Develop Reference

How to create and pre-populate sqlite database file with Android Room?

I want to create the sqlite database file DatabaseName.db with few entities that should be created in path of application (/data/data/MyApplicationName/databases/DatabaseName.db) when I try to execute the snippet code bellow, however the DatabaseName.db file is not there. Why ?
MyDatabaseSample db = Room.databaseBuilder(context,
MyClass.class,
"DatabaseName.db")
.addCallback(new RoomDatabase.Callback() {
#Override
public void onCreate(#NonNull SupportSQLiteDatabase ssdb) {
super.onCreate(db);
Log.d(TAG, "Database created - populate database");
}).build();
The database is created in the path of application only if I create an instance of a entity object and insert it in database right after get the database reference db. As I want to pre-populate database just after database creation, I think just make sense do it inside onCreate method of callback, but onCreate will never be called. So, How can I create the "DatabaseName.db" file with all tables representing entities and populate the database using callback ?
OBS: I am using Room version use 1.1.0-alpha2 and compiling with SDK android API 27.

I think you need to define some Room entities before pre-populate the db that's what i have done and it works just as expected, here is some code of what i have done so far:
public class DatabaseCreator {
private static MyDatabaseSample appDatabase;
private static final Object LOCK = new Object();
public synchronized static MyDatabaseSample getDBInstance(final Context context){
if(appDatabase == null) {
synchronized (LOCK) {
if (appDatabase == null) {
RoomDatabase.Callback appDBCallback = new RoomDatabase.Callback() {
#Override
public void onCreate(#NonNull SupportSQLiteDatabase db) {
super.onCreate(db);
try {
ReadScript.insertFromFile(context, R.raw.populate_db, db);
} catch (IOException e) {
Log.d("DB Population Error", e.toString());
}
}
};
appDatabase = Room.databaseBuilder(context,
MyDatabaseSample.class, "DatabaseName").addCallback(appDBCallback).build();
}
}
}
return appDatabase;
}
}
The code above is a singleton that uses the Callback's onCreate to pre-populate the db using a "raw resource" (To add raw resources to your project just create a folder inside your res folder like this "res/raw") that contains an sql script. To read the script i have used this code:
public class ReadScript {
public static int insertFromFile(Context context, int resourceCode, SupportSQLiteDatabase db) throws IOException {
// Reseting Counter
int result = 0;
// Open the resource
InputStream insertsStream = context.getResources().openRawResource(resourceCode);
BufferedReader insertReader = new BufferedReader(new InputStreamReader(insertsStream));
// Iterate through lines (assuming each insert has its own line and theres no other stuff)
while (insertReader.ready()) {
String insertStmt = insertReader.readLine();
if(insertStmt != null){
if(insertStmt.isEmpty()) continue;
db.execSQL(insertStmt);
result++;
Log.d("Statement #", Integer.toString(result));
}
}
insertReader.close();
// returning number of inserted rows
return result;
}
}
And then you just create the db instance by doing:
MyDatabaseSample db = DatabaseCreator.getDBInstance(getContext());
Note: You can try to create tables inside the raw script but i haven't tried it yet.
Goog luck.

