We Keep Coding

Is there any way to delete entries of an arraylist dynamically

As you can see from the image below I want to select something from my table ( which changes whenever I press a button from the vertical box to the left i.e "Overview", "Orders" ... ) and delete the record from an array ( i.e. where the content comes from ).
The method I approached bellow works but it is not elegant since I have to create at most 8 if statements for each button id. Is there any way to delete the content dynamically. Is there any way for the JVM to figure out which record belongs to which array list?
TableController
#FXML
private TableView<Object> defaultTableView;
public void delete(){
if( MockServer.getServer().currentButton.equals("btnIngredients"))
MockServer.getServer().removeIngredient(defaultTableView.getSelectionModel().getSelectedItem());
else if ( MockServer.------.equals("btnOrders"))
MockServer.getServer().removeOrder(defaultTableView.getSelectionModel().getSelectedItem());
}
Controller
#FXML
private TableController tableController;
#FXML
public void deleteRecord(ActionEvent event){
tableController.delete();
}
MockServer
public class MockServer implements ServerInterface {
public Restaurant restaurant;
public ArrayList<Dish> dishes = new ArrayList<Dish>();
public ArrayList<Drone> drones = new ArrayList<Drone>();
public ArrayList<Ingredient> ingredients = new ArrayList<Ingredient>();
public ArrayList<Order> orders = new ArrayList<Order>();
public ArrayList<Staff> staff = new ArrayList<Staff>();
public MockServer(){}
public ArrayList<Ingredient> getIngredients() { return this.ingredients; }
public ArrayList<Order> getOrders() { return this.orders; }
public ArrayList<Staff> getStaff() { return this.staff; }
....
static public ServerInterface getServer(){
return server;
}
#Override
public void removeIngredient(Ingredient ingredient) {
int index = this.ingredients.indexOf(ingredient);
this.ingredients.remove(index);
this.notifyUpdate();
}
}

This pseudocode will need refactoring since I don't have all the code that you are using but I wish that you will get the general idea
Ok I believe that in the button click code you have to tell your mock server which list is currently used try adding this to the mock server
List currentList = null;
public void setCurrentList(String listName) { // you can use integer but the best is to use enum type setCurrentList(enum) this way you will get tapeSafety
switch(listName){
case "ingredients" : currentList = ingredients ; break;
//other cases
default : throw new Exception(" list not referred error with key value"+listName);
}
}
public void delete(Object o){
int index = this.currentList.indexOf(o);
this.currentList.remove(index);
}
now you can update you controller delete as bellow
public void delete(){
MockServer.getServer().delete(defaultTableView.getSelectionModel().getSelectedItem());
}
Why this should work?
you have to know that there is a good practice that says code to an interface, not an implementation
As you know List in java is an interface so when I assigned the ingredients object this interface will reference the same ArrayList as the object and it will take all it behaviours (how to search for an ingredient object etc...) this way when we will use the currentList on runtime after a button click we are sure that the currentList will be the same as the clicked list and pointing to the same list in the memory
Wish this simple and really resume explanation could help you

