabel可以解析html中的br，所以利用这个特点，可以动态构建显示的标题，在换行处添加<br>标记，实现换行显示，代码如下：

import java.awt.Component;
import java.awt.Dimension;
import java.awt.FontMetrics;

import javax.swing.JLabel;
import javax.swing.JTable;
import javax.swing.UIManager;
import javax.swing.table.DefaultTableCellRenderer;
import javax.swing.table.JTableHeader;
import javax.swing.table.TableColumnModel;

public class HeaderRendererHh extends DefaultTableCellRenderer {

	public Component getTableCellRendererComponent(JTable table, Object value,
			boolean isSelected, boolean hasFocus, int row, int column) {

		JTableHeader header = table.getTableHeader();
		setForeground(header.getForeground());
		setBackground(header.getBackground());
		setFont(header.getFont());
		setOpaque(true);
		setBorder(UIManager.getBorder("TableHeader.cellBorder"));

		// 得到列的宽度
		TableColumnModel columnModel = table.getColumnModel();
		int width = columnModel.getColumn(column).getWidth();

		value = getShowValue(value.toString(), width);
		setText(value.toString());
		setSize(new Dimension(width, this.getHeight()));

		setHorizontalAlignment(JLabel.CENTER);

		return this;
	}

	private Object getShowValue(String value, int colWidth) {
		// 根据当前的字体和显示值得到需要显示的宽度
		FontMetrics fm = this.getFontMetrics(this.getFont());
		int width = fm.stringWidth(value.toString());
		int test = fm.stringWidth("好");
		System.out.println(test * value.length());
		System.out.println(width);
		if (width < colWidth) {
			return value;
		}
		StringBuffer sb = new StringBuffer("<html>");
		char str;
		int tempW = 0;
		for (int i = 0; i < value.length(); i++) {
			str = value.charAt(i);
			tempW += fm.charWidth(str);
			if (tempW > colWidth) {
				sb.append("<br>");
				tempW = 0;
			}
			sb.append(str);
		}
		sb.append("</html>");
		return sb.toString();
	}
}

 

两种方法在使用时只要给对应的列添加headerRenderer就可以了，如：

HeaderRendererHh renderer = new HeaderRendererHh();
TableColumnModel cmodel = table.getColumnModel();
for (int i = 0; i < cmodel.getColumnCount(); i++) {
	cmodel.getColumn(i).setHeaderRenderer(renderer);
}