I am new to Android development and I want to ensure I'm learning decent practices for doing things. Right now this is my database class, which currently allows me to make a new instance of the singleton, as well as create a profiles table, as well as add/retrieve from the profiles table.
This is my code so far:
public class DatabaseHelper extends SQLiteOpenHelper {
private static volatile SQLiteDatabase mDatabase;
private static DatabaseHelper mInstance = null;
private static Context mContext;
private static final String DB_NAME = "database.db";
private static final int DB_VERSION = 1;
public static final String PROFILES_TABLE = "PROFILES";
public static final String PROFILES_COLUMN_ID = "_ID";
public static final String PROFILES_COLUMN_NAME = "NAME";
private static final String DB_CREATE_PROFILES_TABLE =
"CREATE TABLE " + PROFILES_TABLE + " ("
+ PROFILES_COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, "
+ PROFILES_COLUMN_NAME + " TEXT UNIQUE NOT NULL)";
public static synchronized DatabaseHelper getInstance(Context context) {
if (mInstance == null) {
mInstance = new DatabaseHelper(context.getApplicationContext());
try {
mInstance.open();
}
catch (SQLException e) {
e.printStackTrace();
}
}
return mInstance;
}
private DatabaseHelper(Context context) {
super(context, DB_NAME, null, DB_VERSION);
mContext = context;
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(DB_CREATE_PROFILES_TABLE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
@Override
public void onConfigure(SQLiteDatabase db){
super.onConfigure(db);
db.setForeignKeyConstraintsEnabled(true);
}
public synchronized void open() throws SQLException {
mDatabase = getWritableDatabase();
}
public synchronized void close() {
mDatabase.close();
}
public synchronized long addNewProfile(String name) {
ContentValues values = new ContentValues();
values.put(DatabaseHelper.PROFILES_COLUMN_NAME, name);
return mDatabase.insertWithOnConflict(DatabaseHelper.PROFILES_TABLE, null, values, SQLiteDatabase.CONFLICT_IGNORE);
}
public synchronized Profile getProfileById(long profileId) {
Cursor cursor = mDatabase.query(
DatabaseHelper.PROFILES_TABLE, // table
new String[]{DatabaseHelper.PROFILES_COLUMN_ID, DatabaseHelper.PROFILES_COLUMN_NAME}, // column names
DatabaseHelper.PROFILES_COLUMN_ID + " = ?", // where clause
new String[]{profileId + ""}, // where params
null, // groupby
null, // having
null); // orderby
cursor.moveToFirst();
Profile profile = null;
if (!cursor.isAfterLast()) {
String profileName = getStringFromColumnName(cursor, DatabaseHelper.PROFILES_COLUMN_NAME);
profile = new Profile(profileId, profileName);
cursor.moveToNext();
}
cursor.close();
return profile;
}
public synchronized List<Profile> getAllProfiles() {
List<Profile> profiles = new ArrayList<>();
Cursor cursor = mDatabase.query(
DatabaseHelper.PROFILES_TABLE, // table
new String[]{DatabaseHelper.PROFILES_COLUMN_ID, DatabaseHelper.PROFILES_COLUMN_NAME}, // column names
null, // where clause
null, // where params
null, // groupby
null, // having
DatabaseHelper.PROFILES_COLUMN_NAME); // orderby
cursor.moveToFirst();
while (!cursor.isAfterLast()) {
long profileId = getLongFromColumnName(cursor, DatabaseHelper.PROFILES_COLUMN_ID);
String profileName = getStringFromColumnName(cursor, DatabaseHelper.PROFILES_COLUMN_NAME);
profiles.add(new Profile(profileId, profileName));
cursor.moveToNext();
}
cursor.close();
return profiles;
}
private synchronized long getLongFromColumnName(Cursor cursor, String columnName) {
int columnIndex = cursor.getColumnIndex(columnName);
return cursor.getLong(columnIndex);
}
private synchronized String getStringFromColumnName(Cursor cursor, String columnName) {
int columnIndex = cursor.getColumnIndex(columnName);
return cursor.getString(columnIndex);
}
}
For reference (this may or may not be necessary, but I am posting it just in case), my Profile class, which is something I use in several other places in the app:
public class Profile {
private long mId;
private String mName;
public Profile(long id, String name) {
mId = id;
mName = name;
}
public long getId() {
return mId;
}
public void setId(long id) {
mId = id;
}
public String getName() {
return mName;
}
public void setName(String name) {
mName = name;
}
}
My questions:
Is it proper to be storing the field names of the table in the database class like this, or should I be moving it to its own separate class (for example a
ProfileSqlclass of some kind that holds all the names).Should I be decoupling the query logic from this class somehow? How do I do this? What if I have several tables, queries, thread methods, etc? Do these all go in their own separate classes, too? If I add CRUD functions for several tables, this class could get very large very quickly.
Should I be somehow tying any of this stuff into my Profile class itself, which I use in several other places in my app? For instance should I be including the profile table SQL stuff (the create table string and the table/column names) in the Profile class, or is this meddling things together that shouldn't be?
As you can see I am mostly asking where stuff should go. Right now I am just kind of lumping it all together into one database class.
I am hoping that this example is short enough to where someone can show me the proper way to restructure all of this so I can take those skills and apply them going forward.
