Develop Reference

How to get current fragment from MainActivity

I've done some research but I really couldn't find the answer.
I have single activity with side menu, and holder. I have many (non support) fragments, and all of them are using same holder (one at a time).
When user uses menu (it's in main activity), and goes another page, I want to add name of the current fragment to backstack (using .addToBackStack(Fragment1.class.getName())), but I couldn't find how to get current fragment.
I don't want to implement interface etc to keep track of current fragment. There is a super simple way using fragmentManger isn't there?

You can get your current fragment like this:
if (getFragmentManager().getBackStackEntryCount() > 1) {
Fragment f = getFragmentManager().findFragmentById(R.id.content_frame);
if (f instanceof BlankFragment) {
// Do something
}
}

OK,
If you want to get latest entry from backstack(thanks to #AndroidGeek);
fragmentManager.getBackStackEntryAt(fragmentManager.getBackStackEntryCount()-1);
and, if you want to get currently active fragment (thanks to #Salman500 #AndroidGeek);
Fragment f = getFragmentManager().findFragmentById(R.id.fragment_holder);

you can use this to get fragment id for non support fragment
Fragment fragment = getFragmentManager().findFragmentById(R.id.fragment_id);
if(fragment!=null)
{
getFragmentManager()
.beginTransaction()
.addToBackStack(null)
.commit();
}

You can keep track of fragments in the main activity (with variables) and access them there. Example:
FragmentManager manager = getSupportFragmentManager();
FragmentTransaction transaction= manager.beginTransaction();
MyFragment myFragment = new MyFragment();
myFragment.doSomething();
Adding to the back-stack:
FragmentTransaction fragment = getSupportFragmentManager().beginTransaction();
fragment.addToBackStack(fragment);
fragment.commit();
This is answered here: get currently displayed fragment

Just use addToBackStack() before you commit() the fragment trancsaction. See it here
So your code will look like :
...
fragmentTransaction.replace(R.id.holder, newFragmentToShow, newFragmentTag);
fragmentTransaction.addToBackStack();
fragmentTransaction.commit();
...
EDIT : after OP was edited
You do not need the fragment class to call addToBackStack() as you have mentioned in the OP. The String argument is an optional string just to keep the state for the backstack state. You should see the documentation
It is all internally managed and the current active fragment is automatically added to the backStack, you may call it from where ever you want, it will always use current active fragment.

Preloading a fragment when popBackStack

I have a problem with the backstack behaviour. That is what I am doing:
add(fragment1) + addToBackStack(null)
replace(fragment2) + addToBackStack(null)
What is happening:
Fragment 1 is added and in the backstack
Then the second fragment replaces the first one and it is added to the backstack.
Now I want to change my last backstacked fragment with a new transaction which put a new backstack fragment so:
[frag1, frag2] becomes [frag1, frag3]
but this transaction made by a popBackStack + replace is making the frag1 to load by calling its onCreateView and onActivityCreated. I know this is the expected behaviour since this is how backstack works, but I am trying to find a way to avoid this preload.
Edit
In this question I am using the concept of backstack fragment for the transaction to be more clear. Every transaction here is an add+remove (which is a replace).
The code for replace I am using is:
public int replaceFragment(BaseFragment newFragment, boolean addToBackStack, boolean animated, PopStackMode popMode) {
if (popMode != null) {
getSupportFragmentManager().popBackStack(newFragment.getFragmentTag(), popMode == PopStackMode.POP_INCLUSIVE ? FragmentManager
.POP_BACK_STACK_INCLUSIVE : 0);
}
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
if (animated) {
ft.setCustomAnimations(R.anim.slide_in_left, 0, R.anim.slide_out_right, 0);
}
ft.replace(R.id.fragment_container, newFragment, newFragment.getFragmentTag());
if (addToBackStack) {
ft.addToBackStack(newFragment.getFragmentTag());
}
return ft.commit();
}
You can see I am creating a navigation history based on the fragment backstack, as it was kind of a browser. When a "page" is added there is a fragment and a backstack transaction. In this context, I trying to:
Remove the current fragment.
Remove the transaction from the backstack.
Add a new fragment without poping and loading the previous backstack fragment.
I hope it is more clear.
Edit 2
I have filled a request feature for a flag that supports this behavior. Find it here.

