Develop Reference

OnBackPress Not working for Fragment in Android

How can we get the onBackPressed callback only in the fragment class? Instead ,now it is going to the onBackPressed in the activity classes? I need to restrict sending the callback to Activity on backpress from fragment.
example::
#Override
public void onBackPressed() {
Log.d("SKT", "backPressHere");
}

Implement this in the Activity and restriction part you can handle via the interface.

The fragment itself does not have a return button, but instead you can put this code in the onBackPressed() method in the activity to which the fragment is attached, and with the getSupportFragmentManager() method you can control the examples of running fragments or delete and return do.
here is example :
#Override
public void onBackPressed() {
int count = getSupportFragmentManager().getBackStackEntryCount();
if (count == 0) {
// no fragment attach
super.onBackPressed();
} else {
// fragment attach
getSupportFragmentManager().popBackStack();
}
}

The fragment does not receive the onBackPressed callback. You should implement dispatching the event in the activity.
public interface BackPressedSupport{
/**
* return true if the fragment consumed the event. otherwise false.
*/
boolean onBackPressed();
}
In your Activity :
#Override
public void onBackPressed() {
Fragment f = getActiveFragment();
if (f instanceof BackPressedSupport && (BackPressedSupport f).onBackPressed()){
return;
}
super.onBackPressed();
// Other backPressed handling of activity.
}
public Fragment getActiveFragment() {
if (getSupportFragmentManager().getBackStackEntryCount() == 0) {
return null;
}
String tag = getSupportFragmentManager().getBackStackEntryAt(getSupportFragmentManager().getBackStackEntryCount() - 1).getName();
return getSupportFragmentManager().findFragmentByTag(tag);
}
In your Fragment:
public MyFragment extends Fragment implements BackPressedSupport {
/* Your code */
#Override
public boolean onBackPressed() {
/* Handle backpressed */
Log.d("SKT", "backPressHere");
return true ; // tell the activity to stop handling this backPressed event
// return false; // keep the default behaviour
}
}

Fragment and back button

I have a problem with the back/up button in a Fragment.
I have an Activity in which I have some fragments. In one Fragment, that I call "1", I have a list view. When I click on any item it goes to another fragment "2".
I need functionality such that the back/up button only works in Fragment 2 but not in Fragment 1.
Is there a way this can be done?
I have tried this in the Activity, but I don't understand how can this help:
#Override
public void onBackPressed() {
int count = getFragmentManager().getBackStackEntryCount();
if (count == 0) {
super.onBackPressed();
//additional code
} else {
getFragmentManager().popBackStack();
}
}
When i change from fragment 1 to fragment 2 i have this code:
fragment = new MaterialesFragment();
FragmentManager fragmentManager3 = getFragmentManager();
fragmentManager3.beginTransaction().replace(R.id.frame, fragment).addToBackStack("tagMateriales").commit();
Thanks a lot :-)

Try to use addToBackStack() method on the FragmentTransaction object you use to replace the fragment2 into the screen:
fragmentManager.beginTransaction().replace(R.id.content_frame,fragment2).addToBackStack("tagHere").commit();
You can pass null as the parameter if you don't need the actual tag.

Please use this code for your 'fragment 2'
public void showFragmentWithoutStack(Fragment fragment, String tag, int id) {
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
transaction.add(id, fragment, tag);
transaction.commitAllowingStateLoss();
}
Where tag might be String class name, id of your root view in activity (Because fragment should appear on the top layer).

