Develop Reference

Adding data to SQLite

I'm creating my first data enabled app but am struggling with the last part - actually adding and retrieving the data. For now I am only concerned with adding data to the table. Following this tutorial I have created model classes for my tables and a DBHelper class with all my CRUD methods (I can post all these if required but not sure they are necessary to answer this question. Please correct me if I am wrong!). Unfortunately the tutorial ends here and doesn't go into detail on how to pass the data from the UI of the app into the DB.
After some Google searches I have found an example of how to pass some data to these methods but only how to pass one piece of data at a time, so only really useful if my table has just one field - mine has more than one.
For example, if I have a a table for "Todo" tasks, in my dbhelper my create method may be;
public void createTodo(String todoText) {
ContentValues contentValues = new ContentValues();
contentValues.put("todo", todoText);
// Insert into DB
db.insert("todos", null, contentValues);
}
so from my activity I just need
dao.createTodo(todoTextValue);
For my app I will be adding more than one field at a time, so my create method looks like this;
public long createSite(Site site){
SQLiteDatabase database = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KEY_SITE_NAME, site.getSiteName());
values.put(KEY_SITE_LAT, site.getSiteLat());
values.put(KEY_SITE_LON, site.getSiteLon());
values.put(KEY_CREATED_AT, site.getSiteCreatedDateTime());
// Insert Row
long siteid = database.insert(TABLE_SITES, null, values);
So my question really is how I can pass all the different bits of data to the createSite method.

I don't know if this really needs an answer, but well here's a code...
Assuming your Site class is like this.
public class Site {
private String siteName;
private double siteLat;
private double siteLon;
private Date siteCreatedDateTime;
// getters and setters here
}
You then pass the data from your EditText value to your new Site object. It will look like this in your activity.
EditText siteNameInput = (EditText) findViewById(R.id.siteNameInput);
EditText siteLatInput = (EditText) findViewById(R.id.siteLatInput);
EditText siteLonInput = (EditText) findViewById(R.id.siteLonInput);
EditText siteCreatedDateTimeInput = (EditText) findViewById(R.id.siteCreatedDateTimeInput);
String siteName = siteNameInput.getText().toString();
String siteLat = siteLatInput.getText().toString();
String siteLon = siteLonInput.getText().toString();
String siteCreatedDateTime= siteCreatedDateTimeInput.getText().toString();
Site site = new Site();
site.setSiteName(siteName);
site.setSiteLat(siteLat);
site.setSiteLon(siteLon);
site.setSiteCreatedDateTime(siteCreatedDateTime);
dao.createSite(site);
Hope this helps you... You can learn more on Object-Oriented programming in Java here

public long createSite(Model site,String name, String address){
SQLiteDatabase database = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KEY_NAME, site.name);
values.put(KEY_ADDRESS, site.address);
// Insert Row
long siteid = database.insert(TABLE_SITES, null, values);
to add elements to the class you just add
public class Model {
String name;
String address;
//add year as many as you need
Model(String name, String address){
this.name=name;
this.address=address;
}
}
And in you activity you call this
In java to add a new object in this case Model
Model x = new Model("josh","Ireland");
and you just pass to
dao.createTodo(x);

Todo and Site are models. Each variable represents a column of that table. You need to create a custom model for each of your tables. The createSite method takes an object of type Site and adds it as a row in the TABLE_SITES in the DB. values.put(...)takes columnName, value. So here you give your own column names and values.
Instead of getting into all this I suggest you use an orm like active android:
http://www.activeandroid.com/

How to load database data, and store it into array list, and show it into ListVIew

