Java JComboBox监听更改选择事件 [英] Java JComboBox listen a change selection event

问题描述

我正在尝试在Java JComboBox中监听选择的更改。我试图使用ActionListener但问题是这样的：动作监听器做这样的事情

I'm trying to listen to a change of selection in a Java JComboBox. I have tried to use an ActionListener but the problem is this: the action listener does something like this

public void actionPerformed(ActionEvent e){
    JComboBox<String> source = ((JComboBox<String>)e.getSource());
    String selected = source.getItemAt(source.getSelectedIndex());

    /*now I compare if the selected string is equal to some others 
      and in a couple of cases I have to add elements to the combo*/
}

您可以注意到，当我需要向组合添加元素时，会触发另一个事件并调用actionPerformed方法再次，即使我不想这样，代码可能循环... :(
有没有办法只听取选择更改而不是通用更改事件？
谢谢

As you can notice, when I need to add elements to the combo another event is fired and the actionPerformed method is called again, even if I don't want that, and the code may loops... :( Is there any way to listen to the selection change only and not to a generic change event? Thanks

推荐答案

你可以尝试<$ h $ c> itemStateChanged（） ItemListener 界面：

class ItemChangeListener implements ItemListener{
    @Override
    public void itemStateChanged(ItemEvent event) {
       if (event.getStateChange() == ItemEvent.SELECTED) {
          Object item = event.getItem();
          // do something with object
       }
    }       
}

并将监听器添加到JComboBox：

And add the listener to your JComboBox:

source.addItemListener(new ItemChangeListener());

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