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In my app I need a database with different tables that I would write before and then just read in the app. I know how to create a new database, write and read it in the app using SQL but I actually don't know with what program (and in which format) I can write the database before adding it in the assets folder.
Would anyone help me with that, please?
You can use http://sqlitebrowser.org/ It run on Mac OS , Windows and Linux
You can use SQLite, which is an on-device SQL implementation. Be aware that this will only support a subset of SQL operations found in most traditional relational DBs. If you need full SQL support you'll have to write back-end web services hosted elsewhere.
You can use SQLiteOpenHelper for creating your database.
Here is my example to create simple database that have store City with 2 filed is City_ID and City_Name:
public class DiLiBusDatabaseHelper extends SQLiteOpenHelper {
private static final String DATABASE_NAME = "DiLiBusDB";
private static final String TBL_CITY = "City";
private static final String CITY_ID_FIELD = "City_ID";
private static final String CITY_NAME_FIEDL = "City_Name";
private SQLiteDatabase database;
private static DiLiBusDatabaseHelper mInstance = null;
Context context;
//synchronized to make sure have only one thread is run at the same time
public static DiLiBusDatabaseHelper getInstance(Context context){
if(mInstance == null){
mInstance = new DiLiBusDatabaseHelper(context.getApplicationContext());
}
return mInstance;
}
private DiLiBusDatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, 2);
this.context = context;
this.database = getWritableDatabase();
}
#Override
public void onCreate(SQLiteDatabase db) {
String query = "CREATE TABLE"+" "+TBL_CITY+"("+CITY_ID_FIELD+" "+"TEXT PRIMARY KEY,"+CITY_NAME_FIEDL+" "+"TEXT"+");";
String queryIndex = "CREATE INDEX city_name_idx ON"+ " "+TBL_CITY +"("+CITY_NAME_FIEDL+");";
db.execSQL(query);
db.execSQL(queryIndex);
}
#Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
}
p/s: I using Singleton pattern to create my database. Moreover, if you want to save your db in SDCard, u can check this link
There are many libraries for database:
Realm
Active Android
Green DAO
This is the simplest way for creating database because you operates on your defined data models.
Related
We try to update sqlite_sequence with the following code.
WeNoteRoomDatabase weNoteRoomDatabase = WeNoteRoomDatabase.instance();
weNoteRoomDatabase.query(new SimpleSQLiteQuery("UPDATE sqlite_sequence SET seq = 0 WHERE name = 'attachment'"));
However, it has no effect at all. I exam the sqlite_sequence table content using SQLite browser. The counter is not reset to 0.
If we try to run the same query manually using SQLite browser on same SQLite file, it works just fine.
Our Room database is pretty straightforward.
#Database(
entities = {Attachment.class},
version = 6
)
public abstract class WeNoteRoomDatabase extends RoomDatabase {
private volatile static WeNoteRoomDatabase INSTANCE;
private static final String NAME = "wenote";
public abstract AttachmentDao attachmentDao();
public static WeNoteRoomDatabase instance() {
if (INSTANCE == null) {
synchronized (WeNoteRoomDatabase.class) {
if (INSTANCE == null) {
INSTANCE = Room.databaseBuilder(
WeNoteApplication.instance(),
WeNoteRoomDatabase.class,
NAME
)
.build();
}
}
}
return INSTANCE;
}
}
Any idea what we had missed out?
Additional information : clearing sqlite_sequence is not working in android room
Room doesn't use SQLiteDatabase - but it uses SupportSQLiteDatabase, while it's source code states, that it delegates all calls to an implementation of {#link SQLiteDatabase}... I could even dig further - but I'm convinced, that this is a consistency feature and not a bug.
