DBHelper.java

/**
     * Database helper. All database (sqlite) calls can go in here
     * 
     * @author Muhammad Riyaz
     * 
     */
    public class DBHelper {
    
    	private static final String DB_NAME = "db_name";
    	private static final int DB_VER = 1;
    	private static final String TAG = DBhelper.class.getSimpleName();
    	
    	// table names
      private static final String TABLE_POSTS = "posts";
    
    	// field names.
    	public static final String C_POST_ID = "post_id";
      public static final String C_POST_URL = "url";
      public static final String C_POST_TITLE = "title";
      public static final String C_POST_CONTENT = "content";
    	
    
    	// Initializations
    	private static DBOpenHelper ourHelper;
    	private static SQLiteDatabase ourDataBase;
    	private int openCounter = 0;
    	private static DBhelper ourInstance;
    
    	public static class DBOpenHelper extends SQLiteOpenHelper {
    		public DBOpenHelper(Context context) {
    			super(context, DB_NAME, null, DB_VER);
    		}
    
    		@Override
    		public void onCreate(SQLiteDatabase db) {
    			// create table queries
          String sql_posts = String
                    .format("create TABLE %s (%s INTEGER PRIMARY KEY, %s TEXT,%s TEXT," +
                                    "%s TEXT)",
                            TABLE_POSTS, C_POST_ID, C_POST_TITLE, 
                            C_POST_URL, C_POST_CONTENT);
            Log.d(TAG, "onCreate sql: " + sql_posts);
            db.execSQL(sql_posts);
    
    			
    
    		}
    
    		@Override
    		public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    			// write here the queries to be executed when the DB_VER upgrades
    			db.execSQL("drop table if exists " + TABLE_POSTS);
    			Log.d(TAG, "On upgrade destroyed table " + TABLE_POSTS);		
    
    			this.onCreate(db);
    		}
    
    	}
    
    	public static synchronized void initDB(Context context) {
    		if (ourInstance == null) {
    			ourInstance = new DBhelper();
    			ourHelper = new DBOpenHelper(context);
    		}
    	}
    
    	public static synchronized DBhelper getInstance() {
    		if (ourInstance == null) {
    			throw new IllegalStateException(
    					DBhelper.class.getSimpleName()
    							+ " is not initialized, call initializeInstance(..) method first.");
    		}
    
    		return ourInstance;
    	}
    
    	public synchronized DBhelper writeOpen() {
    		openCounter++;
    		if (openCounter == 1) {
    			Log.i(TAG, "new write open");
    			ourDataBase = ourHelper.getWritableDatabase();
    		} else {
    			Log.i(TAG, "old write open");
    		}
    		return this;
    	}
    
    	public synchronized DBhelper readOpen() {
    		openCounter++;
    		if (openCounter == 1) {
    			Log.i(TAG, "new read open");
    			ourDataBase = ourHelper.getReadableDatabase();
    		} else {
    			Log.i(TAG, "old read open");
    		}
    		return this;
    	}
    
    	public synchronized void closeDatabase() {
    		openCounter--;
    		if (openCounter == 0) {
    			Log.i(TAG, "closing db");
    			// Closing database
    			ourDataBase.close();
    			// ourDataBase.releaseReference();
    
    		} else {
    			Log.i(TAG, "not closing db. Open connections: " + openCounter);
    		}
    	}
      
      public ArrayList<Post> getPosts(){
        ArrayList<Post> postsArrayList = new ArrayList<>();
        Cursor posts = ourDataBase.query(TABLE_1, null, null, null, null,
                null, null);
        if (posts != null && posts.getCount() > 0) {
           for (int i = 0; i < posts.getCount(); i++) {
                posts.moveToPosition(i);
                postsArrayList.add(new Post(
                        posts.getLong(posts.getColumnIndex(DBHelper.C_POST_ID)),
                        posts.getString(posts.getColumnIndex(DBHelper.C_POST_TITLE)),
                        posts.getString(posts.getColumnIndex(DBHelper.C_POST_CONTENT)),
                        posts.getString(posts.getColumnIndex(DBHelper.C_POST_URL))));
            }
            return postsArrayList;
        } else {
            return null;
        }
      }
      
      public long insertPost(long postID, String postTitle, 
                           String postURL, String postContent) {
            ContentValues cv = new ContentValues();
            cv.put(C_POST_ID, postID);
            cv.put(C_POST_TITLE, postTitle);
            cv.put(C_POST_URL, postURL);
            cv.put(C_POST_CONTENT, postContent);
            Log.i(TAG, "inserted post " + postID + " title: " + postTitle);
            return ourDataBase.insert(TABLE_POSTS, null, cv);
    }
    }

MyActivity.java

public class MyActivity extends AppCompatActivity {
    private static final String TAG = MyActivity.class.getSimpleName();
  
  @Override
    protected void onCreate(Bundle savedInstanceState) {
      
      // reading from DB
      DBHelper helper = DBHelper.getInstance();
      helper.readOpen();
      ArrayList<Post> posts = helper.getPosts();
      helper.closeDatabase();
      
      
      // wrinting to DB
      DBHelper helper = DBHelper.getInstance();
      helper.writeOpen();
      long postInsertedID = helper.insertPost(1,"title","https://urlofthepost","content of the post");
      helper.closeDatabase();
    }
}

MyApplication.java

/**
 * Created by muhammadriyaz
 */
public class MyApplication extends Application {
    private static final String TAG = MyApplication.class.getSimpleName();
  
  @Override
    public void onCreate() {
        super.onCreate();

        // open db instance
        DBHelper.initDB(this);
    }
}

Post.java

public class Post {
    private String title, postUrl, content;
    long id;

    /**
     *
     * @param id
     * @param title
     * @param content
     * @param postUrl
     */
    public Post(long id, String title, String content, String postUrl) {
        this.id = id;
        this.title = title;
        this.content = content;
        this.postUrl = postUrl;
    }

    public String getTitle() {
        return title;
    }

    public long getID() {
        return id;
    }

    public String getContent() {
        return content;
    }

    public String getPostUrl() {
        return postUrl;
    }
}