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email_compose_activity.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"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:importantForAutofill="noExcludeDescendants"
    android:orientation="vertical"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin">

<TextView
        android:id="@+id/email_compose_header"
        style="@style/TextAppearance.AppCompat.Large"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginTop="@dimen/spacing_normal"
        android:gravity="center"
        android:text="@string/navigation_button_email_compose_label"
        app:layout_constraintEnd_toStartOf="@+id/imageButton"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintHorizontal_chainStyle="spread"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

<com.example.android.autofillframework.app.InfoButton
        android:id="@+id/imageButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:background="@drawable/ic_info_black_24dp"
        app:dialogText="@string/email_compose_info"
        app:layout_constraintBottom_toBottomOf="@+id/email_compose_header"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toEndOf="@+id/email_compose_header"
        app:layout_constraintTop_toTopOf="@+id/email_compose_header" />

<TextView
        android:id="@+id/toLabel"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="@dimen/spacing_normal"
        android:layout_marginEnd="@dimen/spacing_normal"
        android:layout_marginStart="@dimen/spacing_normal"
        android:layout_marginTop="@dimen/spacing_normal"
        android:text="@string/to_label"
        app:layout_constraintBottom_toBottomOf="@+id/toText"
        app:layout_constraintEnd_toStartOf="@+id/toText"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="@+id/toText" />

<EditText
        android:id="@+id/toText"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginEnd="@dimen/spacing_normal"
        android:layout_marginTop="@dimen/spacing_normal"
        android:inputType="textEmailAddress"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="@+id/bodyText"
        app:layout_constraintTop_toBottomOf="@+id/email_compose_header" />

<TextView
        android:id="@+id/bodyLabel"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginEnd="@dimen/spacing_normal"
        android:layout_marginStart="@dimen/spacing_normal"
        android:text="@string/body_label"
        app:layout_constraintEnd_toStartOf="@+id/bodyText"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="@+id/placeholder"
        app:layout_constraintBottom_toBottomOf="@+id/placeholder"/>

<EditText
        android:id="@+id/bodyText"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginEnd="@dimen/spacing_normal"
        android:layout_marginStart="@dimen/spacing_normal"
        android:layout_marginTop="@dimen/spacing_normal"
        android:inputType="textMultiLine"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toEndOf="@+id/bodyLabel"
        app:layout_constraintTop_toBottomOf="@+id/toText" />

<View
        android:id="@+id/placeholder"
        android:layout_width="match_parent"
        android:layout_height="36sp"
        app:layout_constraintTop_toTopOf="@+id/bodyText"
        app:layout_constraintStart_toStartOf="parent"
        android:layout_marginStart="8dp" />

<android.support.design.widget.FloatingActionButton
        android:id="@+id/sendButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:backgroundTint="@android:color/holo_purple"
        android:src="@drawable/ic_send_white_24dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent" />

</android.support.constraint.ConstraintLayout>