Java——下拉列表框：JComboBox

import java.awt.Container;
import java.awt.GridLayout;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.util.Vector;

import javax.swing.BorderFactory;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;

//=================================================
// File Name       :	MyComboBox_demo
//------------------------------------------------------------------------------
// Author          :	Common


//类名：MyList
//属性：
//方法：
class MyComboBox{
	private JFrame frame = new JFrame("窗体");					//定义窗体
	private Container cont = frame.getContentPane();			//得到窗体容器
	private JComboBox jcb1  = null;											//定义下拉列表框
	private JComboBox jcb2  = null;											//定义下拉列表框
	public MyComboBox(){
		this.frame.setLayout(new GridLayout(2,2));
		String nations[] = {"中国","美国","韩国","法国","英国"};
		Vector<String> v = new Vector<String>();						//定义一个Vector集合
		v.add("元素1");
		v.add("元素2");
		v.add("元素3");
		this.jcb1 = new JComboBox(nations);
		this.jcb2 = new JComboBox(v);
		//定义一个列表框的边框显示条
		jcb1.setBorder(BorderFactory.createTitledBorder("哪个国家？"));
		jcb2.setBorder(BorderFactory.createTitledBorder("Vector?"));
		jcb1.setMaximumRowCount(3);				//最多显示3个选项
		jcb2.setMaximumRowCount(3);
		cont.add(this.jcb1);
		cont.add(this.jcb2);
		cont.add(new JLabel("下拉列表框"));
		this.frame.setSize(330,200);
		this.frame.setVisible(true);
		this.frame.addWindowListener(new WindowAdapter(){	//加入事件监听
			public void windowClosing(WindowEvent arg0) {			//窗口关闭时触发，按下关闭按钮
			// TODO 自动生成的方法存根
			System.out.println("windowClosing-->窗口关闭");
			System.exit(1);
			}
		});
	}
}


//主类
//Function        : 	MyComboBox_demo
public class MyComboBox_demo {

	public static void main(String[] args) {
		// TODO 自动生成的方法存根
		new MyComboBox();
	}

}

import java.awt.Container;
import java.awt.GridLayout;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.util.Vector;

import javax.swing.AbstractListModel;
import javax.swing.BorderFactory;
import javax.swing.ComboBoxModel;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;

//=================================================
// File Name       :	MyComboBox_demo
//------------------------------------------------------------------------------
// Author          :	Common


//类名：MyComboBox
//属性：
//方法：
class MyComboBoxModel extends AbstractListModel implements ComboBoxModel{
	
	String nations[] = {"中国","美国","韩国","法国","英国"};
	String item = null;
	
	@Override
	public int getSize() {
		// TODO 自动生成的方法存根
		return this.nations.length;
	}

	@Override
	public Object getElementAt(int index) {
		// TODO 自动生成的方法存根
		return this.nations[index];
	}

	@Override
	public void setSelectedItem(Object anItem) {
		// TODO 自动生成的方法存根
		this.item = (String) anItem;
	}

	@Override
	public Object getSelectedItem() {
		// TODO 自动生成的方法存根
		return this.item;
	}
	
}



//类名：MyComboBox
//属性：
//方法：
class MyComboBox{
	private JFrame frame = new JFrame("窗体");					//定义窗体
	private Container cont = frame.getContentPane();			//得到窗体容器
	private JComboBox jcb1  = null;											//定义下拉列表框
	private JComboBox jcb2  = null;											//定义下拉列表框
	public MyComboBox(){
		this.frame.setLayout(new GridLayout(2,2));
//		String nations[] = {"中国","美国","韩国","法国","英国"};
//		Vector<String> v = new Vector<String>();						//定义一个Vector集合
//		v.add("元素1");
//		v.add("元素2");
//		v.add("元素3");
//		this.jcb1 = new JComboBox(nations);
//		this.jcb2 = new JComboBox(v);
		this.jcb1 = new JComboBox(new MyComboBoxModel());		//实例化JComboBox
		//定义一个列表框的边框显示条
		jcb1.setBorder(BorderFactory.createTitledBorder("哪个国家？"));
//		jcb2.setBorder(BorderFactory.createTitledBorder("Vector?"));
		jcb1.setMaximumRowCount(3);				//最多显示3个选项
//		jcb2.setMaximumRowCount(3);
		cont.add(this.jcb1);
//		cont.add(this.jcb2);
		cont.add(new JLabel("下拉列表框"));
		this.frame.setSize(330,200);
		this.frame.setVisible(true);
		this.frame.addWindowListener(new WindowAdapter(){	//加入事件监听
			public void windowClosing(WindowEvent arg0) {			//窗口关闭时触发，按下关闭按钮
			// TODO 自动生成的方法存根
			System.out.println("windowClosing-->窗口关闭");
			System.exit(1);
			}
		});
	}
}


