JComboBoxDemo

最新推荐文章于 2022-09-09 06:15:37 发布

vincentng

最新推荐文章于 2022-09-09 06:15:37 发布

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文章标签： class delete string java

本文链接：https://blog.youkuaiyun.com/vincentng/article/details/6142211

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参照上图的效果，写的一个例子：

package com.luffy.practice;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
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.JTextArea;
import javax.swing.JTextField;
public class JComboBoxDemo extends JFrame implements ItemListener,ActionListener{
	private JButton _addButton;
	private JButton _delButton;
	private JComboBox _itemComboBox;
	private JTextField _itemText;
	private JTextArea _itemTextArea;
	private JPanel _addPanel;
	private JPanel _delPanel;
	private JPanel _showPanel;
	
	public JComboBoxDemo(){
		setSize(300,300);
		setVisible(true);
		setLayout(new FlowLayout());
		_addButton = new JButton("Add");
		_delButton = new JButton("Delete");
		_itemComboBox = new JComboBox();
		_itemText = new JTextField(10);
		_itemTextArea = new JTextArea(5,20);
		_addPanel = new JPanel();
		_delPanel = new JPanel();
		_showPanel = new JPanel();
		
		_itemComboBox.addItem("Item 1");
		_itemComboBox.addItem("Item 2");
		_itemComboBox.addItem("Item 3");
		_itemComboBox.addItem("Item 4");
		
		_delPanel.add(_itemComboBox);
		_delPanel.add(_delButton);
		_addPanel.add(_itemText);
		_addPanel.add(_addButton);
		_showPanel.add(_itemTextArea);
		
		add(_delPanel);
		add(_addPanel);
		add(_showPanel);
		
		//internal class extends WindowAdapter and override windowClosing method
//		this.addWindowListener(new WindowAdapter(){
//			public void windowClosing(WindowEvent we){
//				System.exit(0);
//			}
//		});
		// method exit on close frame
		this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		
		_addButton.addActionListener(this);
		_delButton.addActionListener(this);
		_itemComboBox.addItemListener(this);
		
		validate();
	}
	/**
	 * @param args
	 */
	public static void main(String[] args) {
		new JComboBoxDemo();
	}
	public void itemStateChanged(ItemEvent e) {
		//another case, ItemEvent.DESELECTED
		if(e.getStateChange() == ItemEvent.SELECTED){
			_itemTextArea.append(e.getItem().toString() + " selected./n");
		}
	}
	public void actionPerformed(ActionEvent e) {
		if(e.getSource() == _addButton){
			_itemTextArea.append("Add " +_itemText.getText() + "/n");
			_itemComboBox.addItem(_itemText.getText());
			_itemComboBox.setSelectedItem(_itemText.getText());
		}else if(e.getSource() == _delButton){
			_itemTextArea.append("Delete " +_itemComboBox.getSelectedItem().toString() + "/n");
			_itemComboBox.removeItem(_itemComboBox.getSelectedItem());
		}
	}
}

参照《Java核心技术》，重构后的代码

package com.luffy.practice;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
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.JTextArea;
import javax.swing.JTextField;
public class JComboBoxDemoReconstruction {
	
	public static void main(String[] args) {
		JComboBoxFrame frame = new JComboBoxFrame();
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.setVisible(true);
	}
}
class JComboBoxFrame extends JFrame{
	public JComboBoxFrame(){
		setTitle("JComboBoxDemo");
		setSize(DEFAULT_WIDTH,DEFAULT_HEIGHT);
		
		JComboBoxPanel panel = new JComboBoxPanel();
		add(panel);
	}
	
	public static final int DEFAULT_WIDTH = 300;
	public static final int DEFAULT_HEIGHT = 300;
}
class JComboBoxPanel extends JPanel{
	
	public JComboBoxPanel(){
		_addButton = new JButton("Add");
		_delButton = new JButton("Delete");
		_itemComboBox = new JComboBox();
		_itemText = new JTextField(10);
		_itemTextArea = new JTextArea(TEXTAREA_ROWS,TEXTAREA_COLUMNS);
		_addPanel = new JPanel();
		_delPanel = new JPanel();
		_showPanel = new JPanel();
		
		_itemComboBox.addItem("Item 1");
		_itemComboBox.addItem("Item 2");
		_itemComboBox.addItem("Item 3");
		_itemComboBox.addItem("Item 4");
		
		_delPanel.add(_itemComboBox);
		_delPanel.add(_delButton);
		_addPanel.add(_itemText);
		_addPanel.add(_addButton);
		_showPanel.add(_itemTextArea);
		
		setLayout(new FlowLayout());
		add(_delPanel);
		add(_addPanel);
		add(_showPanel);
		
		_addButton.addActionListener(new ButtonListener());
		_delButton.addActionListener(new ButtonListener());
		_itemComboBox.addItemListener(new ItemChangedListener());
	}
	
	private class ButtonListener implements ActionListener{
		public void actionPerformed(ActionEvent e) {
			// TODO Auto-generated method stub
			if(e.getSource() == _addButton){
				_itemTextArea.append("Add " +_itemText.getText() + "/n");
				_itemComboBox.addItem(_itemText.getText());
				_itemComboBox.setSelectedItem(_itemText.getText());
			}else if(e.getSource() == _delButton){
				_itemTextArea.append("Delete " +_itemComboBox.getSelectedItem().toString() + "/n");
				_itemComboBox.removeItem(_itemComboBox.getSelectedItem());
			}
		}
	}
	
	private class ItemChangedListener implements ItemListener{
		public void itemStateChanged(ItemEvent e) {
			// TODO Auto-generated method stub
			if(e.getStateChange() == ItemEvent.SELECTED){
				_itemTextArea.append(e.getItem().toString() + " selected./n");
			}
		}
		
	}
	
	private JButton _addButton;
	private JButton _delButton;
	private JComboBox _itemComboBox;
	private JTextField _itemText;
	private JTextArea _itemTextArea;
	private JPanel _addPanel;
	private JPanel _delPanel;
	private JPanel _showPanel;
	private static final int TEXTAREA_ROWS = 5;
	private static final int TEXTAREA_COLUMNS = 20;
}

重构前：
1. 所有功能都在一个Class中
2. 有magic number

重构后：
1. 类的结构：
          主类（JComboBoxDemoReconstruction）
          --Frame
            --Panel
               --ButtonListener
               --ItemChangedListener
2. 没了magic number