How to add a ConstraintLayout to a LinearLayout

as the title states, i do have two Elements:

1. LinearLayout:

       <LinearLayout
            android:id="@+id/idContent"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintHorizontal_bias="0.384"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintVertical_bias="0.419"
            android:orientation="horizontal">
   
        </LinearLayout>
   

2. ConstraintsLayout

   <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res                                               `/android"`
   
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/idExample">
   
     <EditText
            android:id="@+id/iddas"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:ems="10"
            android:inputType="date"
           />
    </androidx.constraintlayout.widget.ConstraintLayout>
   

Quesiton: How to add the ConstraintLayout to the LinearLayout?

What i tried:

LinearLayout linear = (LinearLayout) findViewById(R.id.idContent);
ConstraintsLayout cst = (ConstraintsLayout) findViewById(R.id.idExample);
linear.addView(cst);

Issue: Error: Cannot add a null child view to a ViewGroup

I guess it is null because it has never been inflated. Assume the layout that contains the ConstraintsLayout is my_layout.xml, now you should inflate it first, then add it to the LinearLayout:

LayoutInflater layoutInflater = LayoutInflater.from(context);
View cst = layoutInflater.inflate(R.layout.my_layout, null);
linear.addView(cst);