Develop Reference

Best way to handle activity state

I'm making an app that shows another activity when I correctly login however in the home screen when I pressed back and then returned to the app the login activity showed.
I was able to avoid this overriding the onBackPressed this way:
public void onBackPressed()
moveTaskToBack(true);
}
Is this the best way to do it? Is there a more proper way to keep the state of the application when I exit it?

In your login activity after starting intent call finish()
finish destroy your activity and avoid to run it again automatically.

Your issue is that you kept LoginActivity in stack. so when you press back it will kill MainActivity(after login) and since LoginAcitivity still there. it will be shown again. best is to kill LoginAcitivty after starting new activity.
call this in LoginActivity:
Intent intent = new Intent(context, MainActivity.class);
startActivity(intent);
finish();

As you question I understand, you want to clear the entire history stack and start a new activity. For this, in API level 11 a new Intent Flag was added which is: Intent.FLAG_ACTIVITY_CLEAR_TASK
Just to clarify, use this:
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);
For API <=10 now one can use IntentCompat class for the same. One can use IntentCompat.FLAG_ACTIVITY_CLEAR_TASK flag to clear task. So you can support pre API level 11 as well.

Handling Previous Activities

I have a spinner that essentially starts multiple new activities based on onItemSelect();
However, what's happening on my app is if I start the same activity multiple times I have to hit the Android back button multiple times. How do I start the same activity and kill the previous one so that I don't have multiple layouts sitting there open?

Set android:noHistory=true for your <activity> in Manifest.xml. See here
Or, programatically:
Intent intent = new Intent(this, Activity.class);
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(intent);

Use the FLAG_ACTIVITY_CLEAR_TOP activity flag.

When you start a new activity you need to finish your old activity. So when you call your new intent:
startActivity(intent);
finish();
That will end the current activity.

You might want to consider setting the activity launchmode to "singletop" (this can be done in the Android Manifest). Then instead of creating a new activity, it will call OnNewIntent() of the existing activity.

remove activity from stack

I am developing an application in android. I am new in android.
In my application I have a category selection activity from that user have to check a check-box, based on that he will get view on another screen. I have a menu button in 3rd screen in that I have a button for selecting category, when I click on that button its also works fine but when I click back button it will redirect me 2 times at same activity... How to remove this problem? I have used finish() method but its also creates problem its get's me out from the application directly...
I want redirect to selection activity and it should not show me 2 times when I click back button ....
Is there any way please redirect me thank you.

a call to finish() should work so you schould check your code for multiple calling the wrong method or something like this.
Intent intent = new Intent(activity, activityClass.class);
activity.startActivity(intent);
finish();
you should also take a look at the Intent flags:
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK | Intent.FLAG_ACTIVITY_NEW_TASK);
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
intent.addFlags(Intent.FLAG_ACTIVITY_NO_HISTORY);
intent.addFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);

Your question isn't clear enough for me to know if this will solve your problem, but if you include the following attributes on your Activity in AndroidManifest.xml, the so-attributed Activity will never appear in your history list.
android:excludeFromRecents="true"
android:noHistory="true"
As for removing something from the history, I'm not sure how to do that, but I'm interested in the answer!

You should call finish before you call Intent and go to next activity. so the current task is finished and will not be saved in stack and then you intent activity will come on top of stack. If you directly want to go to Selection activity, override onBackPressed() and intent to the activity you want to go to.

There are different flags that you can use to control how your activity interacts with the activity history stack. Two that might be of interest to you are FLAG_ACTIVITY_CLEAR_TOP and FLAG_ACTIVITY_NO_HISTORY.

Clear all activities in a task?

I have a splash screen activity, then a login activity. My history stack looks like:
SplashActivity
LoginActivity
when the user successfully logs in via LoginActivity, I want to start WelcomeActivity, but clear the entire stack:
SplashActivity
LoginActivity // launches WelcomeActivity ->
WelcomeActivity
// but now all three are in the history stack, while I only
// want WelcomeActivity in the stack at this point.
Is there some flag I can use to do that?
// LoginActivity.java
Intent intent = new Intent(this, WelcomeActivity.class);
intent.addFlag(Intent.FLAG_ACTIVITY_CLEAR_TASK);
startActivity(intent);
finish();
Not sure if using the FLAG_ACTIVITY_CLEAR_TASK will clear out all activities in my task or not. I can do this 'manually' by unwinding the stack by using startActivityForResult() calls, but will be more fragile and more code to maintain.
Thanks

Yes that should work fine. You could use:
FLAG_ACTIVITY_CLEAR_TOP
FLAG_ACTIVITY_SINGLE_TOP
FLAG_ACTIVITY_CLEAR_TASK
FLAG_ACTIVITY_NEW_TASK
which ensures that if an instance is already running and is not top then anything on top of it will be cleared and it will be used, instead of starting a new instance (this useful once you've gone Welcome activity -> Activity A and then you want to get back to Welcome from A, but the extra flags shouldn't affect your case above).

