如何按值设置选定的索引JComboBox

Question

我想通过值而不是索引在 JComboBox 中设置选定的索引。怎么做呢？示例

public class ComboItem {

    private String value;
    private String label;

    public ComboItem(String value, String label) {
        this.value = value;
        this.label = label;
    }

    public String getValue() {
        return this.value;
    }

    public String getLabel() {
        return this.label;
    }

    @Override
    public String toString() {
        return label;
    }
}

JComboBox test = new JComboBox();
test.addItem(new ComboItem(0, "orange"));
test.addItem(new ComboItem(1, "pear"));
test.addItem(new ComboItem(2, "apple"));
test.addItem(new ComboItem(3, "banana"));
test.setSelectedItem("banana");

好的，我稍微修改了我的问题。我忘记了我的 JComboBox 中有一个自定义项目，这使得它变得更加困难。我无法执行 setSelectedItem，因为每个项目内都有一个 ComboItem。那么，我该如何完成这件事呢？

Answer 1

setSelectedItem("香蕉")。您可以通过阅读 javadoc。

编辑：既然你改变了问题，我就会改变我的答案。

如果您想选择具有“banana”标签的项目，那么您有两种解决方案：

1. 迭代项目以查找具有给定标签的项目（或该项目的索引），然后调用 setSelectedItem( theFoundItem) （或 setSelectedIndex(theFoundIndex)）
2. 覆盖 ComboItem 中的 equals 和 hashCode，以便两个具有相同名称的 ComboItem 实例是相等的，只需使用 setSelectedItem(new ComboItem(anyNumber, "banana"));

Answer 2

你应该使用模型

comboBox.getModel().setSelectedItem(object);

Answer 3

public static void setSelectedValue(JComboBox comboBox, int value)
    {
        ComboItem item;
        for (int i = 0; i < comboBox.getItemCount(); i++)
        {
            item = (ComboItem)comboBox.getItemAt(i);
            if (item.getValue().equalsIgnoreCase(value))
            {
                comboBox.setSelectedIndex(i);
                break;
            }
        }
    }

希望这有帮助:)

Answer 4

为什么不采用一个集合（可能是一个 Map（例如 HashMap））并将其用作您自己的实现 ComboBoxModel 接口的组合框模型类的核心？然后，您可以通过键字符串而不是整数轻松访问组合框的项目。

例如...

import java.util.HashMap;
import java.util.Map;

import javax.swing.ComboBoxModel;
import javax.swing.event.ListDataListener;

public class MyComboModel<K, V>   implements ComboBoxModel {
   private Map<K, V> nucleus = new HashMap<K, V>();

   // ... any constructors that you want would go here

   public void put(K key, V value) {
      nucleus.put(key, value);
   }

   public V get(K key) {
      return nucleus.get(key);
   }

   @Override
   public void addListDataListener(ListDataListener arg0) {
      // TODO Auto-generated method stub

   }

   // ... plus all the other methods required by the interface
}

Answer 5

例如

import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.SwingUtilities;

public class ComboboxExample {

    private JFrame frame = new JFrame("Test");
    private JComboBox comboBox = new JComboBox();

    public ComboboxExample() {
        createGui();
    }

    private void createGui() {
        comboBox.addItem("One");
        comboBox.addItem("Two");
        comboBox.addItem("Three");
        JButton button = new JButton("Show Selected");
        button.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                JOptionPane.showMessageDialog(frame, "Selected item: " + comboBox.getSelectedItem());
                javax.swing.SwingUtilities.invokeLater(new Runnable() {

                    @Override
                    public void run() {
                        comboBox.requestFocus();
                        comboBox.requestFocusInWindow();
                    }
                });
            }
        });
        JButton button1 = new JButton("Append Items");
        button1.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                appendCbItem();
            }
        });
        JButton button2 = new JButton("Reduce Items");
        button2.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                reduceCbItem();
            }
        });
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLayout(new GridLayout(4, 1));
        frame.add(comboBox);
        frame.add(button);
        frame.add(button1);
        frame.add(button2);
        frame.setLocation(200, 200);
        frame.pack();
        frame.setVisible(true);
        selectFirstItem();
    }

    public void appendCbItem() {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                comboBox.addItem("Four");
                comboBox.addItem("Five");
                comboBox.addItem("Six");
                comboBox.setSelectedItem("Six");
                requestCbFocus();
            }
        });
    }

    public void reduceCbItem() {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                comboBox.removeItem("Four");
                comboBox.removeItem("Five");
                comboBox.removeItem("Six");
                selectFirstItem();
            }
        });
    }

    public void selectFirstItem() {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                comboBox.setSelectedIndex(0);
                requestCbFocus();
            }
        });
    }

    public void requestCbFocus() {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                comboBox.requestFocus();
                comboBox.requestFocusInWindow();
            }
        });
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                ComboboxExample comboboxExample = new ComboboxExample();
            }
        });
    }
}

Answer 6

http://docs .oracle.com/javase/6/docs/api/javax/swing/JComboBox.html#setSelectedItem(java.lang.Object)

test.setSelectedItem("banana");

有一些警告或潜在的意外行为，如 javadoc 中所述。阅读该内容。

Answer 7

当组合框由某个类的构造函数填充时设置选定项目的正确方法（如@milosz 发布）：

combobox.getModel().setSelectedItem(new ClassName(parameter1, parameter2));

在您的情况下，代码将是：

test.getModel().setSelectedItem(new ComboItem(3, "banana"));

Answer 8

只需在执行 comboBox.setSelectedItem 或 comboBox.setSelectedIndex 或 comboModel.setSelectedItem 后调用 comboBox.updateUI()

Answer 9

public boolean  preencherjTextCombox (){
       int x = Integer.parseInt(TableModelo.getModel().getValueAt(TableModelo.getSelectedRow(),0).toString());

       modeloobj = modelosDAO.pesquisar(x);
       Combmarcass.getModel().setSelectedItem(modeloobj.getMarca());  
       txtCodigo.setText(String.valueOf(modeloobj.getCodigo()));
       txtDescricao.setText(String.valueOf(modeloobj.getDescricao()));
       txtPotencia.setText(String.valueOf(modeloobj.getPotencia()));  

       return true;
   }

Answer 10

在我的例子中，构建类 Item(key, value) 作为组合框的项目

SanPhamDTO currentProd = prodDao.getDetailById(id);
Item item = new Item(currentProd.getCategory().getId(), 
currentProd.getCategory().getName());
cbdanhmuc.getModel().setSelectedItem(item)