Java Swing实现JTable检测单元格数据变更事件的方法示例
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2023-12-19 17:08:16
本文实例讲述了java swing实现jtable检测单元格数据变更事件的方法。分享给大家供大家参考，具体如下：
在jtable的初级教程中往往会提到，使用tablemo...
本文实例讲述了java swing实现jtable检测单元格数据变更事件的方法。分享给大家供大家参考，具体如下：
在jtable的初级教程中往往会提到，使用tablemodel的 addtablemodellistener方法可以监听单元格数据的变更，在其事件处理函，数tablechanged中，可以通过e.getcolumn()，e.getfirstrow()，e.getlastrow()，e.gettype()来获取变更发生的位置和变更的类型（插入、更新或删除）。然而该方法存在2个致命的问题：
1.双击单元格使其处于可编辑状态后，即使没有做出任何修改，当单元格失去焦点时，该事件将被激活。
2.通过该事件你可以获取单元格最新的数据，却无法获取原有数据。
经过一番搜索发现该文章已经解决了这个问题table cell listener，作者自己实现了一个单元格监听器tablecelllistener，它订阅了指定table的addpropertychangelistener，根据e.getpropertyname()来识别单元格编辑事件，根据table.isediting()方法来判断单元格正在编辑还是编辑完毕。如果是正在编辑，则记录单元格位置和原因数据；如果已经编辑完毕，则记录新数据并与原有数据进行比对，如果不一致则说明单元格数据发生了变更，则激活指定响应函数。
测试用例如下：
tabledemo.java
/*
* copyright (c) 1995, 2008, oracle and/or its affiliates. all rights reserved.
*
* redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* - neither the name of oracle or the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* this software is provided by the copyright holders and contributors "as
* is" and any express or implied warranties, including, but not limited to,
* the implied warranties of merchantability and fitness for a particular
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* contributors be liable for any direct, indirect, incidental, special,
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* liability, whether in contract, strict liability, or tort (including
* negligence or otherwise) arising in any way out of the use of this
* software, even if advised of the possibility of such damage.
*/
package awtdemo;
/*
* tabledemo.java requires no other files.
*/
import javax.swing.abstractaction;
import javax.swing.action;
import javax.swing.jframe;
import javax.swing.jpanel;
import javax.swing.jscrollpane;
import javax.swing.jtable;
import javax.swing.table.abstracttablemodel;
import java.awt.dimension;
import java.awt.gridlayout;
import java.awt.event.actionevent;
/**
* tabledemo is just like simpletabledemo, except that it
* uses a custom tablemodel.
*/
@suppresswarnings("serial")
public class tabledemo extends jpanel {
private boolean debug = false;
@suppresswarnings("unused")
public tabledemo() {
super(new gridlayout(1,0));
jtable table = new jtable(new mytablemodel());
table.setpreferredscrollableviewportsize(new dimension(500, 70));
table.setfillsviewportheight(true);
//create the scroll pane and add the table to it.
jscrollpane scrollpane = new jscrollpane(table);
//add the scroll pane to this panel.
add(scrollpane);
action action = new abstractaction()
{
public void actionperformed(actionevent e)
{
tablecelllistener tcl = (tablecelllistener)e.getsource();
system.out.printf("cell changed%n");
system.out.println("row : " + tcl.getrow());
system.out.println("column: " + tcl.getcolumn());
system.out.println("old : " + tcl.getoldvalue());
system.out.println("new : " + tcl.getnewvalue());
}
};
tablecelllistener tcl = new tablecelllistener(table, action);
}
class mytablemodel extends abstracttablemodel {
private string[] columnnames = {"first name",
"last name",
"sport",
"# of years",
"vegetarian"};
private object[][] data = {
{"kathy", "smith",
"snowboarding", new integer(5), new boolean(false)},
{"john", "doe",
"rowing", new integer(3), new boolean(true)},
{"sue", "black",
"knitting", new integer(2), new boolean(false)},
{"jane", "white",
"speed reading", new integer(20), new boolean(true)},
{"joe", "brown",
"pool", new integer(10), new boolean(false)}
};
public int getcolumncount() {
return columnnames.length;
}
public int getrowcount() {
return data.length;
}
public string getcolumnname(int col) {
return columnnames[col];
}
public object getvalueat(int row, int col) {
return data[row][col];
}
/*
* jtable uses this method to determine the default renderer/
* editor for each cell. if we didn't implement this method,
* then the last column would contain text ("true"/"false"),
* rather than a check box.
*/
@suppresswarnings({ "unchecked", "rawtypes" })
public class getcolumnclass(int c) {
return getvalueat(0, c).getclass();
}
/*
* don't need to implement this method unless your table's
* editable.
*/
public boolean iscelleditable(int row, int col) {
//note that the data/cell address is constant,
//no matter where the cell appears onscreen.
if (col < 2) {
return false;
} else {
return true;
}
}
/*
* don't need to implement this method unless your table's
* data can change.