android - Check if the room database is populated on startup without Livedata

I'm fairly new to Android and I want to have a database in my app.
I'm introduced to Room the documents say it's the best way to implement databases in the android.
Now I have to pre-populate some data in the database, and make sure that it gets populated before the app startup.
I see that there are many things like LiveData, Repositories, ViewModels and MediatorLiveData.
But I just want to keep it plain and simple, without using the said things how can one find if the database has been populated before the application launch.
I'm getting loads of NullPointerExceptions.
I'm using onCreateCallback() to populate the database but when I try to get the item from database it produces NullPointerException and after some time it may or may not produce the same warning, and the question remains the same what is the best way to know when the database is populated completely.
Here is a Minimal Example
public class MainActivity extends AppCompatActivity {
private TextView nameView;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
nameView = findViewById(R.id.name);
new NamesAsyncTask().execute();
}
private class NamesAsyncTask extends AsyncTask<Void,Void,String> {
private NameDao mNameDao;
#Override
public String doInBackground(Void... params) {
NameDatabase db = NameDatabase.getDatabase(MainActivity.this);
mNameDao = db.nameDao();
String name = mNameDao.getNameByName("Body").name;
return name;
}
#Override
public void onPostExecute(String name) {
nameView.setText(name);
}
}
}
Entity
#Entity(tableName = "name")
public class Name {
#NonNull
#PrimaryKey(autoGenerate = true)
public Integer id;
#NonNull
#ColumnInfo(name = "name")
public String name ;
public Name(Integer id, String name) {
this.id = id;
this.name = name;
}
public Integer getId() {
return this.id;
}
public void setId(Integer id ) {
this.id = id;
}
public String getName() {
return this.name;
}
public void setName(String name) {
this.name = name;
}
}
Dao
#Dao
public interface NameDao {
#Insert
void insertAll(List<Name> names);
#Query("SELECT * from name")
List<Name> getAllNames();
#Query("DELETE FROM name")
void deleteAll();
#Query("SELECT * FROM name WHERE name = :name LIMIT 1")
Name getNameByName(String name);
#Query("SELECT * FROM name WHERE id = :id LIMIT 1")
Name getNameById(int id);
}
Database
#Database(entities = {Name.class}, version = 1)
public abstract class NameDatabase extends RoomDatabase {
public abstract NameDao nameDao();
private static NameDatabase INSTANCE;
public boolean setDatabaseCreated = false;
public static NameDatabase getDatabase(final Context context) {
if (INSTANCE == null) {
synchronized (NameDatabase.class) {
if (INSTANCE == null) {
INSTANCE = buildDatabase(context);
INSTANCE.updateDatabaseCreated(context);
}
}
}
return INSTANCE;
}
private static NameDatabase buildDatabase(final Context appContext) {
return Room.databaseBuilder(appContext, NameDatabase.class,
"name_database").addCallback(new Callback() {
#Override
public void onCreate(#NonNull SupportSQLiteDatabase db) {
super.onCreate(db);
Executors.newSingleThreadScheduledExecutor().execute(() -> {
// Add Delay to stimulate a long running opeartion
addDelay();
// Generate the data for pre-population
NameDatabase database = NameDatabase.getDatabase(appContext);
List<Name> names = createNames();
insertData(database, names);
// notify that the database was created and it's ready to be used
database.setDatabaseCreated();
});
}
}
).build();
}
private void updateDatabaseCreated(final Context context) {
if (context.getDatabasePath("name_database").exists()) {
setDatabaseCreated();
}
}
private boolean setDatabaseCreated() {
return this.setDatabaseCreated = true;
}
protected static List<Name> createNames() {
List<Name> cList = new ArrayList<>();
cList.add(new Name(1, "Body"));
cList.add(new Name(2, "Mind"));
cList.add(new Name(3, "Love"));
cList.add(new Name(4, "Community"));
cList.add(new Name(5, "Career"));
cList.add(new Name(6, "Money"));
cList.add(new Name(7, "Fun"));
cList.add(new Name(8, "Home"));
return cList;
}
private static void insertData(final NameDatabase database, final List<Name> names) {
database.runInTransaction(() -> {
database.nameDao().insertAll(names);
});
}
private static void addDelay() {
try {
Thread.sleep(4000);
} catch (InterruptedException ignored) {
}
}
}
Gives me the exception on String name = mNameDao.getNameByName("Body").name; this line, when I install the app for first time, however if I close the app and start again it does not give the exception anymore. I think because the database has not been populated yet.
I read a post Pre-Populate Database that says on the first call to db.getInstance(context); the database will be populated on in my case NameDatabase.getDatabase(MainActivity.this).
So what shall I do to know if the database has finished populating after the call?

