I am using Fragment activity and a number of fragments to get added and poped out on back press.
Supposed I am adding Fragment B from Fragment A. The title of action bar that I set in A changes by navigating to B; but it is not restoring to A when I pop the fragment B out of the fragment stack as onResume of fragment is not being called.
I am using the code:
FragmentManager fragmentManager = getSupportFragmentManager();
fragmentManager.beginTransaction().add(R.id.container, fragmentToReplace, tag).addToBackStack(tag).commit();
and to pop out the last fragment:
fragmentManager.popBackStack();
How to manage this. Please suggest.
You can use onBackStackChanged listener which will be called whenever a fragment is popped back. To add the listener use this:
getFragmentManager().addOnBackStackChangedListener(this);
In Override function, check the fragment which is popped and according to it you can change the actionbar title:
#Override
public void onBackStackChanged() {
//Check the fragment from the FrameLayout Container R.id.container
// Depending on the Fragment you can change the Title
setTitle("xyz");
}
Create new class in your package and extend with Fragment says TestFragment and create abstract method in it
abstract public String getTitle();
than extend your every fragment with TestFragment and override getTitle() in your fragments.
public String getTitle(){
return "YOUR_FRAGMENT_NAME";
}
getSupportFragmentManager().addOnBackStackChangedListener(
new OnBackStackChangedListener() {
#Override
public void onBackStackChanged() {
Fragment fragment = getSupportFragmentManager().findFragmentById(R.id.content_frame);
this.setTitle(fragment.getTitle());
}
});
Related
OK I found out that I am opening/replacing the fragment in another layout element than the one the tablayout is in. Therefore the underlying fragment is never really left if i understand correctly and also no lifecycle methods are triggered.
I have FragmentA inside a TabLayout from which i call:
//inside FragmentA
#Override
public void onClickView() {
activity.replaceFragment(FragmentB.newInstance(), true);
}
in replaceFragment the passed fragment is added to the backstack in the transaction and then replaces the fragment
public void replaceFragment(Fragment fragment, boolean doAddToBackStack) {
FragmentManager fm = getSupportFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
if (doAddToBackStack) {
String tag = fragment.getClass().toString();
ft.addToBackStack(tag);
}
ft.replace(R.id.mainFragment, fragment);
ft.commit();
}
After that, FragmentB opens, I do my stuff and return via popBackStackImmediate() to FragmentA:
//inside FragmentB
#Override
public void onClickBack() {
activity.getSupportFragmentManager().popBackStackImmediate();
}
and when I go back I need to update something in FragmentA.
According to another post on the platform when returning to a fragment onCreateView() should be called but that does not work for me. According to the fragment lifecycle documentation the onCreateView() is only called the first time the UI is drawn which would explain my troubles.
My question is now what lifecycle method can I use or what other approach should I take to execute code when returning to a fragment from backstack?
According to the following answer you can add a listener to check when it is being called
https://stackoverflow.com/a/52646588/6468214
getSupportFragmentManager().addOnBackStackChangedListener(
new FragmentManager.OnBackStackChangedListener() {
public void onBackStackChanged() {
// Your Code Here
}
});
Problem 1
I have a Navigation Drawer and most of my fragment transactions happens from here.
So say I have 4 Items in my drawer and I am doing the transaction from all of them. So if I am at the fragment [A] and now I click on the fragment [B], I need to come back to the previous fragment i.e. [A]. But if I keep clicking on the Item B of the navigation drawer that opens the fragment [B], I keep adding it to the backstack and when I press the back button, I am still at the same fragment.
Problem 2
How do I achieve the Clear Top behavior that is used for the intents for the fragments. As intents have the power to clear the activities from the stack from the top only, I want to achieve the same behavior.
Problem 1 & 2 solution Idea:
Create an Interface say FragmentInstanceHandler
public interface FragmentInstanceHandler {
public void openFragment(Fragment fragment, String fragmentTag);
}
Create a BaseFragment like below and extend this to all your Fragment classes:
public BaseFragment extends Fragment {
public FragmentInstanceHandler fragmentInstanceHandler;
public void setFragmentInstanceHandler(FragmentInstanceHandler fragmentInstanceHandler) {
this.fragmentInstanceHandler = fragmentInstanceHandler;
}
}
Implement the FragmentInstanceHandler interface to the Activity in which you are going to open all the Fragments. Let's say Activity is MainActivity:
public MainActivity extends Activity implements FragmentInstanceHandler {
private BaseFragment currentFragment;
#Override
public void openFragment(BaseFragment fragment, String fragmentTag) {
FragmentManager fragmentManager = getSupportFragmentManager();
Fragment oldFragmentInstance = fragmentManager .findFragmentByTag(fragmentTag);
boolean fragmentPopped = fragmentManager.popBackStackImmediate (fragmentTag, 0);
if (!fragmentPopped && oldFragmentInstance == null) {
fragment.setFragmentInstanceHandler(this);
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.add(R.id.container, fragment, fragmentTag);
fragmentTransaction.addToBackStack(fragmentTag);
fragmentTransaction.commit();
currentFragment = fragment;
} else if(fragmentPopped ){
currentFragment = oldFragmentInstance;
}
if(mDrawerLayout!= null)
mDrawerLayout.closeDrawers();
}
}
Now whenever you want to open a new Fragment even from any other Fragment you can call method like below, It is advised to provide new tag if you want to have new instance of same Fragment:
fragmentInstanceHandler.openFragment(new MyFragment(), "FragmentNewInstance");
You can tweak FragmentInstanceHandlerto add your own method to replace the current Fragment instead of adding. Above solution just gives you an idea how you can acheive your solution by putting and mananging all your code from one place.
