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我有一個JTable;我想提供一個帶複選框的菜單，表格中的每一列都有一個複選框，以允許用戶選擇要顯示或隱藏的列。我寫了下面的課，幾乎可以工作。基於菜單選擇添加/刪除列
public class SelectableColumns implements ActionListener
{
JTable table = null;
JMenu menu = null; public JMenu getMenu() { return menu; }
public SelectableColumns(JTable table)
{
this.table = table;
menu = new JMenu("Columns");
TableColumnModel columnModel = table.getColumnModel();
Enumeration<TableColumn> enumerator = columnModel.getColumns();
while (enumerator.hasMoreElements())
{
TableColumn column = enumerator.nextElement();
String headerName = column.getHeaderValue().toString();
JCheckBoxMenuItem cbmi = new JCheckBoxMenuItem(headerName, true);
cbmi.addActionListener(this);
column.setIdentifier(cbmi);
menu.add(cbmi);
}
}
@Override
public void actionPerformed(ActionEvent e)
{
JCheckBoxMenuItem source = (JCheckBoxMenuItem)e.getSource();
boolean checked = source.getState();
TableColumnModel columnModel = table.getColumnModel();
int columnIndex = columnModel.getColumnIndex(source); // <<-- fails after removing the column
System.out.printf("Checked: %b, column: %d%n", checked, columnIndex);
TableColumn column = columnModel.getColumn(columnIndex);
if (checked)
{
// add this column back to the table
table.addColumn(column);
int displayedColumns = getDisplayedColumns(columnModel);
table.moveColumn(displayedColumns, displayedColumns-1);
}
else
{
// remove this column from the table
table.removeColumn(column);
}
}
private int getDisplayedColumns(TableColumnModel columnModel)
{
Enumeration<TableColumn> columns = columnModel.getColumns();
int displayedCount = 0;
while (columns.hasMoreElements())
{
displayedCount++;
}
return displayedCount;
}
}
我的問題是，一旦我刪除列，它不再在TableColumnModel;我期望該列在TableColumnModel中，但不再在JTable中。
但我錯了：方法TableColumnModel.getColumn(int index)在列顯示時工作，在顯示列後失敗。當我在調試器中檢查TableColumnModel實例時，很明顯該列已從模型中刪除。
有沒有辦法做我想要的？我可以創建一個列的集合來重新插入缺少的列，但是我讀過的一些文檔讓我相信表只是模型的一個視圖，所以我堅持認爲列在那裏。誰能告訴我在哪裏可以找到它？
非常感謝camickr;我想我會後我結束了與類：
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import java.util.Enumeration;
import javax.swing.JCheckBoxMenuItem;
import javax.swing.JMenu;
import javax.swing.JTable;
import javax.swing.table.TableColumn;
import javax.swing.table.TableColumnModel;
/**
* Holds representation of columns from the given JTable, including
* a JMenu and its action routine for removing them and replacing
* them in the table.
* <P>To use, create an instance with your table after
* it has at least enough data to establish its columns. Then use
* getMenu() for an instance of JMenu, and put it on your menu bar.
* The resulting menu will have checkboxes for all the columns, and
* it handles their removal and addition. No other code in the application
* should remove or add columns; their added/removal state is maintained
* in the SelectableColumns instance.
*
* @author rcook
*/
public class SelectableColumns implements ActionListener
{
JTable table = null;
JMenu menu = null; public JMenu getMenu() { return menu; }
ArrayList<TableColumn> removedColumns = new ArrayList<TableColumn>();
public SelectableColumns(JTable table)
{
this.table = table;
menu = new JMenu("Columns");
TableColumnModel columnModel = table.getColumnModel();
Enumeration<TableColumn> enumerator = columnModel.getColumns();
while (enumerator.hasMoreElements())
{
TableColumn column = enumerator.nextElement();
String headerName = column.getHeaderValue().toString();
JCheckBoxMenuItem cbmi = new JCheckBoxMenuItem(headerName, true);
cbmi.addActionListener(this);
column.setIdentifier(cbmi);
menu.add(cbmi);
}
}
/**
* A Checkbox menu item representing one column has been chosen; it
* could have been checked or unchecked. Put the removed column
* back into the table, or remove it from the table.
*/
@Override
public void actionPerformed(ActionEvent e)
{
JCheckBoxMenuItem source = (JCheckBoxMenuItem)e.getSource();
TableColumnModel columnModel = table.getColumnModel();
boolean checked = source.getState();
TableColumn removedColumn = null;
if (!checked)
{
// remove this column from the table
int columnIndex = columnModel.getColumnIndex(source);
//System.out.printf("Checked: %b, column: %d%n", checked, columnIndex);
TableColumn column = columnModel.getColumn(columnIndex);
table.removeColumn(column);
removedColumns.add(column);
}
else
{
// add this column back to the table
// first find the column in the list of removed columns
for (TableColumn column: removedColumns)
{
if (column.getIdentifier().equals(source))
{
removedColumn = column;
break;
}
}
// as long as we actually have a column, add it back to the
// table
if (removedColumn == null)
{
System.err.println("removedColumn not in the list...");
}
else
{
table.addColumn(removedColumn);
int numDisplayed = columnModel.getColumnCount();
table.moveColumn(numDisplayed-1, numDisplayed-2); // move to next-to-last position
removedColumns.remove(removedColumn);
}
}
}
}
我只是簡單地添加「刪除列」的列表，並用它來添加回任何刪除列被重新檢查，以顯示。我總是回到倒數第二的位置;顯然這對於一般用途來說可以更靈活。我也想過有一個方法可以顯示一個帶有複選框的對話框，這樣用戶就可以同時改變多個列的狀態。但是，對於100行代碼，這是我現在想要的，並說明了我正在尋找的原則以及camickr善意提供的原則。