So, I want to build an app to view some data from database. I already have the database, also already made some entities that have exactly same properties name with the column names in database. And also I put the database into database directory by copying from assets folder.
What I want to achieve is, I want to pull some data, and put it into array list, so I can show it in ListView in fragment.
Is there any convenient way to pull some data without querying (like loadAll() function) ?
For now, I'm using cursor to save the pulled data using query, and assign its properties one by one using set function like setName(String name).
After that, I show the list using CursorAdapter.
It would be like this
public class FrameCursor extends CursorWrapper{
/**
* Creates a cursor wrapper.
*
* #param cursor The underlying cursor to wrap.
*/
public FrameCursor(Cursor cursor) {
super(cursor);
}
public ZFrame getFrame(){
if(isBeforeFirst() || isAfterLast()){
return null;
}
ZFrame frame = new ZFrame();
ZFrameDao frameDao = new ZFrameDao();
int frameEdition = getInt(getColumnIndex(COLUMN_FRAME_EDITION));
int frameId = getInt(getColumnIndex(COLUMN_FRAME_ID));
int frameNumber = getInt(getColumnIndex(COLUMN_FRAME_NUMBER));
int frameType = getInt(getColumnIndex(COLUMN_FRAME_TYPE));
int frameBookmark = getInt(getColumnIndex(COLUMN_FRAME_BOOKMARK));
int frameGlyph = getInt(getColumnIndex(COLUMN_FRAME_GLYPH));
int frameLesson = getInt(getColumnIndex(COLUMN_FRAME_LESSON));
String frameAllReading = getString(getColumnIndex(COLUMN_FRAME_ALL_READING));
String frameReadingNumber = getString(getColumnIndex(COLUMN_FRAME_READING_NUMBER));
String frameReference = getString(getColumnIndex(COLUMN_FRAME_REFERENCE));
String frameWritingNumber = getString(getColumnIndex(COLUMN_FRAME_WRITING_NUMBER));
frame.setZEDITION(frameEdition);
frame.setZFRAME_ID(frameId);
frame.setZFRAME_NUMBER(frameNumber);
frame.setZFRAME_TYPE(frameType);
frame.setZBOOKMARK(frameBookmark);
frame.setZGLYPH((long)frameGlyph);
frame.setZLESSON((long)frameLesson);
frame.setZALL_READING_NUMBER(frameAllReading);
frame.setZREADING_NUMBER(frameReadingNumber);
frame.setZREFERENCE(frameReference);
frame.setZWRITING_NUMBER(frameWritingNumber);
return frame;
}
}
It would be consume lot of work for doing this for every table.
So anyone could help me?

Why not using CursorLoader ? Use CursorLoader to handle the cursor query issue, and it works perfectly with CursorAdapter, Here is the google's guide

Maybe this is what you need, a light weight orm api? You can go here for more information.

how to delete a record from ORMLITE?

I need to delete a record from ORMLite Database I can delete a record by id using as below
#Override
public void Delete(int id) throws SQLException {
this.dao.deleteById(id);
}
but what if I have to delete a record from same table not by id but by name or any other field
I want something like
public void Deletefromcanteen(String name,MealType mealtype) {
this.dao.deletebyName(name);
}
what query should i write using querybuilder to delete a record where name = name and mealtype = say (lunch)
I tried something like this in my databasehelper class
public void deletefromcanteen(int id, String mealtype) {
try {
Dao<CanteenLog, Integer> canteenDao = getCanteen();
DeleteBuilder<CanteenLog, Integer> deleteBuilder = canteenDao
.deleteBuilder();
deleteBuilder.where().eq("user_id", id).and().eq("meal", mealtype);
canteenDao.delete(deleteBuilder.prepare());
} catch (Exception e) {
...
}
}

deleteBuilder.where().eq("FIELD_NAME", arg);
deleteBuilder.delete();
Update:
For example :
//Get helper
DatabaseHelper helper = OpenHelperManager.getHelper(App.getContext(), DatabaseHelper.class);
//get dao
Dao dao = helper.getDao(YOUR_CLASS.class);
//delete elements from table in field by arg
DeleteBuilder<CanteenLog, Integer> deleteBuilder = dao.deleteBuilder();
deleteBuilder.where().eq("FIELD_NAME", arg);
deleteBuilder.delete();
Good luck!

To save building a query, you can do a select to find the ID, then do a delete by ID. Thsi will be straightforward if you already have the select query set up for this table.

