SchildiChat-android/app/src/main/res/layout/fragment_room_detail.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">

    <android.support.v7.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="0dp"
        android:layout_height="?actionBarSize"
        android:background="?attr/colorPrimary"
        app:contentInsetStartWithNavigation="0dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:popupTheme="@style/ThemeOverlay.AppCompat.Light"
        app:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">

        <android.support.constraint.ConstraintLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent">

            <ImageView
                android:id="@+id/toolbarAvatarImageView"
                android:layout_width="40dp"
                android:layout_height="40dp"
                android:layout_marginBottom="8dp"
                android:layout_marginTop="8dp"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintStart_toStartOf="parent"
                app:layout_constraintTop_toTopOf="parent"
                tools:src="@tools:sample/avatars" />

            <TextView
                android:id="@+id/toolbarTitleView"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_marginEnd="8dp"
                android:layout_marginStart="8dp"
                android:ellipsize="end"
                android:maxLines="1"
                android:textSize="18sp"
                app:layout_constraintBottom_toTopOf="@+id/toolbarSubtitleView"
                app:layout_constraintEnd_toEndOf="parent"
                app:layout_constraintHorizontal_bias="0.0"
                app:layout_constraintStart_toEndOf="@+id/toolbarAvatarImageView"
                app:layout_constraintTop_toTopOf="parent"
                tools:text="@tools:sample/full_names" />

            <TextView
                android:id="@+id/toolbarSubtitleView"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_marginBottom="8dp"
                android:layout_marginEnd="8dp"
                android:layout_marginStart="8dp"
                android:ellipsize="end"
                android:maxLines="1"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintEnd_toEndOf="parent"
                app:layout_constraintHorizontal_bias="0.0"
                app:layout_constraintStart_toEndOf="@+id/toolbarAvatarImageView"
                app:layout_constraintTop_toBottomOf="@+id/toolbarTitleView"
                tools:text="@tools:sample/date/day_of_week" />


        </android.support.constraint.ConstraintLayout>

    </android.support.v7.widget.Toolbar>

    <com.airbnb.epoxy.EpoxyRecyclerView
        android:id="@+id/recyclerView"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:layout_constraintBottom_toTopOf="@+id/composerDivider"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@id/toolbar" />

    <View
        android:id="@+id/composerDivider"
        android:layout_width="match_parent"
        android:layout_height="1dp"
        android:background="@color/pale_grey"
        app:layout_constraintBottom_toTopOf="@+id/composerLayout" />

    <RelativeLayout
        android:id="@+id/composerLayout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent">

        <ImageButton
            android:id="@+id/sendButton"
            android:layout_width="48dp"
            android:layout_height="48dp"
            android:layout_alignParentEnd="true"
            android:background="?android:attr/selectableItemBackground"
            android:src="@drawable/ic_send_white"
            android:tint="?attr/colorAccent"
            android:layout_alignParentRight="true"
            android:layout_centerVertical="true" />

        <EditText
            android:id="@+id/composerEditText"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentLeft="true"
            android:layout_centerVertical="true"
            android:layout_toLeftOf="@id/sendButton"
            android:background="@android:color/transparent"
            android:gravity="center_vertical"
            android:hint="Send a message"
            android:minHeight="48dp"
            android:nextFocusLeft="@id/composerEditText"
            android:nextFocusUp="@id/composerEditText"
            android:padding="16dp"
            android:textSize="14sp" />

    </RelativeLayout>

</android.support.constraint.ConstraintLayout>