android listview异步加载图片类 （优化）

/**

*

* <异步加载图片 缓存的实现>

* <功能详细描述>

*

* @author cyf

* @version [版本号, 2013-11-18]

* @see [相关类/方法]

* @since [产品/模块版本]

*/

public class AsyncImageLoader

{

/**

* 图片缓存

*/

private HashMap<String, SoftReference<Bitmap>> imageCache;

/**

* 正在执行下载的url

*/

private List<String> isDowningUrl;

private Context context;

public AsyncImageLoader(Context context)

{

this.context = context;

imageCache = new HashMap<String, SoftReference<Bitmap>>();

isDowningUrl = new ArrayList<String>();

}

/**

*

* <先读取缓存中的图片，没有在从本地读，本地没有再去网络下载>

* <功能详细描述>

* @param imageUrl

* @param imageCallback

* @param zoomForBitmap

* @return

* @see [类、类#方法、类#成员]

*/

public Bitmap loadDrawable(final String imageUrl, final ImageCallback imageCallback, final BitmapSize bitmapSize)

{

if (imageUrl != null && imageUrl.length() > 0)

{

//先在缓存中查找图片

if (imageCache.containsKey(imageUrl))

{

SoftReference<Bitmap> softReference = imageCache.get(imageUrl);

Bitmap drawable = softReference.get();

if (drawable != null)

{

return drawable;

}

}

final Handler handler = new Handler()

{

public void handleMessage(Message message)

{

imageCallback.imageLoaded((Bitmap)message.obj, imageUrl);

}

};

//listview上下滑动会重复加载item，重复开线程影响效率

if (!isDowningUrl.contains(imageUrl))

{

new Thread()

{

@Override

public void run()

{

isDowningUrl.add(imageUrl);

Bitmap drawable = getBitmap(imageUrl, context);

Bitmap nowBitmap = null;

if (drawable != null)

{

//压缩

nowBitmap = GeneralUtils.zoomPhoto(drawable, bitmapSize);

}

if (nowBitmap != null)

imageCache.put(imageUrl, new SoftReference<Bitmap>(nowBitmap));

isDowningUrl.remove(imageUrl);

Message message = handler.obtainMessage(0, nowBitmap);

handler.sendMessage(message);

}

}.start();

}

}

return null;

}

/**

* 根据网址获得图片，优先从本地获取，本地没有则从网络下载

*

* @param url 图片网址

* @param context 上下文

* @return 图片

*/

public static Bitmap getBitmap(String url, Context context)

{

String imageName = url.substring(url.lastIndexOf("/") + 1, url.length());

File file = new File(getPath(context), imageName);

if (file.exists())

{

return BitmapFactory.decodeFile(file.getPath());

}

return loadImageFromUrl(url, file, context);

}

/**

* 获取图片的存储目录，在有sd卡的情况下为 “/sdcard/本应用包名”

* 没有sd的情况下为“/data/data/本应用包名/cach/images/”

*

* @param context 上下文

* @return 本地图片存储目录

*/

private static String getPath(Context context)

{

String path = null;

boolean hasSDCard = Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED);

String packageName = context.getPackageName() + "/CT/";

if (hasSDCard)

{

path = Environment.getExternalStorageDirectory().getPath() + "/CT/";

}

else

{

path = "/data/data/" + packageName;

}

File file = new File(path);

if (!file.exists())

{

file.mkdirs();

}

return file.getPath();

}

/**

*

* <根据URL下载图片,并保存到本地>

* <功能详细描述>

* @param imageURL

* @param context

* @return

* @see [类、类#方法、类#成员]

*/

public static Bitmap loadImageFromUrl(String imageURL, File file, Context context)

{

Bitmap bitmap = null;

try

{

URL url = new URL(imageURL);

HttpURLConnection con = (HttpURLConnection)url.openConnection();

con.setDoInput(true);

con.connect();

if (con.getResponseCode() == 200)

{

InputStream inputStream = con.getInputStream();

ByteArrayOutputStream OutputStream = new ByteArrayOutputStream();

FileOutputStream out = new FileOutputStream(file.getPath());

byte buf[] = new byte[1024 * 20];

int len = 0;

while ((len = inputStream.read(buf)) != -1)

{

OutputStream.write(buf, 0, len);

}

OutputStream.flush();

OutputStream.close();

inputStream.close();

out.write(OutputStream.toByteArray());

out.close();

bitmap = BitmapFactory.decodeFile(file.getPath());

}

}

catch (MalformedURLException e)

{

e.printStackTrace();

}

catch (IOException e)

{

e.printStackTrace();

}

return bitmap;

}

// 回调接口

public interface ImageCallback

{

public void imageLoaded(Bitmap bitmap, String imagePath);

}

/**

*

* <释放缓存>

* <功能详细描述>

* @see [类、类#方法、类#成员]

*/

public void recycleMemory()

{

Iterator iter = imageCache.keySet().iterator();

while (iter.hasNext())

{

Object key = iter.next();

SoftReference<Bitmap> softReference = (SoftReference<Bitmap>)imageCache.get(key);

Bitmap bitmap = softReference.get();

if (bitmap != null && !bitmap.isRecycled())

{

bitmap.recycle();

}

}

imageCache.clear();

}

}