jtable中表头换行显示

xiaoxiao2021-03-01  10

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); }

 

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