java引出Android NinePatch技术的意义

java与Android本署一个平台。大部分技术可以移植。在java标准平台中引入Android NinePatch技术可以使其UI设计大大得到改善：

图片准备：

Android NinePatch技术介绍：http://developer.android.com/tools/help/draw9patch.html

附NinePatch jar包下载：http://download.csdn.net/detail/gaowen_han/5204821

应用NinePatch技术代码：

package com.han;import java.awt.Graphics;import java.awt.Graphics2D;import java.awt.Rectangle;import java.io.IOException;import java.io.InputStream;import javax.swing.BorderFactory;import javax.swing.JButton;import javax.swing.JFrame;import javax.swing.JPanel;import javax.swing.SwingUtilities;import com.android.ninepatch.NinePatch;@SuppressWarnings("serial")public class NinePatchTest extends JPanel {	NinePatch ninePatch;	/**	 * This constructor which serves as a content pane uses a default flow	 * layout and a double-buffering strategy.	 */	public NinePatchTest() {		ninePatch = loadNinePatch("/images/content_bg1.9.png");		add(new JButton("Button 1"));		add(new JButton("Button 2"));		add(new JButton("Button 3"));		add(new JButton("Button 4"));	}	/**	 * @param path	 *            - the image path.	 * @return an NinePatch object, or [email protected] null} if the given path is not	 *         valid or an error occurs during loading.	 */	private NinePatch loadNinePatch(String path) {		InputStream stream = this.getClass().getResourceAsStream(path);		if (stream != null) {			try {				return NinePatch.load(stream, true, false);			} catch (IOException e) {				System.err.println("An error occurs during loading.");				e.printStackTrace();				return null;			}		} else {			System.err.println("Couldn't find the file: " + path);			return null;		}	}	/**	 * To improve the repaint speed, the code block contained in	 * paintComponent() must be able to be executed quickly. For example, we	 * usually put the load image code out of the paintComponent() for rapid UI	 * update.	 * 	 * @see javax.swing.JComponent#paintComponent(java.awt.Graphics)	 */	@Override	protected void paintComponent(Graphics g) {		Graphics2D g2 = (Graphics2D) g;		Rectangle clip = g2.getClipBounds();		ninePatch.draw(g2, clip.x, clip.y, clip.width, clip.height);	}	private static void createAndShowGUI() {		// Create and set up the window.		JFrame frame = new JFrame("NinePatch test");		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);		// Set up the content pane.		JPanel contentPane = new NinePatchTest();		contentPane.setOpaque(true); // content pane must be opaque		contentPane.setBorder(BorderFactory.createEmptyBorder(20, 20, 20, 20));		frame.setContentPane(contentPane);		// Display the window.		frame.pack();		frame.setVisible(true);	}	public static void main(String[] args) {		// Schedule a job for the EDT:		// Creating and showing this application's GUI.		SwingUtilities.invokeLater(new Runnable() {			@Override			public void run() {				createAndShowGUI();			}		});	}}

利用后2幅图（格式.9.png）得到如下效果：

如果使用传统的双线性插值进行图像缩放，我们来对比下效果：

双线性插值应用代码：

package com.han;import java.awt.Graphics;import java.awt.Graphics2D;import java.awt.Rectangle;import java.awt.RenderingHints;import java.awt.image.BufferedImage;import java.io.IOException;import java.io.InputStream;import javax.imageio.ImageIO;import javax.swing.BorderFactory;import javax.swing.JButton;import javax.swing.JFrame;import javax.swing.JPanel;import javax.swing.SwingUtilities;@SuppressWarnings("serial")public class NinePatchTestForCompare extends JPanel {	BufferedImage image;	/**	 * This constructor uses a default flow layout and a double-buffering	 * strategy.	 */	public NinePatchTestForCompare() {		image = loadImage("/images/content_bg2.png");		add(new JButton("Button 1"));		add(new JButton("Button 2"));		add(new JButton("Button 3"));		add(new JButton("Button 4"));	}	/**	 * @param path	 *            - the image path.	 * @return an BufferedImage object, or [email protected] null} if the given path is not	 *         valid or an error occurs during loading.	 */	private BufferedImage loadImage(String path) {		InputStream stream = this.getClass().getResourceAsStream(path);		if (stream != null) {			try {				return ImageIO.read(stream);			} catch (IOException e) {				System.err.println("An error occurs during loading.");				e.printStackTrace();				return null;			}		} else {			System.err.println("Couldn't find the file: " + path);			return null;		}	}	@Override	protected void paintComponent(Graphics g) {		Graphics2D g2 = (Graphics2D) g;		Rectangle clip = g2.getClipBounds();		g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION,				RenderingHints.VALUE_INTERPOLATION_BILINEAR);		g2.drawImage(image, clip.x, clip.y, clip.width, clip.height, null);	}	private static void createAndShowGUI() {		// Create and set up the window.		JFrame frame = new JFrame("NinePatchTestForCompare");		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);		// Set up the content pane.		JPanel contentPane = new NinePatchTestForCompare();		contentPane.setOpaque(true); // content pane must be opaque		contentPane.setBorder(BorderFactory.createEmptyBorder(20, 20, 20, 20));		frame.setContentPane(contentPane);		// Display the window.		frame.pack();		frame.setVisible(true);	}	public static void main(String[] args) {		// Schedule a job for the EDT:		// Creating and showing this application's GUI.		SwingUtilities.invokeLater(new Runnable() {			@Override			public void run() {				createAndShowGUI();			}		});	}}

不用我多说，就可以看出NinePatch技术的优势了。