25---AWT和Swing(10)下拉列表(视频代码)

 

代码一：
 import javax.swing.JFrame ;
 import java.awt.Container ;
 import java.awt.event.WindowEvent ;
 import java.awt.event.WindowAdapter ;
 import java.awt.GridLayout ;
 import javax.swing.JComboBox ;
 import javax.swing.JLabel ;
 import javax.swing.BorderFactory ;
 import java.util.Vector ;
 class MyComboBox{
  private JFrame frame = new JFrame("Welcome TO MLDN") ;
  private Container cont = frame.getContentPane() ; // 得到容器
  private JComboBox jcb1 = null ;
  private JComboBox jcb2 = null ;
  public MyComboBox(){
   this.frame.setLayout(new GridLayout(2,2)) ; // 定义排版
   String nations[] = {"中国","巴西","美国","韩国","意大利","法国"} ;
   Vector<String> v = new Vector<String>() ;
   v.add("MLDN") ; // 增加内容
   v.add("MLDNJAVA") ; // 增加内容
   v.add("智囊团") ; // 增加内容
   this.jcb1 = new JComboBox(nations) ; // 实例化下拉列表框
   this.jcb2 = new JComboBox(v) ; // 实例化下拉列表框

   // 为每一个下拉框增加一个边框
   this.jcb1.setBorder(BorderFactory.createTitledBorder("你喜欢去那个国家旅游？")) ;
   this.jcb2.setBorder(BorderFactory.createTitledBorder("你喜欢的网站？")) ;
   cont.add(this.jcb1) ;
   cont.add(this.jcb2) ;
   cont.add(new JLabel("下拉列表框")) ;
   this.frame.setSize(300,150) ;
   this.frame.setVisible(true) ;
   this.frame.addWindowListener(new WindowAdapter(){
    public void windowClosing(WindowEvent e){
     System.exit(1) ;
    }
   }) ;
  }
 }

 public class JComboBoxDemo01{
  public static void main(String args[]){
   new MyComboBox() ;
  }
 }

代码二：
 import javax.swing.JFrame ;
 import java.awt.Container ;
 import java.awt.event.WindowEvent ;
 import java.awt.event.WindowAdapter ;
 import java.awt.GridLayout ;
 import javax.swing.JComboBox ;
 import javax.swing.JLabel ;
 import javax.swing.JLabel ;
 import javax.swing.AbstractListModel ;
 import javax.swing.BorderFactory ;
 import javax.swing.ComboBoxEditor ;
 import javax.swing.ComboBoxModel ;
 import java.util.Vector ;

 class MyComboBoxModel extends AbstractListModel implements ComboBoxModel{
  private String nations[] = {"中国","巴西","美国","韩国","意大利","法国"} ;
  private String item = null ;
  public Object getSelectedItem(){ // 得到选择的选项
   return this.item ;
  }
  public void setSelectedItem(Object anItem){ // 设置选项
   this.item = (String)anItem ;
  }
  public int getSize(){
   return this.nations.length ;
  }
  public Object getElementAt(int ind){
   return this.nations[ind] ;
  }
 }

 class MyComboBox{
  private String defaultMsg = "请选择或输入国家的名称。" ;
  private JFrame frame = new JFrame("Welcome TO MLDN") ;
  private Container cont = frame.getContentPane() ; // 得到容器
  private JComboBox jcb1 = null ;
  private JComboBox jcb2 = null ;
  public MyComboBox(){
   this.frame.setLayout(new GridLayout(2,1)) ; // 定义排版
   
   this.jcb1 = new JComboBox(new MyComboBoxModel()) ; // 实例化下拉列表框
   this.jcb1.setEditable(true) ; // 表示可以编辑