Intent intent = new Intent(this, NextActivity.class);
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK |
IntentCompat.FLAG_ACTIVITY_CLEAR_TASK);
startActivity(intent);

Use android:noHistory="true" on the splash activity in the manifest file.
<activity
android:name=".activity.SplashActivity"
android:theme="#style/theme_noActionBar"
android:noHistory="true">

finish() removes the activity from the stack. So, if you start LoginActivity and call finish() on SplashActivity, and then you do exact the same to start WelcomeActivity you will get the desired behaviour. No need to use extra flags.

Intent.FLAG_ACTIVITY_NO_HISTORY can work in your case too if you do not want the activity on the history stack.

Just do this to clear all previous activity in a task:
finishAffinity() // if you are in fragment use activity.finishAffinity()
Intent intent = new Intent(this, DestActivity.class); // with all flags you want
startActivity(intent)

In case that all of three activity is involved in the same app(same taskAffinity), you can pick either 1,2 or 3 below. otherwise you should pick 1,2 below.
If you don't want to return back SplashActivity from LoginActivity, you can define activity attribute noHistory in AndroidManifest.xml or you can set FLAG_ACTIVITY_NO_HISTORY into the intent to launch SplashActivity. if SplashActivity is started from Launcher, you should pick way to set activity attribute noHistory.
If you don't want to return back LoginActivity from WelcomeActivity, you can use either activity attribute noHistory or FLAG_ACTIVITY_NO_HISTORY like number 1 above.
If you want to clear back stack on specific situation, you can use FLAG_ACTIVITY_CLEAR_TASK in conjunction with FLAG_ACTIVITY_NEW_TASK(FLAG_ACTIVITY_CLEAR_TASK always must be used in conjunction with FLAG_ACTIVITY_NEW_TASK). But, if the activity being started is involved in other app(i.e different taskAffinity), the task will be launched other task after the task is cleared, not current task. so make sure that the activity being launched is involved in the same app(taskAffinity).

Removing an activity from the history stack

My app shows a signup activity the first time the user runs the app, looks like:
ActivitySplashScreen (welcome to game, sign up for an account?)
ActivitySplashScreenSignUp (great, fill in this info)
ActivityGameMain (main game screen)
so the activities launch each other in exactly that order, when the user clicks through a button on each screen.
When the user goes from activity #2 to #3, is it possible to wipe #1 and #2 off the history stack completely? I'd like it so that if the user is at #3, and hits the back button, they just go to the homescreen, instead of back to the splash screen.
I think I can accomplish this with tasks (ie. start a new task on #3) but wanted to see if there was simpler method,
Thanks

You can achieve this by setting the android:noHistory attribute to "true" in the relevant <activity> entries in your AndroidManifest.xml file. For example:
<activity
android:name=".AnyActivity"
android:noHistory="true" />

You can use forwarding to remove the previous activity from the activity stack while launching the next one. There's an example of this in the APIDemos, but basically all you're doing is calling finish() immediately after calling startActivity().

Yes, have a look at Intent.FLAG_ACTIVITY_NO_HISTORY.

This is likely not the ideal way to do it. If someone has a better way, I will be looking forward to implementing it. Here's how I accomplished this specific task with pre-version-11 sdk.
in each class you want to go away when it's clear time, you need to do this:
... interesting code stuff ...
Intent i = new Intent(MyActivityThatNeedsToGo.this, NextActivity.class);
startActivityForResult(i, 0);
}
#Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (resultCode == R.string.unwind_stack_result_id) {
this.setResult(R.string.unwind_stack_result_id);
this.finish();
}
}
then the one that needs to set off the chain of pops from the stack needs to just call this when you want to initiate it:
NextActivity.this.setResult(R.string.unwind_stack_result_id);
NextActivity.this.finish();
Then the activities aren't on the stack!
Remember folks, that you can start an activity, and then begin cleaning up behind it, execution does not follow a single (the ui) thread.

