I have a bottom navigation bar with 4 menu items, I use FragmentTransaction show() , hide() methods to switch between fragments on tabs click , hide current fragment and show next fragment,
Before using show or hide method I must add fragment first and then use show or hide , until now everything work fine and fragment show with it's final state that's what I want.
But last added fragment with FragmentTransaction add() method is always active and it's view still clickable and switched fragment not clickable or touched.
I don't know why this happen .. any advice ?!!
This my code
private void changeFragment(Fragment fragment) {
if (fragment == null || fragment == currentFragment) return;
FragmentTransaction fragTransaction = getSupportFragmentManager().beginTransaction();
fragTransaction.setReorderingAllowed(true);
fragTransaction.setCustomAnimations(
R.anim.fade_in_transaction,
R.anim.fade_out_transaction
);
if (currentFragment != null && !currentFragment.isHidden()) {
fragTransaction.hide(currentFragment);
}
Fragment savedFragment = getSupportFragmentManager()
.findFragmentByTag(fragment.getClass().getSimpleName());
if (savedFragment == null) {
fragTransaction.add(R.id.container, fragment
, fragment.getClass().getSimpleName());
this.currentFragment = fragment;
} else {
if (savedFragment.isHidden()) {
fragTransaction.show(savedFragment);
}
this.currentFragment = savedFragment;
}
if (getSupportFragmentManager().getPrimaryNavigationFragment() == null) {
if (fragment instanceof FragmentHome) {
fragTransaction.setPrimaryNavigationFragment(fragment);
}
}
fragTransaction.commit();
}
I'm having an special use case where I need to switch between two fragments. The issue I'm having is that for the second fragment I need to persist it's state, and the only thing that seems to be working for that is to add it to the BackStack.
I rely on the support fragment manager to replace the fragments:
public void toggle() {
Fragment fragment = getSupportFragmentManager().findFragmentById(R.id.fragment_container);
if (fragment instanceof FragmentB && null != fragmentA) {
// fragment B is visible - we should show fragment A
getSupportFragmentManager().beginTransaction()
.setCustomAnimations(R.anim.frag_fade_in, R.anim.frag_fade_out,
R.anim.frag_fade_in, R.anim.frag_fade_out)
.replace(R.id.fragment_container, fragmentA)
.commit();
} else if (fragment instanceof FragmentA && null != fragmentB) {
// fragment A is visible - we should show fragment B
boolean isRestored = false;
fragment = getSupportFragmentManager().findFragmentByTag(TAG_FRAG_B);
if (null != fragment) {
// Restore fragment state from the BackStack
fragmentB = (FragmentB) fragment;
isRestored = true;
}
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction()
.setCustomAnimations(R.anim.frag_fade_in,
R.anim.frag_fade_out,
R.anim.frag_fade_in,
R.anim.frag_fade_out);
transaction.replace(R.id.fragment_container, fragmentB, TAG_FRAG_B);
if(!isRestored){
transaction.addToBackStack(TAG_FRAG_B)
}
transaction.commit();
} else {
// Just pop any fragments that were added - usually we won't get in here
getSupportFragmentManager().popBackStack();
}
}
This in combination with the onBackPressed() override:
#Override
public void onBackPressed() {
if (isCurrentFragmentB()) {
toggle();
} else {
// Back key was pressed and we are on fragment A - at this state we simply want to go back to the
// previous section
super.onBackPressed();
}
}
Using this implementation I make sure I reuse fragment B and keep it's state so that it doesn't look like it is created from scratch each time. I also make sure that when I go back, I can go only from fragment B to A and not from fragment A to B.
The issue I encountered is that when super.onBackPressed(); is called and more than one fragment was added(replaced actually, as I want only one active fragment at a time) through the fragment manager, it will throw an exception:
java.lang.IllegalStateException: Fragment already added: FragmentA{af9c26b #0 id=0x7f0e00d3}
This is happening only when the active fragment is FragmentA. I have a suspicion that this is because of the BackStack implementation, but as I've said, I only want the second one to be persisted.
How can I fix this? I am missing something?
I have managed to implement an work-around for this, although it is a little hacky.
Because I need to keep the state of FragmentB, I am forced to add it to the BackStack, but this will actually affect what transition is reversed when onBackPressed() is called.
