Java Swing进度条显示问题 - Java / Java SE

进度条出来了，但是不显示进度，以下是完整代码：
Java code:

package ui;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Container;
import java.awt.Dimension;
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.IOException;
import java.io.InputStreamReader;

import javax.swing.JButton;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.ProgressMonitorInputStream;
import javax.swing.SwingConstants;

public class DataImporter extends JFrame implements ActionListener {

private static final long serialVersionUID = 1L;

JPanel p = new JPanel();

JButton btn = new JButton("选择文件");

JLabel status = new JLabel("", SwingConstants.CENTER);

public DataImporter() {
super("数据导入器");
setBounds(350, 250, 300, 150);
setMinimumSize(new Dimension(300, 150));
setAlwaysOnTop(true);

Container c = getContentPane();

btn.setToolTipText("请选择要导入的数据文件");
btn.setPreferredSize(new Dimension(100, 30));
btn.setFocusPainted(false);

p.add(btn);

status.setForegroun