Question

当选择组合框中的项目时，我想要执行并执行操作，但无论选择哪个项目，它都会执行操作。有人可以帮我解决。

//number of players combo box
        players = new JComboBox();
        contentPane.add(players, BorderLayout.SOUTH);
        players.addItem("1 Player");
        players.addItem("2 Players");
        players.addActionListener(new ActionListener() {

         @Override
        public void actionPerformed(ActionEvent e) {
         makeFrame();
        }
       });
       players.addItem("3 Players");
//end of combo box

Answer 1

为了根据选择的项目更改行为，您需要在ActionListener中检索所选值，并根据所选值更改行为。您可以使用以下内容：

//number of players combo box
//notice that you have to declare players
//as final. If it is a member of the class,
//you can declare it final in the field
//declaration and initialize it in the
//constructor, or if local, just leave it
//as it is here. Unless using Java 8, then it
//doesn't need to be declared final
final JComboBox players = new JComboBox();
contentPane.add(players, BorderLayout.SOUTH);
players.addItem("1 Player");
//your combo box still needs to be final
final JComboBox players = new JComboBox();
contentPane.add(players, BorderLayout.SOUTH);
players.addItem("1 Player");
players.addItem("2 Players");
players.addItem("3 Players");
players.addActionListener(new ActionListener() {
    @Override
    public void actionPerformed(ActionEvent e) {
        String selectedValue = String.valueOf(players.getSelectedItem());
        if (selectedValue != null && (selectedValue.equals("1 Player") || selectedValue.equals("2 Players"))) {
            makeFrame();
        }
        else {
            //do something else
        }
    }
});
//end of combo box

如果您恰好提前知道索引（即，您静态初始化选项列表而不是动态生成列表），您还可以引用.getSelectedIndex()来检索索引，如下所示：< / p>

//number of players combo box
//the combo box still needs to be final here
final JComboBox players = new JComboBox();
contentPane.add(players, BorderLayout.SOUTH);
players.addItem("1 Player");
//your combo box still needs to be final
final JComboBox players = new JComboBox();
contentPane.add(players, BorderLayout.SOUTH);
players.addItem("2 Players");
players.addItem("3 Players");
players.addActionListener(new ActionListener() {
    @Override
    public void actionPerformed(ActionEvent e) {
        int myIndex = players.getSelectedIndex();
        if (myIndex == 0 || myIndex == 1) {
            makeFrame();
        }
        else {
            //do something else
        }
    }
});
//end of combo box

ComboBox中的项目

1 个答案: