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Using specific value of integer variable from TextEdit response in MainActivity, to use in a different class?

I'm attempting to code an app that takes the users numerical specifications from the main activity in the form of a TextEdit input, convert that to an integer and then use that specific value of the integer and use that value in a separate class file which I will use the result of the class in the main activity.
Is this possible? Here's what I've attempted in the global variables of the main activity:
deadzoneValue = findViewById(R.id.TextView_deadzoneInfo);
public EditText threshold, deadzone;
public String deadzoneString = deadzone.getText().toString(); //deadzone being the name of the
public int timeLimit = Integer.parseInt(deadzoneString);
public String thresholdString = threshold.getText().toString();
public static int thresholdLimit = Integer.parseInt(thresholdString);
I'm not sure how to use these in the Deadzone class, which I'm trying to take the specific value and use there.
EDIT: Deadzone.java isn't an activity but a class with functions that are called in the MainActivity.

Using of ClassicSingleton:
public class ClassicSingleton2 {
private static String instance = null;
protected ClassicSingleton2() {
}
public static String getInstance() {
return instance;
}
public static void setInstance(String instance) {
ClassicSingleton2.instance = instance;
}
}
You could change type of instance variable to int ...
And in target code you could get this data:
xRef = ClassicSingleton2.getInstance();
This is very simple.
2:
And using of put (putExtra)
Intent oI = new Intent((FirstActivity)this,SecondActivity.class);
oI.putExtra("XRefCaller",123);
And in target code(activity) :
Bundle oBundle = getIntent().getExtras();
if(oBundle != null){
oXRefCaller = oBundle.getString("XRefCaller",-1);
//checking with -1 if the parameter does not exist or is null
}

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 store variables values in a class i.e "settings"?

OK. After spending literally a few hours trying to get things working I give up.
Basically I am creating a program in which user inputs some values, then after hitting button a new scene is created and depending on the values it was given, different things take place.
My problem - I created "Settings.class" with a few variables with getters and setters. My assumption was to store the values input in there and whenever needed I have easy access to them using getters.
For some reason it doesn't work.
Keep in mind I simplified it as much as I can because It'd look very messy and would be very long if I pasted my original code. I made sure that the core of the problem is the same.
Settings class:
public class Settings {
private boolean diamonds;
public boolean getDiamonds() {
return diamonds;
}
public void setDiamonds(boolean diamonds) {
this.diamonds = diamonds;
}
}
Controller class:
public class Controller implements Initializable {
private Settings settings = new Settings();
private ProblematicOne prob = new ProblematicOne();
public void handleGoAction() throws IOException {
settings.setDiamonds(true);
prob.editText("This shall be set");
/* ..creating new stage and scene here no reason to paste it here, no probs with that.. */
#Override
public void initialize(URL location, ResourceBundle resources) {
}
}
}
And crème de la crème, problematic class:
public class ProblematicOne{
private Setting settings = new Settings();
String toBeEdited = ""; //
public void editText(String text){
if(settings.getDiamonds){ // for some reason it doesn't work; The getter returns false.
toBeEdited = text;
}else if(!settings.getDiamonds){
toBeEdited = "getDiamonds is false";
}
}
}

Alright, first off, what you are trying to do can be achieved by serializing the object (i.e Settings) and storing it. Or, simpler, just write to a file with values and load from there when you want to instantiate the class.
Look at this line in your "ProblematicOne"
private Setting settings = new Settings();
You just created a new instance of Settings. This instance does not have any idea of your Settings instance in your Controller.
Another way is to make your Settings class a singleton and then just reuse it. Example:
Settings.java
public class Settings {
private static Settings instance = null;
private boolean diamonds;
public boolean getDiamonds() {
return diamonds;
}
public void setDiamonds(boolean diamonds) {
this.diamonds = diamonds;
}
private Settings() {}
public static Settings getInstance(){
return instance == null ? new Settings() : instance;
}
}
Then in your Controller class just get the instance using the getInstance() method;
private Settings settings = Settings.getInstance();
Similarly, when you use it again in your ProblematicOne class, use the getInstance() method

