I posted something similar here

From Joachim's answer, from Dianne Hackborn:

http://groups.google.com/group/android-developers/browse_thread/thread/d2a5c203dad6ec42

I ended up just using:

FragmentManager fm = getActivity().getSupportFragmentManager();

for(int i = 0; i < fm.getBackStackEntryCount(); ++i) {

    fm.popBackStack();

}

But could equally have used something like:

FragmentManager.popBackStack(String name, FragmentManager.POP_BACK_STACK_INCLUSIVE)

Which will pop all states up to the named one. You can then just replace the fragment with what you want

To make an answer for Warpzit comment and make it easiere to find for others, use:

fragmentManager.popBackStack(null, FragmentManager.POP_BACK_STACK_INCLUSIVE);

With all due respect to all involved parties; I'm very surprised to see how many of you could clear the entire fragment back stack with a simple

fm.popBackStack(null, FragmentManager.POP_BACK_STACK_INCLUSIVE);

According to Android documentation (regarding the name argument - the "null" in the claimed working proposals).

If null, only the top state is popped

Now, I do realize that I'm lacking knowledge of your particular implementations (like how many entries you have in the back stack at the given point in time), but I would bet all my money on the accepted answer when expecting a well defined behaviour over a wider range of devices and vendors:

(for reference, something along with this)

FragmentManager fm = getFragmentManager(); // or 'getSupportFragmentManager();'

int count = fm.getBackStackEntryCount();

for(int i = 0; i < count; ++i) {

    fm.popBackStack();

}

Accepted answer was not enough for me. I had to use :

FragmentManager fm = getSupportFragmentManager();

int count = fm.getBackStackEntryCount();

for(int i = 0; i < count; ++i) {

    fm.popBackStackImmediate();

}

I just wanted to add :--

Popping out from backstack using following

fragmentManager.popBackStack()

is just about removing the fragments from the transaction, no way it is going to remove the fragment from the screen. So ideally, it may not be visible to you but there may be two or three fragments stacked over each other, and on back key press the UI may look cluttered,stacked.

Just taking a simple example:-

Suppose you have a fragmentA which loads Fragmnet B using fragmentmanager.replace() and then we do addToBackStack, to save this transaction. So the flow is :--

STEP 1 -> FragmentA->FragmentB (we moved to FragmentB, but Fragment A is in background, not visible).

Now You do some work in fragmentB and press the Save button—which after saving should go back to fragmentA.

STEP 2-> On save of FragmentB, we go back to FragmentA.

STEP 3 ->So common mistake would be... in Fragment B,we will do fragment Manager.replace() fragmentB with fragmentA.

But what actually is happenening, we are loading Fragment A again, replacing FragmentB . So now there are two FragmentA (one from STEP-1, and one from this STEP-3).

Two instances of FragmentsA are stacked over each other, which may not be visible , but it is there.

So even if we do clear the backstack by above methods, the transaction is cleared but not the actual fragments. So ideally in such a particular case, on press of save button you simply need to go back to fragmentA by simply doing fm.popBackStack() or fm.popBackImmediate().

So correct Step3-> fm.popBackStack() go back to fragmentA, which is already in memory.

Clear backstack without loops

String backStackEntryName = getSupportFragmentManager().getBackStackEntryAt(0).getName();

getSupportFragmentManager().popBackStack(name, FragmentManager.POP_BACK_STACK_INCLUSIVE);

Where name is the addToBackStack() parameter

getSupportFragmentManager().beginTransaction().

                .replace(R.id.container, fragments.get(titleCode))

                .addToBackStack(name)

I got this working this way:

public void showHome() {

    getHandler().post(new Runnable() {

        @Override

        public void run() {

            final FragmentManager fm = getSupportFragmentManager();

            while (fm.getBackStackEntryCount() > 0) {

                fm.popBackStackImmediate();

            }

        }

    });

}

Works for me and easy way without using loop:

 FragmentManager fragmentManager = getSupportFragmentManager();

 //this will clear the back stack and displays no animation on the screen

 fragmentManager.popBackStackImmediate(null, FragmentManager.POP_BACK_STACK_INCLUSIVE);