java JList.getModel() ClassCastException
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JList.getModel() ClassCastException
提问by Stripies
When I call JList<String>.getModel()and cast it to DefaultListModel<String>it gives me this exception.
当我调用JList<String>.getModel()并将其转换DefaultListModel<String>为它时，它给了我这个例外。
Exception in thread "AWT-EventQueue-0" java.lang.ClassCastException: javax.swing.JList cannot be cast to javax.swing.DefaultListModel
The code that throws it:
抛出它的代码：
private JList<String> list = new JList<String>();
((DefaultListModel<String>) list.getModel()).addElement(...);
It doesn't do it every time though. Most of the time it works perfectly, but other times it throws this exception. I don't understand why this is happening. Is there anything I can do to stop this from happening?
不过也不是每次都这样。大多数时候它运行良好，但其他时候它会抛出这个异常。我不明白为什么会这样。我能做些什么来阻止这种情况发生？
采纳答案by ditkin
You should not assume it is a DefaultListModel. Use the interface ListModel. The JList is returning an internal implementation of ListModel.
你不应该假设它是一个 DefaultListModel。使用接口 ListModel。JList 正在返回 ListModel 的内部实现。
If you need access to the underlying model you should create it, set it in the JList constructor and retain it yourself.
如果您需要访问底层模型，您应该创建它，在 JList 构造函数中设置它并自己保留它。
回答by Nikola Despotoski
I experienced this issue. I found this simple workaround:
我遇到过这个问题。我找到了这个简单的解决方法：
//----instantiation----
JList mList = new JList();
mList.setModel(new DefaultListModel());
/*---- do whatever you want---- */
//Retain it wherever you want with
DefaultListModel model = (DefaultListModel)mList.getModel();
回答by SandroMarques
If you are using NetBeans
如果您使用的是 NetBeans
- Select your jList
- In properties, click the modelbutton
- select the "Custom code" option
- Write
new DefaultListModel ()
- 选择您的jList
- 在属性中，单击模型按钮
- 选择“自定义代码”选项
- 写
new DefaultListModel ()
回答by Black_Zerg
Before JList<String>.getModel(),you must initialize your object JList<String>.setModel(new DefaultModelList())
在JList<String>.getModel(),你必须初始化你的对象之前JList<String>.setModel(new DefaultModelList())