Your issue is that ProblematicClass creates a new instance of settings, so the value is not accessible. You need to pass the same instance into the other class, or make your variables in settings class static, so you can access them without instance:
public class Settings {
private static boolean diamonds;
public static boolean getDiamonds() {
return diamonds;
}
public static void setDiamonds(boolean diamonds) {
this.diamonds = diamonds;
}
}
And use it without instance:
Settings.setDiamonds(true);
Settings.getDiamonds();

in the following class with out setting value to settings object, you are trying to use get, which will return default value.
public class ProblematicOne{
private Setting settings = new Settings();
String toBeEdited = ""; //
public void editText(String text){
if(settings.getDiamonds){ // for some reason it doesn't work; The getter returns false.
toBeEdited = text;
}else if(!settings.getDiamonds){
toBeEdited = "getDiamonds is false";
}
}
}
if you want to use the settings object which you created in the controller then pass settings object to editText method in the ProblematicOne class.

The problem is you are instantiating Setting class twice. You set the
settings.setDiamonds(true); //in one instance
and you expect to retrive this value in second instance in class ProblematicOne.
Try to solve this by instantiating Settings only once in Controller class and pass the same to ProblematicOne. Frame your code such that you instantiate
private Setting settings = new Settings();
only once in your whole application. Consider making this class singleton. Read about singleton instantiation here
http://www.javaworld.com/article/2073352/core-java/simply-singleton.html

Getting value from one activity to another class

can anyone guide me to the right direction, as the situation is
have two classes calssA with Activity while classB is simple java class
1.classA has a editbox where the user inputs some value.
2.classB has a method that computes the user input.
need to get the user input value from classA to classB.
a).cannot get it through passing intent as the other class does not have activity.
b).have tried getter setter method by creating a class thus,calling setter where the user inputs the detail.
and calling the getter in another class.
Still the value is null, so what apparently is missing here.Any guidance to a example or brief explanation would be great.Thanks

You can use your own customized class to store the data and use it any where you need.
DataClass
public class Data {
private String a,b;
private static Data data= new Data( );
/* A private Constructor prevents any other
* class from instantiating.
*/
private Data (){ }
/* Static 'instance' method */
public static Data getInstance( ) {
return data;
}
public String getA()
{
return this.a;
}
public String getB()
{
return this.b;
}
public void setA(String a)
{
this.a = a;
}
public String getB(String b)
{
this.b = b;
}
}
In Activity
Data data = Data.getInstance()
data.setA("Stack");
data.setA("Overflow");
you can use this values in Java file like this
Data data = Data.getInstance()
System.out.println(data.getA());
System.out.println(data.getB());

according to my knowledge here you have to use singleton class.
public class DataHolderClass {
private static DataHolderClass dataObject = null;
private DataHolderClass() {
// left blank intentionally
}
public static DataHolderClass getInstance() {
if (dataObject == null)
dataObject = new DataHolderClass();
return dataObject;
}
private String _ProductNames;
public String get_ProductNames() {
return _ProductNames;
}
public void set_ProductNames(String _ProductNames) {
this._ProductNames = _ProductNames;
}
}
to set data
DataHolderClass.DataHolderClass.set_ProductNames(your data variable);
to get data
DataHolderClass.DataHolderClass.get_ProductNames(your data variable);

You can save the edittext value in SharedPreferences, thus making it available in all activity.
By doing this you can fetch the value in other activity without any hassle.
eg:
SharedPreferences.Editor editor = preferences.edit();
editor.putString("edtTextValue", valueOfEditText);
editor.commit();
Further fetching the value in other activity like this,
preferences.getString("edtTextValue", "");

