When it is ok to use strong references in android and does this code leak?

It is not clear to me when is best to use WeakReference to avoid memory leaks in android. Example:

Code in fragment:

WeakReference

containerView.setDataForDisplay(customer, new CustomListener()
@Override
public void buttonClicked(@NonNull Customer customer)
if(handler != null)
handler.buttonClickedForCustomer(customer);


);


The code inside the custom LinearLayout

LinearLayout

public void setDataForDisplay(List<Customer> customer, CustomListener listener)
// view setup code

someView.setOnClickListener( v ->
if(listener != null)
listener.buttonClicked(v.getTag());

);



The anonymous class CustomListener has a reference to the containing fragment's this.

That anonymous class is passed as a listener to a containing view which in turn does a callback eventually.

CustomListener

this

My question is does this lead to a memory leak?

Should the listener be hold somehow in a WeakReference? How do we decide when it is ok to have a strong reference vs a weak reference?

listener

WeakReference

2 Answers
2

No, this isn't a memory leak.

A simplified reference graph might look something like this:

True, the graph does contain a circular reference, but the garbage collector is perfectly capable of detecting & addressing that situation. The entire graph would be GC'd after the system loses its reference to the Fragment, which is generally going to be right around the time it's dismissed from the screen.

Fragment

I can't contrive a situation where a WeakReference would be needed to prevent a memory leak. (I'm not saying they don't exist, I just can't come up with one.)

WeakReference

I see WeakReferences as a tool for advanced memory management tasks, of the kind that rarely pops up in general application development. Like: Managing a collection of large items, where it's OK if some of them get GC'd (as memory runs out), but you'd rather keep them in RAM.

WeakReferences

IOW: Don't keep around any references you don't need, and you should be OK.

Modern JVM has a very powerful garbage collector. It manages to collect even cyclic references, by detecting objects that are completely isolated form gc roots. You can read more on this topic here:
How Garbage Collection Really Works

By using weak references. however, you can speed up the work of the gc, because this references are to be collected immediately after all strong references on this object are gone.

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