To avoid this, I had to update the logic for the back press and manually handle that case
#Override
public void onBackPressed() {
if (isCurrentFragmentB()) {
toggle();
} else if (isCurrentFragmentA()) {
getSupportFragmentManager().popBackStackImmediate(TAG_FRAG_A, FragmentManager.POP_BACK_STACK_INCLUSIVE);
// Special case - because we added the fragment B to the BackStack in order to easily resume it's state,
// this will fail as it will actually try to add fragment A again to the fragment manager (it
// will try to reverse the last transaction)
super.finish();
} else {
// Usual flow - let the OS decide what to do
super.onBackPressed();
}
}
Also, I've optimized the toggle method a little bit:
public void toggle() {
Fragment fragment = getSupportFragmentManager().findFragmentById(R.id.fragment_container);
#SuppressLint("CommitTransaction") FragmentTransaction transaction =
getSupportFragmentManager().beginTransaction()
.setCustomAnimations(R.anim.frag_fade_in, R.anim.frag_fade_out,
R.anim.frag_fade_in, R.anim.frag_fade_out);
if (fragment instanceof FragmentB && null != fragmentA) {
// fragment B is visible - we should show fragment A
fragment = getSupportFragmentManager().findFragmentByTag(TAG_FRAG_A);
if (null != fragment) {
// Restore fragment state from the BackStack
fragmentA = (FragmentA) fragment;
}
// Replace current fragment with fragment A and commit the transaction
transaction.replace(R.id.fragment_container, fragmentA, TAG_FRAG_A).commit();
} else if (fragment instanceof FragmentA && null != fragmentB) {
// fragment A is visible - we should show fragment B
fragment = getSupportFragmentManager().findFragmentByTag(TAG_FRAG_B);
if (null != fragment) {
// Restore fragment state from the BackStack
fragmentB = (FragmentB) fragment;
}
// Replace current fragment with fragment B
transaction.replace(R.id.fragment_container, fragmentB, TAG_FRAG_B);
if (null == fragment) {
// No entry of the fragment B in the BackStack, we want to add it for future uses
transaction.addToBackStack(TAG_FRAG_B);
}
// Commit the transaction
transaction.commit();
} else {
// Just pop any fragments that were added - usually we won't get in here
getSupportFragmentManager().popBackStack();
}
}
I hope this can help others which need an similar flow.
PS: The fragment I want to persist is SupportMapFragment, so that my map isn't always redrawn, re-centered and populated with data every time I want to show it.
I'm wondering which is the proper way to change Fragments, add them to backstack, and restore the visibile Fragment after a screen rotation.
Currently, I use this method to initialize the first Fragment:
private void inflateInitialFragment() {
FragmentManager manager = getFragmentManager();
Fragment mainFragment = manager.findFragmentByTag(MainMenuFragment.class.getSimpleName());
FragmentTransaction ft = manager.beginTransaction();
if (mainFragment == null) {
ft.replace(R.id.mainContainer, new MainMenuFragment(), MainMenuFragment.class.getSimpleName());
} else if (!(mainFragment.isAdded() && !mainFragment.isDetached() && !mainFragment.isRemoving())) {
ft.replace(R.id.mainContainer, mainFragment, MainMenuFragment.class.getSimpleName());
}
ft.commit();
manager.executePendingTransactions();
}
And then to display new Fragments I have methods like this one:
public void openAwards() {
getFragmentManager().beginTransaction().replace(R.id.mainContainer,
new AwardsFragment(), AwardsFragment.class.getSimpleName()).addToBackStack(null).commit();
}
And to go back to the main screen:
#Override
public void onBackPressed() {
if (getFragmentManager().getBackStackEntryCount() == 0) {
super.onBackPressed();
} else {
getFragmentManager().popBackStack();
}
}
After a few screen rotations, I've got crashes like this one:
java.lang.IllegalStateException: Fragment already added: MainMenuFragment{42c64d90 #0 id=0x7f0b003f MainMenuFragment}
How should I change the visible Fragments and restore them after a screen rotation?
I don't think that saving some string or Fragment each time is a good solution to restore them.
If your Activity extends android.app.Activity you don't need to override onBackPressed(). It will pop your fragments from back stack automatically.
I have a problem with android fragment backstack. This is my situation.
// I can't post images yet, so I passed a link to it.
As you can see, I want to go from Fragment 1 to Fragment 2 and at the end to Fragment 3, but when I press back button at Fragment 3, I want to back to Fragment 1.
I do this like I describe on pic, but when I press Back Button nothing happen and when I press it second time, the app is closing.
My BackStack looks as expected, I have on it only "Main" entry.
