问题
This is a fairly common problem, and the solution I've used is similar to what I searched and found later. One implements a ListCellRenderer with a JLabel that enables or disables itself based on the current selected index:
public Component getListCellRendererComponent(JList list, Object value,
int index, boolean isSelected, boolean cellHasFocus) {
setText(value.toString());
UIDefaults defaults = UIManager.getDefaults();
Color fc;
if (index == 1) {
setEnabled(false);
fc = defaults.getColor("Label.disabledForeground");
setFocusable(false);
} else {
// fc = defaults.getColor("Label.foreground");
fc = list.getForeground();
setEnabled(list.isEnabled());
setFocusable(true);
}
setForeground(fc);
setBackground(isSelected ? list.getSelectionBackground() : list
.getBackground());
return this;
}
The problem is that even though visually the list item shows up as disabled, it can still be selected despite the setFocusable call.
How do I actually disable it?
回答1:
You need some way to discourage the ComboBox from been able to set the item(s) that can't be selected from been selected.
The easiest way I can think of is to trap the change in the selection within the model itself.
public class MyComboBoxModel extends DefaultComboBoxModel {
public MyComboBoxModel() {
addElement("Select me");
addElement("I can be selected");
addElement("Leave me alone");
addElement("Hit me!!");
}
@Override
public void setSelectedItem(Object anObject) {
if (anObject != null) {
if (!anObject.toString().equals("Leave me alone")) {
super.setSelectedItem(anObject);
}
} else {
super.setSelectedItem(anObject);
}
}
}
Now this is a quick hack to prove the point. What you really need is someway to mark certain items as unselectable. The easiest way I can think of is to provide a property in the item, such as isSelectable for example.
Failing that, you could construct a special ComboBoxModel that maintain a separate inner model that contained a reference to all the unselectable items, so that a quick model.contains(item) could be used to determine if the item is selectable or not.
来源：https://stackoverflow.com/questions/11895822/disabling-individual-jcombobox-items