размещение элементов в android

<?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"
    tools:context="hfad.com.messenger.CreateMessageActivity">

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/send"
        android:onClick="onSendMessage"
        tools:layout_editor_absoluteX="48dp"
        tools:layout_editor_absoluteY="16dp" />

    <EditText
        android:id="@+id/editText"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:ems="10"
        android:inputType="textPersonName"
        android:maxEms="10"
        android:text="Name"
        tools:layout_editor_absoluteX="48dp"
        tools:layout_editor_absoluteY="306dp" />
</android.support.constraint.ConstraintLayout>

        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"

        app:layout_constraintHorizontal_bias="0.685"
        app:layout_constraintVertical_bias="0.209