SQLiteDatabase.execSQL() still works fine, but with SupportSQLiteDatabase.execSQL() the same UPDATE or DELETE queries against internal tables have no effect and do not throw errors.
my MaintenanceHelper is available on GitHub. it is important that one initially lets Room create the database - then one can manipulate the internal tables with SQLiteDatabase.execSQL(). while researching I've came across annotation #SkipQueryVerification, which could possibly permit UPDATE or DELETE on table sqlite_sequence; I've only managed to perform a SELECT with Dao... which in general all hints for the internal tables are being treated as read-only, from the perspective of the publicly available API; all manipulation attempts are being silently ignored.
i think query is wrong, you should try below query
weNoteRoomDatabase.query(new SimpleSQLiteQuery("UPDATE sqlite_sequence SET seq = 0 WHERE name = attachment"));
I'm using room database version 2.2.5
Here I'm unable to execute this query using Room Dao structure, so make one simple class and access method as like this and I got successful outcomes so this one is tested result. I'm using RxJava and RxAndroid for same.
public class SqlHelper {
private static SqlHelper helper = null;
public static SqlHelper getInstance() {
if (helper == null) {
helper = new SqlHelper();
}
return helper;
}
public Completable resetSequence(Context context) {
return Completable.create(emitter -> {
try {
AppDatabase.getDatabase(context)
.getOpenHelper()
.getWritableDatabase()
.execSQL("DELETE FROM sqlite_sequence WHERE name='<YOUR_TABLE_NAME>'");
emitter.onComplete();
} catch (Exception e) {
emitter.onError(e);
}
});
}
}
Execute:
SqlHelper.getInstance()
.resetQuizSequence(context)
.subscribeOn(Schedulers.io()
.observeOn(AndroidSchedulers.mainThread())
.subscribe(() -> {}, error -> {});
Table sql_sequence is not managed by Room, so you need to edit it using a SupportSQLiteDatabase.
Try this:
String sqlQuery = "DELETE FROM sqlite_sequence WHERE name='attachment'";
weNoteRoomDatabase().getOpenHelper().getWritableDatabase().execSQL(sqlQuery);
This works for me - Room 2.2.6
String sqlQuery = "DELETE FROM sqlite_sequence WHERE name='attachment'";
<YourDatabase>.getInstance(mContext).getOpenHelper().getWritableDatabase().execSQL(sqlQuery);
I am using SQLCipher v3.5.7 and observed an unexpected behavior from SQLiteDatabase with incorrect password.
I encrypted the database with "key1".
Closed the database connection.
Then I tried to open my database with "key2", the SQLiteDatabase is not throwing an exception. Instead, it is updating the old password (key1) to new password (key2). I verified this by opening the .db file in SQLiteBrowser.
Can somebody help me why it is behaving this way?
private static SQLiteCipherDatabaseHelper createDBConnection(Context context, String databasePath, final String key) throws SQLiteDatabaseException {
if (dbInstance == null) {
dbInstance = new SQLiteCipherDatabaseHelper(context, databasePath);
String path = context.getDatabasePath(databasePath).getPath();
File dbPathFile = new File(path);
if (!dbPathFile.exists()) {
dbPathFile.getParentFile().mkdirs();
}
setDatabaseWithDBEncryption(key);
}
return dbInstance;
}
private static void setDatabaseWithDBEncryption(String encryptionKey) throws SQLiteDatabaseException {
loadSQLCipherLibs();
try {
sqliteDatabase = SQLiteDatabase.openOrCreateDatabase(new File(context.getDatabasePath(databasePath).getPath()), encryptionKey, null);
} catch (Exception e) {
SyncLogger.getSharedInstance().logFatal("SQLiteCipherDatabaseHelper", "Failed to open or create database. Please provide a valid encryption key");
throw new SQLiteDatabaseException(SyncErrorCodes.EC_DB_SQLCIPHER_FAILED_TO_OPEN_OR_CREATE_DATABASE, SyncErrorDomains.ED_OFFLINE_OBJECTS, SyncErrorMessages.EM_DB_SQLCIPHER_FAILED_TO_OPEN_OR_CREATE_DATABASE, e);
}
}
Have you upgrade your db version ??
private static final int DATABASE_VERSION = 2;//from 1 to 2
private static class OpenHelper extends SQLiteOpenHelper {
OpenHelper(Context context) // constructor
{
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
#Override
public void onCreate(SQLiteDatabase db) {
}
#Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
{
//Changes in db mentioned here
}
}
Are you actually populating the database with tables and data after keying it? It seems most likely that for some reason you are recreating the database each time you run the test. Have you verified that the actual database is encrypted by pulling it off the device and examining the file? Perhaps you are recreating a new database each time you run the test, in which case the new key would just be used.
