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How to keep timer running when closing the app?

i have code like this , i wanna make timer keep running when i close the app.
private void startStop() {
if (timerStatus == TimerStatus.STOPPED) {
setTimerValues();
setProgressBarValues();
timerStatus = TimerStatus.STARTED; startCountDownTimer();
} else {
timerStatus = TimerStatus.STOPPED;
stopCountDownTimer();
}
}

Assuming you want something like starting the timer, see the progress bar move and if you come back to your app after an hour, it should have advanced by that time.
The easiest approach would be to store the time at which the timer was started in a shared preference and update your timer periodically using System.currentTimeMillis()-startTime
All left to do is restore the shared preference in your Activity's onCreate

Entering app exactly as it was left

I know there must be douzens of answers to this question out there, but either i cant't find them or I don't understand them.
The Question:
How do I get my app to exactly start as it was left?
F.e. dynamicly added checkBoxes shouldn't dissapear!

There is no "out of the box" way of doing it. You could save the current state of your Activity in some way (More on persistence)
Then you need to be able to rebuild the desired state of the persisted state in your Activity lifecycle
You could save and load with the shared preferences for example:
public void saveState(YourState state) {
SharedPreferences sharedPreferences = app.getSharedPreferences(R.string.preference_file_key, Context.MODE_PRIVATE)
sharedPreferences.edit()
.putString("CustomAtt", state.getCustomAtt())
}
public YourState loadState() {
SharedPreferences sharedPreferences = app.getSharedPreferences(R.string.preference_file_key, Context.MODE_PRIVATE)
String customAtt = sharedPreferences.getString("CustomAtt", "DefaultValue")
return new YoutState(customAtt)
}
And use it like this
#Override
protected void onCreate(Bundle savedInstanceState) {
YourState state = loadState();
// Rebuild your activity based on state
someView.setText(state.getCustomAtt())
}

You can store such values in SharedPreferences.
https://developer.android.com/training/basics/data-storage/shared-preferences.html
It is using key-value approach for saving. So you can save some values and read it from SharedPreferences whenever you want to.
This is the best approach for small data, that can be used on the app launch. So you can quit your app and the data is still present - so can be read on the next app launch.

Or save the condition of your program to a text file, so that the program can "translate" it back into conditions before it stops, or what I do not recommend, it saves every object created with ObjectOutputStream.

Where to put welcome activity code

I searched a lot but i did not find my answer. I have developed an android application where on the very first lunch user will be shown a welcome screen made of viewpager. The problem is i don't know which place is the best to put the welcome activity code in my application.
The simplest way it could be that in the main activity at the very fist line even before super.onCreate(), inside onCreate method where i try to get the shared preference value and then evaluate whether it is fist lunch. If it is, then i start the welcome activity as shown below
public class MainActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
boolean welcome = sharedPreferences.getBoolean(getString(R.string.key_welcome), true);
if (welcome) {
// go and start welcoming activity
Intent intent = new Intent(this, WelcomeSlideActivity.class);
startActivity(intent);
}
super.onCreate();
}
}
But i found another approach to deal with it. It is Application class. Since Application class is the first one, which runs even before any other codes in my application. So i thought, i would be nice to do it there as shown below
public class App extends Application {
#Override
public void onCreate() {
super.onCreate();
SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
boolean welcome = sharedPreferences.getBoolean(getString(R.string.key_welcome), true);
if (welcome) {
// go and start welcoming activity
Intent intent = new Intent(this, WelcomeSlideActivity.class);
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(intent);
}
}
}
So i am in dilemma, which one would be the best option to choose. And i am even not sure if i am doing it in the right way since there is no such documentation in android developer website or anywhere.

Have a look at how to create splash screens the correct way. https://www.bignerdranch.com/blog/splash-screens-the-right-way/
As for using the Application class - this is primarily used for Application-wide configuration for maintaining a global application state. Hence starting an activity from here does not make much sense as it's purpose has changed into becoming an entry point into the application rather than providing state for the app as a whole.
Furthermore, why not make the WelcomeSlideActivity the first 'launcher' activity? Then in there, you can create the logic of whether to launch the next activity without history or whether to show the current view.
Ideally, you should create a splash screen activity, which determines whether to show the WelcomeSlideActivity Or the MainActivity. The advantage of this is that while he app determines which Activity to launch, the user is presented with a splash screen that informs the user that the app has started

How to show different page if user is first time user (Android)

I have a blank-ish Android Project and what I want to do is take the user to a different "page/screen" if it is their first time only.
I know the logic for this but since I'm new to Android, I'm unsure of how to code this.
Below are the steps I believe I need to take in order to accomplish this:
App loads. If Local storage contains setting "FirstTimeUser", then it is not their first time using the app. Show the MainActivity page. If FirstTimeUser setting does not exist, it is their first time using the app (or they have uninstalled and reinstalled it), so instead, show WelcomeActivity page.
After viewing Welcome activity page, create FirstTimeUser setting and set to False.
But how do I code this for an Android app?

Use shared preferences as shown:
//declare as global
SharedPreferences prefs = null;
//and in your onCreate method:
prefs = getSharedPreferences("packageNameHere", MODE_PRIVATE);
if (prefs.getBoolean("firstrun", true)) {
//do stuff here if first run
//make sure to flag the boolean as false
prefs.edit().putBoolean("firstrun", false).commit();
}
else{
//if not first run, do something else
}

There is something called "SharedPreferences" that i believe your looking for.
http://developer.android.com/reference/android/content/SharedPreferences.Editor.html

Detect First Run

I am trying to detect if my app has been run before, by using this code:
(This is in my default Android activity)
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (savedInstanceState == null) {
Log.w("activity", "first time");
setContentView(R.layout.activity_clean_weather);
} else {
Log.w("activity", "second time");
setContentView(R.layout.activity_clean_weather);
}
}
When I first run the app it says first time, when I run it a second time, first time, and a third, first time....
I am using an actual Android device and I am not using the run button each time. I run the app once with the Eclipse run button, then I close the app and press on its icon on my phone.
Is there something wrong with my code?

savedInstanceState is more for switching between states, like pausing/resuming, that kind of thing. It must always be created by you, also.
What you want in this case is SharedPreferences.
Something like this:
public static final String PREFS_NAME = "MyPrefsFile"; // Name of prefs file; don't change this after it's saved something
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
SharedPreferences settings = getSharedPreferences(PREFS_NAME, 0); // Get preferences file (0 = no option flags set)
boolean firstRun = settings.getBoolean("firstRun", true); // Is it first run? If not specified, use "true"
if (firstRun) {
Log.w("activity", "first time");
setContentView(R.layout.activity_clean_weather);
SharedPreferences.Editor editor = settings.edit(); // Open the editor for our settings
editor.putBoolean("firstRun", false); // It is no longer the first run
editor.commit(); // Save all changed settings
} else {
Log.w("activity", "second time");
setContentView(R.layout.activity_clean_weather);
}
}
I basically took this code directly from the documentation for Storage Options and applied it to your situation. It's a good concept to learn early.

You may use a self-defined shared preference to archive your goal.

The fact is that savedInstanceState holds persistent data across activities. As such if you restart the app, savedInstanceState will be null across runs. You should either use a Preference or some data base entry to keep track of your first run. I myself use a SharedPreference for this purpose.

savedInstanceState will be null if the app is not already loaded in memory. If you want to detect whether the app has run for the very first time, you have to apply different technique, such as using sharedPrefs / DB to store a property for the first run.
i.e. Check sharedPrefs for property "firstRun"
if exists, then it is not a first run
else it is the first run
set the firstRun property to true