方法JComboBox.removeAllItems()
是否会触发ItemStateChanged事件..?
如果是这样,我如何确定由于用户操作或由于方法removeAllItems()..的调用而生成事件的天气。
我在组合框的itemStateChanged()方法中有一些代码,当用户在组合框中更改他的选择时它将工作正常,但是通过代码的性质,它会在调用它时引发空指针异常由于在该组合框上调用removeAllItems()。如果我可以确定事件的原因是removeAllItems()方法并返回控件,那么我的问题就会解决。我该怎么做呢..?
UPDATE
后你的人都挂上了答案,我用下面的代码...如何识别事件的来源..?
@Override
public void itemStateChanged(ItemEvent e) {
if(e.getSource()==branch_list)
{
if(!UserConstants.FID.contains("hod"))
{
ignoreEvents=true;//static boolean variable not used by any other methods
year_list.removeAllItems();
year_list.addItem(" ");
sem_list.removeAllItems();
sem_list.addItem(" ");
branch_list.removeAllItems();
branch_list.addItem(" ");
if(branch_list.getSelectedItem().equals(" "))
return;
Iterator year_it=DatabaseConnector.map.get(branch_list.getSelectedItem().toString()).keySet().iterator();
while(year_it.hasNext())
{
year_list.addItem(year_it.next());
}
ignoreEvents=false;
}
return;
}
else if(e.getSource()==year_list)
{
if((branch_list.getSelectedItem()==null)||branch_list.getSelectedItem().toString().equals(" ")||ignoreEvents)
return;
sem_list.removeAllItems();
section_list.removeAllItems();
sem_list.addItem(" ");
section_list.addItem(" ");
Iterator i=DatabaseConnector.map.get(branch_list.getSelectedItem().toString()).get(year_list.getSelectedItem().toString()).iterator();
int first=0;
while(i.hasNext())
{
String cur=i.next().toString();
if(first==0)
{
sem_list.addItem(cur.charAt(0));
section_list.addItem(cur.charAt(1));
first++;
}
else
{
section_list.addItem(cur.charAt(1));
}
}
}
}
I am getting the following error:-
Exception in thread "AWT-EventQueue-0" java.lang.StackOverflowError
at sun.nio.cs.SingleByteEncoder.encodeArrayLoop(SingleByteEncoder.java:91)
at sun.nio.cs.SingleByteEncoder.encodeLoop(SingleByteEncoder.java:130)
at java.nio.charset.CharsetEncoder.encode(CharsetEncoder.java:544)
at sun.nio.cs.StreamEncoder.implWrite(StreamEncoder.java:252)
at sun.nio.cs.StreamEncoder.write(StreamEncoder.java:106)
at java.io.OutputStreamWriter.write(OutputStreamWriter.java:190)
at java.io.BufferedWriter.flushBuffer(BufferedWriter.java:111)
at java.io.PrintStream.write(PrintStream.java:476)
at java.io.PrintStream.print(PrintStream.java:619)
at java.io.PrintStream.println(PrintStream.java:756)
at attendence.Home.itemStateChanged(Home.java:427)
等...........
这应该给组合框实例,不是吗? – aioobe 2011-01-12 13:32:22
aioobe是正确的使用getSource()返回的组合框的实例,但是这不会解决问题... – sasidhar 2011-01-12 13:36:53
请看我的更新,并尽早帮助我... – sasidhar 2011-01-12 17:34:55