Java Swing 和 JComboBox 事件
我有一个 JComboBox ，其中包含多个值。我需要能够检测用户何时单击 JComboBox 但不更改当前选定的项目。
发生这种情况时，itemStateChanged 和 actionPerformed 都不会触发。
我应该使用什么事件？
I have a JComboBox with multiple values in it. I need to be able to detect when the user clicks the JComboBox but does not change the currently selected item.
Neither itemStateChanged nor actionPerformed fire when this happens.
What event should I be using?
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按下鼠标按钮时记录组合框的状态，并将其与释放鼠标按钮时组合框的值进行比较怎么样？
MouseListener< /a> 到JComboBoxmousePressed()方法 将框的状态记录到临时变量mouseReleased()< /code> 方法将框的值与临时变量的值进行比较此时，这是一个简单的相等检查。
How about recording the combo box's state when the mouse button is pressed, and comparing it to the value the box has when the mouse button is released?
MouseListenerto theJComboBoxmousePressed()method to record the box's state to a temp variablemouseReleased()method to compare the box's value to the temp variable's valueAt this point, it's a simple equality check.
使用
addMouseListener方法将MouseListener添加到JComboBox中。您将需要扩展MouseAdapter并仅重写mouseClicked方法。Add a
MouseListenerto theJComboBoxusing itsaddMouseListenermethod. You will want to extendMouseAdapterand override only themouseClickedmethod.如果用户使用键盘打开弹出窗口，然后使用退出键关闭弹出窗口怎么办？
我会使用 PopupMenuListener。这应该处理鼠标和键盘操作。这个概念与其他建议相同。当显示弹出窗口时，您可以保存选定的索引。当关闭时，您可以比较所选索引以查看它是否已更改。
What if the user users the keyboard to open the popup and then uses the escape key to close the popup?
I would use a PopupMenuListener. This should handle both mouse and keyboard actions. The concept would be the same as other suggestions. When the popup is displayed you save the selected index. When is closes you compare the selected index to see it it has changed.
我专门研究了鼠标右键单击项目，所以这是一个略有不同的问题。
但对我来说，解决方案是
子类
JComboBox用子类DefaultListCellRenderer替换getCellRenderer()。在单元格渲染器中拦截
getListCellRendererComponent()，它具有boolean isSelected、boolean cellHasFocus参数，可用于监视鼠标事件和dolist.setToolTipText().我确信非最终选择更改将到达那里，在那里它可以被拦截。
I was looking specifically at right mouse click on items, so it's a slightly different problem.
But the solution for me was to
Subclass
JComboBoxsubstitutinggetCellRenderer() with a subclassedDefaultListCellRenderer.In the cell renderer intercept
getListCellRendererComponent()which hasboolean isSelected,boolean cellHasFocusparameters and can be used to watch for mouse events and dolist.setToolTipText().I'm sure the non-final selection change will get there, where it can be intercepted.