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overriding back method in fragment class in android

how to quit the app whenever i press the back button from certain fragments.I found out that system.exit(1) closes the app. but i could now override method for handling back key.Is there any method to override back key ? if yes How can i perform it?

onBackPressed() function in activity will help

write this in your onBackPressed()
if (fragmentManager.getBackStackEntryCount() == 1) {
if (isPressed) {
finish();
} else {
StringUtils.displayToastShort(this, "press again to exit");
isPressed = true;
}
}

What you should do, is when you add a fragment add a tag with it, like
fragmentTransaction.replace(android.R.id.content, fragment, "My_Tag");
And then in activity onBackPressed()
fragment= (AddFriends)getFragmentManager().findFragmentByTag("My_Tag");
if (fragment!= null && fragment.isVisible()) {
//Exit from your app here
finish();
}
Hope this helps you.

Try this function for opening a fragment
public void openFragment(Fragment fragment)
{
FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransac‌​tion();
fragmentTransaction.replace(R.id.fragment_container,fragment);
fragmentTransaction.commit();
}
and when you want to open a fragment call this function like this
openFragment(new AddFriends());
Using above function it will exit the app with back button press.

I solved it in following way.
First make a class with static integer variable(say a).
Override back methods on mainActivity and choose the fragment you want to open on back pressed as per the value on static variable.
[note:whenever new fragments are opened update static variable with new value and according to this value override back method on main activity]

How to save fragment state while navigating through activity

May be the title of the question is not clear . Or I have failed to describe what I am looking for .
I have two activity in my app . Lets say their name is "ActivityA" and "ActivityB" . Under "ActivityA" there are few fragments . Lets say their name is "FragmentA" "FragmentB" "FragmentC" "FragmentD" etc . The default fragment is "FragmentA" , that means when the activity starts "FragmentA" starts .
Now , if I navigate to "ActivityB" , and came back to "ActivityA" , it always open "FragmentA" . But what I want is if I navigate to "FragmentB" , and then navigate to "ActivityB" , and back to "ActivityA" it starts "FragmentA" , but I want "FragmentB" to start ,in which I was beforer

You might be restarting ActivityA from ActivityB via startActivity() instead of finishing ActivityB. If it is so, just finish your ActivityB. Then you will be on the last shown fragment in your ActivityA.
Or you can also use onSaveInstanceState method to keep trace of your Fragments. This answer can help you with this.
Or using following with your ActivityA can also solves your issue:
<activity android:name=".ActivityA" android:launchMode="singleTop">

Not sure if I understand you correctly, but I think what you need to do is startActivityForResult when you call your ActivityB. When you press BackButton you provide your necessary information about the fragment to be called and catch these infos in ActivityB's onActivityResult then navigate to the desired Fragment.

Create a method that returns the last visible fragment
public Fragment getVisibleFragment(){
FragmentManager fragmentManager = MainActivity.this.getSupportFragmentManager();
List<Fragment> fragments = fragmentManager.getFragments();
if(fragments != null){
for(Fragment fragment : fragments){
if(fragment != null && fragment.isVisible())
return fragment;
}
}
return null;
}
Create an instance of Fragment class and set it to null
Fragment lastVisibleFragment = null;
in onPause save the last fragment
#Override
protected void onPause() {
super.onPause();
lastVisibleFragment = getVisibleFragment();
}
Then in onResume() add the last fragment you were in if not null
#Override
protected void onResume() {
super.onResume();
if(lastVisibleFragment !=null){
getSupportFragmentManager().beginTransaction()
.add(yourFrameLayout, lastVisibleFragment)
.commit();
}
else{ //Add first fragment you were adding}
}

Unable to close FragmentActivity correctly

I'm facing a strange problem inside my app. From a fragment, if i push a button, i start new FragmentActivity that contains a fragment and some other elements, but if i would go back to previous Activity (that contain fragment that start the current activity), i need to push back button twice.
First time fragmentActivity seem close itself, but it reopens again. I close FragmentActivity as always:
#Override
public void onBackPressed() {
super.onBackPressed();
finish();
}
so what's wrong?

i start new FragmentActivity that contains a fragment and some other elements
You're most likely adding that FragmentTransaction to the backstack, which is why it's consuming the back button press. You shouldn't need to override onBackPressed() at all. Instead, look at the code where you add the Fragment to the new FragmentActivity and ensure you're not calling .addToBackStack() on the initial transaction. For example, typically in onCreate() you would do something like this:
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.your_container_id, new YourInitialFragment())
.commit();
}
}

Finishing current activity from a fragment

I have a fragment in an activity that I am using as a navigation drawer. It contains buttons that when clicked start new activities (startActivity from a fragment simply calls startActivity on the current activity).
For the life of me I can't seem to figure out how I would finish the current activity after starting a new one.
I am looking to achieve something like this in the fragment:
#Override
public void onClick(View view) {
// TODO Auto-generated method stub
if (view == mButtonShows) {
Intent intent = new Intent(view.getContext(), MyNewActivity.class);
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(intent);
finish();
}
}
But it seems Fragment.class does not implement finish() (like it implements startActivity(...)).
I would like the activity backstack cleared when they launch the 2nd activity. (so pressing back from the new activity would technically drop them back to the launcher)

When working with fragments, instead of using this or refering to the context, always use getActivity(). You should call
Java
getActivity().finish();
Kotlin
activity.finish()
to finish your activity from fragment.

