Pre populating the database with agents and agencies

app/src/main/java/fr/romanet/vj/apps/myrealestateagency/database/RealEstateAgencyDatabase.java

@@ -1,8 +1,15 @@
 package fr.romanet.vj.apps.myrealestateagency.database;
 
+import android.content.Context;
+
+import androidx.annotation.NonNull;
 import androidx.room.Database;
+import androidx.room.Room;
 import androidx.room.RoomDatabase;
 import androidx.room.TypeConverters;
+import androidx.sqlite.db.SupportSQLiteDatabase;
+
+import java.util.concurrent.Executors;
 
 import fr.romanet.vj.apps.myrealestateagency.dao.AgencyDao;
 import fr.romanet.vj.apps.myrealestateagency.dao.AgencyWithAgentsDao;
@@ -28,4 +35,32 @@ public abstract class RealEstateAgencyDatabase extends RoomDatabase {
     public abstract AgencyWithPropertiesDao agencyWithPropertiesDaoDao();
     public abstract DollarCurrencyDao dollarCurrencyDao();
 
+    private static RealEstateAgencyDatabase INSTANCE;
+
+    public synchronized static RealEstateAgencyDatabase getInstance(Context context) {
+        if (INSTANCE == null) {
+            INSTANCE = buildDatabase(context);
+        }
+        return INSTANCE;
+    }
+
+    private static RealEstateAgencyDatabase buildDatabase(final Context context) {
+        return Room.databaseBuilder(context,
+                RealEstateAgencyDatabase.class,
+                "my-real_estate_agency_db")
+                .addCallback(new Callback() {
+                    @Override
+                    public void onCreate(@NonNull SupportSQLiteDatabase db) {
+                        super.onCreate(db);
+                        Executors.newSingleThreadScheduledExecutor().execute(new Runnable() {
+                            @Override
+                            public void run() {
+                                getInstance(context).agencyDao().insertPreData(Agency.populateAgencyTable());
+                                getInstance(context).agentDao().insertPreAgents(Agent.populateAgentsTable());
+                            }
+                        });
+                    }
+                })
+                .allowMainThreadQueries().build();
+    }
 }