在java中添加项目运行时组合框

Question

我已经创建了一个组合框Swing我想在其他函数中添加项目。但问题是，项目不会调用该函数后会显示：

public void addItems() 
{ 
    combo.addItem(""); 
    // i want to add items here when this function is being called 
    // but those items are not displaying after calling this function 
    // i m calling this function on button click 
} 

Answer 1

对我的作品在此SSCCE：

import java.awt.BorderLayout; 
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.SwingUtilities; 
import javax.swing.UnsupportedLookAndFeelException; 

public class TestComboBox { 

    private int count = 0; 

    protected void initUI() { 
     final JFrame frame = new JFrame(TestComboBox.class.getSimpleName()); 
     frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
     final JComboBox comboBox = new JComboBox(new Object[] { "Something", "Stuff", "Beep" }); 
     JButton add = new JButton("Add item"); 
     add.addActionListener(new ActionListener() { 

      @Override 
      public void actionPerformed(ActionEvent e) { 
       comboBox.addItem("Item-" + count++); 
      } 
     }); 
     frame.add(comboBox); 
     frame.add(add, BorderLayout.SOUTH); 
     frame.pack(); 
     frame.setBounds(50, 50, 300, frame.getHeight()); 
     frame.setVisible(true); 
    } 

    public static void main(String[] args) throws ClassNotFoundException, InstantiationException, IllegalAccessException, 
      UnsupportedLookAndFeelException { 
     SwingUtilities.invokeLater(new Runnable() { 

      @Override 
      public void run() { 
       new TestComboBox().initUI(); 
      } 
     }); 
    } 
} 

Answer 2

如果你的组合框有MutableComboBoxModel，你可以做以下

MutableComboBoxModel model = (MutableComboBoxModel)combo.getModel(); 
model.addElement(elementToAdd); 

这相当于调用JComboBox#addItem（参见下面的实现）：

public void addItem(Object anObject) { 
    checkMutableComboBoxModel(); 
    ((MutableComboBoxModel)dataModel).addElement(anObject); 
} 

但我认为最好的做法是直接修改模型，如果你想在模型上进行修改而不是通过视图（除了为用户提供在视图中编辑的能力）

Answer 3

你需要调用：

repaint(); 
validate();