Android开源框架Universal-Image-Loader学习四——LimitedMemoryCache的一些子集

LRULimitedMemoryCache源码：

/**
* (cache size limited)Size of all stored bitmaps will not to exceed size limit.
* (删除策略LRU)When cache reaches limit size then the least recently used bitmap is deleted from cache.
* NOTE: This cache uses strong and weak references for stored Bitmaps.
* 限定值内的使用强引用
*/
public class LRULimitedMemoryCache extends LimitedMemoryCache {

private static final int INITIAL_CAPACITY = 10;
private static final float LOAD_FACTOR = 1.1f;

/** LRU */
private final Map<String, Bitmap> lruCache = Collections.synchronizedMap(new LinkedHashMap<String, Bitmap>(INITIAL_CAPACITY, LOAD_FACTOR, true));

/**构造函数 */
public LRULimitedMemoryCache(int maxSize) {
super(maxSize);
}

@Override
public boolean put(String key, Bitmap value) {
if (super.put(key, value)) {
lruCache.put(key, value);
return true;
} else {
return false;
}
}

@Override
public Bitmap get(String key) {
lruCache.get(key); // call "get" for LRU logic
return super.get(key);
}

@Override
public Bitmap remove(String key) {
lruCache.remove(key);
return super.remove(key);
}

@Override
public void clear() {
lruCache.clear();
super.clear();
}

@Override
protected int getSize(Bitmap value) {
return value.getRowBytes() * value.getHeight();
}

@Override
protected Bitmap removeNext() {
Bitmap mostLongUsedValue = null;
synchronized (lruCache) {
Iterator<Entry<String, Bitmap>> it = lruCache.entrySet().iterator();
if (it.hasNext()) {
Entry<String, Bitmap> entry = it.next();
mostLongUsedValue = entry.getValue();
it.remove();
}
}
return mostLongUsedValue;
}

@Override
protected Reference<Bitmap> createReference(Bitmap value) {
return new WeakReference<Bitmap>(value);
}
}
FIFOLimitedMemoryCache源码：
/**
* Limited {@link Bitmap bitmap} cache. Provides {@link Bitmap bitmaps} storing. Size of all stored bitmaps will not to
* exceed size limit.
* 删除策略：FIFO
* NOTE:This cache uses strong and weak references for stored Bitmaps. Strong references - for limited count of
* Bitmaps (depends on cache size), weak references - for all other cached Bitmaps.
*/
public class FIFOLimitedMemoryCache extends LimitedMemoryCache {

private final List<Bitmap> queue = Collections.synchronizedList(new LinkedList<Bitmap>());

public FIFOLimitedMemoryCache(int sizeLimit) {
super(sizeLimit);
}

@Override
public boolean put(String key, Bitmap value) {
if (super.put(key, value)) {
queue.add(value);
return true;
} else {
return false;
}
}

@Override
public Bitmap remove(String key) {
Bitmap value = super.get(key);
if (value != null) {
queue.remove(value);
}
return super.remove(key);
}

@Override
public void clear() {
queue.clear();
super.clear();
}

@Override
protected int getSize(Bitmap value) {
return value.getRowBytes() * value.getHeight();
}

@Override
/*删除策略：删除头结点，即FIFO*/
protected Bitmap removeNext() {
return queue.remove(0);
}

@Override
protected Reference<Bitmap> createReference(Bitmap value) {
return new WeakReference<Bitmap>(value);
}
}


LargestLimitedMemoryCache源码：

/**
* Limited {@link Bitmap bitmap} cache. Provides {@link Bitmap bitmaps} storing. Size of all stored bitmaps will not to
* exceed size limit.
* 删除策略： 删除size最大的bitmap
* NOTE:This cache uses strong and weak references for stored Bitmaps. Strong references - for limited count of
* Bitmaps (depends on cache size), weak references - for all other cached Bitmaps
*/
public class LargestLimitedMemoryCache extends LimitedMemoryCache {

private final Map<Bitmap, Integer> valueSizes = Collections.synchronizedMap(new HashMap<Bitmap, Integer>());

public LargestLimitedMemoryCache(int sizeLimit) {
super(sizeLimit);
}

@Override
public boolean put(String key, Bitmap value) {
if (super.put(key, value)) {
valueSizes.put(value, getSize(value));
return true;
} else {
return false;
}
}

@Override
public Bitmap remove(String key) {
Bitmap value = super.get(key);
if (value != null) {
valueSizes.remove(value);
}
return super.remove(key);
}

@Override
public void clear() {
valueSizes.clear();
super.clear();
}

@Override
protected int getSize(Bitmap value) {
return value.getRowBytes() * value.getHeight();
}

@Override
/*删除策略：遍历map查找最大值*/
protected Bitmap removeNext() {
Integer maxSize = null;
Bitmap largestValue = null;
Set<Entry<Bitmap, Integer>> entries = valueSizes.entrySet();
synchronized (valueSizes) {
for (Entry<Bitmap, Integer> entry : entries) {
if (largestValue == null) {
largestValue = entry.getKey();
maxSize = entry.getValue();
} else {
Integer size = entry.getValue();
if (size > maxSize) {
maxSize = size;
largestValue = entry.getKey();
}
}
}
}
valueSizes.remove(largestValue);
return largestValue;
}

@Override
protected Reference<Bitmap> createReference(Bitmap value) {
return new WeakReference<Bitmap>(value);
}
}