How to programmatically add TextViews and align them in a Layout

I want to create some TextViews (and Buttons) and than put them on the RelativeLayout within the ConstraintLayout (also could be LinearLayout or anythign else that will work)... My goal is to put for each button a textview left of it and them center that pait in the Layout. (Thats what I am trying to do with Layoutparams). But why am I getting a NullPointer Exception?

XML Layout:

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.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:id="@+id/welcomeiqlinear"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context="com.example.william.httprequest.Welcome_InitialQuestions">

<TextView
    android:id="@+id/textView14"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginLeft="8dp"
    android:layout_marginRight="8dp"
    android:layout_marginTop="16dp"
    android:text="@string/wilkommen"
    android:textAlignment="center"
    android:textSize="35sp"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toRightOf="parent"
    app:layout_constraintTop_toTopOf="parent" />

<TextView
    android:id="@+id/textView28"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginLeft="8dp"
    android:layout_marginRight="8dp"
    android:layout_marginTop="24dp"
    android:text="@string/wilkommen_t1"
    android:textAlignment="center"
    app:layout_constraintHorizontal_bias="0.0"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toRightOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/textView14" />

<Button
    android:id="@+id/startinitialbtn"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginBottom="8dp"
    android:layout_marginLeft="8dp"
    android:layout_marginRight="8dp"
    android:backgroundTint="@color/aqua"
    android:elevation="0dp"
    android:text="@string/start_btn"
    android:textColor="@color/white"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toRightOf="parent" />

<RelativeLayout
    android:id="@+id/onetimerelative"
    android:layout_width="0dp"
    android:layout_height="0dp"
    android:layout_marginBottom="8dp"
    android:layout_marginEnd="8dp"
    android:layout_marginStart="8dp"
    android:layout_marginTop="8dp"
    app:layout_constraintBottom_toTopOf="@+id/startinitialbtn"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/textView28"
    app:layout_constraintVertical_bias="1.0">

</RelativeLayout>

</android.support.constraint.ConstraintLayout>

Java Code:

@Override
        public void onResponse(String response) {

            //Log.i(TAG, "MY_PROFILE_DATA: "+ response);

            studiesList = new LinkedList<String>();

            try {
                JSONObject jsonObject1 = new JSONObject(response);
                JSONArray jArray = jsonObject1.getJSONArray("data");

                if (jArray != null) {
                    for (int i = 0; i < jArray.length(); i++) {
                        studiesList.add(jArray.getString(i));
                    }
                }

            } catch (JSONException e) {
                e.printStackTrace();
            }

            Iterator<String> itr=studiesList.iterator();
            //Log.i(TAG,"Questionnaire_DATA: "+ studiesList.toString());
            int i = 1;
            while(itr.hasNext())
            {
                if(i==1) {

                    Log.i(TAG, "Questionnaire_DATA: " + itr.next());

                    //add textViews
                    TextView textView = new 
                    TextView(getApplicationContext());

                    textView.setText("Fragebogen " + i);


                    //add buttons
                    Button button = new Button(getApplicationContext());
                    button.setText("Offen");
                    button.setId(i);

                    RelativeLayout.LayoutParams lp = 
                   (RelativeLayout.LayoutParams) 
                    otrelativeLayout.getLayoutParams();
                    lp.addRule(RelativeLayout.ALIGN_PARENT_LEFT, 0);
                    lp.addRule(RelativeLayout.RIGHT_OF, button.getId());
                    lp.addRule(RelativeLayout.ALIGN_BASELINE, button.getId());

                    textView.setLayoutParams(lp);

                    otrelativeLayout.addView(button);
                    otrelativeLayout.addView(textView);
                    i++;
                } else {





                }
            }

Error:

FATAL EXCEPTION: main

Process: com.example.william.httprequest, PID: 26073

java.lang.ClassCastException: 
android.support.constraint.ConstraintLayout$LayoutParams cannot be cast to 
android.widget.RelativeLayout$LayoutParams

I really would appreciate any help :)

Solution

The Android documentation for View.getLayoutParams() states that the returned layout parameters are supplied to the parent of this View. That explains the ClassCastException: when calling getLayoutParams() on your RelativeLayout, you are retrieving layout parameters that describes how it should be laid out in its parent ConstraintLayout, hence an instance of ConstraintLayout.LayoutParams.

You have to instantiate a new RelativeLayout.LayoutParams for each TextView or Button you'd like to add as a child of your RelativeLayout, configure its parameters, set it with View.setLayoutParams(ViewGroupe.LayoutParams) then add the newly created View to its RelativeLayout parent.