android中图片的三级缓存cache策略(内存/文件/网络)

/*
* 图片管理
* 异步获取图片，直接调用loadImage()函数，该函数自己判断是从缓存还是网络加载
* 同步获取图片，直接调用getBitmap()函数，该函数自己判断是从缓存还是网络加载
* 仅从本地获取图片，调用getBitmapFromNative()
* 仅从网络加载图片，调用getBitmapFromHttp()
*
*/
public class ImageManager implements IManager
{
private final static String TAG = "ImageManager";

private ImageMemoryCache imageMemoryCache; //内存缓存

private ImageFileCache imageFileCache; //文件缓存

//正在下载的image列表
public static HashMap<String, Handler> ongoingTaskMap = new HashMap<String, Handler>();

//等待下载的image列表
public static HashMap<String, Handler> waitingTaskMap = new HashMap<String, Handler>();

//同时下载图片的线程个数
final static int MAX_DOWNLOAD_IMAGE_THREAD = 4;

private final Handler downloadStatusHandler = new Handler(){
public void handleMessage(Message msg)
{
startDownloadNext();
}
};

public ImageManager()
{
imageMemoryCache = new ImageMemoryCache();
imageFileCache = new ImageFileCache();
}

/**
* 获取图片，多线程的入口
*/
public void loadBitmap(String url, Handler handler)
{
//先从内存缓存中获取，取到直接加载
Bitmap bitmap = getBitmapFromNative(url);
if (bitmap != null)
{
Logger.d(TAG, "loadBitmap:loaded from native");
Message msg = Message.obtain();
Bundle bundle = new Bundle();
bundle.putString("url", url);
msg.obj = bitmap;
msg.setData(bundle);
handler.sendMessage(msg);
}
else
{
Logger.d(TAG, "loadBitmap:will load by network");
downloadBmpOnNewThread(url, handler);
}
}
/**
* 新起线程下载图片
*/
private void downloadBmpOnNewThread(final String url, final Handler handler)
{
Logger.d(TAG, "ongoingTaskMap'size=" + ongoingTaskMap.size());

if (ongoingTaskMap.size() >= MAX_DOWNLOAD_IMAGE_THREAD)
{
synchronized (waitingTaskMap)
{
waitingTaskMap.put(url, handler);
}
}
else
{
synchronized (ongoingTaskMap)
{
ongoingTaskMap.put(url, handler);
}
new Thread()
{
public void run()
{
Bitmap bmp = getBitmapFromHttp(url);
// 不论下载是否成功，都从下载队列中移除,再由业务逻辑判断是否重新下载
// 下载图片使用了httpClientRequest，本身已经带了重连机制
synchronized (ongoingTaskMap)
{
ongoingTaskMap.remove(url);
}

if(downloadStatusHandler != null)
{
downloadStatusHandler.sendEmptyMessage(0);

}
Message msg = Message.obtain();
msg.obj = bmp;
Bundle bundle = new Bundle();
bundle.putString("url", url);
msg.setData(bundle);

if(handler != null)
{
handler.sendMessage(msg);
}
}
}.start();
}
}
/**
* 依次从内存，缓存文件，网络上加载单个bitmap,不考虑线程的问题
*/
public Bitmap getBitmap(String url)
{
// 从内存缓存中获取图片
Bitmap bitmap = imageMemoryCache.getBitmapFromMemory(url);
if (bitmap == null)
{
// 文件缓存中获取
bitmap = imageFileCache.getImageFromFile(url);
if (bitmap != null)
{
// 添加到内存缓存
imageMemoryCache.addBitmapToMemory(url, bitmap);
}
else
{
// 从网络获取
bitmap = getBitmapFromHttp(url);
}
}
return bitmap;
}

/**
* 从内存或者缓存文件中获取bitmap
*/
public Bitmap getBitmapFromNative(String url)
{
Bitmap bitmap = null;
bitmap = imageMemoryCache.getBitmapFromMemory(url);

if(bitmap == null)
{
bitmap = imageFileCache.getImageFromFile(url);
if(bitmap != null)
{
// 添加到内存缓存
imageMemoryCache.addBitmapToMemory(url, bitmap);
}
}
return bitmap;
}