In your activity class create
public static String valueEntered;
valueEntered=mEdtTxt.getText().toString();
and in your java class where you want
String enteredValue=ClassA.valueEntered;

how do I access this class

import android.content.Context;
import android.content.SharedPreferences;
import android.net.Uri;
public class LoadSettings
{
public static void LoadMySettings (Context ctx)
{
SharedPreferences sharedPreferences = ctx.getSharedPreferences("MY_SHARED_PREF", 0);
String strSavedMem1 = sharedPreferences.getString("gSendTo", "");
String strSavedMem2 = sharedPreferences.getString("gInsertInto", "");
String cCalId = sharedPreferences.getString("gCalID", "");
setInsertIntoStr(strSavedMem2);
setSendToStr(strSavedMem1);
}
private static String cSendToStr;
private static String cInsertIntoStr;
private int cCalId;
private Uri cCalendars;
public String getSendToStr()
{
return this.cSendToStr;
}
public static void setSendToStr(String pSendToStr)
{
cSendToStr = pSendToStr;
}
public String getInsertIntoStr()
{
return this.cInsertIntoStr;
}
public static void setInsertIntoStr(String pInsertIntoStr)
{
cInsertIntoStr = pInsertIntoStr;
}
}
from the calling class i have tryed lots the current is.
LoadSettings.LoadMySettings(this);
but when i try to get some data for example.
textSavedMem1.setText(LoadSettings.getSendToStr());
i get a Null error.

LoadMySettings is not a class but a method (so it should start with a lower case, if you follow Oracle/Sun's naming conventions for the Java language).
You access it indeed by calling LoadSettings.loadMySettings(someContext), where someContext is the context to pass around. In your example, we don't know what this refers to, so maybe your error lies there.
Then when you do this: textSavedMem1.setText(LoadSettings.getSendToStr());
You call a non-static method, so that should be either using an instance of LoadSettings or, more likely considering your code, you could change getSendToStr to be:
public static String getSendToStr()
{
return cSendToStr;
}
Though that seems to be rather bad design.
Maybe if you tell us more about what you try to do, we can help more, as as such our answers will just take you one step further.
EDIT: Ok, I just figured out what you are trying to do...
You need to go back and learn basic Java concepts and read on access modifiers, and constructors first, and OO semantics in Java in general.
Change your class to this:
public class LoadSettings
{
public LoadSettings(Context ctx)
{
SharedPreferences sharedPreferences =
ctx.getSharedPreferences("MY_SHARED_PREF", 0);
String strSavedMem1 = sharedPreferences.getString("gSendTo", "");
String strSavedMem2 = sharedPreferences.getString("gInsertInto", "");
String cCalId = sharedPreferences.getString("gCalID", "");
setInsertIntoStr(strSavedMem2);
setSendToStr(strSavedMem1);
}
private String cSendToStr;
private String cInsertIntoStr;
private int cCalId;
private Uri cCalendars;
public String getSendToStr()
{
return cSendToStr;
}
public void setSendToStr(String pSendToStr)
{
cSendToStr = pSendToStr;
}
public String getInsertIntoStr()
{
return cInsertIntoStr;
}
public void setInsertIntoStr(String pInsertIntoStr)
{
cInsertIntoStr = pInsertIntoStr;
}
}
And create a new instance of LoadSettings with:
LoadSettings mySettings = new LoadSettings(someContext);
You can then correctly invoke:
textSavedMem1.setText(mySettings.getSendToStr());

Haylem has the right of it, but I just wanted to add a comment:
There are basically two design patterns in Java for what you're trying to do. One is the static class where all the methods and variables are static and you access them as e.g.
LoadSettings.loadMySettings(this);
string = LoadSettings.getSendToStr()
// etc.
The other pattern is the "singleton" class where you create exactly one instance of the class and you access the instance:
LoadSettings ls = new LoadSettings(this);
ls.loadMySettings();
string = ls.getSendToStr();
Either way is good, but what you're doing is a mish-mash of both methods and it won't work.