Also, when I add to backstack Fragment 2 I can back normally from Frag3 to Frag2 to Frag1 (but this is not what I want).
//Edit:
First:
I debug my app a little and I notice that when I press back button, Fragment is poped out from backstack and his lifecycle methods were invoked, but current fragment (Fragment 3) do nothing (I logged his onPause and onStop methods and they weren't invoked). Maybe this is a problem?
Second:
I found a solution that I implement onBackStackChange listener and in onBackStacChange method I simply replace Fragment3 with Fragment1. This works, but is it correct?
do it using....
FragmentManager fmManager = activity.getSupportFragmentManager();
if (fmManager.getBackStackEntryCount() > 0) { fmManager.popBackStack(fmManager.getBackStackEntryAt(fmManager.getBackStackEntryCount()-2).getId(), fmManager.POP_BACK_STACK_INCLUSIVE); }
-2 is because you want to go two 2 fragment step back
#Override
public void onPageScrollStateChanged(int state) {
int currentPage = mChannelPager.getCurrentItem();
if (currentPage == mChannelsList.size() - 1 || currentPage == 0) {
previousState = currentState;
currentState = state;
if (previousState == 1 && currentState == 0) {
mChannelPager.setCurrentItem((currentPage == 0 ? mChannelsList.size() - 1 : 0), false);
}
}
}
});
Write this code in your onPageChangeListner's onPageScrollStateChanged(int state)
1) Add First Fragment using below code
android.support.v4.app.FragmentManager fm = getActivity().getSupportFragmentManager();
android.support.v4.app.FragmentTransaction ft=fm.beginTransaction();
if (fm.findFragmentById(R.id.fragment_container) != null) {
ft.hide(fm.findFragmentById(R.id.fragment_container));
}
ft.add(R.id.fragment_container, new OneFragment(),OneFragment.class.getCanonicalName())
.addToBackStack(OneFragment.class.getCanonicalName()).commit();
2) Add Second Fragment From First fragment using below code
android.support.v4.app.FragmentManager fm = getActivity().getSupportFragmentManager();
android.support.v4.app.FragmentTransaction ft=fm.beginTransaction();
if (fm.findFragmentById(R.id.fragment_container) != null) {
ft.hide(fm.findFragmentById(R.id.fragment_container));
}
ft.add(R.id.fragment_container,new TwoFragment(),TwoFragment.class.getCanonicalName())
.addToBackStack(TwoFragment.class.getCanonicalName()).commit();
3) Add Third Fragment From Second fragment using below code
android.support.v4.app.FragmentManager fm = getActivity().getSupportFragmentManager();
android.support.v4.app.FragmentTransaction ft=fm.beginTransaction();
if (fm.findFragmentById(R.id.fragment_container) != null) {
ft.hide(fm.findFragmentById(R.id.fragment_container));
}
ft.add(R.id.fragment_container, new ThreeFragment(),ThreeFragment.class.getCanonicalName())
.addToBackStack(ThreeFragment.class.getCanonicalName()).commit();
4) onBackPressed() please write below code
#Override
public void onBackPressed() {
hideKeyboard(MainActivity.this);
Fragment currentFragment = this.getSupportFragmentManager().findFragmentById(R.id.fragment_container);
if (currentFragment.getClass().getName().equalsIgnoreCase(ThreeFragment.class.getName())) { // Using this code come from third fragment to first fragment
Fragment f = this.getSupportFragmentManager().findFragmentByTag(TwoFragment.class.getCanonicalName());
if (f != null) {
this.getSupportFragmentManager().popBackStackImmediate(f.getClass().getCanonicalName(), FragmentManager.POP_BACK_STACK_INCLUSIVE);
}
}else {
super.onBackPressed();
}
}
I'm working on an android application, that uses a navigation drawer to switch between two fragments. However, each time I switch, the fragment is completely recreated.
Here is the code from my main activity.