I have 4 button to replace fragment in activity [fragment A , fragment B , fragment C , fragment D] and then I replace fragment A to activity and I change value in fragment A after that I replace fragment B to fragment A and replace fragment C to fragment B . But I want to replace fragment A to fragment C . How to save state in fragment A.
Code when I commit fragment
private void beginFragmentTransaction(BaseFragment fragment) {
String tag = fragment.getClass().getName();
currentFragmentTag = tag;
boolean fragmentPopped = getChildFragmentManager().popBackStackImmediate(tag, 0);
if (!fragmentPopped) {
getChildFragmentManager().beginTransaction()
.replace(R.id.container, fragment, tag)
.addToBackStack(tag)
.commit();
}
}
Diagram to replace
fragment A -------> fragment B
fragment B -------> fragment C
fragment C -------> fragment A
PS. I don't want to use back button to back to fragment A , I want to replace fragment A and restore data in the first commit.
Instead of restoring the state during onCreate() you may choose to implement onRestoreInstanceState(), which the system calls after the onStart() method. The system calls onRestoreInstanceState() only if there is a saved state to restore, so you do not need to check whether the Bundle is null.
FYI : this is a sample code. Just for your reference.
public class MainFragment extends Fragment {
private String title;
private double rating;
private int year;
#Override
public void onSaveInstanceState(Bundle savedInstanceState) {
super.onSaveInstanceState(savedInstanceState);
savedInstanceState.putString(TITLE, "Gladiator");
savedInstanceState.putDouble(RATING, 8.5);
savedInstanceState.putInt(YEAR, 2000);
}
#Override
public void onActivityCreated(#Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
title = savedInstanceState.getString(TITLE);
rating = savedInstanceState.getDouble(RATING);
year = savedInstanceState.getInt(YEAR);
}
}
FYI : This really a good thread check this also Once for all, how to correctly save instance state of Fragments in back stack?
If you want to save the state of previous tabs and don't want to refresh/recreate view use this code and change the value according to the tabs limit
ViewPager mViewPager = (ViewPager)findViewById(R.id.pager);
mViewPager.setOffscreenPageLimit(2);
you can show and hide fragments for saving the states,
or use the navigation component latest version
I have done many programs, where I have implemented multiple Fragments inside a Single Activity, but not when using Single Activity to host multiple Fragments as Tabs and then on Tap show another Fragments...
Using MaterialViewPager library, in which I am calling different different Fragments to show views in their respective Tabs.
Like For the First Tab, I am using two Fragments, where
In First Fragment, I am using RecyclerView... to show list of Menus.
And in Second Fragment, I am using RecyclerView... to show list of Items under particular Menu.
So here my question is How to call Fragment from Fragment.
mRecyclerView.addOnItemTouchListener(new RecyclerItemClickListener(getActivity(), mRecyclerView ,new RecyclerItemClickListener.OnItemClickListener() {
#Override
public void onItemClick(View view, int position) {
Value value = valueList.get(position);
List<Learning> learning = value.getLearning();
// using when putting "item" data into same recyclerview
// but on back press just exiting, not showing list of Menus again
/**
learningAdapter = new LearningAdapter(learning, R.layout.card_learning, getActivity());
mRecyclerView.setAdapter(learningAdapter);
**/
ItemFragment fragment = new ItemFragment();
replaceFragment(fragment);
}
Method replaceFragment
public void replaceFragment(Fragment someFragment) {
FragmentTransaction transaction = getFragmentManager().beginTransaction();
// using Fragment not Activity, so where can I use frame_container in xml
transaction.replace(R.id.frame_container, someFragment);
transaction.addToBackStack(null);
transaction.commit();
}
you can have a callback interface that is implemented by the activity which hosts these two fragments. Fragment A will use the call back to notify the activity to replace A with fragment B. Depending on your need, you can pass parameters across through the callback method itself.
