程序添加JComboBox的item也能触发itemStateChanged事件吗

程序添加JComboBox的item也能触发itemStateChanged事件吗

直接看实例:

package share;

import java.awt.EventQueue;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;

import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;

import com.string.widget.util.ValueWidget;

public class TestJComboBox extends JFrame {

	private JPanel contentPane;
	private JComboBox<String> comboBox;

	/**
	 * Launch the application.
	 */
	public static void main(String[] args) {
		EventQueue.invokeLater(new Runnable() {
			public void run() {
				try {
					TestJComboBox frame = new TestJComboBox();
					frame.setVisible(true);
				} catch (Exception e) {
					e.printStackTrace();
				}
			}
		});
	}

	/**
	 * Create the frame.
	 */
	public TestJComboBox() {
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		setBounds(100, 100, 450, 300);
		contentPane = new JPanel();
		contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
		setContentPane(contentPane);
		GridBagLayout gbl_contentPane = new GridBagLayout();
		gbl_contentPane.columnWidths = new int[]{0, 0, 0};
		gbl_contentPane.rowHeights = new int[]{0, 0};
		gbl_contentPane.columnWeights = new double[]{1.0, 0.0, Double.MIN_VALUE};
		gbl_contentPane.rowWeights = new double[]{0.0, Double.MIN_VALUE};
		contentPane.setLayout(gbl_contentPane);
		
		comboBox = new JComboBox<String>();
		GridBagConstraints gbc_comboBox = new GridBagConstraints();
		gbc_comboBox.insets = new Insets(0, 0, 0, 5);
		gbc_comboBox.fill = GridBagConstraints.HORIZONTAL;
		gbc_comboBox.gridx = 0;
		gbc_comboBox.gridy = 0;
		contentPane.add(comboBox, gbc_comboBox);
		
		JButton btnAddItem = new JButton("add item");
		GridBagConstraints gbc_btnAddItem = new GridBagConstraints();
		gbc_btnAddItem.gridx = 1;
		gbc_btnAddItem.gridy = 0;
		contentPane.add(btnAddItem, gbc_btnAddItem);
		
		
		comboBox.addItemListener(new ItemListener()
        {
            @Override
            public void itemStateChanged(ItemEvent arg0)
            {
                System.out.println("itemStateChanged");
            }
        });
		init222();
		
	}
	private void init222(){
		comboBox.addItem("a");
		comboBox.addItem("b");
		comboBox.addItem("c");
	}

}

 

启动的时候,控制台打印:

itemStateChanged

说明启动之后,执行了itemStateChanged 方法,说明了触发了itemStateChanged 事件.

总结:程序添加addItem 也能触发itemStateChanged 事件

如何把init222 方法放在comboBox.addItemListener 前就不会触发itemStateChanged 事件