/* The click listener for ListView in the navigation drawer */
private class DrawerItemClickListener implements ListView.OnItemClickListener {
#Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
selectItem(position);
}
}
private void selectItem(int position) {
android.support.v4.app.Fragment fragment;
String tag;
android.support.v4.app.FragmentManager; fragmentManager = getSupportFragmentManager();
switch(position) {
case 0:
if(fragmentManager.findFragmentByTag("one") != null) {
fragment = fragmentManager.findFragmentByTag("one");
} else {
fragment = new OneFragment();
}
tag = "one";
break;
case 1:
if(fragmentManager.findFragmentByTag("two") != null) {
fragment = fragmentManager.findFragmentByTag("two");
} else {
fragment = new TwoFragment();
}
tag = "two";
break;
}
fragment.setRetainInstance(true);
fragmentManager.beginTransaction().replace(R.id.container, fragment, tag).commit();
// update selected item and title, then close the drawer
mDrawerList.setItemChecked(position, true);
setTitle(mNavTitles[position]);
mDrawerLayout.closeDrawer(mDrawerList);
}
I've set up some debug logging, and every time selectItem is called, one fragment is destroyed, while the other is created.
Is there any way to prevent the fragments from being recreated, and just reuse them instead?
After #meredrica pointed out that replace() destroys the fragments, I went back through the FragmentManager documentation. This is the solution I've come up with, that seems to be working.
/* The click listener for ListView in the navigation drawer */
private class DrawerItemClickListener implements ListView.OnItemClickListener {
#Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
selectItem(position);
}
}
private void selectItem(int position) {
android.support.v4.app.FragmentManager; fragmentManager = getSupportFragmentManager();
switch(position) {
case 0:
if(fragmentManager.findFragmentByTag("one") != null) {
//if the fragment exists, show it.
fragmentManager.beginTransaction().show(fragmentManager.findFragmentByTag("one")).commit();
} else {
//if the fragment does not exist, add it to fragment manager.
fragmentManager.beginTransaction().add(R.id.container, new OneFragment(), "one").commit();
}
if(fragmentManager.findFragmentByTag("two") != null){
//if the other fragment is visible, hide it.
fragmentManager.beginTransaction().hide(fragmentManager.findFragmentByTag("two")).commit();
}
break;
case 1:
if(fragmentManager.findFragmentByTag("two") != null) {
//if the fragment exists, show it.
fragmentManager.beginTransaction().show(fragmentManager.findFragmentByTag("two")).commit();
} else {
//if the fragment does not exist, add it to fragment manager.
fragmentManager.beginTransaction().add(R.id.container, new TwoFragment(), "two").commit();
}
if(fragmentManager.findFragmentByTag("one") != null){
//if the other fragment is visible, hide it.
fragmentManager.beginTransaction().hide(fragmentManager.findFragmentByTag("one")).commit();
}
break;
}
// update selected item and title, then close the drawer
mDrawerList.setItemChecked(position, true);
setTitle(mNavTitles[position]);
mDrawerLayout.closeDrawer(mDrawerList);
}
I also added this bit, but I'm not sure if it's necessary or not.
#Override
public void onDestroy() {
super.onDestroy();
FragmentManager fragmentManager = getSupportFragmentManager();
if(fragmentManager.findFragmentByTag("one") != null){
fragmentManager.beginTransaction().remove(fragmentManager.findFragmentByTag("one")).commit();
}
if(fragmentManager.findFragmentByTag("two") != null){
fragmentManager.beginTransaction().remove(fragmentManager.findFragmentByTag("two")).commit();
}
}
Use the attach/detach method with tags:
Detach will destroy the view hirachy but keeps the state, like if on the backstack; this will let the "not-visible" fragment have a smaller memory footprint. But mind you that you need to correctly implement the fragment lifecycle (which you should do in the first place)
Detach the given fragment from the UI. This is the same state as when it is put on the back stack: the fragment is removed from the UI, however its state is still being actively managed by the fragment manager. When going into this state its view hierarchy is destroyed.
The first time you add the fragment
FragmentTransaction t = getSupportFragmentManager().beginTransaction();
t.add(android.R.id.content, new MyFragment(),MyFragment.class.getSimpleName());
t.commit();
then you detach it
FragmentTransaction t = getSupportFragmentManager().beginTransaction();
t.detach(MyFragment.class.getSimpleName());
t.commit();
and attach it again if switched back, state will be kept
FragmentTransaction t = getSupportFragmentManager().beginTransaction();
t.attach(getSupportFragmentManager().findFragmentByTag(MyFragment.class.getSimpleName()));
t.commit();
But you always have to check if the fragment was added yet, if not then add it, else just attach it:
if (getSupportFragmentManager().findFragmentByTag(MyFragment.class.getSimpleName()) == null) {
FragmentTransaction t = getSupportFragmentManager().beginTransaction();
t.add(android.R.id.content, new MyFragment(), MyFragment.class.getSimpleName());
t.commit();
} else {
FragmentTransaction t = getSupportFragmentManager().beginTransaction();
t.attach(getSupportFragmentManager().findFragmentByTag(MyFragment.class.getSimpleName()));
t.commit();
}
The replace method destroys your fragments. One workaround is to set them to Visibility.GONE, another (less easy) method is to hold them in a variable. If you do that, make sure you don't leak memory left and right.