It can be done also like that
DatabaseHelper.getInstance().getDao(YourObject.class).delete(yourObjectInstance);

If you are using Kotlin, you will need to do something like this instead since the type inference is not currently working correctly for the fluent syntax:
val deleteBuilder = dao.deleteBuilder()
val where = deleteBuilder.where().eq("address", address)
deleteBuilder.setWhere(where)
deleteBuilder.delete()

If you already have an instance of the object (or object list) you want to delete, just do :
//Get helper
DatabaseHelper helper =
OpenHelperManager.getHelper(App.getContext(), DatabaseHelper.class);
// delete 'em !
helper.getDao(YourObject.class).delete(yourObjectInstance);
If you don't have the instance to delete or you want to do it SQL way(!):
//Get helper
DatabaseHelper helper =
OpenHelperManager.getHelper(App.getContext(), DatabaseHelper.class);
//get dao
Dao dao = helper.getDao(YOUR_CLASS.class);
//delete elements from table in field by arg
DeleteBuilder<CanteenLog, Integer> deleteBuilder = dao.deleteBuilder();
deleteBuilder.where().eq("FIELD_NAME", "FIELD_VALUE");
deleteBuilder.delete();
If you need a more complicated Where logic, then use deleteBuilder.where().or() or deleteBuilder.where().and() to add more constraints.

What to do with Cursor after a SQLite query?

This is my first time using a database and I'm not really sure how this works. I made the database and made a query that returns a cursor and... now what? What is a cursor, really? Can I just use that to navigate through my data or do I have to put it in an ArrayList or ListActivity or what?

You need to iterate the cursor to get your results.
Use cursor.moveToFirst() and/or cursor.moveToNext() (with a while loop). Then you can use the getX() method, like cursor.getInt() or cursor.getString().
For example, ir your are expecting one result from your query:
if (cursor.moveToFirst()) {
String name = cursor.getString(cursor.getColumnIndex('NAME'));
int age = cursor.getInt(cursor.getColumnIndex('AGE'));
} else {
// oops nothing found!
}

First call cursor.moveToFirst(). Each time you call cursor.moveToNext() it will move to the next row. Make sure when you are done with your cursor you call cursor.deactivate() or you will get errors in your log cat.

Iterate over the returned Cursor instance
public List<Object[]> cursorToTableRows(Cursor cursor) {
List<Object[]> result = new ArrayList<Object[]>(cursor.getCount());
cursor.move(0);
cursor.moveToNext();
while (cursor.isAfterLast() == false) {
Object[] tableRow = new Object[cursor.getColumnCount()];
for(int i=0; i<cursor.getColumnNames().length; i++) {
int columnIndex = cursor.getColumnIndex(cursor.getColumnName(i));
String columnValue = cursor.getString(columnIndex);
tableRow[i] = columnValue;
}
result.add(tableRow);
cursor.moveToNext();
}
cursor.close();
return result;
}
Then create the desired objects.
public List<Vehicle> getVehicles() {
List<Vehicle> vehicles = new ArrayList<Vehicle>();
Cursor cursor = null;
List<Object[]> objects = cursorToTableRows(cursor);
for(Object[] row : objects) {
int i=0;
Vehicle vehicle = new Vehicle(row[i++].toString(), row[i++].toString()));
vehicles.add(vehicle)
}
return vehicles;
}

from Developer.android: This interface provides random read-write access to the result set returned by a database query.
In other words: query returns you a set of data represented by a cursor. First you need to make sure you got a valid cursor (not null) and then try to move it to desired position in the data set (use moveToXXX methods). In order to obtain data pointed by cursor use getXXX methods. When done using it make sure to call close to release resources.

According to this link it looks like you can iterate through the query return using something like:
cursor.next();
And grab the data at the location you are looking for using:
cursor.getString(0)

After you successfully have your Cursor setup, you would typically want to display that to a view in some form.
Have a look at the following answer for a detailed, but simple example of using a Cursor Adapter to pair up your newly-minted Cursor with your desired XML View:
https://stackoverflow.com/a/20532937/293280

Android: How to create my own cursor class?

I'm using Sqlite in Android and to get a value from the database I use something like this:
Cursor cursor = sqliteDatabase.rawQuery("select title,category from table", null);
int columnIndexTitle = cursor.getColumnIndex("title");
iny columnIndexCategory = cursor.getColumnIndex("category");
cursor.moveToFirst();
while (cursor.moveToNext()) {
String title = cursor.getString(columnIndexTitle);
String category = cursor.getString(columnIndexCategory);
}
cursor.close();
I want to create my own Cursor so that I can do getColumnIndex() and getString() with one method. Something like this:
String title = cursor.getString("title");
I want to create my own class that extends the cursor that I get from sqliteDatabase.rawQuery, but I'm not sure how to accomplish this. Should I extend SQLiteCursor or how should I do this? Is it even a possible and is it a good idea?