First, you should understand that the backstack doesn't save fragments, but it saves transactions instead. When you call popBackStack what it actually does is revert the previous transaction. More on this here.
I think that you can do this:
Name your transactions by providing a unique name to your addToBackStack instead of null. i.e. addToBackStack("frag1").
Don't call popBackStack + replace, but instead just call replace.
Then, in your activity, override your onBackPressed and if the current fragment being displayed is Frag3 (you can check this using findFragmentByTag if you provided a tag in the replace method) you can call getSupportFragmentManager().popBackStackImmediate("frag1", FragmentManager.POP_BACK_STACK_INCLUSIVE); (otherwise call the super.onBackPressed)

how can i handle the fragment1 onclick perform in fragment2?

I am develop the app using the fragments and i am facing one fragment1 adding to the another fragment2
fragment1 onclicks performing fragment2 .I didn't findout the solution for that. please guide anyone know
I am using the following code to add the fragment
Fragment2 fragment2=new Fragment2();
FragmentManager fragmentManager = activity.getFragmentManager();
android.app.FragmentTransaction ft=fragmentManager.beginTransaction();
ft.add(R.id.container,fragment2);
ft.hide(new Fragment1());
ft.addToBackStack(Fragment1.class.getName());
ft.commit();
The above to use adding onefragment1 adding to fragment2.Fragment1 onclicks perform to fragment2 . i didn't findout mistake.
please guide me anyone know .Advance thanks to all

nested Fragments are not recommended and for adding a fragment to a container from another Fragment use the parent Activity to do so , you can define a function inside Parent Activity which replace current Fragment with your second Fragment and call it from your first.

Adding a fragment to another fragment is the concept of nested fragments and not recommended. You should replace the fragment instead of adding. Use the following:
Fragment fragment = new Fragment2();
FragmentManager fragmentManager = getFragmentManager();
fragmentManager.beginTransaction().addToBackStack("fragment").replace(R.id.frame_container, fragment).commit();

Android fragments over each other

I've been working with fragments for a while now, but I regularly encounter a problem that just annoys me. Fragments remain drawn over each other some times. Now, I managed to isolate one use case for this, and it goes like this:
Add Fragment A (also use addToBackStack with a name "backstack_state")
Replace Fragment A with Fragment B (use addToBackStack)
Replace Fragment B with Fragment C WITHOUT using addToBackStack
at a given point use popBackStack("backstack_state", 0) and here comes the issue:
The backstack is popped until Fragment A but Fragment C is overlaid with Fragment A, both are visible at the same time. Is this normal behavior or is it me who makes a mistake?
Here's a remark also: all the fragments have transparent background.
Thanks!

This happens because the top fragment (in this case Fragment C) is not removed. You have to remove it first inside a fragment transaction. Try this:
FragmentManager fragmentManager = getFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
Fragment topFragment = fragmentManager.findFragmentById(R.id.fragment_container);
if (topFragment != null) {
fragmentTransaction.remove(topFragment);
}
fragmentTransaction.commit();
fragmentManager.popBackStack("backstack_state", 0);

Navigate back to activity from fragment

I have class Demo and I am extends the demo by FragmentActivity class. Also I have another class Fragment1 extends Fragment. And the onclick of button i am navigate from activity Demo to the Fragment Fragment1. Now I want to come back on Demo from the Fragment1. So how can I back to Demo activity?
Thanks.

Your question is lacking a lot of detail, so I'm taking a stab in the dark here, but...
I presume in your onClick code, you use the Fragment Manager to create a new Fragment Transaction, then add the fragment to that transaction and commit it?
Your problem with the activity being closed when you hit the back button is likely because your fragment was not added to something called the "back stack". You can find to documentation here http://developer.android.com/reference/android/app/FragmentTransaction.html#addToBackStack%28java.lang.String%29, but crucially the main thing you need to do is modify your code to include the line below:
FragmentManager fragmentManager = getFragmentManager()
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.add(R.id.fragment_container, new Fragment1());
fragmentTransaction.addToBackStack("Transaction ID"); // <-- This is key!
fragmentTransaction.commit();
Once that's done, Android will remember the adding of the fragment as a navigation act, and should reverse the transaction when the back button is hit.
If this wasn't what you're looking for, or if it doesn't work, please provide some more detail and some code samples and I can take another look.

Try adding the fragment you want to go back to manually to the backstack.
FragmentTransaction transaction = getFragmentManager().beginTransaction();
YourFragmentName myFragment = new YourFragmentName();
transaction.replace(R.id.fragment_container, myFragment);
//if you with to add it to backStack, do this, otherwise skip the line below
transaction.addToBackStack(null);
transaction.commit();