Java JComboBox 选择更改侦听器？
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JComboBox Selection Change Listener?
提问by Allain Lalonde
I'm trying to get an event to fire whenever a choice is made from a JComboBox.
每当从JComboBox.
The problem I'm having is that there is no obvious addSelectionListener()method.
我遇到的问题是没有明显的addSelectionListener()方法。
I've tried to use actionPerformed(), but it never fires.
我尝试使用actionPerformed()，但它永远不会触发。
Short of overriding the model for the JComboBox, I'm out of ideas.
缺少覆盖模型的JComboBox，我没有想法。
How do I get notified of a selection change on a JComboBox?**
我如何在JComboBox? **上收到选择更改的通知？
Edit:I have to apologize. It turns out I was using a misbehaving subclass of JComboBox, but I'll leave the question up since your answer is good.
编辑：我必须道歉。事实证明，我使用了一个行为不端的子类JComboBox，但由于您的回答很好，所以我将这个问题搁置一旁。
采纳答案by jodonnell
It should respond to ActionListeners, like this:
它应该响应ActionListeners，如下所示：
combo.addActionListener (new ActionListener () {
public void actionPerformed(ActionEvent e) {
doSomething();
}
});
@John Calsbeekrightly points out that addItemListener()will work, too. You may get 2 ItemEvents, though, one for the deselection of the previously selected item, and another for the selection of the new item. Just don't use both event types!
@John Calsbeek正确地指出这addItemListener()也行得通。ItemEvents但是，您可能会得到 2 ，一个用于取消选择先前选择的项目，另一个用于选择新项目。只是不要同时使用这两种事件类型！
回答by John Calsbeek
I would try the itemStateChanged()method of the ItemListenerinterface if jodonnell's solution fails.
我会尝试itemStateChanged()的方法ItemListener如果jodonnell的解决方案失败接口。
回答by JavaKeith
You may try these
你可以试试这些
int selectedIndex = myComboBox.getSelectedIndex();
-or-
-或者-
Object selectedObject = myComboBox.getSelectedItem();
-or-
-或者-
String selectedValue = myComboBox.getSelectedValue().toString();
回答by Viacheslav
Code example of ItemListenerimplementation
ItemListener实现代码示例
class ItemChangeListener implements ItemListener{
@Override
public void itemStateChanged(ItemEvent event) {
if (event.getStateChange() == ItemEvent.SELECTED) {
Object item = event.getItem();
// do something with object
}
}
}
Now we will get only selected item.
现在我们将只获得选定的项目。
Then just add listener to your JComboBox
然后只需将侦听器添加到您的 JComboBox
addItemListener(new ItemChangeListener());
回答by Craig Wayne
I was recently looking for this very same solution and managed to find a simple one without assigning specific variables for the last selected item and the new selected item. And this question, although very helpful, didn't provide the solution I needed. This solved my problem, I hope it solves yours and others. Thanks.
我最近正在寻找这个非常相同的解决方案，并设法找到了一个简单的解决方案，而无需为最后一个选定项目和新选定项目分配特定变量。这个问题虽然很有帮助，但并没有提供我需要的解决方案。这解决了我的问题，我希望它能解决你和其他人的问题。谢谢。
回答by Ahuramazda
Here is creating a ComboBox adding a listener for item selection change:
这是创建一个 ComboBox，为项目选择更改添加一个侦听器：
JComboBox comboBox = new JComboBox();
comboBox.setBounds(84, 45, 150, 20);
contentPane.add(comboBox);
JComboBox comboBox_1 = new JComboBox();
comboBox_1.setBounds(84, 97, 150, 20);
contentPane.add(comboBox_1);
comboBox.addItemListener(new ItemListener() {
public void itemStateChanged(ItemEvent arg0) {
//Do Something
}
});