There are a lot of way to do this job. In my opinion the most elegant is the following. I would isolate the logic in each component. Every fragment implements an interface like "IBackHandler" that allows activity and fragment to communicate. In the activity onBackPressed asks first the fragment (if it is instantiated) what to do and then acts.
The interface:
public interface IBackHandler {
boolean doBack();
}
The fragment that implements that interface and put its logic to handle the back button pressed:
public class YourFragment1 extends YourBaseFragment implements IBackHandler {
// your code
#Override
public boolean doBack() {
// return true means that you have done your stuff
//and you don't want 'super.onBackPressed()' to be called
return true; // this means do nothing
}
}
Fragment 2:
public class YourFragment2 extends YourBaseFragment implements IBackHandler {
// your code
#Override
public boolean doBack() {
return false; //this means: call 'super.onBackPressed()'
}
}
Your Activity:
public class YourActivity extends YourBaseActivity {
//your code
#Override
public void onBackPressed() {
Fragment currentFragment = getFragmentManager().findFragmentById(R.id.yourFragment);
if (currentFragment instanceof IBackHandler) {
if (!((IBackHandler) currentFragment).doBack()) {
super.onBackPressed();
}
} else
super.onBackPressed();
}
}
You could think that this is overengineering but I can reassure you that in this way you'll always be able to control what'happening in your flow.
Hope this help!

In order to use the onBackPressed() method override in the Activity as you have in the question, you also need to add this to your Fragment:
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
// Assuming MainActivity is the Activity subclass name
if (getActivity() instanceof MainActivity) {
((MainActivity) getActivity()).onBackPressed();
}
return true;
default:
return super.onOptionsItemSelected(item);
}
}
In order to show/hide the back button, add these methods to your Activity:
public void showUpButton() {
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
}
public void hideUpButton() {
getSupportActionBar().setDisplayHomeAsUpEnabled(false);
}
Then, when you want to show or hide the back/up button from a Fragment, call these methods.
In your case, you could hide the back/up button from onResume() in Fragment 1:
((MainActivity) getActivity()).hideUpButton();
And then show it in onResume() in Fragment 2:
((MainActivity) getActivity()).showUpButton();

I solved this problem use this code when change fragment:
String fragmentIndexString="fragmenttwo";//or fragmentone something
transaction.addToBackStack();
This is full code in Activity:
FirstFragment firstFragment; // my first fragment
SecondFragment secondFragment; // my second fragment
public static String FIRST="asfasgasg"; //first fragment index
public static String SECOND="gsadgsagd"; //second fragment index
...
/* u can change fragment by using setFragment funiction */
public void setFragment(String page){
FragmentTransaction transaction = fragmentManager.beginTransaction();
switch (page){
case FIRST:
if(firstFragment==null) firstFragment= SettingFragment.newInstance();
if (!firstFragment.isAdded()) {
transaction.replace(R.id.fragmentcontainer, firstFragment);
transaction.addToBackStack(INDEX);
transaction.commit();
} else {
transaction.show(firstFragment);
}
break;
case SECOND:
if(secondFragment==null) secondFragment= SettingFragment.newInstance();
if (!secondFragment.isAdded()) {
transaction.replace(R.id.fragmentcontainer, secondFragment);
transaction.addToBackStack(INDEX);
transaction.commit();
} else {
transaction.show(secondFragment);
}
break;
default:
setFragment(INDEX);
}
}
#Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if(keyCode == KeyEvent.KEYCODE_BACK && event.getAction() == KeyEvent.ACTION_DOWN){
if(fragmentManager.getBackStackEntryCount()>1){
fragmentManager.popBackStack();
return true;
}
}
return super.onKeyDown(keyCode, event);
}

How to get click event of DrawerArrowDrawable

I am using DrawerArrowDrawable to animate the hamburger icon during the opening and closing of Navigation drawer. Following is the code snippet I used for that:
DrawerArrowDrawable drawerArrow = new DrawerArrowDrawable(this);
toolbar.setNavigationIcon(drawerArrow)
mDrawerToggle.syncState();
Now when I open a fragment I use actionBar.setHomeAsUpIndicator(R.drawable.back_icon); & actionBar.setDisplayHomeAsUpEnabled(true); in that very fragment, to change the navigation icon as a back icon. The icon changes but the functionality of that button stays same i.e., it opens the navigation drawer, but I want to go back to the previous fragment (by using popBackStack).
I tried to override onOptionsItemSelected :
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
FragmentManager fm = getSupportFragmentManager();
if (fm.getBackStackEntryCount() > 0) {
fm.popBackStack();
}
break;
}
}
But the control never reaches in the above block when I press the navigation icon.
If I get to know that How to intercept the click event of DrawerArrowDrawable? I would be able to run popBackStack and do what I want to do.