It's worth noting that this behavior is covered in the SQLCipher for Android Test project.
https://github.com/sqlcipher/sqlcipher-android-tests/blob/master/src/main/java/net/zetetic/tests/InvalidPasswordTest.java
If you suspect an issue you can try running the test suite on your device, or create a new test case to verify the behavior with your own code.
I am making Android app for practicing driving licence theory tests. I will have about 3000 questions. Question object would have several atributes (text, category, subcategory, answers, group). I will create them and put in app, so data won't ever change. When user chooses category, app would go througt data, look which question meets requirements (that user selected) and put it in list for displaying. What should I use to store data/questions, XML or SQLite? Thanks in advance.
Edit:
I forgot to mentiont that app won't use internet connection. Also, I planned to make simple java app for entering data. I would copy text from government's website (I don't have access to their database and I have to create mine), so I thought to just put question's image url to java program and it would download it and name it automaticaly. Also, when entering new question's text it would tell me if that question already exist before I enter other data. That would save me time, I wouldn't have to save every picture and name it my self. That is what I thought if using XML. Can I do this for JSON or SQLite?
If you do not have to perform complex queries, I would recommend to store your datas in json since very well integrated in android apps using a lib such as GSON or Jackson.
If you don't want to rebuild your app / redeploy on every question changes. You can imagine to have a small webserver (apache, nginx, tomcat) that serves the json file that you will request on loading of the app. So that you will download the questions when your app is online or use the cached one.
XML is a verbose format for such an usage, and does not bring much functions....
To respond to your last question, you can organise your code like that :
/**
* SOF POST http://stackoverflow.com/posts/37078005
* #author Jean-Emmanuel
* #company RIZZE
*/
public class SOF_37078005 {
#Test
public void test() {
QuestionsBean questions = new QuestionsBean();
//fill you questions
QuestionBean b=buildQuestionExemple();
questions.add(b); // success
questions.add(b); //skipped
System.out.println(questions.toJson()); //toJson
}
private QuestionBean buildQuestionExemple() {
QuestionBean b= new QuestionBean();
b.title="What is the size of your boat?";
b.pictures.add("/res/images/boatSize.jpg");
b.order= 1;
return b;
}
public class QuestionsBean{
private List<QuestionBean> list = new ArrayList<QuestionBean>();
public QuestionsBean add(QuestionBean b ){
if(b!=null && b.title!=null){
for(QuestionBean i : list){
if(i.title.compareToIgnoreCase(b.title)==0){
System.out.println("Question "+b.title+" already exists - skipped & not added");
return this;
}
}
System.out.println("Question "+b.title+" added");
list.add(b);
}
else{
System.out.println("Question was null / not added");
}
return this;
}
public String toJson() {
ObjectMapper m = new ObjectMapper();
m.configure(Feature.ALLOW_SINGLE_QUOTES, true);
String j = null;
try {
j= m.writeValueAsString(list);
} catch (JsonProcessingException e) {
e.printStackTrace();
System.out.println("JSON Format error:"+ e.getMessage());
}
return j;
}
}
public class QuestionBean{
private int order;
private String title;
private List<String> pictures= new ArrayList<String>(); //path to picture
private List<String> responseChoice = new ArrayList<String>(); //list of possible choices
public int getOrder() {
return order;
}
public void setOrder(int order) {
this.order = order;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public List<String> getPictures() {
return pictures;
}
public void setPictures(List<String> pictures) {
this.pictures = pictures;
}
public List<String> getResponseChoice() {
return responseChoice;
}
public void setResponseChoice(List<String> responseChoice) {
this.responseChoice = responseChoice;
}
}
}
CONSOLE OUTPUT
Question What is the size of your boat? added
Question What is the size of your boat? already exists - skipped & not added
[{"order":1,"title":"What is the size of your boat?","pictures":["/res/images/boatSize.jpg"],"responseChoice":[]}]
GIST :
provides you the complete working code I've made for you
https://gist.github.com/jeorfevre/5d8cbf352784042c7a7b4975fc321466
To conclude, what is a good practice to work with JSON is :
1) create a bean in order to build your json (see my example here)
2) build your json and store it in a file for example
3) Using android load your json from the file to the bean (you have it in andrdoid)
4) use the bean to build your form...etc (and not the json text file) :D
I would recommend a database (SQLite) as it provides superior filtering functionality over xml.