I think because the database has not been populated yet.
Correct. You have forked one background thread (AsyncTask). That thread is forking a second background thread, via your getDatabase() call, as your database callback is forking its own thread via Executors.newSingleThreadScheduledExecutor().execute(). Your AsyncTask is not going to wait for that second thread.
Remove Executors.newSingleThreadScheduledExecutor().execute() from your callback. Initialize your database on the current thread (which, in this case, will be the AsyncTask thread). Make sure that you only access the database from a background thread, such as by having your database access be managed by a repository.

I hope I'm not late! Just a bit of a background before I answer.
I was also searching for a solution regarding this problem. I wanted a loading screen at startup of my application then it will go away when the database has finished pre-populating.
And I have come up with this (brilliant) solution: Have a thread that checks the sizes of the tables to wait. And if all entities are not size 0 then notify the main UI thread. (The 0 could also be the size of your entities when they finished inserting. And it's also better that way.)
One thing I want to note is that you don't have to make the variables in your entity class public. You already have getters/setters for them. I also removed your setDatabaseCreated boolean variable. (Believe me, I also tried to have a volatile variable for checking but it didn't work.)
Here's the solution: Create a Notifier class that notifies the main UI thread when the database has finished pre-populating. One problem that arises from this is memory leaks. Your database might take a long time to pre-populate and the user might do some configuration (like rotating the device for example) that will create multiple instances of the same activity. However, we can solve it with WeakReference.
And here's the code...
Notifier class
public abstract class DBPrePopulateNotifier {
private Activity activity;
public DBPrePopulateNotifier(Activity activity) {
this.activity = activity;
}
public void execute() {
new WaitDBToPrePopulateAsyncTask(this, activity).execute();
}
// This method will be called to set your UI controllers
// No memory leaks will be caused by this because we will use
// a weak reference of the activity
public abstract void onFinished(String name);
private static class WaitDBToPrePopulateAsyncTask extends AsyncTask<Void, Void, String> {
private static final int SLEEP_BY_MILLISECONDS = 500;
private WeakReference<Activity> weakReference;
private DBPrePopulateNotifier notifier;
private WaitDBToPrePopulateAsyncTask(DBPrePopulateNotifier notifier, Activity activity) {
// We use a weak reference of the activity to prevent memory leaks
weakReference = new WeakReference<>(activity);
this.notifier = notifier;
}
#Override
protected String doInBackground(Void... voids) {
int count;
Activity activity;
while (true) {
try {
// This is to prevent giving the pc too much unnecessary load
Thread.sleep(SLEEP_BY_MILLISECONDS);
}
catch (InterruptedException e) {
e.printStackTrace();
break;
}
// We check if the activity still exists, if not then stop looping
activity = weakReference.get();
if (activity == null || activity.isFinishing()) {
return null;
}
count = NameDatabase.getDatabase(activity).nameDao().getAllNames().size();
if (count == 0) {
continue;
}
// Add more if statements here if you have more tables.
// E.g.
// count = NameDatabase.getDatabase(activity).anotherDao().getAll().size();
// if (count == 0) continue;
break;
}
activity = weakReference.get();
// Just to make sure that the activity is still there
if (activity == null || activity.isFinishing()) {
return null;
}
// This is the piece of code you wanted to execute
NameDatabase db = NameDatabase.getDatabase(activity);
NameDao nameDao = db.nameDao();
return nameDao.getNameByName("Body").getName();
}
#Override
protected void onPostExecute(String name) {
super.onPostExecute(name);
// Check whether activity is still alive if not then return
Activity activity = weakReference.get();
if (activity == null|| activity.isFinishing()) {
return;
}
// No need worry about memory leaks because
// the code below won't be executed anyway
// if a configuration has been made to the
// activity because of the return statement
// above
notifier.onFinished(name);
}
}
}
MainActivity
public class MainActivity extends AppCompatActivity {
private TextView nameView;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
nameView = findViewById(R.id.name);
new DBPrePopulateNotifier(this) {
#Override
public void onFinished(String name) {
// You set your UI controllers here
// Don't worry and this won't cause any memory leaks
nameView.setText(name);
}
}.execute();
}
}
As you can see, our Notifier class has a thread in it that checks if the entities are not empty.
I didn't change anything in your other classes: Name, NameDao and NameDatabase except that I removed the boolean variable in NameDatabase and made private the variables in Name.
I hope that this answers your question perfectly. As you said, no LiveData, Repository, etc.
And I really hope I ain't late to answer!
Now I want to write down what I tried before I came up to the final solution.
Keep in mind that what I am trying to do here is for my app to show a progress bar (that infinite spinning circle) and put it away after the database has finished pre-populating.
Tried:
1. Thread inside thread
Practically, there's a thread that checks if the size of an entity is still 0. The query is done by another thread.
Outcome: Failed. Due to my lack of knowledge, you cannot start a thread within another thread. Threads can only be started from the main thread.
Tables' sizes loop checker
A thread that queries the tables to be checked if they have been initialized through an infinite loop. Only breaks if all sizes of the tables to be checked are greater than 0.
Outcome: Solution. This is by far the most elegant and working solution to this problem. It doesn't cause memory leaks because as soon as a configuration has been made, the thread that loops continually will break.
Static variable
A static volatile variable in the database class in which will turn to true when the thread has finished inserting the values.
Outcome: Failed. For unknown reason that I still search for, it won't run the thread for initializing the database. I have tried 3 versions of the code implementation but to no avail. Hence, a failure.
Initialize database then notify
A listener that is defined in the UI thread then passed by argument to the repository. All database initialization is done also in the repository. After populating the database, it will then notify/call the listener.
Outcome: Failed. Can cause memory leaks.
As always, happy coding!

