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How to display different text in a textview according to date in android app?

I am very new at coding and want to develop an android app that display new content according the day you are opening the app.
For example : 20 days to eat better
Day 1 (user open the app), then the message is "XXXXXX"
Day 2 (user open the app), the the message is "YYYYY"
Day 1 is a the day the user download the app.
I understood that I need to use "timestamp" as a string, but how can I do it ?
Thanks for your help !

I'm not quite sure about what you are trying to achieve. But based on what I understood. You just want to get the current day
Calendar calendar = Calendar.getInstance();// sets the current date
calendar.get(Calendar.DATE);// gets the current day returns an integer value
calendar.getTime();// gets the current date and returns a Date Object
You can start from here. The calendar class offers you different values for the current calendar date. I'm pretty sure all you need to know is available if you just tried to search the web. But to give you something to work on, experiment with the Calendar class for date manipulations.
EDIT:
If you want to display a certain string based on the date/day. What you can do is to create an array and user the date/day value to get the string.
String[] stringArray = {"Text1", "Text2", "Text3", "Text4", "Text5", "Text6", "Text7"};
String theStringYouWant = stringArray[calendar.get(Calendar.DATE)];
You can use this approach if you have short strings and limited record. But if you have tons of data, you might want to utilize a database to store your data, and use this approach.

set repeated reminder that repeats every month

I am taking two dates from the user in my android code. I want to set reminder for every month which are in between those two dates.
If first date is : 1st jan 2015 and other date is 1st Feb 2016 then I want to set reminder for the 1st day every month in between these two dates. I tried using alarm manager but couldnt able to repeat alarm. Please help. thank you

One method might be to have your alarm receiver set the next alarm when it is called (e.g. it activates on 1 Jan 2015 and sets the next one for 1 Feb 2015), so you're always setting one ahead.

First you'll need to create 2 Calendar objects to store the dates to store the dates set by the user. Then proceed by either creating pending intents for each date in a for loop by incrementing the value of month. Assign all the pending intents to your AlarmManager and fire them with FLAG_ONE_SHOT.
Please provide your code so we could better understand your problem.

android: timezone offset for "Europe/Russia" [duplicate]

This question already has an answer here:
android timezone difference is 1 hour less then expected
(1 answer)
Closed 9 years ago.
I need an offset for "Europe/Russia" to UTC.. in hours. here is my code:
Calendar mCalendar = new GregorianCalendar();
mCalendar.setTimeZone( TimeZone.getTimeZone("Europe/Moscow"));
TimeZone mTimeZone = mCalendar.getTimeZone();
int remote_offset = mTimeZone.getRawOffset()/1000/60/60;
For UTC it should be -4 hours. BUT! some user got 3 hours difference!!
I think, the problem is, Russia doesn't use winter time. And some devices now that, but some not.. how could I implement allway to get "-4" hours?
Regards

First, Russia isn't UTC-4.
The problem has to do with Russia not having daylight saving time. But your issue is probably only happening with android 2.x device and less. The daylight saving time was removed before 4.x as far as I remember (if it's a user input). On the other hand, if you receive a date that was created by the device without user input, you don't have to convert it as it's already as UTC.
But as I said, Russia isn't -4. Russia/Moscow will be +4 hours. But Russia is larger than Moscow really!
Look here: http://en.wikipedia.org/wiki/Time_in_Russia
UTC+03:00 MSK−1: Kaliningrad Time Europe/Kaliningrad
UTC+04:00 MSK: Moscow Time Europe/Moscow, Europe/Volgograd, Europe/Samara
UTC+06:00 MSK+2: Yekaterinburg Time Asia/Yekaterinburg
UTC+07:00 MSK+3: Omsk Time Asia/Omsk, Asia/Novosibirsk, Asia/Novokuznetsk
UTC+08:00 MSK+4: Krasnoyarsk Time Asia/Krasnoyarsk
UTC+09:00 MSK+5: Irkutsk Time Asia/Irkutsk
UTC+10:00 MSK+6: Yakutsk Time Asia/Yakutsk
UTC+11:00 MSK+7: Vladivostok Time Asia/Vladivostok, Asia/Sakhalin
UTC+12:00 MSK+8: Magadan Time Asia/Magadan, Asia/Kamchatka, Asia/Anadyr
So what you'll have to do is to check if we're in winter and that the TimeZone is one of those. If the timezone is one of those, you can add one more hour when you want to show. And remove 1 hour when you want to convert to UTC.
I don't believe it's possible to update the TimeZone on the android phones and that also means that it's not exactly possible to do that unless you find an alternative library for Dates that has timezones built-in and which are updated.
You could subclass the DateObject with the functions that you use to behave just like the old date object, all you'll have to do is to make sure it behaves differently on android2.x and not on android 4.x+.
Also check this: http://www.joda.org/joda-time/
I checked there and I guess it could be usable and less hacky than my suggestion above. The TimeZones are up to date so it could just work for every phone since it shouldn't use the internal timezones. On the other hand, if you have functions that require the Date, it might get tricky.
My suggestion is make sure you use UTC everywhere and use JodaTime to format the date with timezones and to do "datetime" operations. If you make sure that your Java Date never contain a TimeZone other than UTC. It should work.

