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android 缓存图片

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幽映每白日，清辉照衣裳。这篇文章主要讲述android 缓存图片相关的知识，希望能为你提供帮助。
【android 缓存图片】public class MemoryCache {

private static final String TAG = "MemoryCache";
private Map< String, Bitmap> cache=Collections.synchronizedMap(
new LinkedHashMap< String, Bitmap> (10,1.5f,true)); //Last argument true for LRU ordering
private long size=0; //current allocated size
private long limit=1000000; //max memory in bytes

public MemoryCache(){
//use 25% of available heap size
setLimit(Runtime.getRuntime().maxMemory()/4);
}

public void setLimit(long new_limit){
limit=new_limit;
Log.i(TAG, "MemoryCache will use up to "+limit/1024./1024.+"MB");
}

public Bitmap get(String id){
try{
if(!cache.containsKey(id))
return null;
//NullPointerException sometimes happen here http://code.google.com/p/osmdroid/issues/detail?id=78
return cache.get(id);
}catch(NullPointerException ex){
ex.printStackTrace();
return null;
}
}

public void put(String id, Bitmap bitmap){
try{
if(cache.containsKey(id))
size-=getSizeInBytes(cache.get(id));
cache.put(id, bitmap);
size+=getSizeInBytes(bitmap);
checkSize();
}catch(Throwable th){
th.printStackTrace();
}
}

private void checkSize() {
Log.i(TAG, "cache size="+size+" length="+cache.size());
if(size> limit){
Iterator< Entry< String, Bitmap> > iter=cache.entrySet().iterator(); //least recently accessed item will be the first one iterated
while(iter.hasNext()){
Entry< String, Bitmap> entry=iter.next();
size-=getSizeInBytes(entry.getValue());
iter.remove();
if(size< =limit)
break;
}
Log.i(TAG, "Clean cache. New size "+cache.size());
}
}

public void clear() {
try{
//NullPointerException sometimes happen here http://code.google.com/p/osmdroid/issues/detail?id=78
cache.clear();
size=0;
}catch(NullPointerException ex){
ex.printStackTrace();
}
}

long getSizeInBytes(Bitmap bitmap) {
if(bitmap==null)
return 0;
return bitmap.getRowBytes() * bitmap.getHeight();
}
}









































































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