跨活动访问领域数据库

Question

我有3种不同的活动。 1扩展Application和realm在此活动中配置。 2.数据从第二个活动添加到Realm。 3.数据将显示在第3个活动中。我无法完成第3部分。我无法在第3个活动中获得Realm的实例。以下是申请书（我提到的第一项活动）

@Override
    public void onCreate() {
        super.onCreate();
        Realm.init(this);
        RealmConfiguration realmConfiguration = new RealmConfiguration.Builder().build();
        Realm.setDefaultConfiguration(realmConfiguration);
    }

以下是向第二个活动（PurchaseDetailsActivity）内部的片段中添加数据的代码。

private void addDataToRealm(DBPurchase model) {
        mRealm.beginTransaction();
        DBPurchase dbPurchaseModel = new DBPurchase();
        dbPurchaseModel.setId(id);
        dbPurchaseModel.setAmountPayed(model.getAmountPayed());
        dbPurchaseModel.setCredit(model.getCredit());
        mRealm.insertOrUpdate(dbPurchaseModel); 
        mRealm.commitTransaction();
        id++;

最后一个是第3个活动中的片段。

@Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_purchase_items, container, false);
        purchaseTotalListAdapter = new PurchaseTotalListAdapter(getContext(), mDBPurchaseArrayList, PurchasesTotalListFragment.this);
        RecyclerView recyclerView = (RecyclerView) view.findViewById(R.id.recycler_view);
        recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
        recyclerView.setAdapter(purchaseTotalListAdapter);
        Realm.getDefaultInstance();
        return view;
    }