One way that works pre API 11 is to start ActivityGameMain first, then in the onCreate of that Activity start your ActivitySplashScreen activity. The ActivityGameMain won't appear as you call startActivity too soon for the splash.
Then you can clear the stack when starting ActivityGameMain by setting these flags on the Intent:
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TOP);
You also must add this to ActivitySplashScreen:
#Override
public void onBackPressed() {
moveTaskToBack(true);
}
So that pressing back on that activity doesn't go back to your ActivityGameMain.
I assume you don't want the splash screen to be gone back to either, to achieve this I suggest setting it to noHistory in your AndroidManifest.xml. Then put the goBackPressed code in your ActivitySplashScreenSignUp class instead.
However I have found a few ways to break this. Start another app from a notification while ActivitySplashScreenSignUp is shown and the back history is not reset.
The only real way around this is in API 11:
intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK);

I use this way.
Intent i = new Intent(MyOldActivity.this, MyNewActivity.class);
i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK)
startActivity(i);

I know I'm late on this (it's been two years since the question was asked) but I accomplished this by intercepting the back button press. Rather than checking for specific activities, I just look at the count and if it's less than 3 it simply sends the app to the back (pausing the app and returning the user to whatever was running before launch). I check for less than three because I only have one intro screen. Also, I check the count because my app allows the user to navigate back to the home screen through the menu, so this allows them to back up through other screens like normal if there are activities other than the intro screen on the stack.
//We want the home screen to behave like the bottom of the activity stack so we do not return to the initial screen
//unless the application has been killed. Users can toggle the session mode with a menu item at all other times.
#Override
public void onBackPressed() {
//Check the activity stack and see if it's more than two deep (initial screen and home screen)
//If it's more than two deep, then let the app proccess the press
ActivityManager am = (ActivityManager)this.getSystemService(Activity.ACTIVITY_SERVICE);
List<RunningTaskInfo> tasks = am.getRunningTasks(3); //3 because we have to give it something. This is an arbitrary number
int activityCount = tasks.get(0).numActivities;
if (activityCount < 3)
{
moveTaskToBack(true);
}
else
{
super.onBackPressed();
}
}

In the manifest you can add:
android:noHistory="true"
<activity
android:name=".ActivityName"
android:noHistory="true" />
You can also call
finish()
immediately after calling startActivity(..)

Just set noHistory="true" in Manifest file.
It makes activity being removed from the backstack.

It is crazy that no one has mentioned this elegant solution. This should be the accepted answer.
SplashActivity -> AuthActivity -> DashActivity
if (!sessionManager.isLoggedIn()) {
Intent intent = new Intent(context, AuthActivity.class);
intent.setFlags(Intent.FLAG_ACTIVITY_NO_HISTORY);
context.startActivity(intent);
finish();
} else {
Intent intent = new Intent(context, DashActivity.class);
context.startActivity(intent);
finish();
}
The key here is to use intent.setFlags(Intent.FLAG_ACTIVITY_NO_HISTORY); for the intermediary Activity. Once that middle link is broken, the DashActivity will the first and last in the stack.
android:noHistory="true" is a bad solution, as it causes problems when relying on the Activity as a callback e.g onActivityResult. This is the recommended solution and should be accepted.

It's too late but hope it helps. Most of the answers are not pointing into the right direction. There are two simple flags for such thing.
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);
From Android docs:
public static final int FLAG_ACTIVITY_CLEAR_TASK
Added in API level 11
If set in an Intent passed to Context.startActivity(), this flag will cause any existing task that would be associated with the
activity to be cleared before the activity is started. That is, the
activity becomes the new root of an otherwise empty task, and any old
activities are finished. This can only be used in conjunction with
FLAG_ACTIVITY_NEW_TASK.

Just call this.finish() before startActivity(intent) like this-
Intent intent = new Intent(ActivityOne.this, ActivityTwo.class);
this.finish();
startActivity(intent);

Removing a activity from a History is done By setting the flag before the activity You Don't want
A->B->C->D
Suppose A,B,C and D are 4 Activities if you want to clear B and C then
set flag
intent.setFlags(Intent.FLAG_ACTIVITY_NO_HISTORY);
In the activity A and B
Here is the code bit
Intent intent = new Intent(this,Activity_B.class);
intent.setFlags(Intent.FLAG_ACTIVITY_NO_HISTORY);
startActivity(intent);

if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
super.finishAndRemoveTask();
}
else {
super.finish();
}

Here I have listed few ways to accomplish this task:
Go to the manifest.xml- and put android:noHistory="true", to remove the activity from the stack.
While switching from present activity to some other activity, in intent set flag as (Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK). It is demonstrated in the example below.
Intent intent = new Intent(CurrentActivity.this, HomeActivity.class);
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK |
Intent.FLAG_ACTIVITY_CLEAR_TASK)
startActivity(intent);here
Note :Putting the intent flags can cause blank screen for sometime (while switching activity).

Try this:
intent.addFlags(Intent.FLAG_ACTIVITY_LAUNCHED_FROM_HISTORY)
it is API Level 1, check the link.