What is cursor.setNotificationUri() used for?

Question

I did research on how to use ContentProviders and Loaders from this tutorial

How I see it: We have an Activity with ListView,

Answer 1

CursorLoader registers observer for the cursor, not to the URI.

Look into CursorLoader's source code below. Notice that CursorLoader registers contentObserver to the cursor.

/* Runs on a worker thread */
    @Override
    public Cursor loadInBackground() {
        synchronized (this) {
            if (isLoadInBackgroundCanceled()) {
                throw new OperationCanceledException();
            }
            mCancellationSignal = new CancellationSignal();
        }
        try {
            Cursor cursor = getContext().getContentResolver().query(mUri, mProjection, mSelection,
                    mSelectionArgs, mSortOrder, mCancellationSignal);
            if (cursor != null) {
                try {
                    // Ensure the cursor window is filled.
                    cursor.getCount();
                    cursor.registerContentObserver(mObserver);
                } catch (RuntimeException ex) {
                    cursor.close();
                    throw ex;
                }
            }
            return cursor;
        } finally {
            synchronized (this) {
                mCancellationSignal = null;
            }
        }

The Cursor needs to call method setNotificationUri() to register mSelfObserver to the uri.

//AbstractCursor.java
public void setNotificationUri(ContentResolver cr, Uri notifyUri, int userHandle) {
        synchronized (mSelfObserverLock) {
            mNotifyUri = notifyUri;
            mContentResolver = cr;
            if (mSelfObserver != null) {
                mContentResolver.unregisterContentObserver(mSelfObserver);
            }
            mSelfObserver = new SelfContentObserver(this);
            mContentResolver.registerContentObserver(mNotifyUri, true, mSelfObserver, userHandle); // register observer to the uri
            mSelfObserverRegistered = true;
        }
    }

Inside the contentProvider's insert, update, delete methods, you need to call getContext().getContentResolver().notifyChange(uri, null); to notify change to the uri observers.

So if you don't call cursor#setNotificationUri(), your CursorLoader will not receive notification if data underlying that uri changes.