Well actually...
I wouldn't have the Fragment try to finish the Activity. That places too much authority on the Fragment in my opinion. Instead, I would use the guide here: http://developer.android.com/training/basics/fragments/communicating.html
Have the Fragment define an interface which the Activity must implement. Make a call up to the Activity, then let the Activity decide what to do with the information. If the activity wishes to finish itself, then it can.

As mentioned by Jon F Hancock, this is how a fragment can 'close' the activity by suggesting the activity to close. This makes the fragment portable as is the reason for them. If you use it in a different activity, you might not want to close the activity.
Code below is a snippet from an activity and fragment which has a save and cancel button.
PlayerActivity
public class PlayerActivity extends Activity
implements PlayerInfo.PlayerAddListener {
public void onPlayerCancel() {
// Decide if its suitable to close the activity,
//e.g. is an edit being done in one of the other fragments?
finish();
}
}
PlayerInfoFragment, which contains an interface which the calling activity needs to implement.
public class PlayerInfoFragment extends Fragment {
private PlayerAddListener callback; // implemented in the Activity
#Override
public void onAttach(Activity activity) {
super.onAttach(activity);
callback= (PlayerAddListener) activity;
}
public interface PlayerAddListener {
public void onPlayerSave(Player p); // not shown in impl above
public void onPlayerCancel();
}
public void btnCancel(View v) {
callback.onPlayerCancel(); // the activity's implementation
}
}

You should use getActivity() method in order to finish the activity from the fragment.
getActivity().finish();

This does not need assertion, Latest update in fragment in android JetPack
requireActivity().finish();

In Fragment use getActivity.finishAffinity()
getActivity().finishAffinity();
It will remove all the fragment which pushed by the current activity from the Stack with the Activity too...

Every time I use finish to close the fragment, the entire activity closes. According to the docs, fragments should remain as long as the parent activity remains.
Instead, I found that I can change views back the the parent activity by using this statement:
setContentView(R.layout.activity_main);
This returns me back to the parent activity.
I hope that this helps someone else who may be looking for this.

Very simple...
1- just grab activity by getActivity() in the fragment
2- then call finish();
So just getActivity().finish(); will finish the parent activity.

Try this. There shouldn't be any warning...
Activity thisActivity = getActivity();
if (thisActivity != null) {
startActivity(new Intent(thisActivity, yourActivity.class)); // if needed
thisActivity.finish();
}

You have two options for Java and Kotlin. However, logic of both ways are same. You should call activity after call finish() method.
Answer for Kotlin,
If your activity cannot be null, use Answer_1. However, if your activity can be null, use Answer_2.
Answer_1: activity!!.finish()
Answer_2: activity?.finish()
Answer for Java,
getActivity().finish();

To finish activity in a Fragment use:
getActivity().finish();

Simple solution:
activity?.finish()

yes Fragment.class does not implement finish()
When working with fragments, instead of using this or refering to the context, always use getActivity(). You should call

How to get a Fragment to remove itself, i.e. its equivalent of finish()?

I'm converting an app to use fragments using the compatibility library.
Now currently I have a number of activities (A B C D) which chain onto one another, D has a button 'OK' which when pressed calls finish which then bubbles up through onActivityResult() to additionally destroy C and B.
For my pre Honycomb fragment version each activity is effectively a wrapper on fragments Af Bf Cf Df. All activities are launched via startActivityForResult() and onActivityResult() within each of the fragments can happily call getActivity().finish()
The problem that I am having though is in my Honeycomb version I only have one activity, A, and fragments Bf, Cf, Df are loaded using the FragmentManager.
What I don't understand is what to do in Df when 'OK' is pressed in order to remove fragments Df, Cf, and Bf?
I tried having the fragment popping itself off the stack but this resulted in an exception. onActivityResult() is useless because I have not loaded up the fragment using startActivityForResult().
Am I thinking about this completely the wrong way? Should I be implementing some sort of listener that communicates with either the parent fragment or activity in order to do the pop using the transaction manager?

