ch9_22.java

60多个javaSwing范例

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class ch9_22 extends JFrame implements ItemListener,ActionListener
{
    String [] fontsize={"12","14","16","18","20","22","24","26","28"};
    String defaultMessage="请选择或直接输入文字大小";
    Font font=null;
    JComboBox jcb=null;
    JLabel label=null;
    public ch9_22()
    {
        super("测试下拉列表框");
        setBounds(20,20,600,400);
        getContentPane().setLayout(null);        
    }
    public static void main(String [] args)
    {
        ch9_22 f=new ch9_22();
        
        f.font=new Font("SansSerif",Font.PLAIN,12);
        
        f.label=new JLabel("中国人民");
        f.label.setBounds(300,20,80,50);
        f.label.setFont(f.font);
        

       
        JComboBox jcb=new JComboBox(f.fontsize);
        jcb.setBorder(BorderFactory.createTitledBorder("列表"));
        jcb.setBounds(20,20,180,50);
        jcb.setEditable(true);
        ComboBoxEditor editor=jcb.getEditor();
        jcb.configureEditor(editor,f.defaultMessage);
        jcb.addItemListener(f);
        jcb.addActionListener(f);
        
        
        f.getContentPane().add(jcb);
        f.getContentPane().add(f.label);
        
        f.show();
    }
    public void actionPerformed(ActionEvent e)
    {
        boolean isaddItem=true;
        int fontsize=0;
        String tmp=(String)jcb.getSelectedItem();
        try
        {
            fontsize=Integer.parseInt(tmp);
            for(int i=0;i<jcb.getItemCount();i++)
            {
                if(jcb.getItemAt(i).equals(tmp))
                {
                    isaddItem=false;
                    break;
                }
            }
            if(isaddItem)
            {
                jcb.insertItemAt(tmp,0);
            }
            font=new Font("SansSerif",Font.PLAIN,fontsize);
            label.setFont(font);
        }
        catch(NumberFormatException ne)
        {
            jcb.getEditor().setItem("你输入的为非整数，请从新输入");
        }
    }
    public void itemStateChanged(ItemEvent e)
    {
        if(e.getStateChange()==ItemEvent.SELECTED)
        {
            int fontsize=0;
            try
            {
                fontsize=Integer.parseInt((String)e.getItem());
                label.setText("目前字形大小:"+fontsize);
            }catch(NumberFormatException ne)
            {
            }
        }
    }
}