   // 为每一个下拉框增加一个边框
   this.jcb1.setBorder(BorderFactory.createTitledBorder("你喜欢去那个国家旅游？")) ;
   ComboBoxEditor editor = null ;
   editor = this.jcb1.getEditor() ; /// 得到编辑对象
   this.jcb1.configureEditor(editor,defaultMsg) ;// 指定默认值
   this.jcb1.setMaximumRowCount(3) ;
   cont.add(this.jcb1) ;
   cont.add(new JLabel("下拉列表框")) ;
   this.frame.setSize(180,150) ;
   this.frame.setVisible(true) ;
   this.frame.addWindowListener(new WindowAdapter(){
    public void windowClosing(WindowEvent e){
     System.exit(1) ;
    }
   }) ;
  }
 }

 public class JComboBoxDemo02{
  public static void main(String args[]){
   new MyComboBox() ;
  }
 }

代码三：
 import javax.swing.JFrame ;
 import java.awt.Container ;
 import java.awt.Font ;
 import java.awt.event.WindowEvent ;
 import java.awt.event.ActionListener ;
 import java.awt.event.ItemListener ;
 import java.awt.event.ItemEvent ;
 import java.awt.event.ActionEvent ;
 import java.awt.event.WindowAdapter ;
 import java.awt.GridLayout ;
 import javax.swing.JComboBox ;
 import javax.swing.JLabel ;
 import javax.swing.ComboBoxEditor ;
 import javax.swing.BorderFactory ;
 import java.util.Vector ;
 class MyComboBox implements ItemListener,ActionListener{
  private JFrame frame = new JFrame("Welcome TO MLDN") ;
  private Container cont = frame.getContentPane() ; // 得到容器
  private JComboBox jcb1 = null ;
  private JLabel label = new JLabel("www.MLDNJAVA.cn") ; // 定义标签
  private String fontSize[] = {"10","12","14","16","18","20","22","24","26","48","72"} ;
  public MyComboBox(){
   this.frame.setLayout(new GridLayout(2,2)) ; // 定义排版
   this.jcb1 = new JComboBox(fontSize) ; // 实例化下拉列表框

   this.jcb1.addItemListener(this) ;
   this.jcb1.addActionListener(this) ;

   this.jcb1.setEditable(true) ; // 表示可以编辑

   // 为每一个下拉框增加一个边框
   this.jcb1.setBorder(BorderFactory.createTitledBorder("你喜欢去那个国家旅游？")) ;
   ComboBoxEditor editor = null ;
   editor = this.jcb1.getEditor() ; /// 得到编辑对象
   this.jcb1.configureEditor(editor,"12") ;// 指定默认值
   this.jcb1.setMaximumRowCount(3) ;

   this.changeFontSize(12) ; // 默认值
   cont.add(this.jcb1) ;

   cont.add(label) ;
   this.frame.setSize(300,150) ;
   this.frame.setVisible(true) ;
   this.frame.addWindowListener(new WindowAdapter(){
    public void windowClosing(WindowEvent e){
     System.exit(1) ;
    }
   }) ;
  }
  public void itemStateChanged(ItemEvent e){
   if(e.getStateChange()==ItemEvent.SELECTED){ // 判断是否是选中
    String itemSize = (String)e.getItem() ;
    try{
     this.changeFontSize(Integer.parseInt(itemSize)) ;
    }catch(Exception e1){
     
    }
   }
  }

  public void actionPerformed(ActionEvent e){
   String item = (String)this.jcb1.getSelectedItem() ;
   int size = 12 ; // 设置一个默认大小
   try{
    size = Integer.parseInt(item) ;
   }catch(Exception e1){}
   this.changeFontSize(size) ;
   // 判断给定的size是否存在，如果不存在则需要将新的内容设置上去
   if(!this.isExists(item))
   {
    this.jcb1.addItem(jcb1.getSelectedItem()) ;
   }
  }
  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 ;
  }
  public void changeFontSize(int size){
   System.out.println("*************" + size) ;
   Font fnt = new Font("Serief",Font.BOLD,size) ;
   this.label.setFont(fnt) ;
  }

 }

 public class JComboBoxDemo03{
  public static void main(String args[]){
   new MyComboBox() ;
  }
 }