/**
* 通过网络下载图片,与线程无关
*/
public Bitmap getBitmapFromHttp(String url)
{
Bitmap bmp = null;

try
{
byte[] tmpPicByte = getImageBytes(url);

if (tmpPicByte != null)
{
bmp = BitmapFactory.decodeByteArray(tmpPicByte, 0,
tmpPicByte.length);
}
tmpPicByte = null;
}
catch(Exception e)
{
e.printStackTrace();
}

if(bmp != null)
{
// 添加到文件缓存
imageFileCache.saveBitmapToFile(bmp, url);
// 添加到内存缓存
imageMemoryCache.addBitmapToMemory(url, bmp);
}
return bmp;
}

/**
* 下载链接的图片资源
*
* @param url
*
* @return 图片
*/
public byte[] getImageBytes(String url)
{
byte[] pic = null;
if (url != null && !"".equals(url))
{
Requester request = RequesterFactory.getRequester(
Requester.REQUEST_REMOTE, RequesterFactory.IMPL_HC);
// 执行请求
MyResponse myResponse = null;
MyRequest mMyRequest;
mMyRequest = new MyRequest();
mMyRequest.setUrl(url);
mMyRequest.addHeader(HttpHeader.REQ.ACCEPT_ENCODING, "identity");
InputStream is = null;
ByteArrayOutputStream baos = null;
try {
myResponse = request.execute(mMyRequest);
is = myResponse.getInputStream().getImpl();
baos = new ByteArrayOutputStream();
byte[] b = new byte[512];
int len = 0;
while ((len = is.read(b)) != -1)
{
baos.write(b, 0, len);
baos.flush();
}
pic = baos.toByteArray();
Logger.d(TAG, "icon bytes.length=" + pic.length);
}
catch (Exception e3)
{
e3.printStackTrace();
try
{
Logger.e(TAG,
"download shortcut icon faild and responsecode="
+ myResponse.getStatusCode());
}
catch (Exception e4)
{
e4.printStackTrace();
}
}
finally
{
try
{
if (is != null)
{
is.close();
is = null;
}
}
catch (Exception e2)
{
e2.printStackTrace();
}
try
{
if (baos != null)
{
baos.close();
baos = null;
}
}
catch (Exception e2)
{
e2.printStackTrace();
}
try
{
request.close();
}
catch (Exception e1)
{
e1.printStackTrace();
}
}
}
return pic;
}

/**
* 取出等待队列第一个任务，开始下载
*/
private void startDownloadNext()
{
synchronized(waitingTaskMap)
{
Logger.d(TAG, "begin start next");
Iterator iter = waitingTaskMap.entrySet().iterator();

while (iter.hasNext())
{

Map.Entry entry = (Map.Entry) iter.next();
Logger.d(TAG, "WaitingTaskMap isn't null,url=" + (String)entry.getKey());

if(entry != null)
{
waitingTaskMap.remove(entry.getKey());
downloadBmpOnNewThread((String)entry.getKey(), (Handler)entry.getValue());
}
break;
}
}
}

public String startDownloadNext_ForUnitTest()
{
String urlString = null;
synchronized(waitingTaskMap)
{
Logger.d(TAG, "begin start next");
Iterator iter = waitingTaskMap.entrySet().iterator();

while (iter.hasNext())
{
Map.Entry entry = (Map.Entry) iter.next();
urlString = (String)entry.getKey();
waitingTaskMap.remove(entry.getKey());
break;
}
}
return urlString;
}

/**
* 图片变为圆角
* @param bitmap:传入的bitmap
* @param pixels：圆角的度数，值越大，圆角越大
* @return bitmap:加入圆角的bitmap
*/
public static Bitmap toRoundCorner(Bitmap bitmap, int pixels)
{
if(bitmap == null)
return null;
Bitmap output = Bitmap.createBitmap(bitmap.getWidth(), bitmap.getHeight(), Config.ARGB_8888);
Canvas canvas = new Canvas(output);
final int color = 0xff424242;
final Paint paint = new Paint();
final Rect rect = new Rect(0, 0, bitmap.getWidth(), bitmap.getHeight());
final RectF rectF = new RectF(rect);
final float roundPx = pixels;
paint.setAntiAlias(true);
canvas.drawARGB(0, 0, 0, 0);
paint.setColor(color);
canvas.drawRoundRect(rectF, roundPx, roundPx, paint);
paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
canvas.drawBitmap(bitmap, rect, rect, paint);
return output;
}

public byte managerId()
{
return IMAGE_ID;
}
}