Day displayed in Kotlin instead of variable - android-studio

Question

I am new to kotlin and android studio and i am trying to have the day displayed in a text view. My problme is that only the number 1 to 7 is displayed acording to the current day but not the name of the day what do i have to change to fix this?
val day = Calendar.getInstance().get(Calendar.DAY_OF_WEEK)
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
fun dayOfWeek() {
val day = Calendar.getInstance().get(Calendar.DAY_OF_WEEK)
println(
when (day) {
1 -> "Sunday"
2 -> "Monday"
3 -> "Tuesday"
4 -> "Wednesday"
5 -> "Thursday"
6 -> "Friday"
7 -> "Saturday"
else -> "Time has stopped"
}
)
}
tag = findViewById(R.id.Tag)
tag.text = day.toString()

Answer 1

java.time
The java.util Date-Time API and their formatting API, SimpleDateFormat are outdated and error-prone. It is recommended to stop using them completely and switch to the modern Date-Time API*.
Solution using java.time, the modern Date-Time API: There are a couple of ways to do it as shown below:
import java.time.LocalDate;
import java.time.ZoneId;
import java.time.format.DateTimeFormatter;
import java.time.format.TextStyle;
import java.util.Locale;
public class Main {
public static void main(String[] args) {
// If you want to deal with the system timezone, you can simply use
// LocalDate.now() instead of LocalDate.now(ZoneId.systemDefault()). In order to
// deal with a specific timezone, replace ZoneId.systemDefault() with the
// applicable ZoneId e.g. ZoneId.of("Asia/Kabul")
LocalDate date = LocalDate.now(ZoneId.systemDefault());
String dow = date.getDayOfWeek().getDisplayName(TextStyle.FULL, Locale.ENGLISH);
System.out.println(dow);
// Alternatively,
DateTimeFormatter dtf = DateTimeFormatter.ofPattern("EEEE", Locale.ENGLISH);
dow = dtf.format(date);
System.out.println(dow);
}
}
ONLINE DEMO
Learn more about the modern Date-Time API from Trail: Date Time.
* If you are working for an Android project and your Android API level is still not compliant with Java-8, check Java 8+ APIs available through desugaring. Note that Android 8.0 Oreo already provides support for java.time.

Answer 2

In your code, day is an Int property.
You have created a function called dayOfWeek() that you never call so that code never runs.
When you do tag.text = day.toString(), it is looking at the day property, not the day variable inside your function. It is usually a bad idea to name a variable the same thing as some property in the same class because it makes the code confusing to read. But that doesn't matter either way in this case because both of them are Ints.
In your dayOfWeek() function, you are using a when expression to covert day to a String, but you are just printing it. You are not storing it in a variable such that it can be used for anything else, like setting it on a TextView.
You can make your function return a String, and use it that way. I would also move your function outside the onCreate() function. It is unusual to create a function inside another function for this kind of task.
val day = Calendar.getInstance().get(Calendar.DAY_OF_WEEK)
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
tag = findViewById(R.id.Tag)
tag.text = getDayOfWeekText()
}
fun getDayOfWeekText() {
return when (day) {
1 -> "Sunday"
2 -> "Monday"
3 -> "Tuesday"
4 -> "Wednesday"
5 -> "Thursday"
6 -> "Friday"
7 -> "Saturday"
else -> "Time has stopped"
}
}
Or to do this the easy way, and with proper language support:
tag.setText(DateTimeFormatter.ofPattern("EEEE").format(LocalDate.now()))