Android Fragment - Using activity's loadermanager instead of Fragment's. Is it Ok?

Question

Given a fragment which loads (a lot of) data from the database using a loader.

Problem :

I have a pager adapter which destroys the fragment when the user moves away from the tab holding it and recreates it when user gets back to that tab. Because of this recreation, a new loader is created everytime and the data gets loaded everytime.

Question :

To avoid recreating loader everytime the fragment is created, is it ok to use getActivity.getSupportLoaderManager.initLoader(loaderId, null, false) in the onActivityCreated method of the fragment?

I have tried it, tested it and it seems to be working fine. But I'm not convinced that it is right.

Answer 1

Actually, checking the source code, you end up doing the same.

Fragment.getLoaderManager:

/**
 * Return the LoaderManager for this fragment, creating it if needed.
 */
public LoaderManager getLoaderManager() {
    if (mLoaderManager != null) {
        return mLoaderManager;
    }
    if (mActivity == null) {
        throw new IllegalStateException("Fragment " + this + " not attached to Activity");
    }


    mCheckedForLoaderManager = true;
    mLoaderManager = mActivity.getLoaderManager(mWho, mLoadersStarted, true);
    return mLoaderManager;
}

mWho is basically the fragment ID.

final void setIndex(int index, Fragment parent) {
    mIndex = index;
    if (parent != null) {
        mWho = parent.mWho + ":" + mIndex;
    } else {
        mWho = "android:fragment:" + mIndex;
    }
}

The difference in Activity.getLoaderManager() is that who will be (root)

So even though you can do what you are asking, calling it directly from the Fragment might be a better approach

• Activity source code
• Fragment source code

Disclaimer: I only checked the source code in the latest version, but I don't expect it to be very different