21.文件打开、关闭对话框

效果：

 

点击“打开文件...”：

选择一个文件打开：

点“取消”：

点击“保存文件...”：

 选择一个文件保存：

选择“取消”：

package com.lvshitech.gui;

import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.File;

import javax.swing.JButton;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;

public class JFileChooserDemo extends JFrame {
	public JFileChooserDemo() {
		super("使用JFileChooser");
		
		// 操作结果展示文本框
		final JTextArea ta = new JTextArea(5, 20);
		ta.setMargin(new Insets(5, 5, 5, 5));
		ta.setEditable(false);
		JScrollPane sp = new JScrollPane(ta);	// 带滚动条
		
		final JFileChooser fc = new JFileChooser();	// 文件选择器
		
		// 打开按钮
		JButton openButton = new JButton("打开文件...");
		openButton.addActionListener(new ActionListener() {
			@Override
			public void actionPerformed(ActionEvent e) {
				int returnVal = fc.showOpenDialog(JFileChooserDemo.this);
				if (returnVal == JFileChooser.APPROVE_OPTION) {		// JFileChooser.APPROVE_OPTION = 0
					File file = fc.getSelectedFile();
					ta.append("打开：" + file.getName() + "\n");
				} else {
					ta.append("取消打开命令。\n");
				}
			}
		});
		
		// 保存按钮
		JButton saveButton = new JButton("保存文件...");
		saveButton.addActionListener(new ActionListener() {
			@Override 
			public void actionPerformed(ActionEvent e) {
				int returnVal = fc.showSaveDialog(JFileChooserDemo.this);
				if (returnVal == JFileChooser.APPROVE_OPTION) {
					File file = fc.getSelectedFile();
					ta.append("保存：" + file.getName() + "\n");
				} else {
					ta.append("取消保存命令。\n");
				}
			}
		});
		
		// 按钮标签
		JPanel buttonPanel = new JPanel();
		buttonPanel.add(openButton);
		buttonPanel.add(saveButton);
		
		// 点击Tab键的时候在这两个按钮之间切换选中
		openButton.setNextFocusableComponent(saveButton);
		saveButton.setNextFocusableComponent(openButton);
		
		// 添加到容器
		Container container = getContentPane();
		container.add(buttonPanel, BorderLayout.NORTH);
		container.add(sp, BorderLayout.CENTER);
	}
	public static void main(String[] args) {
		JFrame frame = new JFileChooserDemo();
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.pack();
		frame.setVisible(true);
	}
}