Нативная разработка мобильных приложений

catalog.json
в методе 
onCreate
и его запись в базу данных!
Java
public class DbHelper extends SQLiteOpenHelper {
private Context mContext;

---

Запись книг в хранилище 

329
public DbHelper(Context context, String name, 
SQLiteDatabase.CursorFactory factory,
int version) {
super(context, name, factory, version);
mContext = context;
}
@Override
public void onCreate(SQLiteDatabase database) {
database.execSQL(BOOKS_CREATE_TABLE);
database.execSQL(AUTHORS_CREATE_TABLE);
database.execSQL(BRIDGE_CREATE_TABLE);
InputStream stream = null;
try {
stream = mContext.getAssets().open("catalog.json");
String json = Files.getStringFromStream(stream);
Books books = new Gson().fromJson(json, Books.class);
for (Book book : books) {
BookTransactions.write(database, book);
}
} catch (IOException e) {
e.printStackTrace();
} finally {
if (stream != null) {
try {
stream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
Log.d("MyApp", BookTransactions.read(database, "978-0439136365").getTitle());
}
@Override
public void onUpgrade(SQLiteDatabase database, int i, int i1) {
// ничего не делает
}
public static final String BOOKS_TABLE_NAME = "BOOKS";
public static final String BOOKS_COLUMN_TITLE = "TITLE";
public static final String BOOKS_COLUMN_ISBN = "ISBN";
public static final String BOOKS_COLUMN_PAGECOUNT = "PAGECOUNT";
public static final String BOOKS_COLUMN_ISFICTION = "ISFICTION";
public static final String AUTHORS_TABLE_NAME = "AUTHORS";
public static final String AUTHORS_COLUMN_ID = "ID";
public static final String AUTHORS_COLUMN_NAME = "NAME";
public static final String BRIDGE_TABLE_NAME = "BOOK_AUTHOR_BRIDGE";
public static final String BRIDGE_COLUMN_BOOK_ID = "BOOK_ID";
public static final String BRIDGE_COLUMN_AUTHOR_ID = "AUTHOR_ID";
public static final String BOOKS_CREATE_TABLE = "CREATE TABLE IF NOT EXISTS " +
BOOKS_TABLE_NAME + " (" +

---

330

Сохранность данных
BOOKS_COLUMN_TITLE + " TEXT," +
BOOKS_COLUMN_ISBN + " TEXT," +
BOOKS_COLUMN_PAGECOUNT + " INT," +
BOOKS_COLUMN_ISFICTION + " BOOL);";
public static final String AUTHORS_CREATE_TABLE = "CREATE TABLE IF NOT EXISTS " +
AUTHORS_TABLE_NAME + " (" +
AUTHORS_COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT," +
AUTHORS_COLUMN_NAME + " TEXT)";
public static final String BRIDGE_CREATE_TABLE = "CREATE TABLE IF NOT EXISTS " +
BRIDGE_TABLE_NAME +
" (" +
BRIDGE_COLUMN_BOOK_ID + " INTEGER REFERENCES BOOKS," +
BRIDGE_COLUMN_AUTHOR_ID + " INTEGER REFERENCES AUTHORS)";
}
Kotlin
class DbHelper(private val context: Context, name: String,
factory: SQLiteDatabase.CursorFactory,
version: Int) : 
SQLiteOpenHelper(mContext, name, factory, version) {
override fun onCreate(database: SQLiteDatabase) {
database.execSQL(BOOKS_CREATE_TABLE)
database.execSQL(AUTHORS_CREATE_TABLE)
database.execSQL(BRIDGE_CREATE_TABLE)
val stream = context.assets.open("catalog.json")
stream.use { s ­>
val json = Files.getStringFromStream(s)
val books = Gson().fromJson(json, Books::class.java)
for (book in books) {
BookTransactions.write(database, book)
}
}
}
override fun onUpgrade(database: SQLiteDatabase, i: Int, i1: Int) {
// ничего не делает
}
companion object {
const val BOOKS_TABLE_NAME = "BOOKS"
const val BOOKS_COLUMN_TITLE = "TITLE"
const val BOOKS_COLUMN_ISBN = "ISBN"
const val BOOKS_COLUMN_PAGECOUNT = "PAGECOUNT"
const val BOOKS_COLUMN_ISFICTION = "ISFICTION"
const val AUTHORS_TABLE_NAME = "AUTHORS"
const val AUTHORS_COLUMN_ID = "ID"
const val AUTHORS_COLUMN_NAME = "NAME"
const val BRIDGE_TABLE_NAME = "BOOK_AUTHOR_BRIDGE"
const val BRIDGE_COLUMN_BOOK_ID = "BOOK_ID"

---

Запись книг в хранилище 

331
const val BRIDGE_COLUMN_AUTHOR_ID = "AUTHOR_ID"
const val BOOKS_CREATE_TABLE = 
"CREATE TABLE IF NOT EXISTS " + BOOKS_TABLE_NAME +
" (" +
BOOKS_COLUMN_TITLE + " TEXT," +
BOOKS_COLUMN_ISBN + " TEXT," +
BOOKS_COLUMN_PAGECOUNT + " INT," +
BOOKS_COLUMN_ISFICTION + " BOOL);"
const val AUTHORS_CREATE_TABLE = 
"CREATE TABLE IF NOT EXISTS " + AUTHORS_TABLE_NAME +
" (" + 
AUTHORS_COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT," +
AUTHORS_COLUMN_NAME + " TEXT)"
const val BRIDGE_CREATE_TABLE = 
"CREATE TABLE IF NOT EXISTS " + BRIDGE_TABLE_NAME +
" (" +
BRIDGE_COLUMN_BOOK_ID + " INTEGER REFERENCES BOOKS," +
BRIDGE_COLUMN_AUTHOR_ID + " INTEGER REFERENCES AUTHORS)"
}
}
Теперь при первой попытке получить экземпляр 
SqliteDatabase
в классе 
Db­
Helper
запустится метод 
onCreate
и заполнит базу данных содержимым файла 
catalog.json
, который устанавливается вместе с приложением, в специальном 
каталоге 
assets
! Неплохо!
Мы потратили много времени на создание слоя хранения данных. Зато те
-
перь готовы показать на экране сохраненные книги, но прежде чем двинуться 
дальше, реализуем все то же самое в iOS.
iOS
В Android мы использовали базу данных, к которой можно выполнять запросы 
SQL для получения данных. В iOS есть возможность работать с хранилищем не
-
посредственно из кода на Swift, без посредничества SQL: механизм Core Data.