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Launch an activity only once after Install

I have QR scanner app. There are 3 activities in the app.
1) Main activity - Button to open camera and start scanning
2) QR activity - Scan a QR code
3) Web Activity - On successful scanning, open a web page in the app
Here, the Main activity and QR activity should only launch once, only after the initial install. I read somewhere about using shared preferences. But I am a little confused as to where do I check the variable, as in which activity. Should I check my shared variable in the Main Activity?
This is my first app. Sorry if this is a silly doubt.

It's correct, you have to do it with SharedPreferences.
Here is a good explaination about how to use them
On the first activity shown, you have to add in the onCreate method those lines:
//this retrieve the sharedpreference element
SharedPreference myPref = this.getSharedPreferences(
"prefName", Context.MODE_PRIVATE);
//this retrieve the boolean "firstRun", if it doesn't exists, it places "true"
var firstLaunch = myPref.getBoolean("firstLaunch", true);
//so, if it's not the first run do stuffs
if(!firstLaunch){
//start the next activity
finish();
}
//else, if it's the first run, add the sharedPref
myPref.edit().putBoolean("firstLaunch", false).commit();
hope this helps

To complete #Pier Giorgio Misley answer you can put the "firstLaunch" check on your Main Activity or alternatively put it in another "splash" activity
For putting it in the main activity simply set the ui to some neutral color until you decide if you should finish the activity and launch the Web Activity or show the Main Activity logic
Alternatively, you can create a "splash" screen which can function as a bridge activity (which shows some logo or a nice background color) which check the varible and decide which activity to open Android splash

As pier mentioned, saving that it has been seen once is the way to go. However, I have found on some older devices, shared preferences is not reliable!
I recommend instead using SQLite database.
Create a table as follows
TABLE NAME: SEEN_ACTIVITY
Column 1: ID INT PRIMARY KEY
Column 2: SEEN VARCHAR
Then, once the activity has been launched, check if there is a record for id = '0' in SEEN_ACTIVITY. If not, then insert one as follows, (0, true).
Then, every time the app launches, check to see if the record exists of (0, true). If not, launch the extra activity.

My MainActivity.java
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_splash);
new Handler().postDelayed(new Runnable() {
#Override
public void run() {
SharedPreferences settings = getSharedPreferences("prefName",MODE_PRIVATE);
boolean firstLaunch = settings.getBoolean("firstLaunch", true);
if(firstLaunch == false) {
SharedPreferences.Editor editor=settings.edit();
editor.putBoolean("firstRun",true);
editor.commit();
Intent i = new Intent(SplashActivity.this, MainActivity.class);
startActivity(i);
finish();
}
else {
Intent i = new Intent(SplashActivity.this, ScannerActivity.class);
startActivity(i);
finish();
}
}
}, SPLASH_TIME_OUT);
}
Wrote this code in a new Splash Activity

Android: How to go back previous Activity

I have four activities
ListActivity
Itemdetail_Activity
record1_Act
record2_act.
I can go from ListActivity -> record1_Act and from ListActivity <-record1_Act properly but when I want to go from Itemdetail_Activity -> record2_act and return back from Itemdetail_Activity <- record2_act it always goes record2_act to ListActivity.
I even used i.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK); but it does not work. How to solve this issues?
Here is my code
Intent i = new Intent(record2_act.this, Itemdetail_Activity.class);
i.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK);
startActivity(i);
Intent i = new Intent(record1_Act.this, ListActivity.class);
i.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK);
startActivity(i);
finish();

After starting activity remove finish() call because it will clear that activity from stack and i see you have used finish in your code. also you do not need to set these flags.

In activity 4, implement onBackPressed() as,
#Override
public void onBackPressed()
{
Intent i = new Intent(4.this, 3.class);
startActivity(i);
}
call this method if you have any back button. And if you want to link the backpress for every activity you need to implement onBackPressed() method in every activity.

you can call onBackPressed() if previous activity not finished also you can use :
this.finish();
// Or
Activity currentActivity = this;
currentActivity.finish();
and if previous you finished activity you have to track user in activities and make list of activities, then move to :
activitiList.get(activityList.size() - 2);
// activityList.size() - 1 is last activity and activityList.size() - 2 is previous activity

Do check if ItemDetailsActivity is NOT calling finish()

When good time to start another activity

I have an Android Best Practice question. I have to following code, which is working nicely, but I think it is not so elegant. So, my question is: at which point of activity life cycle is nice to start another activity ?
public class LoginActivity extends ActionBarActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
ParentPreferences parentPreferences = new ParentPreferences(getApplicationContext());
if (parentPreferences.isPassExists()) {
Intent i = new Intent(this, MainActivity.class);
startActivity(i);
} else {
setContentView(R.layout.login);
}
}
}
The task is about: if the parent has already made a password to protect the app, than we don't need to show the LoginActivity. I don't know, is it "healthy" for an Activity to give an intent to launch, when nor the onCreate nor the other lifecycle methods completed.
What are you thoughts guys ?

