Getting Android Fragment no view found for ID

First of, I've checked this question has been done and have tested the solutions that are explained on this site (although I may have committed errors in doing them as there are so many possible causes for the error).

I mean solutions like the ones offered here:

https://stackoverflow.com/questions/7508044/android-fragment-no-view-found-for-id

And here:

https://stackoverflow.com/questions/22761814/android-fragment-no-view-found-for-id-0x7f040034

So, I'm explaining my particular case.

First of, I'm setting the layout like this in my fragment:

 public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        root = inflater.inflate(R.layout.activity_calendario_laboral, container, false);
        return root;
    }

That layout is, summarized, as it follows:

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/main_content"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:id="@+id/principal">
[...]
</LinearLayout>
</FrameLayout>

Once the view has been created I get to call this method:

final Fragment thisFragment=this;
KotlinClass.Companion.setCalendarViewdateListener(calendarView,thisFragment,R.id.principal);

In that method of KotlinClass I get to call this function:

setFragment(FichajesFragment(), fragment,"Fichajes",id);

Being the parameter fragment the thisFragment passed to setCalendarViewdateListener function.

I've finally defined setFragment like this:

private fun setFragment(fragment: Fragment, fragment2: Fragment, tag: String, id: Int) {
                    val fragmentManager: FragmentManager = fragment2.activity!!.getSupportFragmentManager();
 val fragmentTransaction = fragmentManager.beginTransaction()
 for (activeFragment in fragmentManager.fragments) {
          fragmentTransaction.remove(activeFragment)
 }
 fragmentTransaction.add(id, fragment, tag)
 fragmentTransaction.commit()
 fragmentManager.executePendingTransactions()
 
}

It raises an exception when executing fragmentManager.executePendingTransactions() telling that no view found for id, refering to the principal id of the linearlayout.

What am I missing?

If I understand correctly, I think in your layout file you have to specify parameter:
tools:context=".FragmentName"

I noticed several issues, but the main problem why your app is crashing is because of this part:

 val fragmentManager: FragmentManager = fragment2.activity!!.getSupportFragmentManager();
 val fragmentTransaction = fragmentManager.beginTransaction()
 for (activeFragment in fragmentManager.fragments) {
          fragmentTransaction.remove(activeFragment)
 }

Into fragmentManager you stored the fragmentManager that belongs to the activity that hosts the fragment2, in your case the fragment with the layout including the Linearlayout with @+id/principal id. Then in your for loop, you remove all the fragments that are managed by that fragmentManager, which means you removed the fragment2 from it too. So when you later call:

fragmentTransaction.add(id, fragment, tag)

it can't find any view with the id @+id/principal, because the fragment containing that Linearlayout (fragment2) was just removed.

So for your code to work, remove the for loop and the app should not crash anymore. But the way your code samples look, I assume you want to add FichajesFragment as part of the fragment2, in which case you are using wrong fragmentManager; instead of the activity one, you should use the one that belongs to fragment2, i.e.:

val fragmentManager: FragmentManager = fragment2.childFragmentManager

One more note: I got confused by the R.layout.activity_calendario_laboral, but the layout is actually for the fragment, if I understood it correctly, so just so you know.