使用DefaultListModel从JList中删除元素时出错 [英] Error removing element from JList with DefaultListModel
问题描述
我有一个标准的 JList ，它将在程序运行时更改。为了让生活更轻松，我创建了一个 DefaultListModel 并将其分配给 JList ：
I have a standard JList that will be changed while the program is running. In order to make life easier I have created a DefaultListModel and assigned it to the JList:
JList CharList = new JList();
DefaultListModel CharListModel = new DefaultListModel();
CharList.setModel(CharListModel);
我可以将文件加载到列表中，稍后我可以将项目添加到列表中这个：
I am able to load a file into the list, and later I can add items to the list like this:
File ChFile = new File (CharListFile);
FileReader freeder = new FileReader (ChFile);
BufferedReader breeder = new BufferedReader(freeder);
String line;
while((line=breeder.readLine())!=null)
{
int pos = CharList.getModel().getSize();
CharListModel.add(pos, line);
}
...
...
//and to add items..
int pos = CharList.getModel().getSize();
CharListModel.add(pos, NewCharName);
但是，我需要能够从列表中删除项目，这给了我一些可观的麻烦！
However, I need to be able to remove items from the list, and this is giving me some considerable trouble!
我尝试过最明显的方法（是的，选择了一个项目，我已经检索了索引和该索引处的字符串）：
I have tried the most obvious way (Yes an item is selected, and I have already retrieved both the index and the string at that index):
CharListModel.removeElement(CharList.getSelectedValue());
然而，这给了我一个' java.lang.ArrayIndexOutOfBoundsException：-1 '错误。
However, this gives me a 'java.lang.ArrayIndexOutOfBoundsException: -1' error.
我已经尝试了你在下面的代码中看到的所有排列（有些被注释掉但是你明白了）：
I have tried all of the permutations that you can see in the code below (Some are commented out but you get the idea):
DefaultListModel model = (DefaultListModel) CharList.getModel();//CharListModel;
int selectedIndex = CharList.getSelectedIndex();
if (selectedIndex != -1) {
//model.remove(selectedIndex);
//model.removeElement(CharList.getSelectedValue());
//model.removeElementAt(selectedIndex);
}
以及其他一些排列：
CharListModel.removeElementAt(CharList.getSelectedIndex());
//or
CharListModel.remove(CharList.getSelectedIndex());
//or
CharList.remove(SelItemIndex);
在每种情况下，我都会得到相同的' ArrayIndexOutOfBoundsException '错误，即使之前找到的所选索引没有任何问题。是的，我知道我刚才说'以前'所以有些东西可能会改变一些东西，但这里是我试图删除元素之前直接运行的代码：
In each case I get the same 'ArrayIndexOutOfBoundsException' error, even though the selected index is previously found with no trouble. And yes, I know I just said 'previously' so something could have changed things, but here is the code that runs directly before I try to remove the element:
int SelItemIndex = CharList.getSelectedIndex();
if(SelItemIndex == -1)
{
JOptionPane.showMessageDialog(null, "You have to select something!");
return;
}
String SelItem = CharList.getModel().getElementAt(SelItemIndex).toString();
//Create warning
final JComponent[] inputs = new JComponent[]
{
new JLabel("<html>Bla Bla " + SelItem + " Are you sure?</html>")
};
int n = JOptionPane.showConfirmDialog( null, inputs,"Deletion Confirmation Warning", JOptionPane.YES_NO_OPTION);
if( n == 1)
{
//Do not delete
return;
}
在尝试删除所选元素之前，这就是全部。
That is all there is before trying to remove the selected element.
对于我的生活，我不知道为什么这不起作用！我错过了一些非常愚蠢的东西吗？
For the life of me I don't know why this is not working! Am I missing something really silly here?
在 ActionPerformed中 JButton的事件我使用过这段代码 - 代码中的注释解释了为什么会这么混乱！：
In the ActionPerformed event of a JButton I have used this code - The comments in the code explain why this is so confusing!:
DefaultListModel CharListModel = (DefaultListModel)CharList.getModel();
if( CharListModel.contains(CharList.getSelectedValue()) == true)
{
//Selected item is found
int selItemIndex = CharListModel.indexOf(CharList.getSelectedValue());
if(selItemIndex != -1)
{
//Selected item index is NOT -1 and is correct
CharListModel.remove(selItemIndex);
//Exception in thread "AWT-EventQueue-0" java.lang.ArrayIndexOutOfBoundsException: -1
}
else
{
//NEVER reached
JOptionPane.showMessageDialog(null, "OUCH!");
}
}
如您所见，所选项目的索引是正确的，直到删除它，然后我再次获得越界异常。我也在同一个地方尝试了这个但结果相同：
As you can see, the index of the selected item is correct right up to the point of removing it, whereupon I once again get the out of bounds exception. I also tried this in the same place but with the same results:
CharListModel.removeElement(CharList.getSelectedValue());
更加混乱
尝试为了弄清楚发生了什么，我创建了一个新的 DefaultListModel ，枚举旧的，并将每个名称放入新模型中，除了我要删除的名称（记住我可以得到索引，对象和文本，我只是不能删除它。）
Even more confusion
In an attempt to work out what is going on I have created a new DefaultListModel, enumerated the old one, and put each name into the new model, except the one that I want to remove (Remember I can get the index, the object and the text, I just cant delete it).
这已经奏效了，我现在有一个 DefaultListModel 中包含正确的项目，但是，我尝试 CharList.setModel（NewModel）; 的那一刻我再次获得了界限例外。
This has worked and I now have a DefaultListModel with the correct items in it, however, the moment that I try to CharList.setModel(NewModel); I once again get the out of bounds exception.
这让我脱掉了头发！任何人都可以提供任何想法尝试吗？
This has got me pulling out hair! Can anyone offer any ideas to try?
根本不是一个解决方案，但要解决这个令人抓狂的问题我是使用上面列出的方法，我在其中创建列表模型的副本，减去我要删除的项目，然后在使用 setModel 时简单地捕获异常，因为更新后的列表模型很好地添加到列表中，后续操作（如添加项目等）工作正常，直到我尝试再次删除项目为止！
Not really a resolution at all, but to work around this maddening problem I am using the method laid out above, where I create a copy of the list model, minus the item that I want to delete and then simply catch the exception when using setModel, since the updated list model is added to the list just fine, and subsequent actions such as adding items etc. work okay, right up until I try to delete an item again anyway!
谢谢，如果你试图提供帮助 - 如果你对如何解决这个问题有任何想法，请务必发布！
Thanks if you tried to help - and if you have any ideas about how to hunt down this problem, by all means post away!
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推荐答案
作为参考，我将以下代码添加到此示例的。如果它没有帮助，更新您的问题可能是一个有用的 sscce 。
For reference, I added the code below to this example. If it's not helpful, it may be a useful sscce for updating your question.
panel.add(new JButton(new AbstractAction("Remove") {
@Override
public void actionPerformed(ActionEvent e) {
int index = list.getSelectedIndex();
if (index != -1) {
model.remove(index);
}
}
}));
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