Logging in onCreateCallback ofc!

How to get inserted row id after inserting row in room to the main thread

I want to return the inserted row Id to use it to update some value in the same row
#Entity(tableName = "course")
public class Course {
#PrimaryKey(autoGenerate = true)
private int id;
private String firebaseId;
}
#Dao
public interface CourseDao {
#Insert(onConflict = REPLACE)
long insertCourse(Course course);
#Query("UPDATE course SET firebaseId = :firebaseId WHERE id = :id")
void updateFirebaseId(int id, String firebaseId);
}
the problem is I cant return the Id to the main thread
public class Repository {
private static final Object LOCK= new Object();
private static Repository sInstance;
private final CourseDao mCourseDao;
private final AppExecutors mAppExecutors;
public void insertCourse(final Course course) {
mAppExecutors.diskIO().execute(new Runnable() {
#Override
public void run() {
mCourseDao.insertCourse(course);
}
});
}
public void updateCourse(final Course course) {
mAppExecutors.diskIO().execute(new Runnable() {
#Override
public void run() {
mCourseDao.updateCourse(course);
}
});
}
}
I tried to use liveData but its not supported on insert
Error:(34, 20) error: Methods annotated with #Insert can return either void, long, Long, long[], Long[] or List<Long>.
Is it possible to return the id of Course once the insertion is completed without writing a separate select query?

LiveData is not supported for insert.
I feel there are 2 approaches to do insert operation in the background thread and send the result (long) back to Activity:
Using LiveData, I personally like this approach:
public class Repository {
private LiveData<Long> insertedId = MutableLiveData()
public void insertCourse(final Course course) {
mAppExecutors.diskIO().execute(new Runnable() {
#Override
public void run() {
Long id = mCourseDao.insertCourse(course);
insertId.setValue(id);
}
});
}
}
Using Rx:
return Single.fromCallable(() -> mCourseDao.insertCourse(course));
Here, you'll get Single<Long> which you can observe in your Activity
Note: Repository will return Long to ViewModel and in your ViewModel will have the LiveData and setValue stuff.

