Java JFrame简单程序（SimpleJFrame.java）

package com.learn.JFrame;

import java.awt.TextArea;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;

import javax.swing.Icon;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextField;

public class SimpleJFrame extends JFrame implements ActionListener {

/**
*
*/
private static final long serialVersionUID = 1L;

JButton button;
JButton Select;
JButton btnOK;

JTextField textfield;
JPanel p;
JFileChooser fc = new JFileChooser();
TextArea area;

public SimpleJFrame() {
p = new JPanel(); // 建立一个面板
this.getContentPane().add(p);// 把面板添加到框架
p.add(new JButton("文本"));// 把一个文本按钮添加到面板
textfield = new JTextField(10);
p.add(textfield); // 把一个文本框添加到面板
Select = new JButton("浏览");
p.add(Select); // 把一个浏览按钮添加到面板
Select.addActionListener(this);
btnOK = new JButton("确定");
p.add(btnOK);// 把一个确定按钮添加到面板
btnOK.addActionListener(this);
}

public static void main(String[] args) {
SimpleJFrame frame = new SimpleJFrame();
frame.setSize(400, 400);
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}

@Override
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
// 当按下选择按钮，打开一个文件选择，文本框显示文件路径
if (e.getSource() == Select) {
int intRetVal = fc.showOpenDialog(this);
if (intRetVal == JFileChooser.APPROVE_OPTION) {
textfield.setText(fc.getSelectedFile().getPath());
}
} else if (e.getSource() == btnOK) { // 当按下确定按钮，生成一个新框架，框架里面有一个文本域，显示打开文件的内容
JFrame f = new JFrame();
f.setSize(400, 400);
f.setLocationRelativeTo(null);
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
String extensionName = getExtensionName(textfield.getText());
if ("txt".equals(extensionName)) {
f.setTitle("显示文本");
area = new TextArea();
// 获取文本值
String text = readTxt(textfield.getText());
area.setText(text);
f.add(area);
f.setVisible(true);
} else if ("jpg".equals(extensionName) || "png".equals(extensionName) || "gif".equals(extensionName)) {
f.setTitle("显示图片");
Icon img = new ImageIcon(textfield.getText());
JLabel label = new JLabel(img);
// 添加滚动条
JScrollPane jsp = new JScrollPane(label);
f.add(jsp);
f.setVisible(true);
} else {
JOptionPane.showMessageDialog(null, "请选择txt/jpg/png/gif格式的文件！");
}
}
}

private String getExtensionName(String filename) {
if ((filename != null) && (filename.length() > 0)) {
int dot = filename.lastIndexOf('.');
if ((dot > -1) && (dot < (filename.length() - 1))) {
return filename.substring(dot + 1);
}
}
return filename;
}

private String readTxt(String path) {
if (path == null || "".equals(path)) {
return "";
}
StringBuffer sb = new StringBuffer();
File file = new File(path);
InputStreamReader read = null;
BufferedReader reader = null;
try {
read = new InputStreamReader(new FileInputStream(file), "gb2312");
reader = new BufferedReader(read);
String line;
while ((line = reader.readLine()) != null) {
sb.append(line);
sb.append("\n");
}
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (read != null) {
try {
read.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if (reader != null) {
try {
reader.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

}
return sb.toString();
}
}