Add example for room database

Author: anandgaurav10

app/src/main/java/com/sample/MainActivity.java

@@ -31,9 +31,13 @@
 import com.sample.database.ContactDBHelper;
 import com.sample.database.ExtTestDBHelper;
 import com.sample.database.PersonDBHelper;
+import com.sample.database.room.User;
+import com.sample.database.room.UserDBHelper;
 import com.sample.utils.Utils;
 
+import java.util.ArrayList;
 import java.util.HashSet;
+import java.util.List;
 import java.util.Set;
 
 public class MainActivity extends AppCompatActivity {
@@ -108,6 +112,19 @@ protected void onCreate(Bundle savedInstanceState) {
             }
         }
 
+        // Room database
+        UserDBHelper userDBHelper = new UserDBHelper(getApplicationContext());
+        if (userDBHelper.count() == 0) {
+            List<User> userList = new ArrayList<>();
+            for (int i = 0; i < 20; i++) {
+                User user = new User();
+                user.id = (long) (i + 1);
+                user.name = "user_" + i;
+                userList.add(user);
+            }
+            userDBHelper.insertUser(userList);
+        }
+
         Utils.setCustomDatabaseFiles(getApplicationContext());
     }
 

app/src/main/java/com/sample/database/room/AppDatabase.java

@@ -0,0 +1,14 @@
+package com.sample.database.room;
+
+import android.arch.persistence.room.Database;
+import android.arch.persistence.room.RoomDatabase;
+
+/**
+ * Created by anandgaurav on 12/02/18.
+ */
+@Database(entities = {User.class}, version = 1)
+public abstract class AppDatabase extends RoomDatabase {
+
+    public abstract UserDao userDao();
+
+}

app/src/main/java/com/sample/database/room/User.java

@@ -0,0 +1,17 @@
+package com.sample.database.room;
+
+import android.arch.persistence.room.Entity;
+import android.arch.persistence.room.PrimaryKey;
+
+/**
+ * Created by anandgaurav on 12/02/18.
+ */
+@Entity(tableName = "users")
+public class User {
+
+    @PrimaryKey
+    public Long id;
+
+    public String name;
+
+}

app/src/main/java/com/sample/database/room/UserDBHelper.java

@@ -0,0 +1,30 @@
+package com.sample.database.room;
+
+import android.arch.persistence.room.Room;
+import android.content.Context;
+
+import java.util.List;
+
+/**
+ * Created by anandgaurav on 12/02/18.
+ */
+
+public class UserDBHelper {
+
+    private final AppDatabase appDatabase;
+
+    public UserDBHelper(Context context) {
+        appDatabase = Room.databaseBuilder(context, AppDatabase.class, "User-Database")
+                .allowMainThreadQueries()
+                .build();
+    }
+
+    public void insertUser(List<User> userList) {
+        appDatabase.userDao().insertAll(userList);
+    }
+
+    public int count() {
+        return appDatabase.userDao().loadAll().size();
+    }
+
+}

app/src/main/java/com/sample/database/room/UserDao.java

@@ -0,0 +1,33 @@
+package com.sample.database.room;
+
+import android.arch.persistence.room.Dao;
+import android.arch.persistence.room.Delete;
+import android.arch.persistence.room.Insert;
+import android.arch.persistence.room.OnConflictStrategy;
+import android.arch.persistence.room.Query;
+
+import java.util.List;
+
+/**
+ * Created by anandgaurav on 12/02/18.
+ */
+
+@Dao
+public interface UserDao {
+
+    @Query("SELECT * FROM users")
+    List<User> loadAll();
+
+    @Query("SELECT * FROM users WHERE id IN (:userIds)")
+    List<User> loadAllByIds(List<Integer> userIds);
+
+    @Insert(onConflict = OnConflictStrategy.REPLACE)
+    void insert(User user);
+
+    @Insert(onConflict = OnConflictStrategy.REPLACE)
+    void insertAll(List<User> users);
+
+    @Delete
+    void delete(User user);
+
+}