Your callback interface:
public interface YourCallback {
public void methodWhichReplacesFragmentAwithB(params...);
}
Your Activity hosting fragments:
public class YourActivity extends ... implements YourCallback {
..
..
#Override
public void methodWhichReplacesFragmentAwithB(params...) {
//insert replace fragment code here
}
}
Your fragment will have a callback object, YourCallback callbackObj;. This callback object can be initialised using the activity (pass as this from activity) itself since the activity has the implementation of the interface. Now, you can use
callbackObj.methodWhichReplacesFragmentAwithB(actual_params...);
to replace the fragment. This callback interface can be exploited for other communications to parent Activity as well as other fragment hosted in that activity.
To replace fragment,
FragmentTransaction transaction = getActivity().getSupportFragmentManager().beginTransaction();
transaction.replace(R.id.frame_container, someFragment).addToBackStack("null").commit();
You can try this:
YourFragment fragment = new YourFragment();
FragmentTransaction transaction = ((AppCompatActivity) mContext).getSupportFragmentManager()
.beginTransaction();
transaction.replace(R.id.frame, fragment);
transaction.addToBackStack(null);
transaction.commit();
There is One option which i have been using from long time before. I will added the solution with clear example.
So you want to pass the value from fragment A to fragment B
So, here what you want to do is, you have pass the value through the activity.
1) you pass the value from fragment A to activity
2) then activity to fragment B
Step 1: first create an Interface Like below in fragment A
public interface HomePage {
void onHomeButtonsClicked(String clickedButton);
}
public void setOnHomeButtonClicked(HomePage homePage) {
this.homePage = homePage;
}
Step 2: then create the instance like below in Activity. where fragment created in PagerAdapter
((FragmentA) fragment).setOnHomeButtonClicked(new FragmentA.HomePage() {
#Override
public void onHomeButtonsClicked(String buttonClicked) {
pageSelected.onHomeButtonsClicked(selectedPage);
}
}
});
Step 3: then create the interface in Activity like below.
public interface PageSelected {
void onHomeButtonsClicked(String clickedButton);
}
public void setOnHomeButtonClicked(PageSelected pageSelected) {
this.pageSelected = pageSelected;
}
step 3: then add the following method in fragment B in onCreateView or onResume()
((MainActivity) getActivity()).setOnHomeButtonClicked(new MainActivity.PageSelected() {
#Override
public void onHomeButtonsClicked(String clickedButton) {
//fragment B received the value here
}
});
Step 5: finally add the line in fragment A in button click or where you want to pass the value.
homePage.onHomeButtonsClicked("Some String , by this code it is in String. you can change in your own data type");
You can rise your question if you face any difficulties.
Situation:
I have an activity with a FrameLayout in which I change fragments.
I use:
getSupportFragmentManager().beginTransaction()
.replace(R.id.content, fragment)
.addToBackStack("name")
.commit)
All works fine the problem is when I go back in the stack the previous fragment is reloaded and all the data is lost.
Possible solution:
restore fragment state - I want to avoid this because most of the data is retrieved from the server and it takes a lot of time
use .add(R.id.content, fragment) instead of .add(R.id.content, fragment) but in this case my fragments must have a solid background otherwise they overlay each other. The problem is that I can't set a solid background because of some design constraints.
Question:
How can i use '.add(R.id.content,fragment)' and somehow hide the fragment below it so it won't overlay and I can go back to the previous fragment in the state I left it.
First I would say that there's no need to add the fragment to the backstack if you don't want the user to go back to a previous fragment.
To answer the other question, the FragmentManager has a "hide" method that you can use to keep a fragment in the FragmentManager, but hide it from the user. Then use "show" to reveal it again.
final Fragment oldFragment = methodToGetFragment();
getSupportFragmentManager().beginTransaction()
.add(R.id.content, fragment)
.hide(oldFragment)
.addToBackStack("name")
.commit)
Like stated in the first sentence, the Fragment is going to be popped and the old fragment will be shown when the user presses "back". If you don't want that to happen, then simply remove addToBackStack().
for save data
you can use Activity when replacing fragments, activity is live .
public class MotherActivity extends ActionBarActivity {
private Data data = null;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_adv);
Fragment oldFragment = methodToGetFragment();
getSupportFragmentManager().beginTransaction()
.add(R.id.content, fragment)
.hide(oldFragment)
.addToBackStack("name")
.commit)
}
public void setData(Data data){
....
}
public void getData(){
....}
}
public class FirstFragment extends Fragment {
private AdvActivity act;
......
public void onAttach(Activity activity) {
super.onAttach(activity);
// get data from internet
Data data=getData();
// and save data in mother activity
activity.setData(data);
}
second fragment:
public class SecondFragment extends Fragment {
private AdvActivity act;
private Data data;
......
public void onAttach(Activity activity) {
super.onAttach(activity);
// get data from mother activity
data=activity.getData();
}