Android - Database insert not inserting

I am including a database in my Android application. I am following the guide here:
http://developer.android.com/training/basics/data-storage/databases.html
I have a "DatabaseHelper" class that extends SQLiteOpenHelper as suggested, and I have a Contract that holds the information about the table and implements 'BaseColumns'. Therein, I have a function for inserting a new row into the database:
public static void addUploadInfo(SQLiteOpenHelper dbHelper, UploadInfo info) {
// Gets the data repository in write mode
SQLiteDatabase db = dbHelper.getWritableDatabase();
ContentValues values = info.getContentValues();
// Insert the new row, returning the primary key value of the new row
long newRowId;
newRowId = db.insert(
UploadInfoTable.TABLE_NAME,
null,
values);
db.close(); // Closing database connection
info.setDatabaseId(newRowId);
}
I am using the database to store app related meta data about a file. When I create a new file, I run the above function, and a row is successfully added to the database (and the database is created successfully if needed). I can see it using:
public static List<UploadInfo> getUploadInfoList(SQLiteOpenHelper dbHelper) {
List<UploadInfo> infoList = new ArrayList<>();
SQLiteDatabase db = dbHelper.getReadableDatabase();
String allQuery = "SELECT * FROM " + UploadInfoTable.TABLE_NAME;
Cursor cursor = db.rawQuery(allQuery, null);
if (cursor.moveToFirst()) {
do {
infoList.add(new UploadInfo(cursor));
} while (cursor.moveToNext());
}
cursor.close();
db.close();
return infoList;
}
However, when the app first loads, I insert a few initial entries into the database using:
#Override
public void onResume() {
super.onResume();
DatabaseHelper dbHelper = new DatabaseHelper(getActivity());
for (UploadInfo info: uploadList) {
UploadInfoTable.addUploadInfo(dbHelper, info);
}
}
These entries are assigned a new row ID that appears to be the correct value (not -1 indicating an error). There are no errors in the log. However, they are not found when I next run getUploadInfoList.
I have also tried this alternate insert function:
public static void addUploadInfo(SQLiteOpenHelper dbHelper, UploadInfo info) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
ContentValues values = info.getContentValues();
// Insert the new row, returning the primary key value of the new row
db.beginTransaction();
long newRowId = -1;
try {
newRowId = db.insertOrThrow(
UploadInfoTable.TABLE_NAME,
null,
values);
db.setTransactionSuccessful();
} catch (Exception e) {
e.printStackTrace();
} finally {
db.endTransaction();
}
db.close(); // Closing database connection
info.setDatabaseId(newRowId);
}
but I see the same result. In no case is info null. I always log the contents of the ContentValues. I use final variables for column names, so don't think I have an error in column name. This would show up as a row value of -1 anyway, and it doesn't.
Why would one implementation of the code insert successfully and the other not?

I suspect your code in onResume() is not successfully detecting the upgrade. Rather put all your code having to do with the upgrade in onUpgrade() instead of trying to detect an upgrade in onResume(). That should resolve the issue.

Android: How to close a cursor that returns from Class to Activity

I have: Accounts.java
public class Accounts{
private SQLiteDatabase dbConfig;
public Cursor list(Context context, String db, String where, String order) {
DBHelper dbHelper = new DBHelper(context, db);
dbConfig = dbHelper.getReadableDatabase();
Cursor c = dbConfig.query("accounts", new String[]{ "iId","sName"}, where, null, null, null, order);
return c;
}
}
and: MainActivity.java
Accounts account = new Accounts();
Cursor cursor = account.list(getApplicationContext(), globalDB, null, null);
while (cursor.moveToNext()) {
int id = cursor.getInt(0);
String name = cursor.getString(1);
}
cursor.close();
Running my application I get some logcat messages like:
close() was never explicitly called on database...
What is the best way to prevent it? How can I close a Cursor that returns from other class?
Thanks

After account.list() exits, the underlying database connection is still open, but there are no remaining references to it. So, it has leaked.
You can close the database once you're finished with it, or you can keep it open for the lifetime of your application by having a single global database connection which you open once, share amongst all your activities, and never close.
I recommend the latter approach. It results in much simpler code.

instead of calling cursor.close(); you can call and create a Accounts.close() method that closes both cursor and database

Android: SQLite Query Return 0 Rows Without Reload?