//主类
//Function        : 	MyComboBox_demo
public class MyComboBox_demo {

	public static void main(String[] args) {
		// TODO 自动生成的方法存根
		new MyComboBox();
	}

}

import java.awt.Container;
import java.awt.Font;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.util.Vector;

import javax.swing.AbstractListModel;
import javax.swing.Action;
import javax.swing.BorderFactory;
import javax.swing.ComboBoxModel;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;

//=================================================
// File Name       :	MyComboBox_demo
//------------------------------------------------------------------------------
// Author          :	Common



//类名：MyComboBox
//属性：
//方法：

class MyComboBox implements ItemListener,ActionListener{
	private JFrame frame = new JFrame("窗体");					//定义窗体
	private Container cont = frame.getContentPane();			//得到窗体容器
	private JComboBox jcb1  = null;											//定义下拉列表框
	private JLabel label  = new JLabel("标签");							//定义标签
	private String fontSize[] = {"10","11","12"};
	
	public MyComboBox(){
		this.frame.setLayout(new GridLayout(2,2));

		this.jcb1 = new JComboBox(this.fontSize);		//实例化JComboBox
		//定义一个列表框的边框显示条
		jcb1.setBorder(BorderFactory.createTitledBorder("请选择显示文字大小"));

		jcb1.addItemListener(this); 					//加入选项监听
		jcb1.addActionListener(this); 				//加入动作监听
		
		jcb1.setMaximumRowCount(3);				//最多显示3个选项
		jcb1.setEditable(true);								//设置可编辑文本
		jcb1.configureEditor(jcb1.getEditor(), "12"); 		//定义默认值
		this.changeFontSize(12);     					//设置默认字体

		cont.add(this.jcb1);
		cont.add(label);

		cont.add(new JLabel("下拉列表框"));
		this.frame.setSize(330,200);
		this.frame.setVisible(true);
		this.frame.addWindowListener(new WindowAdapter(){	//加入事件监听
			public void windowClosing(WindowEvent arg0) {			//窗口关闭时触发，按下关闭按钮
			// TODO 自动生成的方法存根
			System.out.println("windowClosing-->窗口关闭");
			System.exit(1);
			}
		});
	}
	@Override
	public void actionPerformed(ActionEvent e) {		//输入信息时触发
		// TODO 自动生成的方法存根
		String itemSize = (String) this.jcb1.getSelectedItem();	//得到选项
		int Size = 12;
		try{
			Size = Integer.parseInt(itemSize);		//字符串转整数
		}catch(Exception ex){
			this.jcb1.getEditor().setItem("输入的不是数字");
		}
		this.changeFontSize(Size);
		if(!this.isExists(itemSize)){
			this.jcb1.addItem(jcb1.getSelectedItem()); 		//不存在，加入下拉选项
		}
	}
	@Override
	public void itemStateChanged(ItemEvent e) {
		// TODO 自动生成的方法存根
		
	}
	
	public void changeFontSize(int size){			//改变文字大小
		Font font = new Font("Serief",Font.BOLD,size);		//定义Font对象
		this.label.setFont(font);													//设置文字大小
	}
	
	public boolean isExists(String item){
		boolean flag = false;
		for(int i =0;i<this.jcb1.getItemCount();i++){
			if(item.equals(this.jcb1.getItemAt(i))){
				flag = true;
			}
		}
		return flag;
	}
	
}



//主类
//Function        : 	MyComboBox_demo
public class MyComboBox_demo {

	public static void main(String[] args) {
		// TODO 自动生成的方法存根
		new MyComboBox();
	}

}