在约束布局中,要实现TextView2在TextView1的下面,需要增加的约束是
A.
app:layout_constraintTop_toTopOf="@id/textview1"
B.
app:layout_constraintTop_toBottomOf="@id/textview1"
C.
app:layout_constraintBottom_toBottomOf="@id/textview1"
D.
app:layout_constraintBottom_toTopOf="@id/textview1"