Unable to fetch existing db file in flutter - mysql

Question

I'm new to flutter and sqflite. For a project I was trying to use an existing database. I have kept my db file in a assest folder. When I run it on my emulator it shows nothing. Can someone tell me where did I do wrong? It's exactly not showing any error, but it's showing something like:
HostComposition ext ANDROID_EMU_CHECKSUM_HELPER_v1
ANDROID_EMU_native_sync_v2 ANDROID_EMU_native_sync_v3
ANDROID_EMU_native_sync_v4 ANDROID_EMU_dma_v1 ANDROID_EMU_direct_mem
ANDROID_EMU_host_composition_v1 ANDROID_EMU_host_composition_v2
ANDROID_EMU_YUV420_888_to_NV21 ANDROID_EMU_YUV_Cache
ANDROID_EMU_async_unmap_buffer GL_OES_EGL_image_external_essl3
GL_OES_vertex_array_object GL_KHR_texture_compression_astc_ldr
ANDROID_EMU_gles_max_version_3_0
W/OpenGLRenderer( 5874): Failed to choose config with EGL_SWAP_BEHAVIOR_PRESERVED, retrying without..
class DatabaseHelper {
static final _databaseName = "lastRandomdb.db";
static final _databaseVersion = 1;
static final table = "Randomdb";
static final columnEmail = "email";
static final columnName = "name";
DatabaseHelper._privateConstructor();
static final DatabaseHelper instance = DatabaseHelper._privateConstructor();
static Database _database;
Future<Database> get database async {
if (database != null) return database;
_database = await _initDatabase();
return _database;
}
_initDatabase() async {
var databasepath = await getDatabasesPath();
String path = join(databasepath, _databaseName);
//check existing
var exists = await databaseExists(path);
if (!exists) {
print("copy database start");
try {
await Directory(dirname(path)).create(recursive: true);
} catch (_) {
//copy
ByteData data = await rootBundle.load(join("assets", _databaseName));
List<int> bytes =
data.buffer.asUint8List(data.offsetInBytes, data.lengthInBytes);
//write
await File(path).writeAsBytes(bytes, flush: true);
}
} else {
print("opening exsisting database");
}
return await openDatabase(path, version: _databaseVersion);
}
//crud
Future<List<Contact>> getAllContacts() async {
Database db = await instance.database;
final List<Map<String, dynamic>> map = await db.query(table);
return List.generate(map.length, (index) {
return Contact.fromMap(map[index]);
});
}
Future<int> getCount() async {
Database db = await instance.database;
return Sqflite.firstIntValue(
await db.rawQuery("SELECT COUNT(EMAIL) FROM $table"));
}
}
this is my model file
final String COL_NAME = "name";
final String COL_EMAIL = "email";
class Contact {
String name, email;
Contact({this.name, this.email});
Contact.map(dynamic obj1) {
this.name = obj1['NAME'];
this.email = obj1['EMAIL'];
}
Map<String, dynamic> toMap() {
var map = <String, dynamic>{
//method
COL_NAME: name,
COL_EMAIL: email,
};
return map;
}
Contact.fromMap(Map<String, dynamic> map) {
//named constructor to return emoloyee model obj
name = map[COL_NAME];
email = map[COL_EMAIL];
}
#override
String toString() {
return 'Contact{name: $name, email: $email}';
}
}

Answer 1

Ok let's evaluate your _initDatabase line by line
first you create the path and check if it exists
var databasepath = await getDatabasesPath();
String path = join(databasepath,_databaseName);
//check existing
var exists = await databaseExists(path);
Seems good, then if it doesn't exist you want to copy it from the AssetFolder
try{
await Directory(dirname(path)).create(recursive: true);
}catch(_){
//copy
ByteData data = await rootBundle.load(join("assets",_databaseName));
List<int> bytes = data.buffer.asUint8List(data.offsetInBytes, data.lengthInBytes);
//write
await File(path).writeAsBytes(bytes, flush: true);
}
you try to create the Directory in the path (I don't know what method is dirname but I will believe it returns the path). If nothing fails then it will run
return await openDatabase(path,version: _databaseVersion);
It will enter the catch and copy the db from asset only if the creation of the Directory throws an error, is there a condition when it will fail that? If not then it will never try to copy the db. If you're sure that creating a Directory won't throw an error you should just run the code without the try catch
await Directory(dirname(path)).create(recursive: true);
ByteData data = await rootBundle.load(join("assets",_databaseName));
List<int> bytes = data.buffer.asUint8List(data.offsetInBytes, data.lengthInBytes);
await File(path).writeAsBytes(bytes, flush: true);