I want to put the text in textView_title and textView_subtitle to the center of the screen. May I know what is a good way to do it? I tried android:layout_gravity and android:gravity and they do not work. 
Below is the XML file with a constraint layout.
    <androidx.constraintlayout.widget.ConstraintLayout
            android:layout_width="0dp"
            android:layout_height="?attr/actionBarSize"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintTop_toTopOf="parent">
        <androidx.constraintlayout.widget.ConstraintLayout
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                app:layout_constraintStart_toStartOf="parent"
                app:layout_constraintEnd_toStartOf="@id/textView_login"
                app:layout_constraintTop_toTopOf="parent"
                app:layout_constraintBottom_toBottomOf="parent">
            <TextView
                    android:id="@+id/textView_title"
                    android:lines="1"
                    android:ellipsize="end"
                    android:layout_width="0dp"
                    android:layout_height="wrap_content"
                    app:layout_constraintStart_toStartOf="parent"
                    app:layout_constraintEnd_toEndOf="parent"
                    app:layout_constraintTop_toTopOf="parent"
                    app:layout_constraintBottom_toTopOf="@id/textView_subtitle"
                    tool:text="textView"/>
            <TextView
                    android:id="@+id/textView_subtitle"
                    android:lines="1"
                    android:ellipsize="end"
                    android:textColor="@color/foodDollarYellow"
                    android:textSize="12sp"
                    android:layout_width="0dp"
                    android:layout_height="wrap_content"
                    app:layout_constraintStart_toStartOf="parent"
                    app:layout_constraintEnd_toEndOf="parent"
                    app:layout_constraintTop_toBottomOf="@id/textView_title"
                    app:layout_constraintBottom_toBottomOf="parent"
                    tool:text="textView"/>
        </androidx.constraintlayout.widget.ConstraintLayout>
        <TextView
                android:id="@+id/textView_login"
                android:textAlignment="textEnd"
                android:text="註冊/登入"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginEnd="16dp"
                app:layout_constraintEnd_toEndOf="parent"
                app:layout_constraintTop_toTopOf="parent"
                app:layout_constraintBottom_toBottomOf="parent"
                tool:ignore="HardcodedText"/>
    </androidx.constraintlayout.widget.ConstraintLayout>

 
     
    