While it might not be the best approach the closest equivalent I can think of that works is this with the support/compatibility library
getActivity().getSupportFragmentManager().beginTransaction().remove(this).commit();
or
getActivity().getFragmentManager().beginTransaction().remove(this).commit();
otherwise.
In addition you can use the backstack and pop it. However keep in mind that the fragment might not be on the backstack (depending on the fragmenttransaction that got it there..) or it might not be the last one that got onto the stack so popping the stack could remove the wrong one...

You can use the approach below, it works fine:
getActivity().getSupportFragmentManager().popBackStack();

What I don't understand is what to do in Df when 'OK' is pressed in order to remove fragments Df, Cf, and Bf?
Step #1: Have Df tell D "yo! we got the OK click!" via calling a method, either on the activity itself, or on an interface instance supplied by the activity.
Step #2: Have D remove the fragments via FragmentManager.
The hosting activity (D) is the one that knows what other fragments are in the activity (vs. being in other activities). Hence, in-fragment events that might affect the fragment mix should be propagated to the activity, which will make the appropriate orchestration moves.

You should let the Activity deal with adding and removing Fragments, as CommonsWare says, use a listener. Here is an example:
public class MyActivity extends FragmentActivity implements SuicidalFragmentListener {
// onCreate etc
#Override
public void onFragmentSuicide(String tag) {
// Check tag if you do this with more than one fragmen, then:
getSupportFragmentManager().popBackStack();
}
}
public interface SuicidalFragmentListener {
void onFragmentSuicide(String tag);
}
public class MyFragment extends Fragment {
// onCreateView etc
#Override
public void onAttach(Activity activity) {
super.onAttach(activity);
try {
suicideListener = (SuicidalFragmentListener) activity;
} catch (ClassCastException e) {
throw new RuntimeException(getActivity().getClass().getSimpleName() + " must implement the suicide listener to use this fragment", e);
}
}
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
// Attach the close listener to whatever action on the fragment you want
addSuicideTouchListener();
}
private void addSuicideTouchListener() {
getView().setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
suicideListener.onFragmentSuicide(getTag());
}
});
}
}

In the Activity/AppCompatActivity:
#Override
public void onBackPressed() {
if (mDrawerLayout.isDrawerOpen(GravityCompat.START)) {
// if you want to handle DrawerLayout
mDrawerLayout.closeDrawer(GravityCompat.START);
} else {
if (getFragmentManager().getBackStackEntryCount() == 0) {
super.onBackPressed();
} else {
getFragmentManager().popBackStack();
}
}
}
and then call in the fragment:
getActivity().onBackPressed();
or like stated in other answers, call this in the fragment:
getActivity().getSupportFragmentManager().beginTransaction().remove(this).commit();

If you are using the new Navigation Component, is simple as
findNavController().popBackStack()
It will do all the FragmentTransaction in behind for you.

See if your needs are met by a DialogFragment. DialogFragment has a dismiss() method. Much cleaner in my opinion.

I create simple method for that
popBackStack(getSupportFragmentManager());
Than place it in my ActivityUtils class
public static void popBackStack(FragmentManager manager){
FragmentManager.BackStackEntry first = manager.getBackStackEntryAt(0);
manager.popBackStack(first.getId(), FragmentManager.POP_BACK_STACK_INCLUSIVE);
}
It's work great, have fun!

OnCreate:
//Add comment fragment
container = FindViewById<FrameLayout>(Resource.Id.frmAttachPicture);
mPictureFragment = new fmtAttachPicture();
var trans = SupportFragmentManager.BeginTransaction();
trans.Add(container.Id, mPictureFragment, "fmtPicture");
trans.Show(mPictureFragment); trans.Commit();
This is how I hide the fragment in click event 1
//Close fragment
var trans = SupportFragmentManager.BeginTransaction();
trans.Hide(mPictureFragment);
trans.AddToBackStack(null);
trans.Commit();
Then Shows it back int event 2
var trans = SupportFragmentManager.BeginTransaction();
trans.Show(mPictureFragment); trans.Commit();

If you need to popback from the fourth fragment in the backstack history to the first, use tags!!!
When you add the first fragment you should use something like this:
getFragmentManager.beginTransaction.addToBackStack("A").add(R.id.container, FragmentA).commit()
or
getFragmentManager.beginTransaction.addToBackStack("A").replace(R.id.container, FragmentA).commit()
And when you want to show Fragments B,C and D you use this:
getFragmentManager.beginTransaction.addToBackStack("B").replace(R.id.container, FragmentB, "B").commit()
and other letters....
To return to Fragment A, just call popBackStack(0, "A"), yes, use the flag that you specified when you add it, and note that it must be the same flag in the command addToBackStack(), not the one used in command replace or add.
You're welcome ;)

To Close a fragment while inside the same fragment
getActivity().onBackPressed();
kotlin -
requireActivity().onBackPressed()

parentFragmentManager.apply {
val f = this#MyFragment
beginTransaction().hide(f).remove(f).commit()
}

Why not just:
getActivity().finish();