toolbar.setNavigationOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
FragmentManager fm = getSupportFragmentManager();
if (fm.getBackStackEntryCount() > 0) {
fm.popBackStack();
}
}
});

Add this listener inside the Navigation Drawer Activity:
private FragmentManager.OnBackStackChangedListener mOnBackStackChangedListener = new FragmentManager.OnBackStackChangedListener() {
#Override
public void onBackStackChanged() {
setActionBarArrowDependingOnFragmentsBackStack();
}
};
Then create this method:
public void setActionBarArrowDependingOnFragmentsBackStack() {
int backStackEntryCount = getFragmentManager().getBackStackEntryCount();
mDrawerToggle.setDrawerIndicatorEnabled(backStackEntryCount == 0);
}
Now override these methods:
#Override
public boolean onOptionsItemSelected(MenuItem item) {
if (mDrawerToggle.isDrawerIndicatorEnabled() && mDrawerToggle.onOptionsItemSelected(item)) {
return true;
} else if (item.getItemId() == android.R.id.home && getFragmentManager().popBackStackImmediate()) {
return true;
}
return super.onOptionsItemSelected(item);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
return super.onCreateOptionsMenu(menu);
}
#Override
public void onDestroy() {
super.onDestroy();
getFragmentManager().removeOnBackStackChangedListener(mOnBackStackChangedListener);
}
Finally add this line inside your onCreate() method:
getFragmentManager().addOnBackStackChangedListener(mOnBackStackChangedListener);

onOptionsItemSelected not called when pressed back button on Action bar - Android

When I press the back button of my action bar, the method onOptionsItemSelected of my fragment it never called. I want to go to the previous fragment when I pressed the button but this method it never calls. This is the code for the Fragment, what it could be the problem?
public class MyFragment extends Fragment {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
((ActionBarActivity)getActivity()).getSupportActionBar().setDisplayHomeAsUpEnabled(true);
((ActionBarActivity)getActivity()).getSupportActionBar().setDisplayShowHomeEnabled(true);
setHasOptionsMenu(true);
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Get item selected and deal with it
switch (item.getItemId()) {
case android.R.id.home:
//called when the up affordance/carat in actionbar is pressed
getActivity().onBackPressed();
return true;
}
return false;
}
Thanks in advance.

First of all this will be received in base activity not fragment.Add your previous fragment to back stack.And from this fragment popup
if(id==android.R.id.home)
{
getSupportFragmentManager().popBackStack();
}
And to check from which fragment it has been called use:
if (fragment instanceof MyFragment)You're done!!

Using onBackPressed() in Android Fragments

I am working on a project and I need to be able to use the back button in each fragment to navigate between previous fragments, I have methods written to do so by using a back arrow in the action bar, however, I want to be able to use the same functionality on the back button pressed. I don't want to use the back stack. Is there a way to do this?
EDIT
Rather than using the back stack I want to be able to call the go back to previous method below when the user clicks the back button. I need to used the gobackpressed method within fragments. Is this possible? I hope this is clear and concise. Apologies for any confusion caused above.
Go Back to Previous
public void gobackToPreviousFragment(String preFragmentTag, Fragment preFragment){
FragmentManager fm = getSupportFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
ft.setCustomAnimations(R.animator.close_slide_in,R.animator.close_slide_out);
ft.show(preFragment);
//**BY REMOVING FRAGMENT, WHEN USER TRIES TO REVISIT, FRAGMENT IS BLACK**
ft.remove(fm.findFragmentByTag(Misc.currentContentFragmentTag));
ft.addToBackStack(null);
ft.commit();
Misc.currentContentFragmentTag = preFragmentTag;
createBar(preFragment);
}
Go Forward
public void gotoNextFragment(String nextTag, Fragment nextFragment){
FragmentManager fm = getSupportFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
ft.setCustomAnimations(R.animator.enter_slide_in, R.animator.enter_slide_out);
boolean newlyCreated = false;
if(nextFragment == null){
nextFragment = Fragment.instantiate(this, nextTag);
newlyCreated = true;
}
//hide current fragment
ft.hide(fm.findFragmentByTag(Misc.currentContentFragmentTag));
if(newlyCreated){
ft.add(R.id.content_frame, nextFragment, nextTag);
}
else{
ft.show(nextFragment);
}
ft.addToBackStack(null);
ft.commit();
Misc.currentContentFragmentTag = nextTag;
createBar(nextFragment);
}
These are how I navigate back and forth, and I'd like to be able to implement the go back method on the onBackPressed(). Does this make sense?

