FossifyGallery/app/src/main/res/layout/activity_medium.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/fragment_holder"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <com.simplemobiletools.commons.views.MyViewPager
        android:id="@+id/view_pager"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

    <android.support.constraint.ConstraintLayout
        android:id="@+id/bottom_actions"
        android:layout_width="match_parent"
        android:layout_height="@dimen/bottom_actions_height"
        android:layout_alignParentBottom="true"
        android:background="@drawable/gradient_background_lighter"
        android:paddingTop="@dimen/medium_margin">

        <ImageView
            android:id="@+id/bottom_properties"
            style="@style/MyBorderlessBackgroundStyle"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:padding="@dimen/medium_margin"
            android:src="@drawable/ic_properties"
            app:layout_constraintEnd_toStartOf="@+id/bottom_edit"
            app:layout_constraintHorizontal_bias="0.5"
            app:layout_constraintStart_toStartOf="parent"/>

        <ImageView
            android:id="@+id/bottom_edit"
            style="@style/MyBorderlessBackgroundStyle"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:padding="@dimen/medium_margin"
            android:src="@drawable/ic_edit"
            app:layout_constraintEnd_toStartOf="@+id/bottom_share"
            app:layout_constraintHorizontal_bias="0.5"
            app:layout_constraintStart_toEndOf="@+id/bottom_properties"/>

        <ImageView
            android:id="@+id/bottom_share"
            style="@style/MyBorderlessBackgroundStyle"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:padding="@dimen/medium_margin"
            android:src="@drawable/ic_share"
            app:layout_constraintEnd_toStartOf="@+id/bottom_delete"
            app:layout_constraintHorizontal_bias="0.5"
            app:layout_constraintStart_toEndOf="@+id/bottom_edit"/>

        <ImageView
            android:id="@+id/bottom_delete"
            style="@style/MyBorderlessBackgroundStyle"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:padding="@dimen/medium_margin"
            android:src="@drawable/ic_delete"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintHorizontal_bias="0.5"
            app:layout_constraintStart_toEndOf="@+id/bottom_share"/>

    </android.support.constraint.ConstraintLayout>
</RelativeLayout>