I think the better way is to create LauncherActivity, and start activitys from them:
For example:
public class LauncherActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
ParentPreferences parentPreferences = new ParentPreferences(getApplicationContext());
Intent intent;
if (parentPreferences.isPassExists()) {
intent = new Intent(this, MainActivity.class);
} else {
intent = new Intent(this, LoginActivity.class);
}
intent.addFlags(Intent.FLAG_ACTIVITY_NO_HISTORY)
startActivity(i);
}
}
Updated:
Refering to Activity | Android Developer
onCreate is a first lifecycle method, сonsequently better to start activity B when A activity just started and does not inflate any layout

I would have the manifest start your MainActivity or whatever you call it. The MainActivity starts by checking if the user has logged in. If not, it starts your LoginActivity, which comes back in onActivityResult() with the result of the login.
It does depend on the requirement for the user to log in every time they start the app, or just once, or once in a while. If the use has to log in every time, than it's ok to start with LoginActivity. Otherwise, starting LoginActivity every time and passing to MainActivity (or whatever) seems just a waste. "Waste" not in the sense of performance, but of clarity of your app.

I think the best solution for you is to add a SplashScreen or like a "fake" screen.
Here you check if he's logged in already and based on it you start the correct activity.
Maybe the absolutely best way would be to do it with fragments, but you have to change a lot of your app.
About when to call it, the onCreate is perfect :)

startActivityForResult(), how does it work?

Im working on my level-selector activity right now and I want to get the result from wich level I chose in my MainGameView, that is run by another activity. How would I go about doing this?
This is what Ive for when you choose level 1:
Button test1 = (Button)findViewById(R.id.test1);
test1.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
setLevel(1);
Intent start = new Intent("nielsen.happy.activities.HAPPYACTIVITY");
startActivityForResult(start, getLevel());
finish();
}
});
but where do I go from here? How do I get this value into my view so I can change bitmaps and other values depending on what level they chose? Is there something I need to do in my "HappyActivity"(MainGameAcitvity) to get the result? cus right now its returning 0
explenation of how games set up: Menu -> levelselector -> Game. So I need to get result from levelselector into game, so it knows what level to start.

(updated corrected response)
Don't use startActivityForResult().
Try this for Activity A:
Intent start = new Intent("nielsen.happy.activities.HAPPYACTIVITY");
start.putExtra("level", getLevel());
startActivity(start);
finish();
Then in Activity B, do this:
Extras mBundle = getIntent().getExtras();
int level = mBundle.getInt("level");
(original, incorrect response)
Lets call activity A the one that houses your sample code above.
Lets call activity B the one that you refer to as HAPPACTIVITY.
Activity A calls startActivityForResult() with a request code.
Activity B starts up and before exiting, you call setResult(int code).
When activity B finishes, A returns to the top via the method onActivityResult().
Implement an onActivityResult() and see what attributes you get.
FYI there is a condition where setResult(RESULT_OK) or setResult(RESULT_CANCELED) will not trigger onActivityResult() in A (I can't recall what the case is).

Using integer from one class in another Android

I need some help with using integer from one activity to another.
I am making some basic math program(game). It gets two random numbers, random operator, and 30 secs to solve math problems as much as you can.
If you solve problem u get 1 point.
Anyway right now, I want to get number of points that user have made and use it in another activity called *RankActivity*.
Main activity is called *BrzoRacunanjeActivity* and it contains button and one *int* called *poenibrojanje* which get number of points that user have made, and when I click on button, it opens new Activity with this line:
startActivity(new Intent(this, RankActivity.class));
As you can see another Activity is called RankActivity, and there I wrote :
*BrzoRacunanjeActivity a1 = new BrzoRacunanjeActivity();*
*System.out.println("Number of points:" + a1.poenibrojanje);;*
and I get all time this reuslt: 09-22 09:09:14.940: INFO/System.out(289): Number of points:0

Try this:
Intent intent = new Intent(this, RankActivity.class);
intent.putExtra("points", pointsVar);
startActivity(intent);
In onCreate of RankActivity:
getIntent().getIntExtra("points", 0);

so you want to pass integer value from one activity to another activity? right...
try:
Intent intent = new Intent(currentclass.this, destination.class);
intent.putExtra("point", pointvalue);
startActivity(intent);
at destination activity:
final int getpoint = getIntent().getExtras().getInt("point");
This will solve your problem.

first of all make
static variable like as public static int poenibrojanje;
in your BrzoRacunanjeActivity.class file now you can use this variable in any other class like as
BrzoRacunanjeActivity.poenibrojanje
or you can use putExtras(); method.
in you main activity.
Intent i = new Intent(this, RankActivity.class);
i.putExtra("Value",poenibrojanje);
in your next activity
int v = (getIntent().getExtras().getInt("Value")) ;