ConstraintLayout issue on android 6

Question

I found a very strange bug using ConstraintLayout in my project. Indeed, this issue is only with android 6.

I'm using the following XML to display a list of buttons for different login possibilities :

<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="match_parent"
android:fitsSystemWindows="true"
tools:context="com.fagets.rainbowsixapp.login.LoginStepOneFragment">

<LinearLayout
    android:id="@+id/linearLayout_login_form"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    tools:layout_constraintRight_creator="1"
    tools:layout_constraintBottom_creator="1"
    android:layout_marginStart="65dp"
    app:layout_constraintBottom_toBottomOf="parent"
    android:layout_marginEnd="65dp"
    app:layout_constraintRight_toRightOf="parent"
    tools:layout_constraintLeft_creator="1"
    android:layout_marginBottom="18dp"
    app:layout_constraintLeft_toLeftOf="parent"
    android:layout_marginLeft="65dp"
    android:layout_marginRight="65dp">

    <com.facebook.login.widget.LoginButton
        xmlns:facebook="http://schemas.android.com/apk/res-auto"
        android:id="@+id/login_button_facebook"
        style="@style/LoginButton"
        android:paddingTop="15dp"
        android:paddingBottom="15dp"
        facebook:com_facebook_login_text="@string/login_connect_facebook"/>

    <Button
        android:id="@+id/login_button_google"
        style="@style/LoginButton"
        android:textColor="@color/login_button_google_text"
        android:background="@drawable/login_button_shape_google"
        android:text="@string/login_connect_google"/>

    <Button
        android:id="@+id/login_button_anonymous"
        style="@style/LoginButton"
        android:background="@drawable/login_button_shape_anonymous"
        android:text="@string/login_connect_anonymous"/>

    <Button
        android:id="@+id/login_button_about"
        style="@style/LoginButton"
        android:background="@android:color/transparent"
        android:text="@string/login_connect_about"
        android:textColor="@color/login_button_google_text"/>

</LinearLayout>

My issue concern the app:layout_constraintBottom_toBottomOf="parent" in the LinearLayout. On Android 6 the LinearLayout is cropped instead of being stick to the bottom. It's correctly working on android 7, and even on android 4.4.2. Just after that, I tried to remove my LinearLayout to only use the ConstraintLayout, but I still have the same issue.

Here is a screenshot on Android 7 :

And here the issue with Android 6 :

Am I doing something wrong ? Or is it an issue with ConstraintLayout library ?

Thanks !

Answer 1

You don't need that additional LinearLayout when you are working with the constranintLayout

XML:

<?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="match_parent">

    <Button
        android:id="@+id/button1"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        app:layout_constraintBottom_toBottomOf="parent"
        android:layout_marginBottom="16dp"
        android:layout_marginRight="8dp"
        app:layout_constraintRight_toRightOf="parent"
        android:layout_marginLeft="8dp"
        app:layout_constraintLeft_toLeftOf="parent" />

    <Button
        android:id="@+id/button2"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginRight="8dp"
        app:layout_constraintRight_toRightOf="parent"
        android:layout_marginLeft="8dp"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintHorizontal_bias="1.0"
        android:layout_marginBottom="16dp"
        app:layout_constraintBottom_toTopOf="@+id/button1" />

    <Button
        android:id="@+id/button3"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginRight="8dp"
        app:layout_constraintRight_toRightOf="parent"
        android:layout_marginLeft="8dp"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintHorizontal_bias="1.0"
        android:layout_marginBottom="16dp"
        app:layout_constraintBottom_toTopOf="@+id/button2" />

</android.support.constraint.ConstraintLayout>