Create the db using DB Browser for SQLite
And then use the library SQLiteAssetHelper in the link-
https://github.com/jgilfelt/android-sqlite-asset-helper
Tutorial on how to use -
http://www.javahelps.com/2015/04/import-and-use-external-database-in.html
You can use Paper https://github.com/pilgr/Paper its a fast NoSQL data storage for Android.
SQLite is the best for your system. because you will have to maintain (text, category, subcategory, answers, group) etc. So if you create db and create table for them. That will be easy to manage and you can relationship with each other which is not possible to XML.
I am making an Android app to learn sqllite. Because I use 7 tables, I decided to create 7 class files in a folder "DBHelper", and want to make 7 files in a folder "DBadapter". Here what the structure looks like:
root
DBHelper: 7 helper files (ex: PersonHelper.java)
DBadapter: 7 adapter files (ex: PersonDAO.java)
But I get an error message with PersonDAO.java: "cannot be accessed from outside package", when I declared the object: "PersonHelper personHelper = new PersonHelper(context);" in the constructor.
Anyone has an idea how to fix that without putting all files in one folder? What is the standard in the industry when creating multiple large tables?
PS: The error is gone once I place all files in one directory.
public class PersonDAO {
private Context context;
//Database info
private static final String DATABASE_NAME = "MyDB";
private static final int DATABASE_VERSION = 1;
//Table helper info
public PersonHelper databaseHelper;
private SQLiteDatabase db = null;
//Constructors
PersonDAO(Context context) {
this.context = context;
databaseHelper = new PersonHelper(context); //Error: "cannot be accessed from outside package"
}
Your constructor of your PersonHelper is probably default like it is in your PersonDAO class. So it can only be accessed from the same package. You have to change it to public to access it from PersonDAO:
public PersonHelper(Context context){
...
}
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I am making an app that my wife can use to check if a certain IC friendly or not. The problem is that I need 5 columns if you will (foodName, safe, try, avoid, foodCategory. Each may or may not have a description of the food name under safe, try, avoid. Should I use a database an .xls file or can I do it in xml?
It depends on your requirement/ useage
use sharedPreferences or sqlite database
if you want to store data for long term use sqlite
and if you want to maintain sessions use SharedPreferences.
SharedPreference
SharedPreferences.Editor editor = getSharedPreferences(MY_PREFS_NAME, MODE_PRIVATE).edit();
editor.putString("name", "Elena");
editor.putInt("idName", 12);
editor.commit();
Retrieve data from preference:
SharedPreferences prefs = getSharedPreferences(MY_PREFS_NAME, MODE_PRIVATE);
String restoredText = prefs.getString("text", null);
if (restoredText != null) {
String name = prefs.getString("name", "No name defined");//"No name defined" is the default value.
int idName = prefs.getInt("idName", 0); //0 is the default value. and it requires API 11
}
And for using Sqlite #Sri Hari have shown you an example..
Create a new SQLite database and store it. her you can store multiple tables safely.
public class DictionaryOpenHelper extends SQLiteOpenHelper {
private static final int DATABASE_VERSION = 2;
private static final String DICTIONARY_TABLE_NAME = "dictionary";
private static final String DICTIONARY_TABLE_CREATE =
"CREATE TABLE " + DICTIONARY_TABLE_NAME + " (" +
KEY_WORD + " TEXT, " +
KEY_DEFINITION + " TEXT);";
DictionaryOpenHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
#Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(DICTIONARY_TABLE_CREATE);
}
}
For storing data in android you can use:
Shared Preferences - Store private primitive data in key-value pairs
Internal Storage - Store private data on the device memory
External Storage - Store public data on the shared external storage
SQLite Databases - Store structured data in a private database
Network Connection - Store data on the web with your own network
server.
IMO for your purposes the most efficient option can be Shared Prefeerences or SQLite Database
More details for storing data you can find here.
Please note that you can look also for some ORMs to make it easier with SQLite Database - GreenDAO, OrmLite,...