I did this before like this:
if (mPrevFrag != fragment) {
// Change
FragmentTransaction ft = fragmentManager.beginTransaction();
if (mPrevFrag != null){
ft.hide(mPrevFrag);
}
ft.show(fragment);
ft.commit();
mPrevFrag = fragment;
}
(you will need to track your pervious fragment in this solution)
I guess you can not directly manipulate the lifecycle mechanisms of your Fragments. The very fact that you can findFragmentByTag is not very bad. It means that the Fragment object is not recreated fully, if it is already commited. The existing Fragment just passes all the lifecycle steps each Fragment has - that means that only UI is "recreated".
It is a very convenient and useful memory management strategy - and appropriate, in most cases. Fragment which is gone, has the resources which have to be utilized in order to de-allocate memory.
If you just cease using this strategy, the memory usage of your application could increase badly.
Nonetheless, there are retained fragments, which lifecycle is a bit different and do not correspond to the Activity they are attached to. Typically, they are used to retain some things you want to save, for example, to manage configuration changes
However, the fragment [re]creation strategy depends on the context - that is, what you would like to solve, and what are the trade-offs that you are willing to accept.
Just find the current fragment calling getFragmentById("id of your container") and then hide it and show needed fragment.
private void openFragment(Fragment fragment, String tag) {
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
Fragment existingFragment = fragmentManager.findFragmentByTag(tag);
if (existingFragment != null) {
Fragment currentFragment = fragmentManager.findFragmentById(R.id.container);
fragmentTransaction.hide(currentFragment);
fragmentTransaction.show(existingFragment);
}
else {
fragmentTransaction.add(R.id.container, fragment, tag);
}
fragmentTransaction.commit();
}
Same idea as Tester101 but this is what I ended up using.
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
Fragment oldFragment = fragmentManager.findFragmentByTag( "" + m_lastDrawerSelectPosition );
if ( oldFragment != null )
fragmentTransaction.hide( oldFragment );
Fragment newFragment = fragmentManager.findFragmentByTag( "" + position );
if ( newFragment == null )
{
newFragment = getFragment( position );
fragmentTransaction.add( R.id.home_content_frame, newFragment, "" + position );
}
fragmentTransaction.show( newFragment );
fragmentTransaction.commit();
Hide easily in kotlin using extensions:
fun FragmentManager.present(newFragment: Fragment, lastFragment: Fragment? = null, containerId: Int) {
if (lastFragment == newFragment) return
val transaction = beginTransaction()
if (lastFragment != null && findFragmentByTag(lastFragment.getTagg()) != null) {
transaction.hide(lastFragment)
}
val existingFragment = findFragmentByTag(newFragment.getTagg())
if (existingFragment != null) {
transaction.show(existingFragment).commit()
} else {
transaction.add(containerId, newFragment, newFragment.getTagg()).commit()
}
}
fun Fragment.getTagg(): String = this::class.java.simpleName
Usage
supportFragmentManager.present(fragment, lastFragment, R.id.fragmentPlaceHolder)
lastFragment = fragment
Here's what I'm using for a simple 2 fragment case in Kotlin:
private val advancedHome = HomeAdvancedFragment()
private val basicHome = HomeBasicFragment()
override fun onCreate(savedInstanceState: Bundle?) {
...
// Attach both fragments and hide one so we can swap out easily later
supportFragmentManager.commit {
setReorderingAllowed(true)
add(R.id.fragment_container_view, basicHome)
add(R.id.fragment_container_view, advancedHome)
hide(basicHome)
}
binding.displayModeToggle.onStateChanged {
when (it) {
0 -> swapFragments(advancedHome, basicHome)
1 -> swapFragments(basicHome, advancedHome)
}
}
...
}
With this FragmentActivity extension:
fun FragmentActivity.swapFragments(show: Fragment, hide: Fragment) {
supportFragmentManager.commit {
show(show)
hide(hide)
}
}
How about playing with the Visible attribute?
this is a little late response.
if you're using view pager for fragments, set the off screen page limit of the fragment to the number of fragments created.
mViewPager.setOffscreenPageLimit(3); // number of fragments here is 3