*/
public void setvalueat(object value, int row, int col) {
if (debug) {
system.out.println("setting value at " + row + "," + col
+ " to " + value
+ " (an instance of "
+ value.getclass() + ")");
}
data[row][col] = value;
firetablecellupdated(row, col);
if (debug) {
system.out.println("new value of data:");
printdebugdata();
}
}
private void printdebugdata() {
int numrows = getrowcount();
int numcols = getcolumncount();
for (int i=0; i < numrows; i++) {
system.out.print(" row " + i + ":");
for (int j=0; j < numcols; j++) {
system.out.print(" " + data[i][j]);
}
system.out.println();
}
system.out.println("--------------------------");
}
}
/**
* create the gui and show it. for thread safety,
* this method should be invoked from the
* event-dispatching thread.
*/
private static void createandshowgui() {
//create and set up the window.
jframe frame = new jframe("tabledemo - www.jb51.net");
frame.setdefaultcloseoperation(jframe.exit_on_close);
//create and set up the content pane.
tabledemo newcontentpane = new tabledemo();
newcontentpane.setopaque(true); //content panes must be opaque
frame.setcontentpane(newcontentpane);
//display the window.
frame.pack();
frame.setvisible(true);
}
public static void main(string[] args) {
//schedule a job for the event-dispatching thread:
//creating and showing this application's gui.
javax.swing.swingutilities.invokelater(new runnable() {
public void run() {
createandshowgui();
}
});
}
}
tablecelllistener.java
package awtdemo;
import java.awt.event.*;
import javax.swing.*;
import java.beans.*;
/*
* this class listens for changes made to the data in the table via the
* tablecelleditor. when editing is started, the value of the cell is saved
* when editing is stopped the new value is saved. when the oold and new
* values are different, then the provided action is invoked.
*
* the source of the action is a tablecelllistener instance.
*/
public class tablecelllistener implements propertychangelistener, runnable
{
private jtable table;
private action action;
private int row;
private int column;
private object oldvalue;
private object newvalue;
/**
* create a tablecelllistener.
*
* @param table the table to be monitored for data changes
* @param action the action to invoke when cell data is changed
*/
public tablecelllistener(jtable table, action action)
{
this.table = table;
this.action = action;
this.table.addpropertychangelistener( this );
}
/**
* create a tablecelllistener with a copy of all the data relevant to
* the change of data for a given cell.
*
* @param row the row of the changed cell
* @param column the column of the changed cell
* @param oldvalue the old data of the changed cell
* @param newvalue the new data of the changed cell
*/
private tablecelllistener(jtable table, int row, int column, object oldvalue, object newvalue)
{
this.table = table;
this.row = row;
this.column = column;
this.oldvalue = oldvalue;
this.newvalue = newvalue;
}
/**
* get the column that was last edited
*
* @return the column that was edited
*/
public int getcolumn()
{
return column;
}
/**
* get the new value in the cell
*
* @return the new value in the cell
*/
public object getnewvalue()
{
return newvalue;
}
/**
* get the old value of the cell
*
* @return the old value of the cell
*/
public object getoldvalue()
{
return oldvalue;
}
/**
* get the row that was last edited
*
* @return the row that was edited
*/
public int getrow()
{
return row;
}
/**
* get the table of the cell that was changed
*
* @return the table of the cell that was changed
*/
public jtable gettable()
{
return table;
}
//
// implement the propertychangelistener interface
//
@override
public void propertychange(propertychangeevent e)
{
// a cell has started/stopped editing
if ("tablecelleditor".equals(e.getpropertyname()))
{
if (table.isediting()){
//system.out.printf("tablecelleditor is editing..%n");
processeditingstarted();
}
else{
//system.out.printf("tablecelleditor editing stopped..%n");
processeditingstopped();
}
}
}
/*
* save information of the cell about to be edited
*/
private void processeditingstarted()
{
// the invokelater is necessary because the editing row and editing
// column of the table have not been set when the "tablecelleditor"
// propertychangeevent is fired.
// this results in the "run" method being invoked
swingutilities.invokelater( this );
}
/*
* see above.
*/
@override
public void run()
{
row = table.convertrowindextomodel( table.geteditingrow() );
column = table.convertcolumnindextomodel( table.geteditingcolumn() );
oldvalue = table.getmodel().getvalueat(row, column);
//这里应对oldvalue为null的情况做处理，否则将导致原值与新值均为空时仍被视为值改变
if(oldvalue == null)
oldvalue = "";
newvalue = null;
}
/*
* update the cell history when necessary
*/
private void processeditingstopped()
{
newvalue = table.getmodel().getvalueat(row, column);
//这里应对newvalue为null的情况做处理，否则后面会抛出异常
if(newvalue == null)
newvalue = "";
// the data has changed, invoke the supplied action
if (! newvalue.equals(oldvalue))
{
// make a copy of the data in case another cell starts editing
// while processing this change
tablecelllistener tcl = new tablecelllistener(
gettable(), getrow(), getcolumn(), getoldvalue(), getnewvalue());
actionevent event = new actionevent(
tcl,
actionevent.action_performed,
"");
action.actionperformed(event);
}
}
}
运行效果：
由图可见，单元格数据修改后，控制台输出内容变更信息！
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