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Unable to set text in fragment

I am trying to call a function from my mainActivity to change a TextView in one of my fragments. I have read a couple posts on the best way of doing it but for some reason, none of them seem to work for me. I know the function is working because once a press the button the toast comes up but for some reason the text won't change. I was wondering what the issue could be, or if I am just missing an additional step.
here is the method being called in my mainActivity
public class MainActivity extends AppCompatActivity implements Tab1Fragment.OnCalcClickListener{
private static final String TAG = "MainActivity";
private SectionsPageAdapter mSectionsPageAdpater;
private ViewPager mViewPager;
Tab1Fragment tab1Fragment = new Tab1Fragment();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Log.d(TAG, "onCreate: Starting");
//initializing FragmentManager so the fragments can communicate
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.add(R.id.container, tab1Fragment);
fragmentTransaction.commit();
//declare sections page adapter
mSectionsPageAdpater = new SectionsPageAdapter(getSupportFragmentManager());
//Set up the view pager with the sections adapter
mViewPager = (ViewPager) findViewById(R.id.container);
setUpViewPager(mViewPager);
//create a tab layout object and set it's id to tabs (mainActivity.xml)
TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(mViewPager);
//
}
// create a sections page view adapter
private void setUpViewPager(ViewPager viewPager){
SectionsPageAdapter adapter = new SectionsPageAdapter(getSupportFragmentManager());
adapter.addFragment(new Tab1Fragment(), "Day");
adapter.addFragment(new Tab2Fragment(), "Info");
adapter.addFragment(new Tab3Fragment(), "Week");
viewPager.setAdapter(adapter);
}
//initialise calculator object
Calculator mainCalculator = new Calculator();
#Override
public void calculateClick(int to_calculate) {
switch (to_calculate){
case 1:
Toast.makeText(getBaseContext(),"working", Toast.LENGTH_SHORT).show();
mainCalculator.freqDay = mainCalculator.freqDay + 1;
mainCalculator.freqWeek = mainCalculator.freqWeek + 1;
mainCalculator.getTotalDay();
tab1Fragment.updateInfo();
break;
}
}
Here is the code for my fragment
public class Tab1Fragment extends Fragment implements
View.OnClickListener{
private static final String TAG = "Tab1Fragment";
//Establishing the buttons & Methods
Button btn1;
Button btn2;
TextView dayView;
OnCalcClickListener onCalcClickListener;
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.tab1_fragment, container, false);
//Connecting the buttons to the xml
btn1 = (Button) view.findViewById(R.id.btn_1);
btn1.setOnClickListener(this);
btn2 = (Button) view.findViewById(R.id.btn_2);
btn2.setOnClickListener(this);
dayView = (TextView) view.findViewById(R.id.total_Sales_Day);
return view;
}
//Onclick listener for buttons
public void setOnClickListener(View.OnClickListener listener) {
btn1.setOnClickListener(listener);
btn2.setOnClickListener(listener);
}
//method that will bring data back from activity and set the text
public void updateInfo(){
Toast.makeText(getContext(),"65", Toast.LENGTH_SHORT).show();
dayView.setText("test");
}

To make calls to methods from your fragment in the activity class you need something like this:
public static class MainActivity extends Activity
implements HeadlinesFragment.OnHeadlineSelectedListener{
...
public void onArticleSelected(int position) {
// The user selected the headline of an article from the HeadlinesFragment
// Do something here to display that article
ArticleFragment articleFrag = (ArticleFragment)
getSupportFragmentManager().findFragmentById(R.id.article_fragment);
if (articleFrag != null) {
// If article frag is available, we're in two-pane layout...
// Call a method in the ArticleFragment to update its content
articleFrag.updateArticleView(position);
} else {
// Otherwise, we're in the one-pane layout and must swap frags...
// Create fragment and give it an argument for the selected article
ArticleFragment newFragment = new ArticleFragment();
Bundle args = new Bundle();
args.putInt(ArticleFragment.ARG_POSITION, position);
newFragment.setArguments(args);
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
// Replace whatever is in the fragment_container view with this fragment,
// and add the transaction to the back stack so the user can navigate back
transaction.replace(R.id.fragment_container, newFragment);
transaction.addToBackStack(null);
// Commit the transaction
transaction.commit();
}
}
}
Here the activity is calling the updateArticleView method from the fragment, instead of your updateInfo method, but you will get the idea.
Also pay attention to the one-pane scenario, where you need to swap the content and push the arguments using a Bundle object.
See Deliver a Message to a Fragment for more details.

