Confusion regarding documentation for Android Inflator.

I don't usually answer my own questions, but after doing a little more research on this, I thought that maybe it would help someone else. While Marcin's answer is correct, I'm just answering in a little more detail.

According to the code:

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    return inflater.inflate(R.layout.example_fragment, container, false);
}

      

        
        
        
      

    

The second parameter container is a frameelayout with the id fragment_container, which it uses to add the fragment to the layout.

Now if we dive deeper into the inflating method of the LayoutInflater class, this is the code (I'm just highlighting the relevant parts of the code, not all of it):

// The view that would be returned from this method.
View result = root;

// Temp is the root view that was found in the xml.                     
final View temp = createViewFromTag(root, name, attrs, false);

      

        
        
        
      

    

First, it creates a temporary view from the provided root.

In case attachToRoot is true, it does the following:

if (root != null && attachToRoot) {
    root.addView(temp, params);
}

      

        
        
        
      

    

It adds the temporary view created above to the root view (i.e. container).

In case attachToRoot is false, it does the following:

if (root == null || !attachToRoot) {
   result = temp;   
}

      

        
        
        
      

    

As is quite obvious, in case attachToRoot is true, it simply returns root (fragment_container, that is, the activity id uses to place the fragment inside it.) After adding a temporary view to it (the root representation in example_fragment in this case)).

In case attachToRoot is false, it just returns the root of the fragment xml, that is, the container parameter is only used to get the layoutParams for the root view of the fragment (since it has no root, so it needs parameters from somewhere).

The problem if true arises in the above example because the return value is the root (fragment_container with added time view, and the fragment_container instance already has a parent by default.). Now, if you try to do a fragment transaction, you are trying to add a child fragment_container (which already has a parent to another xml (the frame you defined to add the fragment).

Due to this, Android throws the following exception:

if (child.getParent() != null) {
            throw new IllegalStateException("The specified child already has a parent. " + 
"You must call removeView() on the child parent first.");
    }

      

        
        
        
      

    

The problem with setting it to true and return is that the returned image already has a parent, so it cannot be used otherwise. Another way: you can create a separate view group inside onCreateView (maybe LinearLayout), set the parameter to true and return the view. Then it will work fine because there will be no existing parent in the view group.

This is my understanding of the above problem, maybe I am wrong, in which case I would like any Android expert to fix it.

The view returned from the onCreateView () method of the fragment will be attached to the fragment container by the system. Thus, the third parameter of the inflate () method must be false in this case. If you set it to true it will be anchored to the root twice. Therefore, in this case, you must set it to false.

Inflate now inflates layout parameters from the second parameter of the inflate () method not from the third boolean parameter.