My application has a SQLite database to contain a list of highways. It shows them all in a list. It first tries to query the database for the roads. If the query doesn't return any, it calls another method that downloads a list from a remote server, and populates the database. After that returns, it immediately queries the database again.
That's how it should work. How it actually works is, the first query always returns nothing. It goes straight to downloading a fresh list, it inserts the list into the database, and queries again. The second query always returns the correct result. The strange thing is, I can repeat the operation without even exiting the application. Using the adb shell, I can read the SQLite3 database on the emulator. The data shown in the database is exactly as expected. But the application is behaving as though the data isn't there? Is there some behaviour I'm not aware of? Here's the code.
RoadsDataSource.java
public class RoadsDataSource {
private DataStorage data;
private static Context context;
public RoadsDataSource() {
this.data = new DataStorage(RoadsDataSource.context);
}
private List<Road> getRoads(Integer state) {
List<Road> roads = loadRoadsFromDb(state);
if (roads.isEmpty()) {
Request api = new Request(RoadsDataSource.context);
Roads apiRoads = api.fetchRoads(state);
this.data.storeRoads(apiRoads);
roads = loadRoadsFromDb(state);
}
return roads;
}
private List<Road> loadRoadsFromDb(Integer state) {
SQLiteQueryBuilder query = new SQLiteQueryBuilder();
query.setTables(Queries.ROAD_STATE_MATCHES);
Cursor results = query.query(
this.data.getWritableDatabase(),
new String[] {Tables.ROADS + "." + Tables.Roads.ID, Tables.ROADS + "." + Tables.Roads.TYPE, Tables.ROADS + "." + Tables.Roads.NUMBER},
Queries.ROADS_BY_STATE,
new String[] {state.toString()}, null, null, null
);
List<Road> roads = new ArrayList<Road>();
results.moveToFirst();
while (!results.isAfterLast()) {
roads.add(new Road(results.getInt(0), results.getString(1), results.getInt(2)));
results.moveToNext();
}
results.close();
System.out.println(roads.size());
return roads;
}
}
DataStorage.java
public class DataStorage extends SQLiteOpenHelper {
public void storeRoads(Roads roads) {
SQLiteDatabase db = this.getWritableDatabase();
for (Road road : roads.getRoads()) {
ContentValues roadRow = new ContentValues();
roadRow.put(Tables.Roads.ID, road.getId());
roadRow.put(Tables.Roads.TYPE, road.getType());
roadRow.put(Tables.Roads.NUMBER, road.getNumber());
try {
db.insertOrThrow(Tables.ROADS, null, roadRow);
} catch (SQLException e) {
}
ContentValues linkRow = new ContentValues();
linkRow.put(Tables.StatesRoads.STATE_ID, roads.getState());
linkRow.put(Tables.StatesRoads.ROAD_ID, road.getId());
try {
db.insertOrThrow(Tables.STATES_ROADS, null, linkRow);
} catch (SQLException e) {
}
}
}
}

Mo Kargas is right. Your db helper should look more like this http://code.google.com/p/android-notes/source/browse/trunk/src/com/bitsetters/android/notes/DBHelper.java?r=10
This may fix your issue though Replace
SQLiteDatabase db = this.getWritableDatabase();
with this
SQLiteDatabase db;
try {
db = dbHelper.getWritableDatabase();
} catch (SQLiteException e) {
db = dbHelper.getReadableDatabase();
}

I've had huge issues in the past with not closing the database handle - generally I do all db operations inside an SQLiteOpenHelper subclass, keeping a reference to the db, opening and closing it atomically.

How to optimize the insertion of an entry with multiple Strings and Images into a SQLite database

I defined a method to add an entry in my database helper class and insert data into database using it, but it is not working. This is my method defined in databasehelper class:
public void createchannelEntry(ChannelPoster channel) {
openDB();
ByteArrayOutputStream out = new ByteArrayOutputStream();
channel.getPoster().compress(Bitmap.CompressFormat.PNG, 100, out);
ContentValues cv = new ContentValues();
cv.put(KEY_POSTER, out.toByteArray());
cv.put(KEY_CHANNEL, channel.getChannel());
cv.put(KEY_PATH, channel.getPath());
cv.put(KEY_DBLINK, channel.getDBlink());
mDb.insert(channelS_TABLE, null, cv);
closeDB();
}
this is how I insert data
Bitmap sherlock = BitmapFactory.decodeResource(getResources(), R.drawable.sherlock);
mDB.createchannelEntry(new ChannelPoster(sherlock, "aa" ,"ll" ,"ha" ));
and I have a JavaBean for holding an entry
public class ChannelPoster {
private Bitmap poster;
private String channel;
private String path;
private String dblink;
public ChannelPoster(Bitmap pi, String c, String p, String d) {
poster = pi;
channel = c;
path = p;
dblink = d;
}
public Bitmap getPoster() { return poster; }
public String getChannel() { return channel; }
public String getPath() { return path; }
public String getDBlink() { return dblink; }
}
And because I am adding entries one by one, the program runs very slow, so it's there a faster way to insert many entries? like get all of them in one event?

I suggest not saving the images in the database, but rather saving them as files, and saving a path to them in the database (using a normal TEXT field).
If you don't want to do that, there are two things that will still greatly improve the speed of your processing:
Open and close the database only once around all your inserts
Use a transaction
Something like that:
SQLiteDatabase db = openDB();
db.beginTransaction();
try {
// Add here the loop with all your inserts
db.setTransactionSuccessful();
} finally {
db.endTransaction(); // will rollback and cancel the inserts if not marked as successful
db.close();
}
(the finally is there to make sure you close the transaction and the connection even if it somehow fails during the inserts: in this case ALL your inserts will be cancelled)