When you add the fragment set a tag to it like this:
MyFragment frag = new MyFragment();
frag.setArguments(getIntent().getExtras());
getSupportFragmentManager().beginTransaction().add(R.id.fragment_container, frag, "TAG").commit();
While updating the textview get the instance of fragment using findFragmentByTag()
MyFragment fragment = (MyFragment) getSupportFragmentManager().findFragmentByTag("TAG");
fragment.updateInfo();

ListView of a Fragment (of a ViewPager inside a Fragment) that implements LoaderCallbacks<Cursor> is empty when I return back to it

The ListView inside of a Fragment that contains a ViewPager is empty when I return back to it. This ViewPager is inside of a Fragment because I'm using a Navigation Drawer Layout. I'll try to explain it in more details now:
I am using a Navigation Drawer layout and, consequently, using Fragments. In the main activity, in onCreate, I set the current Fragment with these lines of code:
#Override
protected void onCreate(Bundle savedInstanceState) {
/* More code */
currentFragment = new MainFragment();
FragmentManager fragmentManager = getSupportFragmentManager();
fragmentManager.beginTransaction().replace(R.id.layout_for_fragments, currentFragment).commit();
}
The MainFragment class contains a ViewPager that is initialized with these lines of code in the onCreateView():
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container, false);
/* More code */
ViewPager viewPager = (ViewPager) rootView.findViewById(R.id.main_view_pager);
viewPager.setAdapter(new SimpleFragmentPagerAdapter(getActivity(), getActivity().getSupportFragmentManager()));
/* Code for Tablayout */
return rootView;
}
One of the Fragments of the SimpleFragmentPagerAdapter class is this one that implements LoaderManager.LoaderCallbacks
public class ExpensesFragment extends Fragment implements LoaderManager.LoaderCallbacks<Cursor> {
private ExpenseCursorAdapter mExpenseCursorAdapter;
private static final int EXPENSE_LOADER = 1;
public ExpensesFragment() {
// Required empty public constructor
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_expenses, container, false);
ListView expensesListView = (ListView) rootView.findViewById(R.id.expenses_list_view);
mExpenseCursorAdapter = new ExpenseCursorAdapter(getContext(), null);
expensesListView.setAdapter(mExpenseCursorAdapter);
getLoaderManager().initLoader(EXPENSE_LOADER, null, this);
return rootView;
}
#Override
public Loader<Cursor> onCreateLoader(int id, Bundle args) {
return new CursorLoader(/* arguments */);
}
#Override
public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
mExpenseCursorAdapter.swapCursor(data);
}
#Override
public void onLoaderReset(Loader<Cursor> loader) {
mExpenseCursorAdapter.swapCursor(null);
}
}
On the first run, everything works fine. However, if I click on the navigation drawer menu, which I'm implementing this way, the ListView becomes empty:
public boolean onNavigationItemSelected(#NonNull MenuItem item) {
int id = item.getItemId();
if (id == R.id.nav_main) {
FragmentManager fragmentManager = getSupportFragmentManager();
fragmentManager.beginTransaction().remove(currentFragment).commit();
currentFragment = new MainFragment();
fragmentManager.beginTransaction().replace(R.id.layout_for_fragments, currentFragment).commit();
} else if (id == R.id.nav_blank) {
FragmentManager fragmentManager = getSupportFragmentManager();
fragmentManager.beginTransaction().remove(currentFragment).commit();
currentFragment = new BlankFragment();
fragmentManager.beginTransaction().replace(R.id.layout_for_fragments, currentFragment).commit();
}
drawer.closeDrawer(GravityCompat.START);
return true;
}
The problem also exists when I rotate the device. There is a difference though. When I use the Navigation Drawer menu, none of the methods of the LoaderManager.LoaderCallbacks are called, but when I rotate the device, onLoadFinished is called.
Anyway, the problem persists. Any ideias how to solve it?
Thanks in advance.

I have found the solution!
Basically, I made two mistakes.
The first one is about the rotation of the device.
When the device is rotated, the Activity is destroyed and onCreate is called again. In this case, I should't call new MainFragment(). So, I check if the savedInstanceState is null before I call it, like this:
if (savedInstanceState == null) {
currentFragment = new MainFragment();
FragmentManager fragmentManager = getSupportFragmentManager();
fragmentManager.beginTransaction().
replace(R.id.layout_for_fragments, currentFragment).commit();
}
The second one is about a fragment within a fragment. In this case, I can't simply call getSupportFragmentManager(). I should call getChildFragmentManager() instead and that's it!

How to set a default fragment shown in the main activity?

