Best practices to use realm with a recycler view?

Question

Do you guys have any best practices regarding using realm with a recyclerview ? I know it\'s generic question but I found nothing on it on the internet. For example I run in

Answer 1

ANSWER FOR 0.89.0 AND ABOVE

For the latest versions, you should use RealmRecyclerViewAdapter in the realm-android-adapters repository.

Versions:

• Use 1.5.0 up to 2.X

• Use 2.1.1 up to 4.X

• Use 3.0.0 above 5.X

---

OLD ANSWER FOR OLD VERSIONS:

I made this RealmRecyclerViewAdapter based on the implementation of RealmBaseAdapter.

This is for v0.89.0 AND ABOVE

public abstract class RealmRecyclerViewAdapter
    extends RecyclerView.Adapter { //put this in `io.realm`

    protected LayoutInflater inflater;
    protected OrderedRealmCollection adapterData;
    protected Context context;
    private final RealmChangeListener listener;

    public RealmRecyclerViewAdapter(Context context, OrderedRealmCollection data) {
        if (context == null) {
            throw new IllegalArgumentException("Context cannot be null");
        }
        this.context = context;
        this.adapterData = data;
        this.inflater = LayoutInflater.from(context);
        this.listener = new RealmChangeListener>() {
            @Override
            public void onChange(RealmResults results) {
                notifyDataSetChanged();
            }
        };

        if (data != null) {
            addListener(data);
        }
    }

    private void addListener(OrderedRealmCollection data) {
        if (data instanceof RealmResults) {
            RealmResults realmResults = (RealmResults) data;
            realmResults.addChangeListener(listener);
        } else if (data instanceof RealmList) {
            RealmList realmList = (RealmList) data;
            realmList.realm.handlerController.addChangeListenerAsWeakReference(listener);
        } else {
            throw new IllegalArgumentException("RealmCollection not supported: " + data.getClass());
        }
    }

    private void removeListener(OrderedRealmCollection data) {
        if (data instanceof RealmResults) {
            RealmResults realmResults = (RealmResults) data;
            realmResults.removeChangeListener(listener);
        } else if (data instanceof RealmList) {
            RealmList realmList = (RealmList) data;
            realmList.realm.handlerController.removeWeakChangeListener(listener);
        } else {
            throw new IllegalArgumentException("RealmCollection not supported: " + data.getClass());
        }
    }

    /**
     * Returns how many items are in the data set.
     *
     * @return the number of items.
     */
    @Override
    public int getItemCount() {
        if (adapterData == null) {
            return 0;
        }
        return adapterData.size();
    }

    /**
     * Get the data item associated with the specified position in the data set.
     *
     * @param position Position of the item whose data we want within the adapter's
     * data set.
     * @return The data at the specified position.
     */
    public T getItem(int position) {
        if (adapterData == null) {
            return null;
        }
        return adapterData.get(position);
    }

    /**
     * Get the row id associated with the specified position in the list. Note that item IDs are not stable so you
     * cannot rely on the item ID being the same after {@link #notifyDataSetChanged()} or
     * {@link #updateData(OrderedRealmCollection)} has been called.
     *
     * @param position The position of the item within the adapter's data set whose row id we want.
     * @return The id of the item at the specified position.
     */
    @Override
    public long getItemId(int position) {
        // TODO: find better solution once we have unique IDs
        return position;
    }

    /**
     * Updates the data associated with the Adapter.
     *
     * Note that RealmResults and RealmLists are "live" views, so they will automatically be updated to reflect the
     * latest changes. This will also trigger {@code notifyDataSetChanged()} to be called on the adapter.
     *
     * This method is therefore only useful if you want to display data based on a new query without replacing the
     * adapter.
     *
     * @param data the new {@link OrderedRealmCollection} to display.
     */
    public void updateData(OrderedRealmCollection data) {
        if (listener != null) {
            if (adapterData != null) {
                removeListener(adapterData);
            }
            if (data != null) {
                addListener(data);
            }
        }

        this.adapterData = data;
        notifyDataSetChanged();
    }
}

---

This is for v0.84.0 AND ABOVE, BUT OLDER THAN v0.89.0 (updated for v0.87.5):

