android ---- ImageUtil工具类

package com.itcast.util;

import java.io.BufferedInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.net.URL;
import java.net.URLConnection;
import java.security.MessageDigest;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Environment;
import android.os.Handler;
import android.os.Message;
import android.util.Log;

public class ImageUtil {
	private static final String SDCARD_CACHE_IMG_PATH = Environment
			.getExternalStorageDirectory().getPath() + "/llc/images/";

	/**
	 * 保存图片到SD卡
	 * @param imagePath
	 * @param buffer
	 * @throws IOException
	 */
	public static void saveImage(String imagePath, byte[] buffer)
			throws IOException {
		File f = new File(imagePath);
		if (f.exists()) {
			return;
		} else {
			File parentFile = f.getParentFile();
			if (!parentFile.exists()) {
				parentFile.mkdirs();
			}
			f.createNewFile();
			FileOutputStream fos = new FileOutputStream(imagePath);
			fos.write(buffer);
			fos.flush();
			fos.close();
		}
	}
	
	/**
	 * 从SD卡加载图片
	 * @param imagePath
	 * @return
	 */
	public static Bitmap getImageFromLocal(String imagePath){
		File file = new File(imagePath);
		if(file.exists()){
			Bitmap bitmap = BitmapFactory.decodeFile(imagePath);
			file.setLastModified(System.currentTimeMillis());
			return bitmap;
		}
			return null;
	}
	
	/**
	 * Bitmap转换到Byte[]
	 * @param bm
	 * @return
	 */
	public static byte[] bitmap2Bytes(Bitmap bm){   
	    ByteArrayOutputStream bas = new ByteArrayOutputStream();     
	    bm.compress(Bitmap.CompressFormat.JPEG, 100, bas);     
	    return bas.toByteArray();   
	   }  
	
	/**
	 * 从本地或者服务端加载图片
	 * @return
	 * @throws IOException 
	 */
	public static Bitmap loadImage(final String imagePath,final String imgUrl,final ImageCallback callback) {
		Bitmap bitmap = getImageFromLocal(imagePath);
		if(bitmap != null){
			return bitmap;
		}else{//从网上加载
			final Handler handler = new Handler(){
				@Override
				public void handleMessage(Message msg) {
					if(msg.obj!=null){
						Bitmap bitmap = (Bitmap) msg.obj;
						callback.loadImage(bitmap, imagePath);
					}
				}
			};
			
			Runnable runnable = new Runnable() {
				@Override
				public void run() {
					try {
						URL url = new URL(imgUrl);
						Log.e("图片加载", imgUrl);
						URLConnection conn = url.openConnection();
						conn.connect();
						BufferedInputStream bis = new BufferedInputStream(conn.getInputStream(),8192) ;
						Bitmap bitmap = BitmapFactory.decodeStream(bis);
						//保存文件到sd卡
						saveImage(imagePath,bitmap2Bytes(bitmap));
						Message msg = handler.obtainMessage();
						msg.obj = bitmap;
						handler.sendMessage(msg);
					} catch (IOException e) {
						Log.e(ImageUtil.class.getName(), "保存图片到本地存储卡出错！");
					}
				}
			};
			ThreadPoolManager.getInstance().addTask(runnable);
		}
		return null;
	}

	// 返回图片存到sd卡的路径
	public static String getCacheImgPath() {
		return SDCARD_CACHE_IMG_PATH;
	}

	public static String md5(String paramString) {
		String returnStr;
		try {
			MessageDigest localMessageDigest = MessageDigest.getInstance("MD5");
			localMessageDigest.update(paramString.getBytes());
			returnStr = byteToHexString(localMessageDigest.digest());
			return returnStr;
		} catch (Exception e) {
			return paramString;
		}
	}

	/**
	 * 将指定byte数组转换成16进制字符串
	 * 
	 * @param b
	 * @return
	 */
	public static String byteToHexString(byte[] b) {
		StringBuffer hexString = new StringBuffer();
		for (int i = 0; i < b.length; i++) {
			String hex = Integer.toHexString(b[i] & 0xFF);
			if (hex.length() == 1) {
				hex = '0' + hex;
			}
			hexString.append(hex.toUpperCase());
		}
		return hexString.toString();
	}
	
	/**
	 * 
	 * @author Mathew
	 *
	 */
	public interface ImageCallback{
		public void loadImage(Bitmap bitmap,String imagePath);
	}
	
}