Why doesn't the Guideline work when I use CardView within ConstraintLayout? - android-studio

Question

I hope to design a UI to dsiplay two columns with latest ConstraintLayout layout, so I use Guideline, it can work when I use Code B (Please see Image B),
But Code A can't display two columns (Would you please see the Image A) after I add CardView control to the layout, what's wrong with my code?
Image A
Image B
Code A
<?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:layout_width="match_parent"
android:layout_height="wrap_content">
<android.support.v7.widget.CardView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="5dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent">
<android.support.constraint.Guideline
android:id="#+id/guideLine"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical"
app:layout_constraintGuide_begin="100dp" />
<RadioButton
android:id="#+id/radioButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Select"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toLeftOf="#+id/guideLine"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintBottom_toBottomOf="parent"
/>
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintLeft_toRightOf="#+id/guideLine"
app:layout_constraintTop_toTopOf="parent"
>
<TextView
android:id="#+id/textViewUsername"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:padding="15dp"
android:text="Hello" />
<TextView
android:id="#+id/textViewAddress"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:padding="15dp"
android:text="Jack" />
</LinearLayout>
</android.support.v7.widget.CardView>
</android.support.constraint.ConstraintLayout>
Code B
<?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:layout_width="match_parent"
android:layout_height="wrap_content">
<android.support.constraint.Guideline
android:id="#+id/guideLine"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical"
app:layout_constraintGuide_begin="100dp" />
<RadioButton
android:id="#+id/radioButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Select"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toLeftOf="#+id/guideLine"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintBottom_toBottomOf="parent"
/>
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintLeft_toRightOf="#+id/guideLine"
app:layout_constraintTop_toTopOf="parent"
>
<TextView
android:id="#+id/textViewUsername"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:padding="15dp"
android:text="Hello" />
<TextView
android:id="#+id/textViewAddress"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:padding="15dp"
android:text="Jack" />
</LinearLayout>

Answer 1

For the Guideline to work, it needs to be the child of a ConstraintLayout and a sibling of the view that is going to use it as a constraint.
In your case, setting the CardView as the root view and the ConstraintLayout inside it would solve the issue.
See this XML as an example:
<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView
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:layout_width="match_parent"
android:layout_height="wrap_content"
>
<android.support.constraint.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="5dp"
>
<android.support.constraint.Guideline
android:id="#+id/guideLine"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical"
app:layout_constraintGuide_begin="100dp"
/>
<RadioButton
android:id="#+id/radioButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Select"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toLeftOf="#id/guideLine"
app:layout_constraintTop_toTopOf="parent"
/>
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical"
app:layout_constraintLeft_toRightOf="#id/guideLine"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
>
<TextView
android:id="#+id/textViewUsername"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:padding="15dp"
android:text="Hello"
/>
<TextView
android:id="#+id/textViewAddress"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:padding="15dp"
android:text="Jack"
/>
</LinearLayout>
</android.support.constraint.ConstraintLayout>
</android.support.v7.widget.CardView>