LruCache
open class LruCache<K : Any!, V : Any!>
| kotlin.Any | |
| ↳ | androidx.collection.LruCache |
Static library version of android.util.LruCache. Used to write apps that run on API levels prior to 12. When running on API level 12 or above, this implementation is still used; it does not try to switch to the framework's implementation. See the framework SDK documentation for a class overview.
Summary
| Public constructors | |
|---|---|
| Public methods | |
|---|---|
| Int |
Returns the number of times |
| Unit |
evictAll()Clear the cache, calling |
| Int |
Returns the number of values that have been evicted. |
| V? |
get(@NonNull key: K)Returns the value for |
| Int |
hitCount()Returns the number of times |
| Int |
maxSize()For caches that do not override |
| Int |
Returns the number of times |
| V? |
put(@NonNull key: K, @NonNull value: V)Caches |
| Int |
putCount()Returns the number of times |
| V? |
remove(@NonNull key: K)Removes the entry for |
| open Unit |
Sets the size of the cache. |
| Int |
size()For caches that do not override |
| MutableMap<K, V>! |
snapshot()Returns a copy of the current contents of the cache, ordered from least recently accessed to most recently accessed. |
| String |
toString() |
| open Unit |
trimToSize(maxSize: Int)Remove the eldest entries until the total of remaining entries is at or below the requested size. |
| Protected methods | |
|---|---|
| open V? |
create(@NonNull key: K)Called after a cache miss to compute a value for the corresponding key. |
| open Unit |
entryRemoved(evicted: Boolean, @NonNull key: K, @NonNull oldValue: V, @Nullable newValue: V?)Called for entries that have been evicted or removed. |
| open Int |
sizeOf(@NonNull key: K, @NonNull value: V)Returns the size of the entry for |
Public constructors
<init>
LruCache(maxSize: Int)
| Parameters | |
|---|---|
maxSize |
Int: for caches that do not override sizeOf, this is the maximum number of entries in the cache. For all other caches, this is the maximum sum of the sizes of the entries in this cache. |
Public methods
get
@Nullable fun get(@NonNull key: K): V?
Returns the value for key if it exists in the cache or can be created by create. If a value was returned, it is moved to the head of the queue. This returns null if a value is not cached and cannot be created.
hitCount
fun hitCount(): Int
Returns the number of times get returned a value that was already present in the cache.
maxSize
fun maxSize(): Int
For caches that do not override sizeOf, this returns the maximum number of entries in the cache. For all other caches, this returns the maximum sum of the sizes of the entries in this cache.
missCount
fun missCount(): Int
Returns the number of times get returned null or required a new value to be created.
put
@Nullable fun put(
@NonNull key: K,
@NonNull value: V
): V?
Caches value for key. The value is moved to the head of the queue.
| Return | |
|---|---|
V? |
the previous value mapped by key. |
remove
@Nullable fun remove(@NonNull key: K): V?
Removes the entry for key if it exists.
| Return | |
|---|---|
V? |
the previous value mapped by key. |
resize
open fun resize(maxSize: Int): Unit
Sets the size of the cache.
| Parameters | |
|---|---|
maxSize |
Int: The new maximum size. |
size
fun size(): Int
For caches that do not override sizeOf, this returns the number of entries in the cache. For all other caches, this returns the sum of the sizes of the entries in this cache.
snapshot
fun snapshot(): MutableMap<K, V>!
Returns a copy of the current contents of the cache, ordered from least recently accessed to most recently accessed.
toString
fun toString(): String
trimToSize
open fun trimToSize(maxSize: Int): Unit
Remove the eldest entries until the total of remaining entries is at or below the requested size.
| Parameters | |
|---|---|
maxSize |
Int: the maximum size of the cache before returning. May be -1 to evict even 0-sized elements. |
Protected methods
create
@Nullable protected open fun create(@NonNull key: K): V?
Called after a cache miss to compute a value for the corresponding key. Returns the computed value or null if no value can be computed. The default implementation returns null.
The method is called without synchronization: other threads may access the cache while this method is executing.
If a value for key exists in the cache when this method returns, the created value will be released with entryRemoved and discarded. This can occur when multiple threads request the same key at the same time (causing multiple values to be created), or when one thread calls put while another is creating a value for the same key.
entryRemoved
protected open fun entryRemoved(
evicted: Boolean,
@NonNull key: K,
@NonNull oldValue: V,
@Nullable newValue: V?
): Unit
Called for entries that have been evicted or removed. This method is invoked when a value is evicted to make space, removed by a call to remove, or replaced by a call to put. The default implementation does nothing.
The method is called without synchronization: other threads may access the cache while this method is executing.
| Parameters | |
|---|---|
evicted |
Boolean: true if the entry is being removed to make space, false if the removal was caused by a put or remove. |
newValue |
V?: the new value for key, if it exists. If non-null, this removal was caused by a put. Otherwise it was caused by an eviction or a remove. |
sizeOf
protected open fun sizeOf(
@NonNull key: K,
@NonNull value: V
): Int
Returns the size of the entry for key and value in user-defined units. The default implementation returns 1 so that size is the number of entries and max size is the maximum number of entries.
An entry's size must not change while it is in the cache.