JComboBox如何显示项目的右端？

Question

我有以下Java代码：

import java.awt.BorderLayout;
import java.awt.Dimension;
import javax.swing.JComboBox;
import javax.swing.JFrame;

public class EnumsRightVisible {

    public void show() {
        JFrame frame = new JFrame("Combo box");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        String[] items = {"aaaaaaaaa__________zzzzzzzzz",
                          "aaaaaaaaa__________zzzzzzzzz",
                          "aaaaaaaaa__________zzzzzzzzz"};
        JComboBox combo = new JComboBox(items);
        combo.setPreferredSize(new Dimension(100,20));
        frame.add(combo, BorderLayout.CENTER);
        frame.setLocation(600, 100);
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String args[]) {
        EnumsRightVisible enumsRightVisible = new EnumsRightVisible();
        enumsRightVisible.show();
    }
}

运行它，你可以看到可见文本是左向的。

请注意，这段代码并不能解决我的问题（它将文本向右对齐，但仅在组合框展开时）：

((JLabel)comboBox.getRenderer()).setHorizontalAlignment(JLabel.RIGHT);

如何在同一窗口中显示文本的右端（...__zzzzzz）？提前致谢！

Answer 1

import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;

public class ComboBoxDemo extends JFrame {

    public ComboBoxDemo() {
        JComboBox comboBox = new JComboBox();
        
        ((JLabel)comboBox.getRenderer()).setHorizontalAlignment(JLabel.RIGHT);
        
        comboBox.addItem("Apple");
        comboBox.addItem("Orange");
        comboBox.addItem("Mango");
        
        getContentPane().add(comboBox, "North");
        setSize(200, 100);
        this.setLocationRelativeTo(null);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
    }

    public static void main(String[] args) {
                new ComboBoxDemo().setVisible(true);
    }
}

import java.awt.Component;
import java.awt.ComponentOrientation;
import javax.swing.DefaultListCellRenderer;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.ListCellRenderer;

public class ComboBoxDemo extends JFrame {

    public ComboBoxDemo() {
        JComboBox comboBox = new JComboBox();

        setListCellRendererOf(comboBox);
        
        comboBox.addItem("Apple");
        comboBox.addItem("Orange");
        comboBox.addItem("Mango");

        getContentPane().add(comboBox, "North");
        setSize(200, 100);
        this.setLocationRelativeTo(null);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
    }

    private void setListCellRendererOf(JComboBox comboBox) {
        comboBox.setRenderer(new ListCellRenderer() {
            
            @Override
            public Component getListCellRendererComponent(JList list, Object value, int index, boolean isSelected, boolean cellHasFocus) {

                Component component = new DefaultListCellRenderer()
                        .getListCellRendererComponent(list, value, index, isSelected, cellHasFocus);

                component.setComponentOrientation(ComponentOrientation.RIGHT_TO_LEFT);
                return component;
            }
        });
    }
    public static void main(String[] args) {
                new ComboBoxDemo().setVisible(true);
    }
}

Answer 2

使用自定义渲染器，该渲染器使用FontMetrics测量字符串的宽度，并手动执行省略号（…）。更多信息请点击此处：http://docs.oracle.com/javase/tutorial/uiswing/components/combobox.html#renderer