Bottom sheet fragment memory leak

Question

I am using leakcanary and it says your bottom sheet fragment is leaking. But i can't see where the problem is.

How can i fix that leak?

public class TokensExplainedFragment extends BottomSheetDialogFragment implements HasSupportFragmentInjector {

    private static final String TAG = "TokensExplainedFragment";
    private View mainView;

    @Inject
    DispatchingAndroidInjector<Fragment> childFragmentInjector;

    @Inject
    SessionManager sessionManager;

    @Inject
    ViewModelProviderFactory providerFactory;

    public TokensExplainedFragment() {
    }

    @Override
    public void onAttach(Context context) {
        AndroidSupportInjection.inject(this);
        super.onAttach(context);
    }

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        mainView = inflater.inflate(R.layout.fragment_tokens_explained, container, false);
        return mainView;
    }

    @Override
    public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
    }

    @Override
    public Dialog onCreateDialog(Bundle savedInstanceState) {
        BottomSheetDialog dialog = (BottomSheetDialog) super.onCreateDialog(savedInstanceState);


        dialog.setOnShowListener(new DialogInterface.OnShowListener() {
            @Override
            public void onShow(DialogInterface dialog) {
                BottomSheetDialog d = (BottomSheetDialog) dialog;

                FrameLayout bottomSheet = (FrameLayout) d.findViewById(com.google.android.material.R.id.design_bottom_sheet);
                BottomSheetBehavior.from(bottomSheet).setState(BottomSheetBehavior.STATE_EXPANDED);
            }
        });

        return dialog;
    }

    @Override
    public AndroidInjector<Fragment> supportFragmentInjector() {
        return childFragmentInjector;
    }
}

This is how i start it:

TokensExplainedFragment bottomSheetFragment = new TokensExplainedFragment();
bottomSheetFragment.show(getActivity().getSupportFragmentManager(), bottomSheetFragment.getTag());

Leak trace:

Answer 1

According to the Android sources, ConnectivityThread is:

Shared singleton connectivity thread for the system. This is a thread for connectivity operations such as AsyncChannel connections to system services. Various connectivity manager objects can use this singleton as a common resource for their handlers instead of creating separate threads of their own.

Here we can see that this thread is running, and a message posted to it and currently executing on that thread has a reference to TokensExplainedFragment.

I suspect TokensExplainedFragment is doing more than what's shared in StackOverflow (e.g. some code using sessionManager), and in that extra code there might be something calling a connectivity system service (e.g. wifi, internet, bluetooth etc). That's likely triggering a delayed post of a message to the connectivity thread, and that post should be canceled but isn't.