Reference Class

Provides an abstract class which describes behavior common to all reference objects.

Syntax

[Android.Runtime.Register("java/lang/ref/Reference", DoNotGenerateAcw=true)]
public abstract class Reference : Java.Lang.Object

Remarks

Provides an abstract class which describes behavior common to all reference objects. It is not possible to create immediate subclasses of Reference in addition to the ones provided by this package. It is also not desirable to do so, since references require very close cooperation with the system's garbage collector. The existing, specialized reference classes should be used instead.

Three different type of references exist, each being weaker than the preceding one: Java.Lang.Ref.SoftReference, Java.Lang.Ref.WeakReference, and Java.Lang.Ref.PhantomReference. "Weakness" here means that less restrictions are being imposed on the garbage collector as to when it is allowed to actually garbage-collect the referenced object.

In order to use reference objects properly it is important to understand the different types of reachability that trigger their clearing and enqueueing. The following table lists these, from strongest to weakest. For each row, an object is said to have the reachability on the left side if (and only if) it fulfills all of the requirements on the right side. In all rows, consider the root set to be a set of references that are "resistant" to garbage collection (that is, running threads, method parameters, local variables, static fields and the like).

Strongly reachable
There exists at least one path from the root set to the object that does not traverse any instance of a java.lang.ref.Reference subclass.
Softly reachable
The object is not strongly reachable.
There exists at least one path from the root set to the object that does traverse a java.lang.ref.SoftReference instance, but no java.lang.ref.WeakReference or java.lang.ref.PhantomReference instances.
Weakly reachable
The object is neither strongly nor softly reachable.
There exists at least one path from the root set to the object that does traverse a java.lang.ref.WeakReference instance, but no java.lang.ref.PhantomReference instances.
Phantom-reachable
The object is neither strongly, softly, nor weakly reachable.
The object is referenced by a java.lang.ref.PhantomReference instance.
The object has already been finalized.

[Android Documentation]

Requirements

Namespace: Java.Lang.Ref
Assembly: Mono.Android (in Mono.Android.dll)
Assembly Versions: 0.0.0.0
Since: Added in API level 1

Strongly reachable	There exists at least one path from the root set to the object that does not traverse any instance of a `java.lang.ref.Reference` subclass.
Softly reachable	The object is not strongly reachable. There exists at least one path from the root set to the object that does traverse a `java.lang.ref.SoftReference` instance, but no `java.lang.ref.WeakReference` or `java.lang.ref.PhantomReference` instances.
Weakly reachable	The object is neither strongly nor softly reachable. There exists at least one path from the root set to the object that does traverse a `java.lang.ref.WeakReference` instance, but no `java.lang.ref.PhantomReference` instances.
Phantom-reachable	The object is neither strongly, softly, nor weakly reachable. The object is referenced by a `java.lang.ref.PhantomReference` instance. The object has already been finalized.