App: layout_marginBottom not working with layout constraints on Android

Question

Is there a reason why the following layout_marginBottom is not working? However, if I use layout_marginTop in the second view, it works well

<android.support.constraint.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#ade4ad">
    <TextView
        android:id="@+id/first"
        android:layout_width="90dp"
        android:layout_height="40dp"
        app:layout_marginBottom="10dp"
        android:background="#000"/>
    <TextView
        android:id="@+id/second"
        android:layout_width="90dp"
        android:layout_height="40dp"
        android:background="#fff"
        app:layout_constraintTop_toBottomOf="@+id/first"/>
</android.support.constraint.ConstraintLayout>

Answer 1

To

android:layout_marginBottom="20dp" 

work well you have to use

app:layout_constraintBottom_toBottomOf="parent"

Answer 2

The top / bottom margin layout only works when:

1. restrictions in the same direction should join their next child neighbor as a unidirectional linked list.
2. the last restriction in the direction should be established.

"layout_constraintBottom_toXXXXX" , .

<android.support.constraint.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="#ade4ad">
    <TextView
        android:id="@+id/first"
        android:layout_width="90dp"
        android:layout_height="40dp"
        app:layout_marginBottom="10dp"
        app:layout_constraintBottom_toTopOf="@+id/second"
        android:background="#000"/>
    <TextView
        android:id="@+id/second"
        android:layout_width="90dp"
        android:layout_height="40dp"
        app:layout_marginBottom="10dp"
        app:layout_constraintBottom_toTopOf="@+id/third"
        android:background="#fff"/>
    <TextView
        android:id="@+id/third"
        android:layout_width="90dp"
        android:layout_height="40dp"
        android:background="#fff"
        app:layout_constraintBottom_toBottomOf="parent"/>
</android.support.constraint.ConstraintLayout>

, , , , "layout_marginTop" .

Answer 3

, ,

<Space
   android:id="@+id/space"
   android:layout_width="wrap_content"
   android:layout_height="80dp"
   app:layout_constraintBottom_toBottomOf="parent"
   app:layout_constraintEnd_toEndOf="parent"
   app:layout_constraintStart_toStartOf="parent" />

    : layout_constraintBottom_toTopOf = "@+id/"

<TextView
    android:id="@+id/howNext"
    style="@style/white_action_btn_no_border"
    android:layout_width="344dp"
    android:layout_height="60dp"
    android:layout_marginBottom="8dp"
    android:layout_marginEnd="8dp"
    android:layout_marginStart="8dp"
    android:text="@string/got_it_next"
    app:layout_constraintBottom_toTopOf="@+id/space"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent" />

Answer 4

, , .

android:layout_marginTop="10dp" app:layout_goneMarginTop="0dp" TextView, .

Answer 5

It is not LinearLayout, or RelativeLayout, it ConstraintLayout, so you need to give Left, Right, Bottom, Top Constraintits layout, in your case, you have to give the TextViewfirst Bottom_Toprestriction on TextViewthe second. so you can get margin between two TextView.

Your layout should look like this.

<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:background="#ade4ad">
    <TextView
        android:id="@+id/first"
        android:layout_width="90dp"
        android:layout_height="40dp" 
        android:background="#000"
        app:layout_constraintTop_toTopOf="parent" 
        app:layout_constraintLeft_toLeftOf="parent" />
    <TextView
        android:id="@+id/second"
        android:layout_width="90dp"
        android:layout_height="40dp"
        android:background="#fff"
        android:layout_marginTop="10dp"
        app:layout_constraintTop_toBottomOf="@+id/first" 
        app:layout_constraintLeft_toLeftOf="@+id/first" 
        app:layout_constraintRight_toRightOf="@+id/first" />
</android.support.constraint.ConstraintLayout>