wemall app商城源码中基于JAVA的Android异步加载图片管理器代码

wemall doraemon是Android客户端程序，服务端采用wemall微信商城，不对原商城做任何修改，只需要在原商城目录下上传接口文件即可完成服务端的配置，客户端可随意定制修改。本文分享其中关于异步加载图片管理器，供技术员参考学习。

package com.inuoer.util;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.UnsupportedEncodingException;
import java.lang.ref.SoftReference;
import java.net.HttpURLConnection;
import java.net.URL;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Map;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;

/**
 * 
 * @author Administrator
 * @desc 异步加载图片管理器
 *
 */
public class LoaderImpl {
	//内存中的软应用缓存
	private Map<String, SoftReference<Bitmap>> imageCache;
	
	//是否缓存图片至本地文件
	private boolean cache2FileFlag = false;
	
	//缓存目录,默认是/data/data/package/cache/目录
	private String cachedDir;
	
	public LoaderImpl(Map<String, SoftReference<Bitmap>> imageCache){
		this.imageCache = imageCache;
	}
	
	/**
	 * 是否缓存图片至外部文件
	 * @param flag 
	 */
	public void setCache2File(boolean flag){
		cache2FileFlag = flag;
	}
	
	/**
	 * 设置缓存图片到外部文件的路径
	 * @param cacheDir
	 */
	public void setCachedDir(String cacheDir){
		this.cachedDir = cacheDir;
	}
	
	/**
	 * 从网络端下载图片
	 * @param url 网络图片的URL地址
	 * @param cache2Memory 是否缓存(缓存在内存中)
	 * @return bitmap 图片bitmap结构
	 * 
	 */
	public Bitmap getBitmapFromUrl(String url, boolean cache2Memory){
		Bitmap bitmap = null;
		try{
			URL u = new URL(url);
			HttpURLConnection conn = (HttpURLConnection)u.openConnection();  
			InputStream is = conn.getInputStream();
			bitmap = BitmapFactory.decodeStream(is);
			
			if(cache2Memory){
				//1.缓存bitmap至内存软引用中
				imageCache.put(url, new SoftReference<Bitmap>(bitmap));
				if(cache2FileFlag){
					//2.缓存bitmap至/data/data/packageName/cache/文件夹中
					String fileName = getMD5Str(url);
					String filePath = this.cachedDir + "/" +fileName;
					FileOutputStream fos = new FileOutputStream(filePath);
					bitmap.compress(Bitmap.CompressFormat.PNG, 100, fos);
				}
			}
			
			is.close();
			conn.disconnect();
			return bitmap;
		}catch(IOException e){
			e.printStackTrace();
			return null;
		}
	}
	
	/**
	 * 从内存缓存中获取bitmap
	 * @param url
	 * @return bitmap or null.
	 */
	public Bitmap getBitmapFromMemory(String url){
		Bitmap bitmap = null;
		if(imageCache.containsKey(url)){
			synchronized(imageCache){
				SoftReference<Bitmap> bitmapRef = imageCache.get(url);
				if(bitmapRef != null){
					bitmap = bitmapRef.get();
					return bitmap;
				}
			}
		}
		//从外部缓存文件读取
		if(cache2FileFlag){
			bitmap = getBitmapFromFile(url);
			if(bitmap != null)
				imageCache.put(url, new SoftReference<Bitmap>(bitmap));
		}
		
		return bitmap;
	}
	
	/**
	 * 从外部文件缓存中获取bitmap
	 * @param url
	 * @return
	 */
	private Bitmap getBitmapFromFile(String url){
		Bitmap bitmap = null;
		String fileName = getMD5Str(url);
		if(fileName == null)
			return null;
		
		String filePath = cachedDir + "/" + fileName;
		
		try {
			FileInputStream fis = new FileInputStream(filePath);
			bitmap = BitmapFactory.decodeStream(fis);
		} catch (FileNotFoundException e) {
			e.printStackTrace();
			bitmap = null;
		}
		return bitmap;
	}
	
	
	/**  
     * MD5 加密  
     */   
    private static String getMD5Str(String str) {   
        MessageDigest messageDigest = null;   
        try {   
            messageDigest = MessageDigest.getInstance("MD5");   
            messageDigest.reset();   
            messageDigest.update(str.getBytes("UTF-8"));   
        } catch (NoSuchAlgorithmException e) {   
//          System.out.println("NoSuchAlgorithmException caught!");   
            return null;
        } catch (UnsupportedEncodingException e) {   
            e.printStackTrace();
            return null;
        }   
   
        byte[] byteArray = messageDigest.digest();   
        StringBuffer md5StrBuff = new StringBuffer();   
        for (int i = 0; i < byteArray.length; i++) {               
            if (Integer.toHexString(0xFF & byteArray[i]).length() == 1)   
                md5StrBuff.append("0").append(Integer.toHexString(0xFF & byteArray[i]));   
            else   
                md5StrBuff.append(Integer.toHexString(0xFF & byteArray[i]));   
        }   
   
        return md5StrBuff.toString();   
    }  

	/**  
     * MD5 加密  
    private static String getMD5Str(Object...objects){
    	StringBuilder stringBuilder=new StringBuilder();
    	for (Object object : objects) {
			stringBuilder.append(object.toString());
		}
    	return getMD5Str(stringBuilder.toString());
    }*/ 
}

原文详情地址：http://git.oschina.net/zzunet/wemall-doraemon/commit/e8f303df5663dc69fe47bb9623222149d40e3956

wemall doraemonAndroid app商城详情地址：http://www.koahub.com/home/product/55

wemall官网地址：http://www.wemallshop.com

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