在两个JComboBox之间共享相同的模型

Question

我有一个人[]有三个人(p1，p2，p3)。Person类有两个属性name和email。

我使用了以下代码。

    Person p1 = new Person("Smith", "[e-mail]");
    Person p2 = new Person("Tom", "[e-mail]");
    Person p3 = new Person("John","[e-mail]");

    Person[] per_arr = new Person[] { p1, p2, p3};

    JFrame frame = new JFrame();
    JPanel panel = new JPanel();
    JComboBox<String> combo1 = new JComboBox<String>();
    JComboBox<String> combo2 = new JComboBox<String>();

    for (Person p : per_arr) {
        combo1.addItem(p.getName());
        combo2.addItem(p.getEmail());
    }
    panel.add(combo1);
    panel.add(combo2);
    frame.setContentPane(panel);
    frame.pack();
    frame.setVisible(true);

但我不想这样用。我想使用两个组合框与相同的型号。我尝试使用DefaultComboBoxModel并重写getElementAt（）方法，如下所示。

public class MyModel extends DefaultComboBoxModel<Object> {

public MyModel(Object[] items) {
    super(items);
}

@Override
public Object getElementAt(int index) {
    if (super.getElementAt(index) instanceof Person) {
        return (Person)super.getElementAt(index);
    } else {
        return null;
    }
}

}

问题是如何使用相同的ComboBoxModel在一个JComboBox中添加Person[]的所有名称，并在另一个JComboBox中添加所有电子邮件。

Answer 1

使用ComboBoxModel的一个实例和JComboBox的两个实例，每个实例具有相同的模型。让每个JComboBox都有一个自定义呈现器，用于显示该JComboBox所需的Person属性。

在下面的示例中，每个组合都获得实现策略模式的单个呈现器的自己的实例，并传递一个函数 ，该函数在调用呈现器时选择正确的属性：

DefaultComboBoxModel model = new DefaultComboBoxModel(…);
JComboBox<String> combo1 = new JComboBox<>(model);
combo1.setRenderer(new PersonRenderer(Person::getName));
JComboBox<String> combo2 = new JComboBox<>(model);
combo2.setRenderer(new PersonRenderer(Person::getEmail));

import java.awt.Component;
import java.awt.EventQueue;
import java.awt.FlowLayout;
import java.util.function.Function;
import javax.swing.DefaultComboBoxModel;
import javax.swing.DefaultListCellRenderer;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;

/**
 * @see http://stackoverflow.com/a/37222598/230513
 */
public class ComboRendererTest {

    private void display() {
        JFrame f = new JFrame("Test");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setLayout(new FlowLayout());
        DefaultComboBoxModel model = new DefaultComboBoxModel(new Person[]{
            new Person("Alpher", "[e-mail]"),
            new Person("Bethe", "[e-mail]"),
            new Person("Gammow", "[e-mail]")});
        JComboBox<String> combo1 = new JComboBox<>(model);
        combo1.setRenderer(new PersonRenderer(Person::getName));
        JComboBox<String> combo2 = new JComboBox<>(model);
        combo2.setRenderer(new PersonRenderer(Person::getEmail));
        f.add(combo1);
        f.add(combo2);
        f.pack();
        f.setLocationRelativeTo(null);
        f.setVisible(true);
    }

    private static class PersonRenderer extends DefaultListCellRenderer {

        Function<Person, String> personAttribute;

        public PersonRenderer(Function<Person, String> personAttribute) {
            this.personAttribute = personAttribute;
        }

        @Override
        public Component getListCellRendererComponent(JList<?> list, Object
            value, int index, boolean isSelected, boolean cellHasFocus) {
            JLabel l = (JLabel) super.getListCellRendererComponent(
                list, value, index, isSelected, cellHasFocus);
            Person p = (Person) value;
            l.setText(personAttribute.apply(p));
            return l;
        }
    }

    private static class Person {

        private final String name;
        private final String email;

        public Person(String name, String email) {
            this.name = name;
            this.email = email;
        }

        public String getName() {
            return name;
        }

        public String getEmail() {
            return email;
        }
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(new ComboRendererTest()::display);
    }
}