public abstract class RealmRecyclerViewAdapter
        extends RecyclerView.Adapter { //put this in `io.realm`
    protected LayoutInflater inflater;
    protected RealmResults realmResults;
    protected Context context;
    private final RealmChangeListener listener;

    public RealmRecyclerViewAdapter(Context context, RealmResults realmResults, boolean automaticUpdate) {
        if (context == null) {
            throw new IllegalArgumentException("Context cannot be null");
        }
        this.context = context;
        this.realmResults = realmResults;
        this.inflater = LayoutInflater.from(context);
        this.listener = (!automaticUpdate) ? null : new RealmChangeListener() {
            @Override
            public void onChange() {
                notifyDataSetChanged();
            }
        };

        if (listener != null && realmResults != null) {
            realmResults.realm.handlerController.addChangeListenerAsWeakReference(listener);
        }
    }

    /**
     * Returns how many items are in the data set.
     *
     * @return count of items.
     */
    @Override
    public int getItemCount() {
        if (realmResults == null) {
            return 0;
        }
        return realmResults.size();
    }

    /**
     * Returns the item associated with the specified position.
     *
     * @param i index of item whose data we want.
     * @return the item at the specified position.
     */
    public T getItem(int i) {
        if (realmResults == null) {
            return null;
        }
        return realmResults.get(i);
    }

    /**
     * Returns the current ID for an item. Note that item IDs are not stable so you cannot rely on the item ID being the
     * same after {@link #notifyDataSetChanged()} or {@link #updateRealmResults(RealmResults)} has been called.
     *
     * @param i index of item in the adapter.
     * @return current item ID.
     */
    @Override
    public long getItemId(int i) {
        // TODO: find better solution once we have unique IDs
        return i;
    }

    /**
     * Updates the RealmResults associated to the Adapter. Useful when the query has been changed.
     * If the query does not change you might consider using the automaticUpdate feature.
     *
     * @param queryResults the new RealmResults coming from the new query.
     */
    public void updateRealmResults(RealmResults queryResults) {
        if (listener != null) {
            // Making sure that Adapter is refreshed correctly if new RealmResults come from another Realm
            if (this.realmResults != null) {
                this.realmResults.realm.removeChangeListener(listener);
            }
            if (queryResults != null) {
                queryResults.realm.addChangeListener(listener);
            }
        }

        this.realmResults = queryResults;
        notifyDataSetChanged();
    }

    public void addChangeListenerAsWeakReference(RealmChangeListener realmChangeListener) {
        if(realmResults != null) {
            realmResults.realm.handlerController.addChangeListenerAsWeakReference(realmChangeListener);
        }
    }
}

---

This is for OLDER THAN 0.84.0:

public abstract class RealmRecyclerViewAdapter
        extends RecyclerView.Adapter { //put this in `io.realm`
    protected LayoutInflater inflater;
    protected RealmResults realmResults;
    protected Context context;

    private final RealmChangeListener listener;

    public RealmRecyclerViewAdapter(Context context, RealmResults realmResults, boolean automaticUpdate) {
        if(context == null) {
            throw new IllegalArgumentException("Context cannot be null");
        }
        this.context = context;
        this.realmResults = realmResults;
        this.inflater = LayoutInflater.from(context);
        this.listener = (!automaticUpdate) ? null : new RealmChangeListener() {
            @Override
            public void onChange() {
                notifyDataSetChanged();
            }
        };

        if(listener != null && realmResults != null) {
            realmResults.getRealm()
                    .addChangeListener(listener);
        }
    }

    @Override
    public long getItemId(int i) {
        // TODO: find better solution once we have unique IDs
        return i;
    }

    public T getItem(int i) {
        if(realmResults == null) {
            return null;
        }
        return realmResults.get(i);
    }

    public void updateRealmResults(RealmResults queryResults) {
        if(listener != null) {
            // Making sure that Adapter is refreshed correctly if new RealmResults come from another Realm
            if(this.realmResults != null) {
                realmResults.getRealm().removeChangeListener(listener);
            }
            if(queryResults != null) {
                queryResults.getRealm().addChangeListener(listener);
            }
        }

        this.realmResults = queryResults;
        notifyDataSetChanged();
    }

    @Override
    public int getItemCount() {
        if(realmResults == null) {
            return 0;
        }
        return realmResults.size();
    }
}