Glide系列-活动缓存和内存缓存

1.活动缓存数据结构用的HashMap

final class ActiveResources {@VisibleForTesting final Map<Key, ResourceWeakReference> activeEngineResources = new             HashMap<>();
}

2.内存缓存LinkedHashMap

public class LruCache<T, Y> {private final Map<T, Entry<Y>> cache = new LinkedHashMap<>(100, 0.75f, true);
}

3.从活动或者内存缓存读取

public class Engine implements EngineJobListener, MemoryCache.ResourceRemovedListener,EngineResource.ResourceListener {private EngineResource<?> loadFromMemory( EngineKey key, boolean isMemoryCacheable, long startTime) {if (!isMemoryCacheable) {//是否支持内存缓存return null;}EngineResource<?> active = loadFromActiveResources(key);//从活动缓存获取if (active != null) {//如果活动缓存不为nullreturn active;}EngineResource<?> cached = loadFromCache(key);//从内存缓存获取if (cached != null) { //如果内存缓存不为nullreturn cached; }return null;}
}

4.从活动缓存获取

public class Engineimplements EngineJobListener,MemoryCache.ResourceRemovedListener,EngineResource.ResourceListener {@Nullableprivate EngineResource<?> loadFromActiveResources(Key key) {EngineResource<?> active = activeResources.get(key); //从活动缓存获取if (active != null) {active.acquire();}return active;}
}

5.从内存缓存获取

从活动缓存中移除这个元素
返回
将获得的元素放入活动缓存

public class Engine implements EngineJobListener, MemoryCache.ResourceRemovedListener,EngineResource.ResourceListener {private EngineResource<?> loadFromCache(Key key) {EngineResource<?> cached = getEngineResourceFromCache(key); //获得内存缓存if (cached != null) {cached.acquire();activeResources.activate(key, cached);//放入活动缓存}return cached;}
}

public class Engine implements EngineJobListener, MemoryCache.ResourceRemovedListener,EngineResource.ResourceListener {private EngineResource<?> getEngineResourceFromCache(Key key) {Resource<?> cached = cache.remove(key);//从内存缓存移除final EngineResource<?> result; //返回的元素是新建的if (cached == null) {result = null;} else if (cached instanceof EngineResource) {// Save an object allocation if we've cached an EngineResource //(the typical case).result = (EngineResource<?>) cached;} else {result = new EngineResource<>(cached,/* isMemoryCacheable= */ true,/* isRecyclable= */ true,key,/* listener= */ this);}return result;}
}