I did it like this in Java
In the environment where you want the id:
public class MyIdClass {
ArrayList<Integer> someIds = new ArrayList<>(); //this could be a primitive it doesn't matter
constructor with repository....{}
#FunctionalInterface //desugaring... normal interfaces are ok I guess?
public interface GetIdFromDao {
void getId(long id);
}
public void insertSomething(
Something something
) {
someRepository.insertSomething(
something,
id -> someIds.add((int)id) //lambda replacement, I think method reference cannot be done because of (int) casting, but if Array is type long it could be done.
);
}
}
In abstract class MyDao...: (something that I cannot stress enough..., work with ABSTRACT CLASS DAO, its more flexible)
#Insert(onConflict = OnConflictStrategy.IGNORE)
protected abstract long protectedInsertSomething(Something something);
public void insert(
Something something,
MyIdClass.GetIdFromDao getIdFromDao
) {
//get long id with insert method type long
long newSomethingId = protectedInsertSomething(something);
getIdFromDao.getId(newSomethingId);
}
Inside Repository, If you use AsyncTask<X, Y, Z>, you can actually pass everything through VarAgrs, even listeners, but be sure to recast them in the order which they get inserted, and use type Object or a common ancestor.
(Something) object[0];
(MyIdClass.GetIdFromDao) object[1];
new InsertAsyncTask<>(dao).execute(
something, //0
getIdFromDao //1
)
Also use #SupressWarnings("unchecked"), nothing happens
Now If you want even further interaction, you can connect a LiveData to the listener, or construct a Factory ViewModel...
an abstract factory ViewModel... that would be interesting.
But I believe DataBinding has an Observable view Model which I guess can be used(?)... I really don't know.

(Using Spring)How to stop DTO from repeating when the map appears to be fine?

In this program I have three numbers the user enters in and I am trying to get the second number in the set to display by being pulled from the DTO so that I can confirm that everything is working fine. But something is going wrong as you'll see by the output...
User Enters: 858508321,858509491,858510385
//This code is what is being executed. (Think of it as main)
private void handleSubmit(final AjaxRequestTarget target) {
List<Long> msgNums = new ArrayList<Long>();
msg_Num = Ta.getInput();
String[] Numbers = msg_Num.split(",");
for(String Number:Numbers){
msgNums.add(Long.valueOf(Number));
}
System.out.println(msgNums.get(1));
List<BulkReplayMessageDTO> brm = messageReplayDao.getMessageResults(msgNums);
System.out.println(brm.get(1).getMsgNum());
}
//This is the DAO
public class MessageReplayDao extends SimpleJdbcDaoSupport {
private final static String sql = "SELECT MSG_NBR, MSG_CPSD_DATA"
+ " FROM nti_raw_msg"
+ " WHERE THRD_NAME IS NOT null AND THRD_NAME NOT LIKE"
+ " 'out%' AND MSG_NBR IN (:messageNumbers)";
public List<BulkReplayMessageDTO> getMessageResults(final List<Long> msgNumList){
SqlParameterSource parameters = new MapSqlParameterSource()
.addValue("messageNumbers", msgNumList);
List<BulkReplayMessageDTO> result = getSimpleJdbcTemplate().query(sql, new MessageReplayMap(), parameters);
return result;
}
}
//The Map
public class MessageReplayMap implements ParameterizedRowMapper<BulkReplayMessageDTO> {
public MessageReplayMap(){
}
LobHandler lobHandler = new DefaultLobHandler();
#Override
public final BulkReplayMessageDTO mapRow(ResultSet rs, int rowNum)
throws SQLException {
final BulkReplayMessageDTO brm = new BulkReplayMessageDTO();
System.out.println(rowNum);
brm.setMsgNum(rs.getLong("MSG_NBR"));
brm.setMSG(CompressionUtils.uncompress(lobHandler.getBlobAsBytes(rs, "MSG_CPSD_DATA")));
return brm;
}
}
//And finally the DTO
public class BulkReplayMessageDTO{
private static Long msgNum;
private static String MSG;
public final Long getMsgNum() {
return msgNum;
}
public final void setMsgNum(final Long msgNumTemp) {
msgNum = msgNumTemp;
}
public final String getMSG(){
return MSG;
}
public final void setMSG(final String MSGTemp){
MSG = MSGTemp;
}
}
Notice that I have printed to the console in the handleSubmit method, and inside my map. The output I get is
858509491
0
1
2
858510385
when it should be
858509491
0
1
2
858509491
I have no clue what the problem could be since I have found other code example that are pretty much the same and mine seems to be pretty similar. I am pretty new to using Spring, so sorry if the answer is really obvious.