So i've encountered a small problem today. I was making a bottom navigation view in my app, and after clicking buttons, it replaces the fragment on the screen (and it works perfectly!).
But just after launching the app, and without clicking any button, there is no fragment on the screen.
I've realized that the fragments are shown only after clicking a button, and I'd like to have a default fragment (kalkulatorFragment).
I've been trying my best to somehow set it up, but no success...
public class Main extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
BottomNavigationView navigation = (BottomNavigationView) findViewById(R.id.navigation);
navigation.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener);
}
private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener
= new BottomNavigationView.OnNavigationItemSelectedListener() {
#Override
public boolean onNavigationItemSelected(#NonNull MenuItem item) {
FragmentManager fm = getFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
kalkulatorFragment kalkulator_fragment = new kalkulatorFragment();
wzoryFragment wzory_fragment = new wzoryFragment();
definicjeFragment definicje_fragment = new definicjeFragment();
switch (item.getItemId()) {
case R.id.kalkulator:
ft.replace(android.R.id.content, kalkulator_fragment);
ft.commit();
return true;
case R.id.wzory:
ft.replace(android.R.id.content, wzory_fragment);
ft.commit();
return true;
case R.id.definicje:
ft.replace(android.R.id.content, definicje_fragment);
ft.commit();
return true;
}
return false;
}

Ok i just figured it out.
I moved the ft.replace to the onCreate() method, so the kalkulatorFragment is going to be shown just after creating an Activity.
public class Main extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
kalkulatorFragment kalkulator_fragment = new kalkulatorFragment();
FragmentManager fm = getFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
ft.replace(android.R.id.content, kalkulator_fragment);
ft.commit();
BottomNavigationView navigation = (BottomNavigationView) findViewById(R.id.navigation);
navigation.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener);
}

You need to use this code OUTSIDE of OnCreate Method:
navigation.setSelectedItemId(R.id.IdOFYourItemFromBottomNavigationMenuItems);
I don't know why, but it wont work inside OnCreate method. You can declare and initialize it inside OnCreate method, just can't set the default item in there.
In my case I am using it inside OnCreateOptionsMenu.

Android - How do I "start" or "initialize" a Fragment from an activity?

I have a class called DummyFragment that extends Fragment.
public class DummyFragment extends Fragment {
public void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setRetainInstance(true);
Log.i("myapp","test");
}
}
Now, in my parent activity, I want to "run" this fragment.
This is my FirstActivity.java:
public class FirstActivity {
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_first);
// How do I run/start my fragment? I want it's onCreate method to fire
Fragment fraggy = new DummyFragment();
}
}
How do I run/start my fragment? I want my DummyFragment's onCreate method to fire.

There's plenty of documentation! Everything you need is already here.
FragmentManager fragmentManager = getFragmentManager()
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
Fragment fraggy = new DummyFragment();
fragmentTransaction.add(R.id.fragment_container, fraggy);
fragmentTransaction.commit();
Of course, you'll need the container in you activity layout.

Removing a fragment not working

I want to remove a fragment and show a toast when I click a textView. My code shows the toast, but doesn't remove the fragment.
My method:
public void hide(View view) {
My_frag myFrag= new My_frag();
FragmentTransaction transaction = getSupportFragmentManager()
.beginTransaction();
transaction.remove(myFrag);
transaction.commit();
Toast.makeText(getApplicationContext(), "Hello", Toast.LENGTH_LONG)
.show();
}
My_frag class:
public class My_frag extends android.support.v4.app.Fragment {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.my_frag_layout, container, false);
}
}

At some point you must create and add the Fragment correct? You are re-creating the fragment in your hide(...) method so you are trying to remove something that has never been added. Sure you may have added an instance, but not the instance you are trying to remove.
Instead, create a global variable Fragment fragToRemove in your Activity. When you create the fragment (that is where ever you do transaction.add(fragToRemove = new My_Frag);) you will hold an instance. then change your transaction.remove(myFrag) to transaction.remove(fragToRemove) and it should work just fine.

Take the instance of Fragment Transaction other than that was taken while adding fragment to activity and call remove method on that and pass the same instance of Fragment which was used at the time.
Example:
public class MainActivity extends AppCompatActivity {
FragmentTransaction fragmentTransaction;
BlankFragment blankFragment;
Button b;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
b = (Button) findViewById(R.id.activity_button);
fragmentTransaction = getSupportFragmentManager().beginTransaction();
blankFragment=new BlankFragment(); //Fragment instance
fragmentTransaction.add(R.id.main_layout,blankFragment).commit();
b.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.remove(blankFragment).commit(); //created different
}
});
}
In the same way you can do in fragments also and can also remove fragment X on the click of component of fragment X.