ScrollView inside of a ConstraintLayout exceeds bounds of parent

Question

I have the following structure for a fragment:

<androidx.constraintlayout.widget.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent" >

<ScrollView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    app:layout_constraintTop_toTopOf="parent"
    app:layout_constraintBottom_toTopOf="@+id/credential_save_button">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">

        ..................
    
    </LinearLayout>

</ScrollView>

<TextView
    android:id="@+id/credential_save_button"
    android:background="@android:color/transparent"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:paddingTop="10dp"
    android:paddingBottom="10dp"
    android:textColor="@color/white"
    android:textSize="@dimen/textSize"
    android:text="@string/save_initialize"
    android:drawableEnd="@drawable/button_right_arrow_blue"
    tools:ignore="UseCompatTextViewDrawableXml"
    app:layout_constraintBottom_toBottomOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

My expectation is that the save button would be locked to the bottom of the fragment, taking up as much height as it needs to, then the rest of the fragment would be filled with the scrollview and its fields.

Instead the scroll view exceeds the bounds of the Fragment, overlapping the save button and other elements on the page. It seems to always exceed the bounds by about half an element at the top and bottom (would guesstimate it as 20-30dp), no matter how many elements I add to it. If it has few elements in it such that it does not need to scroll, then everything appears correct and no elements are exceeding the bounds of the Fragment.

Changing it to a nested scroll view or adding the fill fillViewport attribute to it does not change anything.

Answer 1

Try setting

android:layout_height="0dp"

for the ScrollView to get it to expand from the top of the layout to the top of the TextView.

Also, don't specify match_parent for any child of ConstraintLayout. Always use 0dp and the appropriate constraints.