I have found the problem, and it was a really simple one. In the DTO the variables were made static from a previous problem I was working on. I had forgotten to get rid of it after I had fixed the issue. If I understand the meaning of static, then I had made all the instances of those variables the same. So that is why I could only print out the last number that had been entered in by the user.

Sencha: Iterating a list store of a custom BaseModel subclass

I just started playing with Sencha's Ext GWT yesterday and I've hit a wall. I combined methods from their JSON loaded grid and their editable grid. As a test data set I'm using a list of Stargate Atlantis episodes hence the SGAEpisode which is defined as:
public class SGAEpisode extends BaseModel {
public SGAEpisode() {
}
public SGAEpisode(String season, String episode) {
set("season",season);
set("episode",episode);
}
public void setSeason(String season) {
set("season",season);
}
public String getSeason(){
return get("season");
}
public void setEpisode(String name) {
set("episode",name);
}
public String getEpisode() {
return get("episode");
}
public String toString() {
return "Season: " + get("season") + " episode: " + get("episode");
}
}
the onModuleLoad() starts off with...
ModelType type = new ModelType();
type.setRoot("seasons");
type.addField("Season","season");
type.addField("Episode","episode");
String path = GWT.getHostPageBaseURL() + "senchaapp/sgaepisodes";
final RequestBuilder builder = new RequestBuilder(RequestBuilder.GET,path);
final MVProxy<String> proxy = new SProxy<String>(builder);
JsonLoadResultReader<ListLoadResult<SGAEpisode>> reader = new JsonLoadResultReader<ListLoadResult<SGAEpisode>>(type);
final BaseListLoader<ListLoadResult<SGAEpisode>> loader = new BaseListLoader<ListLoadResult<SGAEpisode>>(proxy,reader);
final ListStore<SGAEpisode> episodes = new ListStore<SGAEpisode>(loader);
so loader.load() works great, populating a grid, I can edit fields, but I don't see commitChanges() doing anything and I can't iterate over the ListStore "episodes" to gather changed or added values. Oh, and SProxy is just a DataProxy subclass to allow me to specify the season's JSON I'm loading into the grid.
If I try either
for(SGAEpisode episode : episodes) {
save(episode);
}
or
for(int i = 0; i < episodes.getCount(); i++) {
save(episodes.getAt(i));
}
I get an exception with the message "com.extjs.gxt.ui.client.data.BaseModel cannot be cast to com.mvsc.sencha.shared.SGAEpisode" Any idea what I'm doing wrong? Everything up to that point was defined/populated with SGAEpisodes.....
Addendum
Ok, so if I try
List<Record> modified = episodes.getModifiedRecords();
for(Record r : modified) {
ModelData md = r.getModel();
save(md.get("season"),md.get("episode"));
}
I can iterate, and get the modified values, but what's the point of having a ModelData subclass if I have to use the base class like this. Which makes me think I don't in fact have to..... little help?
Addendum 2 I tried subclassing BaseModelData instead with no success.

I know its an older post, I had the same issue. This is how I fixed it.
try iterating through the models in listStore.
for(SGAEpisode episode : episodes.getModels()) {
save(episode);
}