java - For(each) 循环两次填充组合框

Question

这个问题已经有答案了:

Why is itemStateChanged on JComboBox is called twice when changed? (10 个回答)

已关闭 6 年前。

我构建了一个组合框，它根据另一个组合框的内容动态填充，依此类推。我决定在填充目标组合框时尝试迭代源数组的内容，尽管这有点糟糕。然而，尽管这会产生组合框内容，但它们会重复。我已经单步执行了代码，并且该数组仅被迭代一次。

 private JComboBox regBuildingSelectBox;
...
 String[] siteSelectStrings = {"Site", "London", "Long Island"};
    JComboBox regSiteSelectBox = new JComboBox(siteSelectStrings);
    regSiteSelectBox.addItemListener(new ItemListener() {
        public void itemStateChanged(ItemEvent arg0) {
            getDropDownVariables gddv = new getDropDownVariables();
            for(String s:
                   gddv.buildingSelectList
                            (regSiteSelectBox.getSelectedItem().toString()))
            {
                regBuildingSelectBox.addItem(s);
            }
        }
    });
    regSiteSelectBox.setBounds(24, 336, 282, 20);
    contentPane.add(regSiteSelectBox);


    regBuildingSelectBox = new JComboBox();

    regBuildingSelectBox.setBounds(24, 367, 282, 20);
    contentPane.add(regBuildingSelectBox);

包含数组的代码如下:

public class getDropDownVariables {

    public String[] buildingSelectList(String site)
    {
        switch (site)
        {
        case "London":
            return new String[]  {"Building", "Harvell", 
                                "LYNX Complex", "Caroline", "Salters"};
        case "Long Island":
            return new String[] {"Building", "Phillips", "Pascal"};
        }
        return new String[] {"Failed to populate buildings"};
    }

结果:

Answer 1

只是一个猜测，但在调用 regBuildingSelectBox.addItem(s); 之前您可能必须先清除它，否则它只会不断添加到列表中而不是替换它。还可能有一种不同的方法来设置值与添加值。