I didn't find any good answer about this problem, so this is my solution.
If you want to get backPress in each fragment do the following.
create interface OnBackPressedListener
public interface OnBackPressedListener {
void onBackPressed();
}
That each fragment that wants to be informed of backPress implements this interface.
In parent activity , you can override onBackPressed()
#Override
public void onBackPressed() {
List<Fragment> fragmentList = getSupportFragmentManager().getFragments();
if (fragmentList != null) {
//TODO: Perform your logic to pass back press here
for(Fragment fragment : fragmentList){
if(fragment instanceof OnBackPressedListener){
((OnBackPressedListener)fragment).onBackPressed();
}
}
}
}

Why don't you want to use the back stack? If there is an underlying problem or confusion maybe we can clear it up for you.
If you want to stick with your requirement just override your Activity's onBackPressed() method and call whatever method you're calling when the back arrow in your ActionBar gets clicked.
EDIT: How to solve the "black screen" fragment back stack problem:
You can get around that issue by adding a backstack listener to the fragment manager. That listener checks if the fragment back stack is empty and finishes the Activity accordingly:
You can set that listener in your Activity's onCreate method:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
FragmentManager fm = getFragmentManager();
fm.addOnBackStackChangedListener(new OnBackStackChangedListener() {
#Override
public void onBackStackChanged() {
if(getFragmentManager().getBackStackEntryCount() == 0) finish();
}
});
}

requireActivity().onBackPressedDispatcher.addCallback(viewLifecycleOwner, object : OnBackPressedCallback(true) {
override fun handleOnBackPressed() {
Log.w("a","")
}
})

In the fragment where you would like to handle your back button you should attach stuff to your view in the oncreateview
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.second_fragment, container, false);
v.setOnKeyListener(pressed);
return v;
}
#Override
public boolean onKey(View v, int keyCode, KeyEvent event) {
// TODO Auto-generated method stub
if( keyCode == KeyEvent.KEYCODE_BACK ){
// back to previous fragment by tag
myfragmentclass fragment = (myfragmentclass) getActivity().getSupportFragmentManager().findFragmentByTag(TAG);
if(fragment != null){
(getActivity().getSupportFragmentManager().beginTransaction()).replace(R.id.cf_g1_mainframe_fm, fragment).commit();
}
return true;
}
return false;
}
};

This works for me :D
#Override
public void onResume() {
super.onResume();
if(getView() == null){
return;
}
getView().setFocusableInTouchMode(true);
getView().requestFocus();
getView().setOnKeyListener(new View.OnKeyListener() {
#Override
public boolean onKey(View v, int keyCode, KeyEvent event) {
if (event.getAction() == KeyEvent.ACTION_UP && keyCode == KeyEvent.KEYCODE_BACK){
// handle back button's click listener
return true;
}
return false;
}
});}

You can try to override onCreateAnimation, parameter and catch enter==false. This will fire before every back press.
#Override
public Animation onCreateAnimation(int transit, boolean enter, int nextAnim) {
if(!enter){
//leaving fragment
Log.d(TAG,"leaving fragment");
}
return super.onCreateAnimation(transit, enter, nextAnim);
}

For a Fragment you can simply add
getActivity().onBackPressed();
to your code

I found a new way to do it without interfaces. You only need to add the below code to the Fragment’s onCreate() method:
//overriding the fragment's oncreate
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
//calling onBackPressedDispatcher and adding call back
requireActivity().onBackPressedDispatcher.addCallback(this) {
//do stuff here
}
}

Use this:
#Override
public void onBackPressed() {
int fragments = getFragmentManager().getBackStackEntryCount();
if (fragments == 1) {
finish();
}
super.onBackPressed();
}