我正在开发一个需要装上比图的申请。 并使用<代码>SoftReference。 我将每一条软性参考与<代码>ReferenceQueue联系起来,并用一个散列图进入。 SoftReference。 如下所示:

public static class MemCache {

    final private ReferenceQueue<Bitmap> queue = new ReferenceQueue<Bitmap>();
    private Map<String, SoftReference<Bitmap>> hash = null;

    public MemCache() {
        hash = Collections.synchronizedMap(
            new LinkedHashMap<String, SoftReference<Bitmap>>()
        );
    }

    public synchronized Bitmap put(String key, Bitmap value) {
        clean();
        SoftReference<Bitmap> ref = new SoftReference<Bitmap>(value, queue);
        SoftReference<Bitmap> res = hash.put(key, ref);
        if (res == null) return null;
        return res.get();
    }

    public synchronized Bitmap get(Object key) {
        clean();
        SoftReference<Bitmap> ref = hash.get(key);
        if (ref == null) return null;
        Bitmap val = ref.get();
        if (val != null) return val;
        hash.remove(key);
        return null;
    }
}

然后,在我撰写<代码>clean()时,如:

    private synchronized void clean() {
        Reference<? extends Bitmap> sv;
        while ((sv = queue.poll()) != null)
            hash.remove(sv);
        Queue<String> toRemove = new LinkedList<String>();
        for(Entry<String, SoftReference<Bitmap>> e : hash.entrySet()){
            if(e.getValue()==null) continue;
            if(e.getValue().get()==null) 
                toRemove.add(e.getKey());
        }
        String s;
        while((s = toRemove.poll())!= null)
            hash.remove(s);
        Log.e("ImageCacheManager", "MemCache Size/2:" + new String(new char[hash.size() / 2]).replace("", "="));
    }

Which check all the SoftReferences in the hash table for not null. The memcache appears good, but if I only wrote:

    private synchronized void clean() {
        Reference<? extends Bitmap> sv;
        while ((sv = queue.poll()) != null)
            hash.remove(sv);
        Log.e("ImageCacheManager", "MemCache Size/2:" + new String(new char[hash.size() / 2]).replace("", "="));
    }

Which only remove the element been put into ReferenceQueue The Log then will print more and more =, even there is some decrease, the tendency is increase

http://www.ibm.com/developerworks/library/j-refs/“rel=“nofollow”http://www.ibm.com/developerwork/library/j-refs/。