Java小程序------虚拟代理_wxjava 挂代理-优快云博客

本文链接：https://blog.youkuaiyun.com/haoyuewuwei/article/details/4477793

本文介绍了一个使用Java实现的CD封面加载器程序。该程序通过ImageProxy类实现了封面图片的懒加载，能够在图片未完全下载之前显示占位文字，并在下载完成后自动更新显示。程序包括了ImageProxy、ImageComponent及ImageProxyTestDrive三个主要类。

Icon.java

import java.awt.Component; import java.awt.Graphics; public interface Icon { public int getIconHeight(); public void paintIcon(final Component c, Graphics g, int x, int y); public int getIconWidth(); }

ImageProxy.java

import java.net.*; import java.awt.*; import java.awt.event.*; import javax.swing.*; class ImageProxy implements Icon { ImageIcon imageIcon; URL imageURL; Thread retrievalThread; boolean retrieving = false; public ImageProxy(URL url) { imageURL = url; } public int getIconWidth() { if (imageIcon != null) { return imageIcon.getIconWidth(); } else { return 800; } } public int getIconHeight() { if (imageIcon != null) { return imageIcon.getIconHeight(); } else { return 600; } } public void paintIcon(final Component c, Graphics g, int x, int y) { if (imageIcon != null) { imageIcon.paintIcon(c, g, x, y); } else { g.drawString("Loading CD cover, please wait...", x+300, y+190); if (!retrieving) { retrieving = true; retrievalThread = new Thread(new Runnable() { public void run() { try { imageIcon = new ImageIcon(imageURL, "CD Cover"); c.repaint(); } catch (Exception e) { e.printStackTrace(); } } }); retrievalThread.start(); } } } }

ImageComponent.java

import java.awt.*; import javax.swing.*; class ImageComponent extends JComponent { private Icon icon; public ImageComponent(Icon icon) { this.icon = icon; } public void setIcon(Icon icon) { this.icon = icon; } public void paintComponent(Graphics g) { super.paintComponent(g); int w = icon.getIconWidth(); int h = icon.getIconHeight(); int x = (800 - w)/2; int y = (600 - h)/2; icon.paintIcon(this, g, x, y); } }

ImageProxyTestDrive.java

import java.net.*; import java.awt.*; import java.awt.event.*; import javax.swing.*; import java.util.*; public class ImageProxyTestDrive { ImageComponent imageComponent; JFrame frame = new JFrame("CD Cover Viewer"); JMenuBar menuBar; JMenu menu; Hashtable cds = new Hashtable(); public static void main (String[] args) throws Exception { ImageProxyTestDrive testDrive = new ImageProxyTestDrive(); } public ImageProxyTestDrive() throws Exception{ cds.put("Ambient: Music for Airports","http://images.amazon.com/images/P/B000003S2K.01.LZZZZZZZ.jpg"); cds.put("Buddha Bar","http://images.amazon.com/images/P/B00009XBYK.01.LZZZZZZZ.jpg"); cds.put("Ima","http://images.amazon.com/images/P/B000005IRM.01.LZZZZZZZ.jpg"); cds.put("Karma","http://images.amazon.com/images/P/B000005DCB.01.LZZZZZZZ.gif"); cds.put("MCMXC A.D.","http://images.amazon.com/images/P/B000002URV.01.LZZZZZZZ.jpg"); cds.put("Northern Exposure","http://images.amazon.com/images/P/B000003SFN.01.LZZZZZZZ.jpg"); cds.put("Selected Ambient Works, Vol. 2","http://images.amazon.com/images/P/B000002MNZ.01.LZZZZZZZ.jpg"); cds.put("MyPicture", "http://www.doutie.com/d/2007-10/2007101721580179081.jpg"); URL initialURL = new URL((String)cds.get("Selected Ambient Works, Vol. 2")); menuBar = new JMenuBar(); menu = new JMenu("Favorite CDs"); menuBar.add(menu); frame.setJMenuBar(menuBar); for(Enumeration e = cds.keys(); e.hasMoreElements();) { String name = (String)e.nextElement(); JMenuItem menuItem = new JMenuItem(name); menu.add(menuItem); menuItem.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent event) { imageComponent.setIcon(new ImageProxy(getCDUrl(event.getActionCommand()))); frame.repaint(); } }); } // set up frame and menus Icon icon = new ImageProxy(initialURL); imageComponent = new ImageComponent(icon); frame.getContentPane().add(imageComponent); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setSize(800,600); frame.setVisible(true); } URL getCDUrl(String name) { try { return new URL((String)cds.get(name)); } catch (MalformedURLException e) { e.printStackTrace(); return null; } } }