I came across this question looking for the best way to create a custom Cursor to use together with a SQLiteDatabase. In my case I needed an extra attribute to the Cursor to carry an additional piece of information, so my use case is not exactly as in the body of the question. Posting my findings in hope it will be helpful.
The tricky part for me was that the SQLiteDatabase query methods returns a Cursor, and I needed to pass on a custom subclass to Cursor.
I found the solution in the Android API: Use the CursorWrapper class. It seems to be designed exactly for this.
The class:
public class MyCustomCursor extends CursorWrapper {
public MyCustomCursor(Cursor cursor) {
super(cursor);
}
private int myAddedAttribute;
public int getMyAddedAttribute() {
return myAddedAttribute;
}
public void setMyAddedAttribute(int myAddedAttribute) {
this.myAddedAttribute = myAddedAttribute;
}
}
Usage:
public MyCustomCursor getCursor(...) {
SQLiteDatabase DB = ...;
Cursor rawCursor = DB.query(...);
MyCustomCursor myCursor = new MyCustomCursor(rawCursor);
myCursor.setMyAddedAttribute(...);
return myCursor;
}

Creating your own getString will cause a map lookup for each call instead of only for getColumnIndex.
Here's the code for SQLiteCursor.getColumnIndex and AbstractCursor.getColumnIndex. If you have many rows, reducing calls to this function will prevent unnecessary string processing and map lookups.

I wouldn't extend it, I'd make a helper:
class MartinCursor {
private Cursor cursor;
MartinCursor(Cursor cursor) {
this.cursor = cursor;
}
String getString(String column) {
....
}
}
or
class MartinCursorHelper {
static String getString(Cursor cursor, String column) {
....
}
}
Personally, I'd do the latter, unless you hate providing this extra argument all the time.
EDIT: I forgot to mention pydave's important point: If you call this in a loop, you're setting yourself up for a noticeable performance impact. The preferred way is to lookup the index once, cache it, and use that instead.

You should make use of the DatabaseUtils.stringForQuery() static method that is already in Android SDK to easily retrieve a value, this example is for String bot there is also method for Long
stringForQuery(SQLiteDatabase db, String query, String[] selectionArgs)
Utility method to run the query on the db and return the value in the first column of the first row.
Something like
String myString=DatabaseUtils.stringForQuery(getDB(),query,selectionArgs);

Came across this looking for a different solution, but just want to add this since I believe the answers are unsatisfactory.
You can easily create your own cursor class. In order to allow functions requiring Cursor to accept it, it must extend AbstractCursor. To overcome the issue of system not using your class, you simply make your class a wrapper.
There is a really good example here.
https://android.googlesource.com/platform/packages/apps/Contacts/+/8df53636fe956713cc3c13d9051aeb1982074286/src/com/android/contacts/calllog/ExtendedCursor.java
public class ExtendedCursor extends AbstractCursor {
/** The cursor to wrap. */
private final Cursor mCursor;
/** The name of the additional column. */
private final String mColumnName;
/** The value to be assigned to the additional column. */
private final Object mValue;
/**
* Creates a new cursor which extends the given cursor by adding a column with a constant value.
*
* #param cursor the cursor to extend
* #param columnName the name of the additional column
* #param value the value to be assigned to the additional column
*/
public ExtendedCursor(Cursor cursor, String columnName, Object value) {
mCursor = cursor;
mColumnName = columnName;
mValue = value;
}
#Override
public int getCount() {
return mCursor.getCount();
}
#Override
public String[] getColumnNames() {
String[] columnNames = mCursor.getColumnNames();
int length = columnNames.length;
String[] extendedColumnNames = new String[length + 1];
System.arraycopy(columnNames, 0, extendedColumnNames, 0, length);
extendedColumnNames[length] = mColumnName;
return extendedColumnNames;
}
That's the general idea of how it will work.
Now to the meat of the problem. To prevent the performance hit, create a hash to hold the column indices. This will serve as a cache. When getString is called, check the hash for the column index. If it does not exist, then fetch it with getColumnIndex and cache it.
I'm sorry I can't add any code currently, but I'm on mobile so I'll try to add some later.