Using a DatePicker in Android dev: How do I compare the date picked to today's date?

I'm really stuck with a certain problem and I'm hoping someone can help me understand the problem and come to a solution. I've looked online a fair bit but can't see an answer unless it's been staring me in the face :-/
Basically, I'm creating a very basic TV Guide app. It parses data from an RSS feed which has days offset (yesterday was -1. today is 0, tomorrow is 1, etc etc) and I'm trying to implement a DatePicker that allows the user to see what is on a particular channel when they select yesterday, today, tomorrow, etc.. but if they pick a date that is out-with the range (at the moment it's a week in advance), a simple Toast message will be displayed.
My questions I guess are, firstly, how do I use maybe an IF ELSE to either parse the specific channel data for the day the user wants or display an error Toast message, and, how do I go about converting the days from what the user has put in compared to the actual date today into integers? If they select yesterday's date it will go to URL "http://example.com/-1/channel", if they select tomorrow's date it will go to URL "http://example.com/1/channel" etc etc etc.
Code is available if anyone needs to see it, but I think if someone would be kind enough to explain the logic, I'd like to see if I can come to the answer myself...
Thanks a lot folks!!

You should use a DatePicker to allow the user to choose the when.
Time in Android is stored on a long (not an int). And the long time can easily be converted back and forth between long (always milli-seconds) and a Date object.
The Date object gives you all sorts of tools to compare before and after, look at months, minutes, hours, etc.
The current time is determined by:
long nowMs = System.currentTimeMillis();
int nowSec = (int)(nowMs / 1000);
There is also a very important Calendar object. This allows you to parse textual date formats as delivered by your http functions in and out of various dates.
For example:
Calendar cal = Calendar.getInstance();
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-mm-dd hh:mm:ss Z");
String text = sdf.format(cal.getTime();
You will have to put all these tools together with a DatePicker example such as the one here Create a DatePicker to complete your TV Guide application.
Reference:
Date
Calendar
DatePicker

EDIT : Check David's Answer its better.
First Filter the date selected with today's date. You can compare it by date.isbefore(date) or date.isafter(date) these booleans will let you tell know if a date is of past or future or present. then to further calculate the days inbetween you can make a method with switch statement that will basically convert the selected date and the current date into miliseconds(Date.getTimeinmiliseconds)
if the date is of past take the difference of present time in miliseconds and past date in miliseconds. If the date is of future do the opposite. Take the difference and convert it to days difference with appropriate sign(negative/positive).
Please refer this link for a better coding example

GregorianCalendar and SQLite

I'm trying to setup a RPG that will keep track of a virtual time. After some reading GregorianCalendar seems to be the best way to do this but I have some questions and hoping someone with experience could give me some insight.
Here is what I'm trying to do. The game will start in the year 1675 and run for about 30 years. At that point the character will retire if they have survived that long. The character will be able to choose from actions I've preset for them through the coarse of the game. Some actions will be short and take a hour, others may take a week or a month. The real question comes from me using SQLite heavily. I want to save the current time as well as how long an action will take in my database. My first thought when setting this up was, if I want to start the game in Aug 15, 1675 to have my data base with 3 rows, set those fields to 8, 15, 1675. Then also have 2 more columns for the time. Pull these int via cursor and set them with something like
GregorianCalendar time = new GregorianCalendar();
time.set(year, month, date, hour, minute);
I figured I would pull how long an action takes in a similar fashion. Have an int X, and then a string to tell whether this time is in minutes, hours, days etc. Then either add this int to the int pulled from database to add to the calendar directly.
Q: If I add it directly to the calendar how would I pull int values from the calendar to store in database to load at a later time (when the player loads their game)?
Q: If I add it to the int stored in the database and set the calendar with this new int what will happen when I add enough to make the int out of scope for the calendar (Date is set to 31 but I add another day)?

You can convert from the GregorianCalendar object to/from UNIX time for example using getTimeInMillis() setTimeInMillis(). GregorianCalendar also has a roll() method:
Adds the specified amount to the specified field and wraps the value
of the field when it goes beyond the maximum or minimum value for the
current date. Other fields will be adjusted as required to maintain a
consistent date.

I would recommend using Joda Time as a substitute for the (somewhat lacking) standard java date and time utilities. It's much more flexible.
It has functions to do date math, it supports several different calendars (ISO8601, Buddhist, Coptic, Ethiopic, Gregorian, GregorianJulian, Islamic, Julian), has support for intervals, durations and periods. It has built in formatters that let you make your output look like just about anything you wish.
If it were me, I would use Joda and store the date in the native format presented by Joda (I don;t remember what that is right offhand) and then pull it out again and use Joda to do all the date math, as well as having it convert it to whatever calendar you wish to use for display to the user.
Otherwise, it seems to me you'd be re-inventing the wheel.