goneMargin is not respected in a wrap_content ConstraintLayout?

问题

I have a ConstraintLayout where its height is wrap_content.

I want its height to be able to collapse or expanding, according to its Child's height. Simple and common enough, right?

Now I have a layout which looks like this:
(First of all, please ignore the abnormal super large margin at the bottom. As you can see, the margin is just 16dp but the preview renders a very large margin.)

My problem is, if the big rectangle's visibility is set to gone,
According to the documentation of ConstraintLayout, if I set its goneMarginTop to a certainValue, it will retain that margin even when its visibility is gone. So that my Request Date will have some space to the bottom of parent.

However, this does not work as expected. Request Date sticked to the bottom of its parent:
(This is again a broken preview. In my real app, I am able to see a complete Request Date)

Have I done something wrong? Here is my complete code:

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:background="@color/colorBasicGrey"
    android:layout_marginBottom="2dp">

    <View
        android:id="@+id/item_indicator"
        android:layout_width="8dp"
        android:layout_height="8dp"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        android:background="@color/white"
        android:layout_marginTop="24dp"
        android:layout_marginLeft="24dp"/>

    <TextView
        android:id="@+id/group_member_label"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/group_member_join_group_request"
        app:layout_constraintTop_toBottomOf="@id/item_indicator"
        app:layout_constraintBottom_toTopOf="@id/item_indicator"
        app:layout_constraintLeft_toRightOf="@id/item_indicator"
        android:layout_marginLeft="8dp"
        style="@style/general45"/>

    <TextView
        android:id="@+id/group_member_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        style="@style/general45"
        android:textAllCaps="true"
        app:layout_constraintBaseline_toBaselineOf="@id/group_member_label"
        app:layout_constraintLeft_toLeftOf="parent"
        android:layout_marginLeft="180dp"
        tools:text="ABCDEFGHIJK"/>

    <TextView
        android:id="@+id/group_request_date_label"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/group_member_request_date_label"
        app:layout_constraintTop_toBottomOf="@id/group_member_label"
        app:layout_constraintLeft_toLeftOf="@id/group_member_label"
        android:layout_marginTop="8dp"
        style="@style/general45"/>

    <TextView
        android:id="@+id/group_request_date"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        style="@style/general45"
        android:textAllCaps="true"
        app:layout_constraintBaseline_toBaselineOf="@id/group_request_date_label"
        app:layout_constraintLeft_toLeftOf="parent"
        android:layout_marginLeft="180dp"
        tools:text="28/10/2017"/>

    <LinearLayout
        android:id="@+id/admin_button_container"
        android:layout_width="0dp"
        android:layout_height="48dp"
        android:layout_marginBottom="16dp"
        android:layout_marginLeft="24dp"
        android:layout_marginRight="24dp"
        android:layout_marginTop="12dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toBottomOf="@id/group_request_date_label"
        app:layout_constraintVertical_bias="0.0"
        app:layout_goneMarginTop="16dp"
        app:layout_goneMarginLeft="24dp"
        app:layout_goneMarginRight="24dp"
        app:layout_goneMarginBottom="0dp"
        android:visibility="gone">

        <!--To simplify the question, I hided elements inside this LinearLayout-->

    </LinearLayout>

</android.support.constraint.ConstraintLayout>

回答1:

Figured it out.

goneMargin is used to indicate the margin to a GONE target, instead of itself being GONE.

Therefore in fact I should put the goneMargin attributes in the Request Date instead of the large rectangle.

来源：https://stackoverflow.com/questions/47133325/gonemargin-is-not-respected-in-a-wrap-content-constraintlayout