文件对话框

应用程序利用文件对话框确定数据文件。程序首先弹出一个界面，有两个按钮：打开文件和保存文件。当点击打开文件按钮时，程序弹出一个打开文件对话框，当点击保存文件时，弹出保存文件对话框。程序还继承 FileFilter 类，定义了 MyFileFilter 类，程序利用这个类设置文件对话框的筛选条件

package ggg.demo;
import java.awt.*;
import javax.swing.*;
import java.io.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.filechooser.*;
import javax.swing.filechooser.FileFilter;
public class TT{
    public static void main(String args[]){
        FrameFiledialog f = new FrameFiledialog();
    }
}
class FrameFiledialog extends JFrame implements ActionListener{
    JFileChooser filedialog = null;
    JLabel lable = new JLabel(" " ,JLabel.CENTER);
    JButton b1,b2;JTextArea text;
    FrameFiledialog(){
        super("带文件对话框的窗口");
        Container con = this.getContentPane();
        con.setLayout(new BorderLayout());
        con.setSize(40,50);
        JPanel p = new JPanel();
        b1 = new JButton("打开文件");
        b2 = new JButton("保存文件");
        b1.addActionListener(this);
        b2.addActionListener(this);
        p.add(b1);
        p.add(b2);
        text = new JTextArea(20,30); JScrollPane jsp = new JScrollPane(text); filedialog = new JFileChooser("D:\\workspace"); filedialog.setControlButtonsAreShown(true);
        filedialog.addChoosableFileFilter(new MyFileFilter("txt"));
        filedialog.addChoosableFileFilter(new MyFileFilter("java"));
        text.setBackground(Color.cyan);
        con.add(jsp,BorderLayout.CENTER);
        con.add(lable,BorderLayout.NORTH);
        con.add(p,BorderLayout.SOUTH);
        this.setVisible(true);
        this.pack();
    }
    public void actionPerformed(ActionEvent e){
        File file = null;
        int result;
        if(e.getSource()==b1){//打开文件
            filedialog.setDialogTitle("打开文件");
            result = filedialog.showOpenDialog(this);
            text.setText("");
            if(result ==JFileChooser.APPROVE_OPTION){
                file = filedialog.getSelectedFile();

                lable.setText("你选择打开的文件名称是：" + file.getName()); }
            else if (result ==JFileChooser.CANCEL_OPTION){
                lable.setText("你没有选择任何文件");
            }
            FileInputStream fileStream = null;
            if(file != null){
                try{
                    fileStream = new FileInputStream(file);
                }catch(FileNotFoundException nfe){
                    lable.setText("文件没有找到");
                    return;
                }
                int readByte;
                try{
                    while((readByte = fileStream.read())!=-1)
                        text.append(String.valueOf((char)readByte));
                    fileStream.close();
                }catch(IOException ie){lable.setText("读取文件出错");}
            }
        }else if (e.getSource()==b2){//保存文件
            filedialog.setDialogTitle("保存文件");
            result = filedialog.showSaveDialog(this);
            file = null;
            String fileName;
            if(result ==JFileChooser.APPROVE_OPTION){
                file = filedialog.getSelectedFile();
                lable.setText("你选择保存的文件名称是：" + file.getName()); }else if(result ==JFileChooser.CANCEL_OPTION){
                lable.setText("你没有选择任何文件");
            }
            FileOutputStream fileStream = null;
            if(file !=null){
                try{fileStream = new FileOutputStream(file);
                }catch(FileNotFoundException nfe){
                    lable.setText("文件没有发现");return;
                }
                String content = text.getText();
                try{
                    fileStream.write(content.getBytes());
                    fileStream.close();
                }catch(IOException ie){lable.setText("写文件出错");}
            }
        }
    }
}
class MyFileFilter extends FileFilter{
    String ext;
    MyFileFilter(String t){ext =t;}
    public boolean accept(File file){
        if(file.isDirectory()) return true;
        String fn = file.getName();
        int index = fn.lastIndexOf('.');
        if(index >0&& index