android.widget.RadioGroup

<android.widget.RadioGroup
            android:id="@+id/rgSex"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:layout_constraintTop_toBottomOf="@+id/tvSex"
            app:layout_constraintBottom_toTopOf="@+id/tvPhone"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            android:orientation="horizontal" >
            <android.widget.RadioButton
                android:id="@+id/rbMale"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="男"
                android:textSize="16sp"
                android:padding="20dp" />
            <android.widget.RadioButton
                android:id="@+id/rbFemale"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="女"
                android:textSize="16sp"
                android:padding="20dp" />
        </android.widget.RadioGroup>

var sex = "未選択"
        rgSex.setOnCheckedChangeListener { _, checkedId ->
            when (checkedId) {
                R.id.rbMale -> {
                    sex = "男"
                }
                R.id.rbFemale -> {
                    sex = "女"
                }
            }
        }