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How do I make a daily action(Android Studio)

I recently started learning about app programing, and I am having a problem.
I want to know how can i make my app do a certain action every time a day is passing.
For example, If i have an int parameter that Equals 10 and today is Sunday.
I need that on Monday the Parameter will be 9,
and on the next day 8, and so on....
Can anyone help me with this?

If you want your app to start every x time, you should use AlarmManager for that and also consider registering for boot_complete broadcast.
If you simply need this for calculation, you should use System.getCurrentTimeMillis to get the current time and make your decisions.

Create Notification when my mobile it´s in a date

I´m trying to create a new Notification that will appear when a day has come.
For example: Today is 8 of September of 2014 and i want create a notification for tomorrow.
It´s like when your calendar reminds you something that you put a month ago
Could someone tell me how can i create a notification like the calendar when i´m in a specific day?
Thank a lot.
EDIT
Thanks you for all the answers, i found a tutorial of AlarmManager and it worked as you all said.

Try using AlarmManager in android
The Alarm Manager is intended for cases where you want to have your application code run at a specific time, even if your application is not currently running. For normal timing operations (ticks, timeouts, etc) it is easier and much more efficient to use Handler.
please refer this
https://developer.android.com/training/scheduling/alarms.html

Run a function on the first day of every month

I want to run a function from my Android application at a fixed time (let's say 8am) on the first day of every month. The function, depending on user's preferences, will either serve a notification or start downloading a file over the Internet (both of which are already taken care of) or do nothing.
I tried using BroadcastReceiver with action android.intent.action.DATE_CHANGED but I read that it is fired only when user changes the date manually (although even then it worked the first 2-3 times I tried and then stopped working). I think an AlarmManager will be able to do what I need done but not really able to figure out how to implement it.
This should run whether or not my application is active/running. What is the optimum way to do this? Any supporting code will be appreciated.

Just start a service when start up. In the service,you could check the date in another thread.

Use an alarm
alarmManager.setInexactRepeating(AlarmManager.RTC_WAKEUP, calendar.getTimeInMillis()/*now*/, TIME_REPEATING, pendingIntent);
The TIME_REPEATING will be your calculate of the first day on the month, and the pendingIntent your service to run the task.
The unique hard work will be know how many time need to pass to the first day of the next month. But it's possible and very pausable to calculate.

Android Service get data from database on specific time

I have an app show my school timetable, now i trying to write a DashClock widget. I need to get current day subject from database on specific time like everyday 12am so i can publish the update to DashClock.
I check AlarmManager, but have no idea how to set the time for run automatically on 12am and how it access to database.
Any example or tutorial?
Please help, thanks in advance.

You can simply use AlarmManager. By using AlarmManager schedule your task on 12 am at repeating basis. And when AlarmManager Triggers you can perform the database operations.
There are plenty of examples out there. This SO answer can be a good start. you can also check this project. Followings are jsut some search results samples in google first page.
link1, link2, link3
I think from next time better search for your answer before posting.

Managing AlarmManager to repeat an action weekly

I've been searching all this morning for a good tutorial in how to use AlarmManager to perform an action weekly. The only thing I've found is this:
Repeat Alarms on Every Monday in Android usig AlarmManager/BroadcastReceiver
but it's different from everything else I've read, and I do not fully understand the code.
Could you please help me?
I'm using a form to complete, and with s pushing button, creating an alarm configured by the user. I read all the inputs but then I don't know how to translate it to make an alarm.
Thank you.